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Rainfall partitioning and cloud water interception in native forest an invaded forest in Hawai'I Volcanoes National Park
Abstract
In many Hawaiian forests, including cloud forests, native plant communities are being displaced by invasive tree species, possibly affecting rainfall partitioning and direct harvesting of cloud droplets by vegetation. In this study, the hydrological impacts of invasive species are examined, using measurements of rainfall (RF), throughfall (TF) and stemflow (SF), and estimation of wet-canopy evaporation and cloud water interception (CWI) by the canopy water balance approach in both native Metrosideros polymorpha-dominated and invaded, Psidium cattleianum-dominated forests within Hawai'i Volcanoes National Park (HAVO). Canopy water storage capacity was found to be more than twice as great at the native site (1·86 mm) compared to the invaded site (0·85 mm). Annual RF, CWI, TF and SF were 3233, 1188, 3700 and 261 mm, respectively, for the native site; and 3735, 734, 3033 and 1091 mm, respectively, for the invaded site. Net RF (TF + SF) was 123 and 110% of RF, respectively, at the two sites. Annual evaporation of water from the wet canopy was also greater at the native site (464 mm) than at the invaded site (347 mm). Low canopy water storage capacity and the exceptionally high SF total at the invaded site are related to morphological characteristics and high stem density of the invasive P. cattleianum tree, which favour efficient transport of intercepted water to the ground via the stems. Despite its more peripheral location near the edge of the orographic cloud, CWI at the native site was higher. The characteristics of the native M. polymorpha tree may facilitate more effective harvesting of cloud water droplets, enhancing CWI at the site. Species invasion results in a lower proportion of RF reaching the forest floor (110 vs 123%) and becoming available for groundwater recharge, suggesting that invasion by P. cattleianum may have significant negative effects on Hawai'i's aquatic ecosystems and water resources. Copyright © 2010 John Wiley & Sons, Ltd.
... Psidium cattleyanum has been suggested as one of the world's top 100 worst invasive species (GISD 2023). It particularly threatens flora on tropical/subtropical islands with histories of intense deforestation and many endemic flora (Macdonald et al. 1991;Auld and Hutton 2004;Shimizu 2006;Kueffer et al. 2009;Baider and Florens 2011;Takahashi et al. 2011;Director of National Parks 2018;Meyer et al. 2019). Examining how ecosystems recover after P. cattleyanum management can reveal if additional barriers to recovery exist that need to be addressed. ...
... We also hypothesized that managed plots would have a higher abundance and richness of seedlings and understory plants (Baider and Florens 2011), as we expected dense P. cattleyanum to suppress the recruitment of some native species. We predicted strong compositional dissimilarity between managed and unmanaged plots, particularly in locations that were managed earlier where there has been more time for species to accumulate (O'Leary et al. 2018), and expected canopy cover (as a proxy for light) (Čuda et al. 2014;Depauw et al. 2021) and soil moisture (as a proxy for environmental L. E. Dann et al. favorability) (Takahashi et al. 2011) would be related to these compositional differences. ...
... Its native range extends from north-eastern Brazil to northern Uruguay (Tng et al. 2016;DeSisto et al. 2020). However, P. cattleyanum has invaded many other locations globally, introduced around the world largely for its edible fruits (Brown and Gurevitch 2004;Kueffer et al. 2010;Takahashi et al. 2011;Tng et al. 2016). It primarily invades tropical and subtropical ecosystems but can encroach into temperate regions (Kueffer et al. 2010;Patel 2012;Tng et al. 2016;Florens et al. 2016). ...
Invasive plant species can drive ecosystem change, particularly on oceanic islands that are vulnerable to plant invasions and subsequent biodiversity loss. While invasive species management is vital for habitat restoration, efficacy of management efforts and the ability of native plants to regenerate varies among studies. The aim of this study was to examine the consequences of managing a thicket-forming woody plant species—Psidium cattleyanum Sabine (strawberry guava)—on subtropical forest regeneration, comparing spatial scales and management periods. We surveyed 15 locations on Norfolk Island, an isolated Pacific Island with a high proportion of endemic and threatened species, by establishing paired managed and unmanaged plots to assess changes in species-area relationships, abundance, richness, and composition of the plant community. Total plant richness was higher in managed plots at the largest scale examined (125 m²). However, there was no significant difference between managed and unmanaged plots in the slopes of species-area relationships when canopy, understory, and seedling strata were combined. Stratum-specific analyses revealed that management-driven changes were most evident in the subcanopy strata, which had significantly higher woody plant abundance and richness in managed plots. Compositional dissimilarity between managed and unmanaged plots was greater in locations with higher moisture levels, suggesting that post-management regeneration is related to environmental conditions. This study suggests that P. cattleyanum suppresses plant recruitment and its removal allows for forest regeneration, indicating that management of dominant invasive woody species facilitates plant recruitment on Norfolk Island if nearby native propagule sources are present.
... Despite the fact that tipping bucket application dates back to 1928 (Nebol'sin, 1928), it has been used for surface/subsurface flows in small study area measurements, such as runoff (Calder and Kidd, 1978;Chow, 1976;Corona et al., 2013;Elder et al., 2014;Hollis & Ovenden, 1987;Khan & Ong, 1997;Klik et al., 2004;Kim et al., 2005;Johnston, 1942;Nehls et al., 2011;Peyrard et al., 2016;Perales-Momparler et al., 2017;Langhans et al., 2019;Wang et al., 2020;Whipkey, 1965), percolation (Lamb et al., 2019;Peyrard et al., 2016;Wang et al., 2020), throughfall (Takahashi et al., 2010;Zabret et al., 2018) and stemflow (Iida et al., 2012;Shimizu et al., 2018;Takahashi et al., 2010;Zabret et al., 2018). ...
... Despite the fact that tipping bucket application dates back to 1928 (Nebol'sin, 1928), it has been used for surface/subsurface flows in small study area measurements, such as runoff (Calder and Kidd, 1978;Chow, 1976;Corona et al., 2013;Elder et al., 2014;Hollis & Ovenden, 1987;Khan & Ong, 1997;Klik et al., 2004;Kim et al., 2005;Johnston, 1942;Nehls et al., 2011;Peyrard et al., 2016;Perales-Momparler et al., 2017;Langhans et al., 2019;Wang et al., 2020;Whipkey, 1965), percolation (Lamb et al., 2019;Peyrard et al., 2016;Wang et al., 2020), throughfall (Takahashi et al., 2010;Zabret et al., 2018) and stemflow (Iida et al., 2012;Shimizu et al., 2018;Takahashi et al., 2010;Zabret et al., 2018). ...
... Calder and Kidd (1978) identified a non-linearity of errors under increased flow, and thus proposed a new calibration curve by correlating the input flow and time interval between tilts. Based on the same central idea of describing the errors considering its non-linearity, other authors have also proposed calibration curves (Iida et al., 2012;Shimizu et al., 2018;Shiraki & Yamato, 2004;Takahashi et al., 2010). ...
Inherent errors in tipping bucket flow meters may limit monitoring data reliability. In this work, we perform the static and dynamic calibration of four large tipping buckets, apply different regression curves and investigate the possible measurement error sources. The volumetric capacity (static calibration) of each piece of equipment was determined. They were tested (dynamic calibration) under ten flow intensities, ranging from low to high rainfall intensities (return period larger than 100 years). For each flow rate, the measurement was recorded during six time intervals (1, 2, 5, 10, 20 and 30 min) and four regression equations - linear, potential, T vs. 1/Q and quadratic - were tested. According to the static calibration, the equipment has a volumetric capacity of 11.63 mL (TB1), 64.16 mL (TB2), 139.86 mL (TB3) and 660.95 mL (TB4). When tested under different flow rates (dynamic calibration), underestimations were identified according to the size of the cavity: TB1 (3.31%), TB2 (5.75%), TB3 (9.33%) and TB4 (13.57%). Among the alternative curves, linear regression showed the best correlation (above 99%) with the monitored data. Using this method, the measurement errors were reduced to −1.35% (TB1), 0.04% (TB2), 3.18% (TB3) and 3.73% (TB4). We investigated how the different variables (tipping speed, cavity volumetric capacity and time interval of data collection) influenced the error. Errors follow a parabolic function of tipping velocity and a linear function of cavity volumetric capacity. The time interval of data collection interfered in the data sampled, however no statistical correlation was found. Among those variables, cavity size is the most important one. Given its low cost we aimed to minimize the inherent error in large tipping buckets flow meters and encourage its application, increasing in-situ collection of hydrological data.
... Though watershed partnerships and other conservation organizations protect and restore native forests for multiple benefits, including biodiversity, cultural value, and water quality for downstream coral reefs, water utilities are most interested in enhancing the quality and quantity of groundwater recharge within priority aquifers. While ecohydrology data are limited in Hawaiʻi, and across the tropics more broadly (Hamel et al., 2017;Wright et al., 2018), existing studies suggest that native-dominated forest stands capture more fog (Takahashi et al., 2011) and transpire less water (Cavaleri et al., 2014;Cavaleri and Sack, 2010;Giambelluca et al., 2008;Kagawa et al., 2009;Miyazawa et al., 2019) than invaded stands dominated by high water-use, non-native species. Feral pigs and other ungulate activity also pose a significant threat to remaining native forests, sometimes causing conversion to bare ground or non-native grass dominated systems (Nogueira-Filho et al., 2009), which leads to greater erosion and runoff (Strauch et al., 2016) and reduced fog interception (due to low stature vegetation) in high elevation areas (Engott, 2011). ...
... Changes in forest land cover type can affect the water balance in multiple ways, including through changes in: actual evapotranspiration (AET) (Giambelluca et al., 2014;Kagawa et al., 2009); fog interception (Takahashi et al., 2011); and potentially the amount of water that infiltrates soils and recharges groundwater aquifers versus runs off as streamflow (Wright et al., 2018). Unfortunately, there were insufficient data available to model changes in infiltration spatially with forest cover change. ...
... Cloud water interception or fog interception has been shown to be important in tropical forests in Hawaiʻi (Giambelluca et al, 2009Scholl et al., 2007;Takahashi et al., 2011). Thus, we also modeled changes in fog interception following USGS methods (Engott 2011) where fog interception is calculated as: ...
Worldwide, water utilities and other water users increasingly seek to finance watershed protection and restoration in order to maintain or enhance water quality and quantity important for drinking water supply and other human use. Hydrologic studies which characterize the relative effectiveness of watershed management activities in terms of metrics important to water users are greatly needed to guide prioritization. To address this need, we worked with a local water utility in Hawaiʻi to develop a novel framework for prioritizing investments in native forest protection and restoration for groundwater recharge and applied it in the utility's priority aquifers and recharge areas. Specifically we combined land cover and water balance modeling to quantify the 50-year cumulative recharge benefits of: 1) protection of native forest from conversion to non-native forest, and 2) restoration of native forest in non-native grasslands. The highest priority areas (80th percentile of benefits) for native forest protection are projected to prevent the loss of over 48,600 m³ per hectare of recharge over 50 years. Incorporating land cover change modeling (versus assuming all areas are equally susceptible to invasion) shifts prioritization towards low to mid-elevation mesic forest areas at the highest risk of invasion by invasive canopy species as well as to high elevation, cloud forest areas at high risk of conversion to non-native grassland or bare ground. We also find that, in the highest priority areas with substantial fog interception, native forest restoration is projected to increase recharge by over 88,900 m³ per hectare over 50 years, but that decreases in recharge occur in areas with low fog interception. This study provides a framework for prioritizing investments in forest protection and restoration for groundwater recharge in a way that incorporates both the threat of conversion as well as changes in hydrologic fluxes. The framework and results can be utilized by current managers and updated as new ecohydrological data become available. The results also provide broad insights on the links between watershed management and groundwater recharge, particularly on islands and in other regions where species invasions threaten source watersheds and where groundwater is a primary water source.
... In the context of plant invasions, a few studies have assessed the rainfall partitioning by exotic species and its association with plant morphological characteristics (Sadeghi et al., 2017;Safeeq & Fares, 2014;Takahashi et al., 2011;Whitworth-Hulse et al., 2020). ...
... Hawaii tropical dry forests ecoregion; Takahashi et al., 2011). In the Central Persian desert basins ecoregion (Iran), Sadeghi et al. (2017) highlighted that stemflow generation could be a key process for explaining the invasion of the smooth-barked tree Ailanthus altissima Mill. ...
... Wilgen et al., 2008). In summary, less rainwater reaching the soil, together with high water consumption of invasive plants, might generate a reduction of water availability for recharging groundwater and also streamflow(Farley et al., 2005;Le Maitre et al., 2015;Takahashi et al., 2011). These results will become increasingly important for the maintenance or increase of human well-being, highlighting the need for further inquiries determining the ecohydrological impacts on water provision of woody invasive species at the catchment scale. ...
Aim: Invasive species have the potential to alter hydrological processes by changing the local water balance. However, general patterns of how rainfall is partitioned into interception, throughfall and stemflow for invasive species worldwide have been seldom explored. We (a) describe the percentage of interception, throughfall and stemflow for invasive woody plant species; (b) analyse the influence of morphological attributes (i.e. life-form, bark roughness, leaf type, leaf phenology and leaf area index) of invasive species on rainfall partitioning; and (c) compare the rainfall partitioning fluxes for co-occurring invasive and native species, testing whether the variation in these fluxes depends on water availability of the study location.
Location: Global.
Time period: Present.
Major taxa studied: Plants.
Methods: We compiled data of 100 studies that assessed rainfall partitioning by invasive species (n = 67) and registered their morphological attributes. By means of a meta-analysis we compared the rainfall partitioning by native and invasive species (n = 47 comparisons) and assessed how their fluxes were affected by water availability.
Results: Interception, throughfall and stemflow ranged from 1.6–59.5, 39.1–92.7 and 0.1–31.6% of total rainfall, respectively. The bark roughness and leaf type were the most important attributes driving rainfall partitioning fluxes. While rough-barked species constrain rainfall inputs by promoting higher losses due to interception, smooth-barked species with broad leaves enhance the amount of rainwater reaching the soil by maximizing stemflow. For pairwise comparisons, invasive species have higher stemflow values than native species for both drylands and humid areas, and higher throughfall in drylands, but less in humid areas.
Main conclusions: Our findings suggest that specific morphological attributes of invasive species determine higher localized water inputs, which may represent an ecohydrological advantage, particularly in water-limited ecosystems. These insights also suggest that the ecological role of stemflow, throughfall and interception should be considered in future plant invasions research.
... Two studies from the upslope Alakahi region of windward Kohala reported significant levels of CWI over multi-year spans, and found that CWI inputs almost equaled rainfall levels during a dry period at one of the sites (Juvik & Nullet, 1995;DeLay, 2005). Another study from near the peak of Kīlauea found that CWI contributed 18.7% of total precipitation (Takahashi et al., 2011). While these studies indicate that CWI could contribute significantly to the crest and high leeward areas of Kohala, no CWI experiments have been conducted in leeward TMCFs like those present at high elevations in Kohala. ...
... In order to estimate CWI at each of our study sites, a simple canopy water balance model is employed (Takahashi et al., 2011): ...
... Many TF studies achieve high spatial coverage by funneling water through large systems of troughs into centralized tippingbucket gauges (e.g. McJannet et al., 2007a;Takahashi et al. 2011); however, due to budgetary constraints, this study was limited to 15 plastic buckets per ʻōhiʻa site. Two buckets at each site were allocated to RF measurements in nearby clearings, bogs, and pastures. ...
Cloud water interception (CWI) is a significant source of water for many tropical montane cloud forests (TMCFs) in Hawai‘i and elsewhere. As vast regions of the Hawaiian Islands have undergone extensive deforestation over the past several centuries, many have suggested that the loss of CWI and other ecohydrological characteristics of tropical forests may have resulted in lower rates of groundwater recharge and subsequent streamflow. Leeward Kohala is one such region where many hectares of closed-canopy TMCF and wet-mesic woodland were lost to the cattle industry, which planted exotic pasture grasses in their stead. Because leeward Kohala’s perched groundwater system is geologically-isolated from the intact forests of windward Kohala, the resulting loss of CWI could have significantly lowered recharge rates and water table levels throughout the leeward slope. But despite reports of reduced flow and increased flashiness in leeward streams, CWI in Kohala’s remaining leeward forests has not yet been quantified.Rainfall (RF) and throughfall (TF) were measured along an elevation gradient spanning the natural transition from mesic koai‘a woodland to closed-canopy ‘ōhi‘a forest atop leeward Kohala, Hawai‘i. By applying a simplified canopy water balance model, combined rates of CWI minus canopy interception losses (Ei) were determined at seven sites for twenty distinct measurement periods. These rates ultimately reflect the additional amount of (or loss of) precipitation contacting the land surface due to the presence of forest vegetation rather than flat pastureland. Near Kohala’s leeward crest, RF totaled 1,104.5±13.7 mm over 133 days while forest cover provided an additional 568.0±15.4 mm of water to the land surface. CWI contributions were progressively lower farther down Kohala’s leeward slope, with Ei appearing to outweigh CWI by 41.3±14.3 mm at the current man-made transition from ‘ōhi‘a forest to pasture. Two lower-elevation sites in remnant koai‘a woodlands exhibited a CWI-elevation trend distinct from that of the ‘ōhi‘a sites, with site D recording 50.9±16.8 mm of additional water input at the forest site compared to 457.2±14.0 mm of nearby pasture RF over the study period. At site E, the driest site, Ei exceeded CWI in almost all measurement periods (73.9±16.6 mm net water loss in the site E forest over the study period). Mean TF/RF across sites was 1.07, indicating CWI generally outweighed canopy Ei and added significant amounts of water to leeward Kohala.Spatial variations in CWI were driven by forest structure in addition to elevation: despite receiving the same amount of RF over the study period, different rates of TF and CWI were recorded between the three forested plots at site B. In general, denser forest tended to exhibit lower TF at both the site scale and gauge scale, although this relationship weakens in wetter periods due to higher canopy saturation. Wet periods with strong trade winds featured the highest overall CWI rates across the elevation transect, and CWI rates at all sites generally decreased when conditions become drier and less windy. While CWI, TF and RF are positively related to elevation, periods with weaker trade winds present flatter versions of these trends due to the waning influence of the orographic moisture responsible for both RF and CWI. Broadly speaking, wetness and elevation appear more explanatory than trade wind strength or forest structure for CWI rates in leeward Kohala.
... In other areas, invasions of fast-growing canopy species can lead to a transition to alien dominated forests, as is the case in most low elevation areas in Hawai'i Hughes and Uowolo, 2006). Although research remains limited, available studies have found that typical invasive trees and stands can have higher transpiration rates (Cavaleri et al., 2005;Cavaleri and Sack, 2010;Kagawa et al., 2009;Giambelluca et al., 2008), and lower fog interception rates (Takahashi et al., 2011), than typical native forest trees and stands. There is clear need for further research on the effects of invasions on hydrologic processes at multiple scales; while islands are particularly vulnerable, invasions increasingly represent important threats to forests worldwide and are a critical driver of global environmental change Holmes et al., 2009;Vitousek et al., 1996). ...
... Changes in forest land cover type can affect the water balance in multiple ways, including through changes in: actual evapotranspiration (Giambelluca et al., 2014;Kagawa et al., 2009); fog interception (Takahashi et al., 2011); and potentially the amount of water that infiltrates soils and recharges groundwater aquifers versus runs off as streamflow (Wright et al., 2018). Unfortunately, there are insufficient data available to model changes in fog interception and infiltration spatially with forest cover change. ...
... For native forest, the representative species was 'ōhi'a lehua (Metrosideros polymorpha) and for nonnative forest, strawberry guava (Psidium cattleyanum) (Giambelluca et al., 2014). Second, other processes, including cloud-water interception (Ponette-González et al., 2014;Takahashi et al., 2011) and infiltration (Wright et al., 2018;Perkins et al., 2018) can be affected by land cover type and characteristics, but we did not have information to include these parameters for different forest types. We thus consider our estimates conservative given that field crews and local experts perceive that native forest captures more fog and infiltrates more water than monotypic non-native forest with a less diverse understory, and Note: sp. ...
... In other areas, invasions of fast-growing canopy species can lead to a transition to alien dominated forests, as is the case in most low elevation areas in Hawai'i Hughes and Uowolo, 2006). Although research remains limited, available studies have found that typical invasive trees and stands can have higher transpiration rates (Cavaleri et al., 2005;Cavaleri and Sack, 2010;Kagawa et al., 2009;Giambelluca et al., 2008), and lower fog interception rates (Takahashi et al., 2011), than typical native forest trees and stands. There is clear need for further research on the effects of invasions on hydrologic processes at multiple scales; while islands are particularly vulnerable, invasions increasingly represent important threats to forests worldwide and are a critical driver of global environmental change Holmes et al., 2009;Vitousek et al., 1996). ...
... Changes in forest land cover type can affect the water balance in multiple ways, including through changes in: actual evapotranspiration (Giambelluca et al., 2014;Kagawa et al., 2009); fog interception (Takahashi et al., 2011); and potentially the amount of water that infiltrates soils and recharges groundwater aquifers versus runs off as streamflow (Wright et al., 2018). Unfortunately, there are insufficient data available to model changes in fog interception and infiltration spatially with forest cover change. ...
... For native forest, the representative species was 'ōhi'a lehua (Metrosideros polymorpha) and for nonnative forest, strawberry guava (Psidium cattleyanum) (Giambelluca et al., 2014). Second, other processes, including cloud-water interception (Ponette-González et al., 2014;Takahashi et al., 2011) and infiltration (Wright et al., 2018;Perkins et al., 2018) can be affected by land cover type and characteristics, but we did not have information to include these parameters for different forest types. We thus consider our estimates conservative given that field crews and local experts perceive that native forest captures more fog and infiltrates more water than monotypic non-native forest with a less diverse understory, and Note: sp. ...
Tropical forests provide a suite of benefits including biodiversity, cultural value, and a range of ecosystem services. Globally, there is increasing interest in incentivizing native forest protection as a multi-benefit natural infrastructure strategy to secure clean and ample water supplies. In addition to conversion to agriculture and other non-forest land uses, non-native species invasion represents a major threat to these systems, particularly on islands. Whereas several recent efforts have quantified the benefits of reforestation or avoided agricultural expansion in tropical forest areas, the hydrologic and associated economic benefits of avoided invasion have received less attention. To address this gap, we quantified the benefits of protecting native forest from conversion to non-native forest in East Maui, Hawai'i in terms of groundwater recharge, a highly valued hydrologic ecosystem service that water utilities increasingly seek to co-finance. Compared with two counterfactual invasion scenarios, the groundwater recharge benefits of planned conservation activities reached 40.9 to 146.3 million cubic meters over 100 years depending on invasion rate assumptions. This translated to 2.70 to 137.6 million dollars of cost savings to the water utility in present value terms (achieved through reducing reliance on more expensive water alternatives) under a range of discount rates and water scarcity assumptions. Our results suggest that investing in native forest conservation provides an important hydrologic ecosystem service benefit that complements the range of benefits provided by these ecosystems. These findings demonstrate that co-financing native forest conservation represents an important supply side option in water resources planning.
... Mean annual precipitation varies between 250 to more than 11000 mm in Hawaii , and from 1000 to 12000 mm on La Réunion Island . The occurrence of fog, likely to increase effective precipitation height, is reported in many oceanic islands such as in Hawaii (US) [Brauman et al., 2010;Giambelluca et al., 2011;Takahashi et al., 2011], La Réunion Island (France) [Gabriel and Jauze, 2008], Madeira Island (Portugal) , Canary Islands (Spain) [García-Santos and Bruijnzeel , 2011], and Galapagos Islands [Pryet et al., 2012]. ...
... Giambelluca et al. [Rutter et al., 1972], running water budget interception model (e.g. Takahashi et al. [2011]). ...
... The occurrence of fog is reported in many oceanic islands and has been investigated by several recent studies such as in Hawaii (US) [Brauman et al., 2010;Giambelluca et al., 2011;Takahashi et al., 2011], La Réunion Island (France) [Gabriel and Jauze, 2008], Madeira Island (Portugal) , and Canary Islands (Spain) [García-Santos and Bruijnzeel , 2011]. ...
With a growing population and limited freshwater resources, the hy- drogeology of the Galapagos Islands remains to a great extent un- known. Rainfall is relatively weak and unevenly distributed in space and time. The economical center of the archipelago, Santa Cruz Is- land, has only small intermittent streams, while several permanent streams are present on San Crist ́obal Island. In the frame of this study, an interdisciplinary approach is used to characterize the hy- drogeology of the archipelago.
A new method has been developed to enhance the interpretation of airborne electromagnetics surveys. With geostatistical interpolation techniques, this method allows the construction of a 3D grid of re- sistivity. SkyTEM surveys completed in Galapagos were processed with this technique, and confronted to surface analysis with remote sensing and field work. The first hydrogeological conceptual model is proposed for San Cristo ́bal Island.
Climatic conditions have been investigated with the installation of a monitoring network along the windward side of Santa Cruz Island. The occurrence of fog during six months of the year presents an addi- tional input in the water budget and increases groundwater recharge. This input has been quantified with a physically based canopy inter- ception model.
The basal aquifer of Santa Cruz Island has been investigated from the analysis of tidal signal propagation, hydraulic tests, as well as fault and fracture mapping. Results show that young basalts, densely fractured by cooling joints, are highly permeable. Because they are poorly connected, faults have a limited impact over regional ground- water flow.
Contrasting hydrogeological configurations in the Galapagos Islands are explained by an evolution pattern. In relatively young islands, such as Santa Cruz, basalts are fractured and permeable. Seawater intrusion is strong and freshwater rapidely flows to the ocean. On the opposite, conditions are more favorable for groundwater storage in older volcanic islands, where the regional permeability is smaller and valley incision leads to the existence of springs.
... According to research, the rate at which different tree species intercept precipitation varies; some can intercept as much as 60.9% of total precipitation (Asadian and Weiler 2009). Some native trees are more effective at harvesting cloud water droplets than invasive species (Takahashi et al. 2011). Other studies also showed that a mix of native species effectively decreases run-off in green roof systems (Fai et al. 2015), and enrichment planting drastically reduces surface water flow, soil erosion and nutrient loss (Chu et al. 2019). ...
... Native forests are vital in regulating hydrologic processes like infiltration, overland flow, and evapotranspiration (Meli et al. 2024). When invasive species replace native forests, hydrological processes may change, affecting nearby ecosystems and water supplies and decreasing the amount of water available for groundwater recharge (Catford 2017;Takahashi et al. 2011). These emphasize how crucial native species are to preserving eco-hydrological processes and how invasive species may have detrimental effects on run-off and water retention. ...
Over the years, excessive stormwater runoff has been a primary environmental concern in almost every part of the world. This study aimed to assess the water absorption capacity and root-shoot ratio of the three native species, namely Vitex parviflora, Pterocarpus indicus, and Diospyrus discolor, in the Philippines. The study used an experimental design with a total number of 63 experimental seedlings. After over a month of transplanting, the researchers collected the data by uprooting 1 sample per box and recording its weight. The uprooted samples were then submerged into a container with enough water, and the plant waited until it absorbed enough water before being weighed again. Root and shoot ratio were also computed using its dry weight. The results showed a significant difference in terms of absorption rate between the three native species. V. parviflora garnered the highest water absorption rate, followed by P. indicus and D. discolor. Root-shoot ratio was highest in D. discolor while lowest in V. parviflora. No significant correlation was found between root and shoot biomass regarding water absorption capacity. These findings highlight the importance of selecting specific tree species for environmental management and flood mitigation efforts in the Philippines.
... In some cases, the canopy water balance method also considers evaporation from the canopy as well as the variation in the volume of water retained by it (HAFKENSCHEID et al., 1998;NULLET, 2011;TAKAHASHI et al., 2011;GONZÁLEZ -MARTÍNEZ;HOLWEDA, 2018). To estimate canopy evaporation, the Penman-Monteith method is normally used (ALLEN et al., 1998). ...
... The high rates of Foot obtained for UMCF and SACF-ECF should partially reflect the effect of CWI, as it is pertinent to note that wind speeds at UMCF and SACF-EFC sites tend to be higher than at lower, sheltered slope sites (LMCF and LMRF) . Therefore, the amount of rainfall measured in locations exposed to wind tends to be underestimated and requires correction for losses around collectors MACJANNET;WALLACE;REDDELL, 2007;NULLET, 2011). According to Bruijnzeel et al. (2011), the magnitude of the correction can be substantial in some locations (>20%). ...
Cloud water interception (CWI) occurs when water contained in fog and wind-driven rain collides with vegetation, merges into larger droplets, and precipitates to the ground. CWI has an important function as an additional source of water and its relationships with tropical cloud forests have often been emphasized. Despite its importance, there is no standardization of measurement methods, nor of the terms that designate the process in Portuguese. Therefore, a systematic analysis of research on CWI is necessary. To this end, the present study carried out a review of the theoretical and methodological aspects of CWI through description and analysis of terminology; history and chronology of studies on the topic; survey of the environmental conditions necessary for the CWI process to occur; analysis of methodological aspects relating to the measurement of CWI; and synthesis and discussion of magnitudes described in scientific literature. As a result, of the 31 publications reviewed, 14 different words were found, the most common being “Cloud Water Interception” (19.4%) and “Fog Drip” (16.1%). In general, CWI is more common in places such as continental edges and islands that are constantly subject to sea breezes. In most cases, the below-canopy measurement approach can be considered more accurate than those obtained by fog collectors. CWI is on average responsible for 42% of effective precipitation (n:41). The values listed show a large variation, between 0.5% and 462%, probably due to the different environmental characteristics of the sampled locations as well as variations in sample sizes.
... En la costa norte de Chile, hasta el Perú, las nubes condensantes reciben el nombre de camanchaca (Larrain et al., 2002), y se producen sobre la Cordillera de la Costa, principalmente de la primera fase volcánica de la formación de las cadenas montañosas andinas . También se producen en Colombia y en el área peri-caribeña, como en Costa Rica y en otros lugares, como las islas del archipiélago de las Hawaii, en especial en Maui (Scholl et al., 2003;Takahashi et al., 2011). Tienen notable relevancia en las islas altas de la Macaronesia, en especial en Madeira (Figueira et al., 2012) y en las Islas Canarias, donde forman los "mares de nubes", principalmente en Tenerife (Santana, 1986;Aboal et al., 2013;Braojos Ruiz, 2015), La Gomera Ritter et al., 2005), Gran Canaria, La Palma y la cumbre de El Hierro. ...
... La interceptación de las nubes es importante en las partes altas del bosque tropical hawaiiano (Giambelluca et al., , 2009Scholl et al., 2007). Según Takahashi et al. (2011), la interceptación de niebla en el Parque Nacional de los Volcanes, en la isla de Hawaii, dividida por la suma de la transcolación y flujo por los troncos, es de 0,29 para bosque natural y 0,16 para bosque no nativo. Para evaluarla se aplican los métodos recomendados por el USGS, como F = R + FI + FCE (Engott, 2011), siendo F = agua interceptada de la niebla R = precipitación FI = fracción de interceptación, que depende de la altitud y el lugar EC = eficiencia de captación (0 para pradera; 0,5 para matorral y arbustos; 1 para bosque) ...
Las rocas volcánicas son el resultado de la salida al exterior de magma, que está formado por silicatos y sílice y contiene substancias disueltas que se separan como vapores y como gases no condensables. El volcanismo es un aporte de materia al exterior y por lo tanto edifica estructuras y crea formaciones, pero también se produce un aumento de la erosión en esos relieves y fenómenos tectónicos que hunden parte de lo edificado o que está en sus proximidades. Los aspectos de destrucción de los relieves creados también son una parte importante del volcanismo y de su relevancia hidrogeológica. La creación y destrucción de los edificios volcánicos se hace en sucesivos eventos localizados, frecuentemente rápidos a escala geológica, a veces violentos, y en eventos sucesivos cada uno de duración de escala humana, con parte del material de las erupciones como lava y parte como tefra, con distribución espacial variable. Esto origina formaciones muy heterogéneas, cuyo comportamiento hidrogeológico puede ser complejo y su entendimiento requiere un buen conocimiento de los procesos geológicos y geoquímicos involucrados. Los clásicos principios de la geología sedimentaria no son directamente aplicables o debe utilizarse con notables precauciones. Bajo un punto de vista hidrogeológico hay aspectos distintos entre las formaciones volcánicas continentales y las de las pequeñas islas volcánicas, en general de menos de 5000 km2. En el continente o en grandes islas hay otras formaciones geológicas y un relieve e hidrografía que ponen en relación aspectos influenciados por el volcanismo, con otros que no lo están. En ellos, las formaciones volcánicas pueden ser hidrogeológicamente dominantes o estar supeditadas y con variaciones espaciales importantes. En pequeñas islas, las formaciones volcánicas y derivadas de las mismas suelen ser dominantes, el relieve puede tener un papel clave, no hay redes fluviales alóctonas y el nivel del mar y sus variaciones son un condicionante muy específico del comportamiento. Bajo un punto de vista geoquímico, cabe distinguir entre componentes mayoritarios, a concentraciones ponderales del orden porcentual, otras minoritarias a concentraciones del orden de partes por millón y componentes traza. Son de interés hidrogeológico aquellos elementos que pueden dar lugar a iones y compuestos solubles en el agua subterránea o que facilitan su incorporación. Los elementos químicos de los componentes mayoritarios son Si, Al, Mg, Ca, Na, K, Fe (con mayor proporción de Fe-II) y P. En las rocas básicas, como el basalto, el Si está únicamente como silicato, pero una parte del mismo forma sílice libre en las rocas ácidas, como la riolita y las intermedias como las andesitas. El Mg y Ca son más abundantes en rocas básicas comunes que en las ácidas, mientras que el contenido en Na y K tienden a ser mayor en las rocas ácidas comunes, pero con relación Na/K menor, aunque hay frecuentes desviaciones de esta tendencia. El Mg, Ca, Na y K pueden pasar al agua subterránea al alterarse la roca por aportes de acidez, con una parte que queda absorbida en los minerales resultantes de la alteración, según sean las condiciones ambientales. Lo mismo puede decirse del Li y Sr.
... For example, management can influence spatial and temporal attributes of downstream water, nutrient, and sediment movement to coastal areas (Ensign and Doyle, 2006;Newcomer-Johnson et al., 2016) as well as overall hydrologic budgets (Strauch et al., 2017). These "ridge-to-reef" processes are especially sensitive on small islands in ocean environments, where watersheds are compact and for some islands systems, invaded by alien species (Takahashi et al., 2011;Santamarta et al., 2014). These factors can negatively impact hydrology budgets (Povak et al., 2017;Strauch et al., 2017) as well as the nearshore reef habitats that support both subsistence and tourism-oriented economies (Povak et al., 2020;Foo and Asner, 2021). ...
... The Hawaiian archipelago continues to be an important laboratory for developing and implementing DSSs in the context of climate change (Vorsino et al., 2014), water resources (Takahashi et al., 2011;Santamarta et al., 2014;Povak et al., 2017), and invasive species management (Giambelluca et al., 2009;Somers and Asner, 2013;Strauch et al., 2017Strauch et al., , 2018. Wall-to-wall remote sensing and other data greatly aids planning and implementation of spatial DSS Marvin et al., 2016;Niemiec et al., 2016). ...
Invasive species alter hydrologic processes at watershed scales, with impacts to biodiversity and the supporting ecosystem services. This effect is aggravated by climate change. Here, we integrated modelled hydrologic data, remote sensing products, climate data, and linear mixed integer optimization (MIP) to identify stewardship actions across space and time that can reduce the impact of invasive species. The study area is the windward coast of Hawai'i Island (USA) across which non-native strawberry guava occurrence varies from extremely dense stands in lower watershed reaches, to low densities in upper watershed forests. We focused on the removal of strawberry guava, an invader that exerts significant impacts on watershed condition. MIP analyses spatially optimized the assignment of effective management actions to increase water yield, generate revenue from enhanced freshwater services, and income from removed biomass. The hydrological benefit of removing guava, often marginal when considered in isolation, was financially quantified, and single-and multiobjective MIP formulations were then developed over a 10-year planning horizon. Optimization resulted in 4.67 million when allowing work schedules with overnight camping to reduce costs. Pareto frontiers of weighted pairs of management goals showed the benefit of clustering treatments over space and time to improve financial efficiency. Values of improved land-water natural capital using payment-for-ecosystem-services schemes are provided for several combinations of spatial, temporal, economical, and ecosystem services flows.
... Runoff and water would likely increase and replenishment of the islands' freshwater aquifer through cloud water interception would likely decrease. (Nanko, et al., 2013;Takahashi, et al., 2011). Because of its potential to outcompete native forest flora and its potential deleterious effects on watershed function, miconia has been prioritised for eradication on the Hawaiian Island of Oʽahu. ...
... Water recharge of the island's aquifers may also be at risk. A study on Hawaiʽi Island found that nativedominated 'ōhi'a forest intercepted 454 mm more cloud water than strawberry guava (Psidium cattleyanum -Myrtaceae) dominated forests due to the differences in bark structure and tree shape (Takahashi, et al., 2011). Miconia has smooth bark similar to strawberry guava and would likely have similar rates of cloud water interception. ...
The invasive tree Miconia calvescens (Melastomataceae) is a priority for control on the Hawaiian Island of Oʽahu due to its potential to replace native ʽōhiʽa (Metrosideros polymorpha, Myrtaceae) forests and degrade watershed function if allowed to establish. The Oʽahu Invasive Species Committee (OISC) is attempting to eradicate this species from the island of Oʽahu. OISC uses a buffer strategy based on estimated seed dispersal distance to determine the area under surveillance. This strategy has worked well enough to suppress the number of trees reaching reproductive age. The number of mature trees removed annually is now less than the number initially removed when the programme started in 2001. In 2016, just 12 mature trees were removed from 54.71 km2 surveyed compared to 2002, when 40 mature trees were removed from 8.26 km2 surveyed, a 96% drop in mature trees per square kilometre surveyed. However, miconia has a long-lived seed bank and can germinate after 20 years of dormancy in the soil. Funding shortages and gaps in surveys due to refusal of private property owners to allow access have resulted in some long-range extensions. OISC’s results suggest that seed bank longevity is an important factor when prioritizing invasive species risk and that allocating more resources at the beginning of a programme to eradicate a species with long-lived seed banks may be a better strategy than starting small and expanding.
... There have been few attempts to model CWI in tropical montane cloud forests worldwide as many factors determine the quantity of CWI deposited including wind speed, canopy height and leaf area index, size of fog particles, and duration of fog (Mulligan & Burke 2005;Takahashi et al. 2011). Models such as WaterWorld (Mulligan 2013) approximate CWI based on cloud frequency, relative humidity, elevation, and leaf area index. ...
Many species of invasive plants are currently considered incipient on O'ahu, existing in small populations, but with a high risk of spreading to new locations and forming much larger populations that can transform habitats. This project uses species distribution modeling (SDM) to model and correlate the presence of these species to climatic information and create products which predict what areas of Hawai'i are climatically suitable for the growth of each species. These maps can be used to prioritize early detection surveys in areas where a species is not yet found, but is climatically suitable as well as to identify high priority habitats which may be invaded if a species continues to spread. In total, 20 species were modeled across the Hawaiian islands including several high risk invaders such as fountain grass (Cenchrus setaceus), devilweed (Chromolaena odorata), and cane ti (Tibouchina herbacea). The majority of models produced have high predictive ability for these species in Hawai'i, although some must be interpreted with caution due to limited data or changes in climatic niche between Hawai'i and the species' native range. Background Species distribution modeling (SDM) has emerged as a powerful tool in ecology not only for predicting the spread of invasive species (Barbet-Massin et al. 2018; Canelles et al. 2021; Meriggi et al. 2022) but also for identifying new populations of endangered species (Allen & McMullin 2019; Eyre et al. 2022), guiding the selection of biological reserves (Guisan et al. 2013), and prioritizing sites for outplanting or release of endangered species (Eyre et al. 2022). SDM uses wild species occurrence data (GPS points) in combination with environmental data such as rainfall and temperature to train a machine learning model which can then predict what areas are climatically suitable for the growth of the species (Urbina-Cardona et al. 2019).
... Understanding native and non-native resource-use strategies under different climate conditions is critical to conservation planning, as invasion by non-native woody species has been observed to negatively impact forest ecosystem hydrology (e.g. groundwater recharge and availability, soil water content), which could in turn limit native species growth or recovery (Cavaleri et al., 2014;Dudley et al., 2020;Hata et al., 2016;Takahashi et al., 2011). ...
... For example, P. cattleyanum has been shown to alter the water balance (Takahashi et al., 2010) and litter nutrient cycling (Enoki & Drake, 2017) Kandert et al., 2021;Zimmerman et al., 2008). However, from a restoration standpoint, the partially invaded forests are not devoid of potential-they still serve as reservoirs of native biodiversity to some degree. ...
Tropical forest understories tend to be light‐limited. The red‐to‐far‐red ratio (R:FR) is a useful and reliable index of light quality and its spatial variability can influence competition between native and non‐native seedlings. While per cent light transmittance has been quantified in some Hawaiian lowland wet forests (HLWF), no information exists on how the spatial distribution of understorey light varies in relation to species invasion, or if patterns of seedling regeneration and light are linked.
We measured the R:FR of light in the understorey to assess light quality in three HLWF forest types: native‐dominated, partially invaded and Psidium cattleyanum‐ (strawberry guava) dominated to quantify light quality in the understorey (0–50 cm height). We also identified relationships between light quality and native and non‐native seedling presence, diversity and abundance. Together, these data can help to determine the restoration potential of HLWF.
Linear mixed‐effect modelling showed that native‐dominated forests had significantly greater R:FR than P. cattleyanum‐dominated forests, demonstrating a transformation in the light environment with increased invasion. Heterogeneity in R:FR varied more across sites than among forest types. In both native‐dominated and partially invaded forests, there were more native seedlings in the low‐quality R:FR (0.0–0.40) category and fewer in the medium‐ (0.41–0.70), and high‐quality (≥0.71) light categories than would be expected by chance, and there were no native seedlings in the P. cattleyanum‐dominated forests.
Native‐dominated forests had greater species richness and abundance of native seedlings than the partially invaded forests, likely due to propagule availability. However, the spatial clustering of seedlings, the mismatch of native seedlings in light environments less suitable, and a considerable proportion of open high‐quality microsites, highlights that conditions are not optimal for native species in HLWF in the long term.
Synthesis and applications. The native‐dominated and partially invaded forests still hold conservation value, despite variation among sites. Seedling additions could be targeted to different R:FR environments and at different spatial scales, but the lack of a strong relationship between R:FR and seedling number suggests that other factors besides light quality should be considered in seedling enrichment or other management activities.
... In a Swiss forest vegetated with Norway spruce, soil CH 4 uptake rates were negatively correlated with soil moisture and decreased from 5.24 μmol m −2 h −1 to nearly zero as the soil moisture increased from 18.4% to 50.7% w/w (20.3% to 56.0% WFPS) (Hiltbrunner et al., 2012). Across our dataset, soil moisture in the native sites was, on average, 28.2% w/w (49.8% WFPS) and significantly decreased to 23.8% w/w (43.4% WFPS) in the invaded sites, probably because of higher evapotranspiration and interception of invasive plant species (Giambelluca et al., 2008;Takahashi et al., 2011). The reduction in soil moisture caused by plant invasion provides more aerobic conditions for CH 4 oxidation and facilitates the diffusion of CH 4 and O 2 from the atmosphere to soil, thereby stimulating terrestrial CH 4 uptakes. ...
Approximately 17% of the land worldwide is considered highly vulnerable to non-native plant invasion, which can dramatically alter nutrient cycles and influence greenhouse gas (GHG) emissions in terrestrial and wetland ecosystems. However, a systematic investigation of the impact of non-native plant invasion on GHG dynamics at a global scale has not yet been conducted, making it impossible to predict the exact biological feedback of non-native plant invasion to global climate change. Here, we compiled 273 paired observational cases from 94 peer-reviewed articles to evaluate the effects of plant invasion on GHG emissions and to identify the associated key drivers. Non-native plant invasion significantly increased methane (CH4) emissions from 129 kg CH4 ha−1 year−1 in natural wetlands to 217 kg CH4 ha−1 year−1 in invaded wetlands. Plant invasion showed a significant tendency to increase CH4 uptakes from 2.95 to 3.64 kg CH4 ha−1 year−1 in terrestrial ecosystems. Invasive plant species also significantly increased nitrous oxide (N2O) emissions in grasslands from an average of 0.76 kg N2O ha−1 year−1 in native sites to 1.35 kg N2O ha−1 year−1 but did not affect N2O emissions in forests or wetlands. Soil organic carbon, mean annual air temperature (MAT), and nitrogenous deposition (N_DEP) were the key factors responsible for the changes in wetland CH4 emissions due to plant invasion. The responses of terrestrial CH4 uptake rates to plant invasion were mainly driven by MAT, soil NH4+, and soil moisture. Soil NO3−, mean annual precipitation, and N_DEP affected terrestrial N2O emissions in response to plant invasion. Our meta-analysis not only sheds light on the stimulatory effects of plant invasion on GHG emissions from wetland and terrestrial ecosystems but also improves our current understanding of the mechanisms underlying the responses of GHG emissions to plant invasion.
... They can have severe, sudden, or long-lasting negative effects on environments, ecosystems, and communities across the United States, which can make it more difficult to cope with the impacts of climate change (Driscoll et al., 2012;Millar & Stephenson, 2015;Stella & Bendix, 2019;Strayer, 2010). Indeed, invasive species have pervasive and costly effects on diverse sectors such as agriculture, health, water resources, and energy with economic costs exceeding US $26 billion annually in North America in recent years (Crystal-Ornelas et al., 2021;Filho et al., 2019;Gutrich et al., 2007;Soto et al., 2022;Takahashi et al., 2011). Globally, these impacts are projected to quadruple every decade, posing catastrophic threats to both society and ecosystems (Intergovernmental Science-Policy Platform on Biodiversity and Ecosystems Services [IPBES], 2023). ...
Executive Order No. 14008 mandated that U.S. federal agencies and departments develop Climate Change Adaptation Plans to enhance the nation's resilience to climate change. Invasive species are documented to reduce the effectiveness of climate adaptation and mitigation actions. In spite of this, only eight of the 26 federal plans directly reference invasive species, and just four meaningfully consider the reciprocal impact of invasive species on climate adaptation efforts. To ensure that climate adaptation planning and processes are effective with associated benefits for biodiversity conservation, a gap analysis of the Climate Change Adaptation Plans was conducted. Five key recommendations were developed that would transform how invasive species are considered within them. Examples of how invasive species have been included in some of the plans are provided, with suggestions for agencies that did not include invasive species on how they might do so, to illustrate that dedicated efforts in prevention, detection, and management of invasive species can safeguard carbon sequestration, protect communities and infrastructure, and minimize economic and biodiversity losses. Although developed based on U.S. federal plans, these recommendations can be used by state and local, as well as international, jurisdictions tasked with implementing climate‐adaptive policies to build resilience across multiple sectors.
... It has been reported that invasive plants have changed the hydrological and meteorological systems of the canopy, affecting rainfall redistribution [8]. Compared with native plants, exotic plants have a lower canopy water storage capacity, resulting in a decrease in freshwater resources in invaded ecosystems [9]. Conversely, invasive plant prevention and control can also alter the surface coverage of forestlands. ...
Background: The hydrological effects of invasive plant control in forestland have not been well studied in the past, and numerous scientific mysteries remain unsolved. The long-term suspension of the unsolved issues will unavoidably influence the sound growth and sustainable management of forest ecosystems. This study investigates the hydrological effects of controlling invasive weeds in forestland. The research aims to understand the impact of invasive weed control on soil and water loss. Methods: Conducted in Eucalyptus benthamii Maiden & Cambage plantations in Central Yunnan, SW China, which are invaded by alien weed Ageratina adenophora (Spreng.) R. M. King & H. Rob., four surface cover treatments were applied to study runoff and sediment yielding properties. The four surface cover treatments were weed harvesting and litter elimination (WH&LE), weed harvesting and litter retention (WH&LR), litter burning and weed renewal (LB&WR), and weed retention and litter retention (WR&LR). Essentially, WH&LE and LB&WR served as integrated management approaches for invasive weeds and litter, WH&LR was an independent weed control measure, and WR&LR served as a research control. Results: Runoff was significantly higher in the LB&WR plots (3.03 mm) compared to the WR&LR plots (1.48 mm) (p < 0.05). The WH&LE plots had higher runoff (2.39 mm) than the WR&LR plots (not statistically significant), while the WH&LR plots had less runoff (1.08 mm) than the WR&LR plots (not significant). Sediment yield was lower in the WH&LR plots (0.50 t/km²) than in the WR&LR plots (0.52 t/km²) (not significant), but significantly higher in the WH&LE plots (2.10 t/km²) and LB&WR plots (1.57 t/km²) than in the WR&LR plots (p < 0.05). Conclusions: Managing invasive weeds independently reduces the risk of soil and water loss, but combined management with litter can exacerbate the issue. Invasive weed control and litter management should be performed separately in slope plantations. This study provides a scientific basis for soil and water conservation, restoration and rehabilitation of plantation ecosystems.
... However, quantifying wet canopy evaporation in cloud forests is still challenging because solely rainfall redistribution measurement cannot capture it, and neither actual fog interception nor evaporation from wet vegetation can be easily quantified directly (e.g., Bruijnzeel, 2005). Takahashi et al. (2011) calculated cloud water interception and wet canopy evaporation in tropical montane cloud forests in Hawai'i using a single-layer canopy water balance model. As a direct method, Chang et al. (2006) quantified the fog water deposition rate on the leaves by recording the increase in weight of the leaves before, during, and after the exposure to various fog and wind conditions at different heights in the tree canopy and modeled it empirically at stand level. ...
... The only two measurement periods during which the rain gauge recorded no rainfall failed to produce any detectable precipitation in our collectors. In plant canopies with many small-diameter stems, high proportions of intercepted cloud water may also travel to the ground via stemflow (Takahashi et al. 2011), which was not measured in this study. ...
The Leeward Kohala Field System (LKFS) on Hawai‘i Island once featured over 60 km2 of productive, rain-fed croplands. For several centuries, its occupants cultivated ‘uala (Ipomoea batatas, sweet potato) as a staple crop between kuaiwi (earthen or rock walls) planted with ko (Saccharum officinarum, sugarcane).These raised ko rows could have influenced ‘uala growth through an array of microclimatic processes, including wind abatement, shading, and the redistribution of moisture. While such effects are frequently mentioned in the literature, efforts to directly quantify them and relate them to ‘uala production have been lacking. We measured wind speeds, precipitation rates, solar illuminance, soil moisture, and ‘uala yields along a transect through three ko rows within the LKFS. Ko rows proved effective windbreaks, reducing near-surface wind speeds by up to 90% and for distances of up to 10 m. The rows also concentrated wind-blown moisture at their upwind edges while creating rain shadows 5–6 m in length. ‘Uala yields peaked at 3.8–6.0 kg m–2 near the center of inter-row space, probably because ‘uala were energy-limited during the wet study period and grew slowly when shaded by the ko. A zone of low turbulence leeward of each ko row also appeared to benefit ‘uala growth. Additional measurements are needed to investigate the landscape-level hydrologic effects of ko row planting. Our findings will help guide ongoing efforts to expand agricultural and educational activities in the LKFS.
... Em alguns casos o método do balanço hídrico dossel também considera a evaporação do dossel assim como a variação do volume de água por ele retida (HAFKENSCHEID et al., 1998;NULLET, 2011;TAKAHASHI et al., 2011;GONZÁLEZ-MARTÍNEZ;HOLWEDA, 2018 áreas de coleta representativas, ou ainda como apresentado em algumas pesquisas (SCHELLEKENS et al., 1998;HAFKENSCHEID;BRUIJNZEEL;RICHARD, 1998) coletores que são posicionados em pontos distintos durante o monitoramento. ...
A interceptação da condensação atmosférica (ICA) ocorre quando a água contida em nevoeiros e precipitações movidas pelo vento, colide com a vegetação, se funde em gotas maiores, e precipita no solo. A ICA tem importante função como fonte adicional de água e suas relações com a florestas nebulares tropicais foram muitas vezes enfatizadas. Apesar de sua importância, não há padronização dos métodos de medição, nem dos termos que designam o processo. Fazendo-se assim necessária uma análise sistemática das pesquisas sobre ICA. Para isso, o presente estudo realizou uma revisão dos aspectos teóricos e metodológicos da ICA por meio da: descrição e análise sobre a terminologia; histórico e cronologia dos estudos sobre o tema; levantamento das condições ambientais necessárias para a ocorrência do processo de ICA; análise dos aspectos metodológicos relativos à medição da ICA; síntese e discussão das magnitudes descritas na literatura científica. Como resultado: das 31 publicações revisadas foram encontrados 14 diferentes vocábulos. Sendo os mais comuns “Cloud Water Interception” (19,4%) e “Fog drip” (16,1%); em geral a ICA é mais frequente em locais como bordas continentais e ilhas constantemente sujeitas a brisas marítimas; na maioria dos casos, a abordagem para a medição abaixo do dossel, pode ser considerada mais precisa que as obtidas por coletores de nevoeiros; a ICA é em média responsável por 42% da precipitação efetiva (n:41). Os valores listados apresentam grande variação, entre 0,5 % e 462%, provavelmente decorrente das distintas características ambientais dos locais amostrados assim como das variações nos tamanhos das amostras.
... In a Swiss forest vegetated with Norway spruce, soil CH 4 uptake rates were negatively correlated with soil moisture and decreased from 5.24 μmol m −2 h −1 to nearly zero as the soil moisture increased from 18.4% to 50.7% w/w (20.3% to 56.0% WFPS) (Hiltbrunner et al., 2012). Across our dataset, soil moisture in the native sites was, on average, 28.2% w/w (49.8% WFPS) and significantly decreased to 23.8% w/w (43.4% WFPS) in the invaded sites, probably because of higher evapotranspiration and interception of invasive plant species (Giambelluca et al., 2008;Takahashi et al., 2011). The reduction in soil moisture caused by plant invasion provides more aerobic conditions for CH 4 oxidation and facilitates the diffusion of CH 4 and O 2 from the atmosphere to soil, thereby stimulating terrestrial CH 4 uptakes. ...
Approximately 17% of the land worldwide is considered highly vulnerable to non‐native plant invasion, which can dramatically alter nutrient cycles and influence greenhouse gas (GHG) emissions in terrestrial and wetland ecosystems. However, a systematic investigation of the impact of non‐native plant invasion on GHG dynamics at a global scale has not yet been conducted, making it impossible to predict the exact biological feedback of non‐native plant invasion to global climate change. Here, we compiled 273 paired observational cases from 94 peer‐reviewed articles to evaluate the effects of plant invasion on GHG emissions and to identify the associated key drivers. Non‐native plant invasion significantly increased methane (CH4) emissions from 129 kg CH4 ha–1 yr–1 in natural wetlands to 217 kg CH4 ha–1 yr–1 in invaded wetlands. Plant invasion showed a significant tendency to increase CH4 uptakes from 2.95 to 3.64 kg CH4 ha–1 yr–1 in terrestrial ecosystems. Invasive plant species also significantly increased nitrous oxide (N2O) emissions in grasslands from an average of 0.76 kg N2O ha–1 yr–1 in native sites to 1.35 kg N2O ha–1 yr–1 but did not affect N2O emissions in forests or wetlands. Soil organic carbon, mean annual air temperature (MAT), and nitrogenous deposition (N_DEP) were the key factors responsible for the changes in wetland CH4 emissions due to plant invasion. The responses of terrestrial CH4 uptake rates to plant invasion were mainly driven by MAT, soil NH4+, and soil moisture. Soil NO3–, mean annual precipitation, and N_DEP affected terrestrial N2O emissions in response to plant invasion. Our meta‐analysis not only sheds light on the stimulatory effects of plant invasion on GHG emissions from wetland and terrestrial ecosystems but also improves our current understanding of the mechanisms underlying the responses of GHG emissions to plant invasion.
... A reduction in the availability of freshwater from this source could lead to the use of other, more expensive methods of freshwater production to meet public demand (Burnett et al. 2020). High elevation 'ōhi'a forests protect watersheds across the state, and, because of their lower water usage compared to fast-growing non-native species, allow for greater recharge of groundwater (Kagawa et al. 2009;Takahashi et al. 2011;Cavaleri et al. 2014). Additionally, a study by Burnett et al. (2017) found that the cost of protecting freshwater by conserving native Hawaiian forests is less than half the cost of freshwater production via large-scale reverse-osmosis of seawater per thousand liters. ...
Metrosideros polymorpha Gaud. (‘ōhi‘a) is the most abundant native forest tree in Hawai‘i and a keystone species of cultural, ecological, and economic importance. ‘Ōhi‘a forests, particularly on Hawaiʻi Island, are being severely impacted by Rapid ‘Ōhi‘a Death (ROD), which is caused by the fungal pathogens Ceratocystis lukuohia and C. huliohia. ROD is characterized by branch dieback, crown wilting, and mortality. Initial disease resistance screening of four varieties of M. polymorpha with C. lukuohia demonstrated that varieties may differ in susceptibility. Several survivors of field or screening-based infections still exist, providing strong impetus for the establishment of the ‘Ōhiʻa Disease Resistance Program (ʻŌDRP). Here, we outline a framework for guiding the ʻŌDRP throughout the process of identifying and developing ROD resistance in M. polymorpha and, possibly, all Hawaiian Metrosideros species. Core ʻŌDRP projects include: (1) evaluating and operationalizing methods for greenhouse-based production and screening of test plants; (2) greenhouse screening of seedlings and rooted cuttings sampled from native Metrosideros throughout Hawaiʻi; (3) establishing field trials to validate results from greenhouse assays; (4) understanding environmental and genetic drivers of resistance to characterize the durability of resistance to ROD; (5) developing remote sensing and molecular methods to rapidly detect ROD-resistant individuals; and (6) conducting breeding trials to improve the degree and durability of ROD resistance. Ultimately, the ʻŌDRP seeks to produce ROD-resistant material for the perpetuation of M. polymorpha across Hawai‘i, with the goal of preserving the ecology, culture, and communities that are dependent on this tree species.
... Stemflow volume and its nutrient contents generally depend on the meteorological factors: such as gross rainfall amount (Levia, 2004;Andre et al., 2008;Gonzalez-Ollauri et al., 2020), rainfall direction and intensity (Muzylo et al., 2012;Owens et al., 2006), fog (McJannet et al., 2007), and drivenwind direction (Dunkerley, 2014;Van Stan et al., 2011), among others. Moreover, stemflow is also influenced by canopy structure which depends on many interrelated factors such as plant species (lida et al., 2005(lida et al., , Cayuela et al., 2018, plant growth stage (Siles et al., 2010), plant density (Schroth et al., 2001), plant morphology (Takahashi et al., 2011), plant age (Buttle & Farnsworth, 2012;Murakami, 2009), succession phase (lida et al., 2005), epiphyte, fungi and bacteria presence (Ceccherini et al., 2008;Hölscher et al., 2004), and branch or bark characteristics (Cayuela et al., 2018;Gonzalez-Ollauri et al., 2020;Van Stan & Levia, 2010). In addition, the seasonality of the rainfall regime can add complexity to rainfall-stemflow relationship. ...
Rainfall is generally partitioned into throughfall, stemflow, and interception in ecosystems. Stemflow variability can affect the hydrology, ecology, and soil chemistry patterns. However, the influence of canopy structure and rainfall characteristics on stemflow production in sugarcane plantations which are important for renewable energy production remain poorly understood. By using funnels attached to the sugarcane stems, the present study determined the stemflow amount during the period of sugarcane growth and its relationship with plant development. Approximately, 14% of gross rainfall reached the soil as stemflow, and the funneling ratios was 60. In general, it was observed a positive relationship between stemflow rates with both leaf area index and plant height. This was attributed to an increasing number of acute branching angles of the sugarcane leaves as well as high stem tillering and density. However, at the end of growth cycle, stemflow rate was lower than in previous periods which can be attributed to changes in sugarcane canopy such as stems inclination and lodging, reducing the effectiveness of water conveyance along the stem. Our study showed the need to include stemflow to better understand the hydrology of sugarcane plantations.
... Ongoing climate change may introduce yet further regime shifts in Hawaiian forests owing to differences between native and non-native trees in their ecohydrology. Differences in canopy structure and epiphyte abundance between native and non-native species cause differences in cloud water interception (Juvik and Nullet, 1995;Takahashi et al., 2011), further exacerbating drought effects. Several studies have shown lower water-use efficiency of non-native plants (see Section 5), with higher transpiration rates reducing local soil moisture (Michaud et al., 2015) and downstream watershed yields (Strauch et al., 2017). ...
As the most remote archipelago in the world, the Hawaiian Islands are home to a highly endemic and disharmonic biota that has fascinated biologists for centuries. Forests are the dominant terrestrial biome in Hawai‘i, spanning complex, heterogeneous climates across substrates that vary tremendously in age, soil structure, and nutrient availability. Species richness is low in Hawaiian forests compared to other tropical forests, as a consequence of dispersal limitation from continents and adaptive radiations in only some lineages, and forests are dominated by the widespread Metrosideros species complex. Low species richness provides a relatively tractable model system for studies of community assembly, local adaptation, and species interactions. Moreover, Hawaiian forests provide insights into predicted patterns of evolution on islands, revealing that while some evidence supports “island syndromes,” there are exceptions to them all. For example, Hawaiian plants are not as a whole less defended against herbivores, less dispersible, more conservative in resource use, or more slow-growing than their continental relatives. Clearly, more work is needed to understand the drivers, sources, and constraints on phenotypic variation among Hawaiian species, including both widespread and rare species, and to understand the role of this variation for ecological and evolutionary processes, which will further contribute to conservation of this unique biota. Today, Hawaiian forests are among the most threatened globally. Resource management failures – the proliferation of non-native species in particular – have led to devastating declines in native taxa and resulted in dominance by novel species assemblages. Conservation and restoration of Hawaiian forests now rely on managing threats including climate change, ongoing species introductions, novel pathogens, lost mutualists, and altered ecosystem dynamics through the use of diverse tools and strategies grounded in basic ecological, evolutionary, and biocultural principles. The future of Hawaiian forests thus depends on the synthesis of ecological and evolutionary research, which will continue to inform future conservation and restoration practices.
... Humans have dramatically affected the hydrologic cycle through land-cover alteration (Abbott et al., 2019). In Pacific Islands, anthropogenic land-cover change has been linked to disruption of hydrologic processes, such as stream baseflow, cloud water interception, infiltration, soil moisture parameters, and surface water runoff (Loague et al., 1996;Ziegler and Giambelluca, 1998;Kagawa et al., 2009;Takahashi et al., 2011;Perkins et al., 2012;Izuka et al., 2018). Expansion of impervious surfaces associated with human development increases surface runoff, thereby decreasing groundwater recharge and other water budget components (e.g. ...
Study region
Oceania, South Pacific, Polynesia.
Study Focus
Changing climates have the potential to significantly impact global water resources availability. On many volcanic islands, groundwater is the primary drinking water source, thereby making it essential to manage this limited resource carefully. In this study, we developed high temporal and spatial resolution groundwater recharge estimates for the Island of Tutuila, American Samoa using the Soil Water-Balance-2 (SWB2) model. Additionally, we predicted future recharge by running the calibrated model with combinations of dynamically downscaled general circulation climate model (GCM) predictions, and future land-cover scenarios developed collectively with local stakeholder groups.
New hydrological insights
Present-day results indicate 57 % of Tutuila’s rainfall becomes groundwater recharge, 8 % evaporates from the canopy, 15 % evapotranspires, and 20 % discharges as stormflow-runoff. Future climate scenarios suggest recharge may increase by 8 % or 14 % depending on global emissions. Land-cover was a less significant driver of hydrologic change, although increases in impervious surfaces showed a negative impact on recharge. This work is maintained as an active open-source project on GitHub, the world’s leading software development platform, thereby enhancing transparency, reproducibility, and participation from stakeholders and managers in American Samoa. This study is the first of its kind from a location within the South Pacific Convergence Zone, and provides insights into how human activities on global and local levels affect the future sustainability of essential resources.
... With seeds readily dispersed by birds and pigs, it has become a dominant invader in wet forests of tropical islands (Lorence and Sussman 1986;Space 2013), for example, forming dense thickets and displacing native species across tens of thousands of hectares in Hawaii (Fig. 2.5). In addition to reducing habitat for many endangered species (State of Hawaii 2011), strawberry guava increases water loss from forested watersheds (Takahashi et al. 2011), impedes sustainable native hardwood forestry (Baker et al. 2009), and serves as the primary reservoir host for a major fruit fly pest of agriculture (Vargas et al. 1990). The USDA Forest Service developed a leaf-galling scale insect (Tectococcus ovatus) as a biological control agent, with the intention of substantially reducing vegetative growth and fruit production of strawberry guava (State of Hawaii 2011). ...
The introduction, establishment, and spread of invasive species in terrestrial and aquatic environments is widely recognized as one of the most serious threats to the health, sustainability, and productivity of native ecosystems (Holmes et al. 2009; Mack et al. 2000; Pyšek et al. 2012; USDA Forest Service 2013). In the United States, invasive species are the second leading cause of native species endangerment and extinction, and their costs to society have been estimated at $120 billion annually (Crowl et al. 2008; Pimentel et al. 2000, 2005). These costs include lost production and revenue from agricultural and forest products, compromised use of waterways and terrestrial habitats, harm to human and animal health, reduced property values and recreational opportunities, and diverse costs associated with managing (e.g., monitoring, preventing, controlling, and regulating) invasive species (Aukema et al. 2011; Pimentel et al. 2005). The national significance of these economic, ecological, and social impacts in the United States has prompted various actions by both legislative and executive branches of the Federal Government (e.g., the Nonindigenous Aquatic Nuisance Prevention and Control Act of 1990; the Noxious Weed Control and Eradication Act of 2002; Executive Order 13112 of 1999, amended in 2016).
... Protection of native vegetation is a priority because native forests in Hawaii are comprised of ecologically-and culturally-valuable plant species more likely to support endemic bird and insect populations. Native vegetation can also have lower evapotranspiration rates and can contribute to stream baseflow via fog drip at high elevations more effectively than nonnative vegetation (Takahashi et al., 2011). Native vegetation cover in this study is characterized by the Hawaii Habitat Quality Dataset, which delineates areas of native forests with limited nonnative vegetation (Price et al., 2012). ...
Functional ecosystems depend on biotic and abiotic connections among different environmental realms, including terrestrial, freshwater, and marine habitats. Accounting for such connections is increasingly recognized as critical for conservation of ecosystems, especially given growing understanding of the way in which anthropogenic landscape disturbances can degrade both freshwater and marine habitats. This need may be paramount in conservation planning for tropical island ecosystems, as habitats across realms are often in close proximity, and because endemic organisms utilize multiple habitats to complete life histories. In this study, we used Marxan analysis to develop conservation planning scenarios across the five largest islands of Hawaii, in one instance accounting for and in another excluding habitat connectivity between inland and coastal habitats. Native vegetation, perennial streams, and areas of biological significance along the coast were used as conservation targets in analysis. Cost, or the amount of effort required for conservation, was estimated using an index that integrated degree and intensity of anthropogenic landscape disturbances. Our results showed that when connectivity is accounted for among terrestrial, freshwater, and marine habitats, areas identified as having high conservation value are substantially different compared to results when connectivity across realms is not considered. We also showed that the trade-off of planning conservation across realms was minimal and that cross-realm planning had the unexpected benefit of selecting areas with less habitat degradation, suggesting less effort for conservation. Our cross-realm planning approach considers biophysical interactions and complexity within and across ecosystems, as well as anthropogenic factors that may influence habitats outside of their physical boundaries, and we recommend implementing similar approaches to achieve integrated conservation efforts.
... Many invasive plants have the capacity to replace native forests by generating monospecific and dense invaded patches (Crooks, 2002;Richardson and Rejmánek, 2011), which could also alter the net amount of rainfall reaching the soil (Imada et al., 2013;Mair and Fares, 2010;Takahashi et al., 2011). However, the hydrometeorological mechanisms behind rainfall partitioning by invasive species, as well as its ecohydrological implications on the invasion processes, remain largely unknown. ...
Vegetation canopy plays a key role in the local water balance by partitioning rainfall into interception, throughfall and stemflow in dry forests. Many invasive plants have the capacity to replace native species and alter the net amount and spatial distribution of rainfall reaching the soil. In this paper, we aimed to compare the rainfall partitioning for the invader Ligustrum lucidum and the dominant native Lithraea molleoides, to evaluate the influence of morphological characteristics on stemflow generation in both species, and to explore spatio-temporal patterns of throughfall at stand scale. Stemflow percentage for L. lucidum was hugely higher than for L. molleoides (18 and 1%, respectively), which overcompensated its lower throughfall percentage (58.1 and 68.6%, respectively). Interception losses were lower for L. lucidum than for L. molleoides (23.2 and 30.6%, respectively). The minimum rainfall amount needed to generate throughfall and stemflow was 1.8 and 0.5 mm for L. lucidum, while 2.2 and 7.2 mm for L. molleoides. The differences in morphological characteristics between species mainly explained the stemflow generation. The increment on tree basal area, projected canopy area, and number of branches favored stemflow in L. lucidum, but not in L. molleoides. The throughfall spatial patterns showed that the dripping from different canopy densities was homogenous in L. lucidum stands, whereas throughfall increase towards more opened-canopies in L. molleoides stands. Lateral inflows were registered from small-scale crown sections at both forest stands, but less frequent in L. lucidum stands. The time stability of throughfall pattern differed between forest stands. Based on our results, relatively higher stemflow and lower interception losses for L. lucidum than for L. Molleoides may represent a competitive advantage in terms of plant invasion in water-limited ecosystems. These findings highlight the need for further inquiries determining the underlying role of rainfall partitioning in the invasion process of woody species.
... Feral pigs (Sus scofa) in Hawai'i have been observed to negatively impact soil and groundcover, and consequently infiltration and runoff (Dunkell et al., 2011;Strauch et al., 2016). Because pigs and other invasive ungulates are also a major pathway for invasive plant seed dispersal, ungulate exclusion from pristine native forest areas upgradient of the aquifer impedes invasion by alien plant species, which tend to have higher evapotranspiration rates (Giambelluca et al., 2008;Kagawa et al., 2009;Cavaleri et al., 2014) and lower fog capture potential (Takahashi et al., 2011) than native canopy tree species. Thus, investment in ungulate-proof fencing, by limiting potential negative impacts of invasive species, supports the maintenance of recharge capture for the downstream groundwater resource (Fig. 1). ...
We develop and operationalize an integrated groundwater and watershed management model using data from the Kīholo aquifer on the west coast of Hawai'i Island. Results from a numerical simulation suggest that investment in fencing (passive management) is preferred to invasive species removal (active management) if we are limited to selecting a single conservation tool. However, using both instruments jointly increases net present value relative to using either instrument independently in most cases tested, and the additional benefit of invasive species removal increases as water becomes scarcer. The general results are largely insensitive to variations in the invasive species uptake rate and recharge benefits of fencing, and in all cases, use of both instruments reduces the loss resulting from the imposition of a safe minimum standard for groundwater-dependent ecosystems more effectively than either instrument alone.
... It is reported that CPA increases as DBH increases (Park & Hattori, 2002). In addition, numerous studies have found that changes in DBH are positively correlated with SF volume (Germer et al., 2010;Park & Hattori, 2002;Takahashi et al., 2011). However, Schooling and Carlyle-Moses (2015) found a negative correlation between DBH and SF for 2 to <5 mm rainfall depth class and reported large DBH trees with larger boles and greater surface area likely afford greater water storage capacity. ...
Stemflow (SF) has been recognized as an important process which can exert considerable effects on the hydrology, biogeochemistry, and ecology of wooded ecosystems. The aim of this study was to quantify the relationship between SF (yields and funneling ratios, FR) of beech (F. orientalis) trees and rainfall characteristics, to evaluate the effects of tree traits on SF yield and the magnitudes of FR in differing rainfall classes. Event‐based measurements were carried out from April 2016 to November 2017 during the leafed‐out periods in a natural uneven‐aged beech stand located in the Hyrcanian forest of Iran. Tree density in the studied plot was 188 tree ha‐1 with a basal area (BA) of 51 m2 ha‐1. SF volume was measured in three diameter classes (10‐40 cm, 40‐70 cm and > 70 cm; n=3 per class). During the 25 rainfall events SF, SF% and FR were 3.22 mm, 0.41% and 1.11 on average, respectively. The linear regression analysis revealed that gross rainfall (GR) had the strongest correlation with SF yield and FR (P value <0.01). The linear regression with the trees structural traits indicated that CPA (crown projected area), DBH (diameter at breast height) and MCP (mosses cover percentage), respectively, strongly influence SF yield for rainfall<15 to >50 mm. FR significantly decreased with increasing tree height (H), DBH and MCP (all p‐values<0.05). Smaller trees concentrated more SF than tall and large DBH trees. Pearson correlation analysis indicated H, CPA and MCP were positively and significantly correlated to DBH (P value <0.01; r≥0.87). Therefore, SF generation in the present study is more associated with DBH. Our findings could assist managers to optimize the management strategies of deciduous forest via promotion of some large DBH trees along with small DBH trees to optimize water inputs via SF in water‐limited forest ecosystems.
... Island-w future land cover scenarios, for both the wet and dry future climate strongly impacted groundwater recharge in localized areas. Th Futures 1 and 4 due to the substantial increases in estimated irriga i can also affect processes that influence groundwater recharge, including cloud-water interception, net precipitation, infiltration, direct runoff, and transpiration [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. ...
This project developed an integrated land cover/hydrological modeling framework using remote sensing and geographic information systems (GIS) data, stakeholder input, climate information and projections, and empirical data to estimate future groundwater recharge on the Island of Maui, Hawaiʻi, USA. End-of-century mean annual groundwater recharge was estimated under four future land cover scenarios: Future 1 (conservation-focused), Future 2 (status-quo), Future 3 (development-focused), and Future 4 (balanced conservation and development), and two downscaled climate projections: a coupled model intercomparison project (CMIP) phase 5 (CMIP5) representative concentration pathway (RCP) 8.5 “dry climate” future and a CMIP3 A1B “wet climate” future. Results were compared to recharge estimated using the 2017 baseline land cover to understand how changing land management and climate could influence groundwater recharge. Estimated recharge increased island-wide under all future land cover and climate combinations and was dominated by specific land cover transitions. For the dry future climate, recharge for land cover Futures 1 to 4 increased by 12%, 0.7%, 0.01%, and 11% relative to 2017 land cover conditions, respectively. Corresponding increases under the wet future climate were 10%, 0.9%, 0.6%, and 9.3%. Conversion from fallow/grassland to diversified agriculture increased irrigation, and therefore recharge. Above the cloud zone (610 m), conversion from grassland to native or alien forest led to increased fog interception, which increased recharge. The greatest changes to recharge occurred in Futures 1 and 4 in areas where irrigation increased, and where forest expanded within the cloud zone. Furthermore, new future urban expansion is currently slated for coastal areas that are already water-stressed and had low recharge projections. This study demonstrated that a spatially-explicit scenario planning process and modeling framework can communicate the possible consequences and tradeoffs of land cover change under a changing climate, and the outputs from this study serve as relevant tools for landscape-level management and interventions.
... These areas have long cattleranching histories, where forests and dryland field systems were converted into large pasture lands early in the 1800s, and where ranching persists today. Given that Hawaiʻi's native forests may have large cloud water interception 36 , deforestation may have led to less water capture over time. The coupled climate and environmental changes likely altered the moisture regime to such a degree that the area's indigenous agroecosystems cannot exist there under current conditions. ...
The value of land-use strategies that increase food production while conserving biodiversity is widely recognized. Many indigenous agroecosystems are productive, adaptive and ecologically principled, but are largely overlooked by planning in terms of their potential to meet current and future food needs. We developed spatial distribution models of indigenous agroecosystems in Hawai‘i to identify their potential past distribution, productive and carrying capacities, and future potential under current land-use and mild-to-severe future climate scenarios. Our results suggest that Hawaiʻi’s traditional agroecosystems could have had production levels comparable to consumption today. Carrying capacity estimates support hypotheses of large pre-colonial Hawaiian populations (>800,000). Urban development has reduced (−13%) traditional agroecosystems but 71% remain agriculturally zoned. Projected effects of three future climate scenarios vary from no change in potential production to decreases of 19% in the driest and warmest end-of-century scenario. This study highlights the food-producing potential of indigenous agriculture even under land-use and climate changes, and the value of their restoration into the future. © 2019, The Author(s), under exclusive licence to Springer Nature Limited.
... Similar to other invasive shade-tolerant woody species (Horvitz et al. 1998), strawberry guava is able to establish in intact forest where it dominates the understory and lower canopy. In Hawaiʻi, this invader changes rain forest structure (Asner et al. 2009), altering ecosystem processes (Takahashi et al. 2011) and reducing suitable habitat for native species (Paul Banko, personal communication). Also, large populations of insect pests of soft agriculturally important fruits such as papaya are supported by decaying strawberry guava fruit presenting a formidable challenge to agricultural production. ...
Understanding actual and potential selection on traits of invasive species requires an assessment of the sources of variation in demographic rates. While some of this variation is assignable to environmental, biotic or historical factors, unexplained demographic variation also may play an important role. Even when sites and populations are chosen as replicates, the residual variation in demographic rates can lead to unexplained divergence of asymptotic and transient population dynamics. This kind of divergence could be important for understanding long- and short- term differences among populations of invasive species, but little is known about it. We investigated the demography of a small invasive tree Psidium cattleianum Sabine in the rainforest of Hawaiʻi at four sites chosen for their ecological similarity. Specifically, we parameterized and analyzed integral projection models (IPM) to investigate projected variability among replicate populations in: (1) total population size and annual per capita population growth rate during the transient and asymptotic periods; (2) population structure initially and asymptotically; (3) three key parameters that characterize transient dynamics (the weighted distance of the structure at each time step from the asymptotic structure, the strength of the sub-dominant relative to the dominant dynamics, and inherent cyclicity in the subdominant); and (4) proportional sensitivity (elasticity) of population growth rates (both asymptotic and transient) to perturbations of various components of the life cycle. We found substantial variability among replicate populations in all these aspects of the dynamics. We discuss potential consequences of variability across ecologically similar sites for management and evolutionary ecology in the exotic range of invasive species.
While the influence of canopy trees on soils in natural and restored forest environments is well studied, the influence of understory species is not. Here, we evaluate the effects of outplanted native woody understory on invasive grass biomass and soil nutrient properties in heavily grass-invaded 30 + year-old plantations of a native N-fixing tree Acacia koa in Hawai‘i. We analyze soils from under A. koa trees with versus without planted woody understory and compare these to soils from under remnant pasture trees of the pre-deforestation dominant, Metrosideros polymorpha where passive recruitment of native woody understory has occurred since the cessation of grazing. Simultaneously, we experimentally planted understory species at three times the density used by managers to see if this could quickly decrease grass biomass and change soil nutrient dynamics. We found that invasive grass biomass declined with understory planting in surveyed and experimental sites. Yet, woody understory abundance had no effect on N cycling. Short-term N availability and nitrification potential were higher under A. koa than M. polymorpha trees regardless of understory. Net N mineralization either did not differ (~ 1 mo) between canopy species or was higher (171 day incubations) under remnant M. polymorpha where organic matter was also higher. The only influence of understory on soil was a positive correlation with loss-on-ignition (organic matter) under M. polymorpha. We also demonstrate differential controls over N cycling under the two canopy tree species. Overall, understory restoration has not changed soil characteristics even as invasive grass biomass declines.
Strawberry guava (waiawī, Psidium cattleyanum Sabine, Myrtaceae) is a small tree invasive on oceanic islands where it may alter forest ecosystem processes and community structure. To better understand the dynamics of its invasion in Hawaiian rainforests in anticipation of the release of a biocontrol agent, we measured growth and abundance of vertical stems ≥0.5 cm DBH for 16 years (2005–2020) in Metrosideros‐Cibotium rainforest on windward Hawai'i Island. Specifically, we compared the growth and abundance of both shoots (originating from seed or from the root mat) and sprouts (originating above ground from established stems) in four replicate study sites. Mean stem density increased from 9562 stems/ha in 2005 to 26,595 stems/ha in 2020, the majority of which were stems <2 cm DBH. Early in the invasion, both density and per capita recruitment of shoots was greater than that of sprouts, but as overall stem density increased, sprout abundance and recruitment came to surpass that of shoots. Relative growth rates among small stems <2 cm DBH declined over time for both shoots and sprouts, but relative growth rates of sprouts were consistently greater than that of shoots after the first 3 years. The capacity of strawberry guava to recruit from both shoots and sprouts facilitates its invasion of rainforest, its persistence in the forest understory, and its response to canopy opening. Strawberry guava thus poses a considerable risk of stand replacement for Hawaiian rainforests. Stand management will require perpetual efforts to control both seed production and sprouting.
Introduction: Runoff measurement and monitoring is a laborious, time-consuming, and costly task. Additionally, common runoff monitoring usually primarily provide water level, requiring information on the stage-discharge relation. Automatic equipment such as flow meter tipping bucket (TB) is a potential option to simplify and provide continuous runoff monitoring in small catchments. However, a proper description of how to size and adapt the design under different flow conditions is still lacking.
Methodology: In this paper we present a novel standardized framework for the design of TB that can be used for low-cost and real-time runoff monitoring under many different conditions. The framework consists of an estimation of the runoff peak rate using the rational equation and a volumetric capacity estimate of the cavity based on runoff rate, operation speed, and inclination angle of TB when at resting position. The proposed framework was implemented in a case study where four TBs were designed for continuous runoff monitoring from experimental plots (100 m²) with different land use (sugarcane, soybean, and bare soil).
Results: During field tests (five months), the designed TBs had a recovery rate of actual runoff ranging from 61% to 81% and were able to capture features poorly studied (starting/ending time and peak flow) that have potential importance in hydrological models.
Discussion: The proposed framework is flexible and can be used for different environmental conditions to provide continuous runoff data records.
https://nca2023.globalchange.gov/chapter/30/
Climate change—especially sea level rise, altered rainfall patterns, and rising ocean and air temperatures—impairs access to clean water and healthy food, undermines human health, threatens cultural resources and the built environment, exacerbates inequities, and disrupts economic activity and diverse ecosystems in Hawaiʻi and the US-Affiliated Pacific Islands. Adaptation efforts that build upon community strengths and center local and Indigenous Knowledge systems improve resilience.
Island floras are diverse with exceptionally high rates of endemicity, and they are also severely threatened. Invasive plants are widespread on islands, but whether islands are particularly susceptible to invasion or island species are more vulnerable to displacement, or both, remains unclear. As part of the “island plant syndrome,” it has been predicted that island plants have convergently evolved conservative resource use, slow growth rates, and weak competitive abilities in response to moderate climates and the presumed absence of competition in communities with relatively low species richness. Yet, functional trait approaches have provided mixed evidence to support this prediction, and direct tests of competition as neighbour effects on plant performance are lacking. Considering the extensive environmental heterogeneity that exists within islands and among islands, it seems more likely that diverse functional strategies, spanning conservative to acquisitive, have evolved in island plants. Furthermore, assessing island plant syndrome predictions through comparisons with invasive species, which are nonrandom subsets of continental plants, is a flawed approach. Future studies that compare functional strategies of native island versus native continental plants and direct tests for competition between native and invasive island plants within the local scale at which competition occurs, and that consider non‐additivities with other simultaneous global threats, are urgently needed to conserve these biodiversity hotspots.
Ceratocystis lukuohia and Ceratocystis huliohia are two newly recognized fungi that have arrived in Hawai‘i and are causing a serious vascular wilt and canker disease, respectively, of ‘ōhi‘a trees (Metrosideros polymorpha), the most common and important tree species in Hawai‘i. Management of these diseases has presented challenges due to unique etiological aspects and the exceptionally pathogenic nature of one of these fungi (C. lukuohia) once it gains access to the tree’s vascular tissue. Careful study of the spread of the pathogens has resulted in an understanding of the role of ambrosia beetles and the frass they produce that carries the pathogen, as well as the wounding of trees by many different agents by which the pathogen can access and infect the vascular tissue.
A variety control measures are being used. These include a state-of-the-art monitoring program to detect diseased and recently killed trees and molecular biology approaches that can confirm if a given tree was infected by Ceratocystis. Based on monitoring more than one million trees have been estimated as killed by the diseases to date. A major part of the program includes the deployment of a field crew that seeks out and fells large infected ‘ōhi‘a trees as these trees are the main source of most of the infective Ceratocystis-laden frass. Long-term control measures also include fencing of some forests to reduce the amount of wounding to ‘ōhi‘a trees by feral cattle and pigs that allows entry of the fungi and quarantine restrictions to ensure there will be no inter-island movement of the pathogens in ‘ōhi‘a products. Finally, methods are also being developed to restore ‘ōhi‘a forests affected by these diseases by determining effective regeneration practices and developing genetically resistant ‘ōhi‘a stock.
Hawai‘i has an active extension program dedicated to providing information on how residents and visitors can contribute to protecting ‘ōhi‘a trees from these diseases. More than 500,000 people have participated in this program. Hawai‘i residents have a very deep appreciation for this tree species and do what they can to help prevent these diseases from destroying more of their most treasured tree species.
The choice to shift among invasive species management strategies depends on ecological, biological, and economic conditions that vary by species, location, and stage of invasion. Typically, as time and area invaded increases, economic returns to management shift away from prevention and eradication, and toward species containment and/or asset protection. This is the case for Miconia calvescens (M. calvescens) in the East Maui Watershed (EMW), Hawaiʻi where the species was introduced to a private nursery and botanical gardens 50 years ago, and subsequently escaped and spread throughout the forests of East Maui. While ground management efforts have been continuous since the early 1990s, this research focuses exclusively on the efficacy and impact of aerial herbicide ballistic technology (HBT) management efforts. We use a 25‐year management data set identifying the location and time of each M. calvescens individual eliminated to develop a spatiotemporal spread model, and use the information on treatment costs and potential avoided damages to assess the relative benefit–cost ratio of management strategies such as inaction, containment, and asset protection, under a number of EMW‐informed biological and economic parameters. The primary goal of the research presented is to develop an operational methodology for evaluating biological and economic outcomes of containment and asset protection management strategies for M. calvescens in East Maui.
Watershed degradation due to invasion threatens downstream water flows and associated ecosystem services. While this topic has been studied across landscapes that have undergone invasive-driven state changes (e.g., native forest to invaded grassland), it is less well understood in ecosystems experiencing within-system invasion (e.g. native forest to invaded forest). To address this subject, we conducted an integrated ecological and ecohydrological study in tropical forests impacted by invasive plants and animals. We measured soil infiltration capacity in multiple fenced (i.e., ungulate-free)/unfenced and native/invaded forest site pairs along moisture and substrate age gradients across Hawaii to explore the effects of invasion on hydrological processes within tropical forests. We also characterized forest composition, structure and soil characteristics at these sites to assess the direct and vegetation-mediated impacts of invasive species on infiltration capacity. Our models show that invasive ungulates negatively affect soil infiltration capacity consistently across the wide moisture and substrate age gradients considered. Additionally, several soil characteristics known to be affected by invasive ungulates were associated with local infiltration rates, indicating that the long-term secondary effects of high ungulate densities in tropical forests may be stronger than effects observed in this study. The effect of invasive plants on infiltration was complex and likely to depend on their physiognomy within existing forest community structure. These results provide clear evidence for managers that invasive ungulate control efforts can improve ecohydrological function of mesic and wet forest systems critical to protecting downstream and nearshore resources and maintaining groundwater recharge.
In forested watersheds, interception loss (EI) and transpiration (ET) constitute the majority of evapotranspiration. Accordingly, their precise evaluations are necessary to understand and quantify fluxes within the hydrologic cycle. EI is commonly measured by tipping-bucket rain gauges and flow meters, while ET is often estimated by sap flow techniques. To obtain reliable estimations of EI and ET, we describe detailed procedures to calibrate tipping-bucket rain gauges and flow meters as well as sap flow techniques. For tipping-bucket rain gauges and flow meters, we measure the one tip static volume, and then changes in the one tip amount with different inflow rates for dynamic calibration. Without proper calibration, the significant evaluation error in EI can range from 40% underestimation to 20% overestimation. We calibrate three sap flow techniques—thermal dissipation (TD), heat field deformation (HFD), and heat ratio (HR) methods—for Japanese cedar (Cryptomeria japonica) from two sites. The clear radial and azimuthal trends in sap flux density (FD) are confirmed for the artificial sap flow generated by a vacuum pump. Among segments sampled at a site, TD and HFD methods do not have any tendencies to overestimate and underestimate FD. While at the other site, TD and HFD methods underestimate FD, and therefore ET, by at least 30%, the HR method shows a 30% overestimation. Thus, we highly recommend the calibration of tipping-bucket rain gauges, flow meters, and sap flow techniques to obtain valid estimates of EI and ET.
Non-native tree (NNT) species have been transported worldwide to create or enhance services that are fundamental for human well-being, such as timber provision, erosion control or ornamental value; yet NNTs can also produce undesired effects, such as fire proneness or pollen allergenicity. Despite the variety of effects that NNTs have on multiple ecosystem services, a global quantitative assessment of their costs and benefits is still lacking. Such information is critical for decision-making, management and sustainable exploitation of NNTs. We present here a global assessment of NNT effects on the three main categories of ecosystem services, including regulating (RES), provisioning (PES) and cultural services (CES), and on an ecosystem disservice (EDS), i.e. pollen allergenicity. By searching the scientific literature, country forestry reports, and social media, we compiled a global data set of 1683 case studies from over 125 NNT species, covering 44 countries, all continents but Antarctica, and seven biomes. Using different meta-analysis techniques, we found that, while NNTs increase most RES (e.g. climate regulation, soil erosion control, fertility and formation), they decrease PES (e.g. NNTs contribute less than native trees to global timber provision). Also, they have different effects on CES (e.g. increase aesthetic values but decrease scientific interest), and no effect on the EDS considered. NNT effects on each ecosystem (dis)service showed a strong context dependency, varying across NNT types, biomes and socioeconomic conditions. For instance, some RES are increased more by NNTs able to fix atmospheric nitrogen, and when the ecosystem is located in low-latitude biomes; some CES are increased more by NNTs in less-wealthy countries or in countries with higher gross domestic products. The effects of NNTs on several ecosystem (dis)services exhibited some synergies (e.g. among soil fertility, soil formation and climate regulation or between aesthetic values and pollen allergenicity), but also trade-offs (e.g. between fire regulation and soil erosion control). Our analyses provide a quantitative understanding of the complex synergies, trade-offs and context dependencies involved for the effects of NNTs that is essential for attaining a sustained provision of ecosystem services.
Isotopes of water (²H/¹H and ¹⁸O/¹⁶O) are commonly used to trace hydrological processes such as moisture recycling, evaporation loss, and moisture source region and often vary temporally in a given region. This study provides a first‐ever characterization of temporally‐variable precipitation mechanisms San Cristóbal Island, Galápagos. We collected fog, rain and throughfall samples over three field seasons to understand the mechanisms driving seasonal and event‐based variability in the isotopic composition of precipitation in Galápagos. We establish that fog is a common phenomenon on San Cristóbal, especially during the dry season, and we found that fog is consistently enriched compared to co‐collected rainfall. We further suggest that the relative contribution of fog formed via different mechanisms (orographic, advective, radiation) varied seasonally. We found that the source region is the most dominant control of the isotopic composition of rainfall in the Galápagos at both the seasonal and event scales, but sub‐cloud evaporative processes (the non‐traditional manifestation of the amount effect) became a dominant control on the isotopic composition of rainfall during the dry season. Overall, our findings suggest that understanding seasonally‐variable water‐generating mechanisms is required for effective water resource management on San Cristóbal Island and other semi‐arid island ecosystems under current and future regimes of climate change.
Large tipping-bucket flow meters (TBFs, one tip > 200 ml) have been employed by hydrologists to quantify various water fluxes in a variety of contexts. The over-arching goal of this study is to develop a generalized correction equation for various TBFs. Based on our testing, we recommend the following to minimize TBF error: (1) periodic checking of the static calibration volume (c) since c is a gauge-specific value which has been found to vary after field deployment; and (2) for dynamic calibration, the use of our newly derived generalized correction equation when the tipping rate is less than 0.2 Hz. In equation form, the generalized correction equation for common TBFs with flat triangular buckets is: V = −0.75Q² + 0.72Q + 1 (R² = 0.843; p <0.0001), where V = v/c and v is the water volume for one tip under dynamic conditions, and Q = q/c [s⁻¹] and q is the water flow rate into the TBF. From our field test in a Japanese cedar forest stand, using stemflow (SF) as an example, we found that use of the generalized correction equation was successful in eliminating the 2–3% error in SF amounts. Moreover, we found that the generalized correction equation performed nearly as well as gauge-specific derived correction equations. Thus, our generalized correction equation is applicable to correct flow estimates of TBFs when one does not have time and/or laboratory set-up for the laborious task of testing individual TBFs themselves. Although our correction procedure may not completely eliminate all error, we recommend use of the generalized correction equation for TBFs to improve the accuracy of water flux calculations in hydrologic studies.
The water budgets of a relatively tall (7-12 m, PMull) and a stunted tropical montane forest (5-8 m, MMor) spaced <30 m apart at ca. 1820 m elevation in the Blue Mountains of Jamaica were determined over 1995 using complementary hydrological and micro-meteorological techniques.
Throughfall measurements were made under primary terra firme rainforest in the Rio Pichis valley, in the Upper Amazon Basin of Peru. Based on 214 precipitation events over nearly 18 months, throughfall was estimated to be 83.1±8.8% of gross precipitation. Regression analysis of all events revealed that gross precipitation is the only significant explanatory variable; the use of one-burst events does not significantly improve the regression relationsihp. Gross precipitation is, however, a poor predictor of throughfall for small rainfall events. The two forest structure parameters, canopy capacity, S, and free throughfall coefficient, p, were determined to be 1.3±0.2 mm and 0.32±0.18 mm. Rainfall intensity was found to influence these parameters. New methods which attempt to minimize the influence of meteorologic variables are used to estimate the potential values of these canopy parameters. -Authors
The suggestion is made that the major contributions that "physical' scientists may make to the study of nutrient flows in tropical forest ecosystems are: (1) detailed (hydro-)pedological surveys enabling the choice of truly regionally representative study sites, (2) a proper quantification of pathways followed by the water through the ecosystem, and (3) a quantification of the supply of nutrients by chemical weathering. -from Author
Rainfall and cloud water interception (CWI) were determined for a mature and a 19-year old secondary lower montane cloud forest in central Veracruz, Mexico. Cloud water was measured using a passive fog gauge, and consisted most likely of a mixture of fog and wind-driven drizzle. CWI by the canopy was derived from the wet canopy water budget as throughfall + stemflow + calculated interception loss minus rainfall. Rainfall interception loss was calculated using the Liu model, parameterized for events with rain-only. Precipitation events with cloud water input occurred exclusively during the dry season (November-April), and were primarily associated with cold fronts. CWI was estimated at 6% of dry season rainfall (640 mm on average) for the secondary forest vs. 8% for the mature forest, whereas annual values were of total rainfall (3180 mm). Infrequent fog occurrence and low wind speeds were the most important reasons for the observed low values of CWI. Total apparent interception loss (i.e. including CWI) was 17% of annual rainfall for the mature forest and 8% for the secondary forest. Post-event evaporation of intercepted water stored in the canopy rather than within-event evaporation dominated interception loss at both forests. Hence, the higher loss observed for the mature forest is considered to reflect a higher canopy storage capacity, related in turn to a higher Leaf Area Index and larger epiphyte biomass.
A linear statistical downscaling technique is applied to the projection of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) climate change scenarios onto Hawaiian rainfall for the late twenty-first century. Hawaii’s regional rainfall is largely controlled by the strength of the trade winds. During the winter months, disturbances in the westerlies can produce heavy rainfall throughout the islands. A diagnostic analysis of sea level pressure (SLP), near-surface winds, and rainfall measurements at 134 weather observing stations around the islands characterize the correlations between the circulation and rainfall during the nominal wet season (November–April) and dry season (May–October). A comparison of the base climate twentieth-century AR4 model simulations with reanalysis data for the period 1970–2000 is used to define objective selection criterion for the AR4 models. Six out of 21 available models were chosen for the statistical downscaling. These were chosen on the basis of their ability to more realistically simulate the modern large-scale circulation fields in the Hawaiian Islands region.
For the AR4 A1B emission scenario, the six analyzed models show important changes in the wind fields around Hawaii by the late twenty-first century. Two models clearly indicate opposite signs in the anomalies. One model projects 20%–30% rainfall increase over the islands; the other model suggests a rainfall decrease of about 10%–20% during the wet season. It is concluded from the six-model ensemble that the most likely scenario for Hawaii is a 5%–10% reduction of the wet-season precipitation and a 5% increase during the dry season, as a result of changes in the wind field. The authors discuss the sources of uncertainties in the projected rainfall changes and consider future improvements of the statistical downscaling work and implications for dynamical downscaling methods.
The 1976-1981 distribution, elevation, and median annual rainfall of six alien plant species in upland habitats on the island of Hawaii are described based on data collected at 7,864 sampling points (stations) along 117 transects within a 1,930-mi 2 (5,000-km ) study area. Focal species were Malabar melastome (Melastoma candidum), banana poka (Passiflora mollissima), fountain grass (Pennisetum setaceum), strawberry guava (Psidium cattleianum), yellow Himalayan raspberry (Rubus ellipticus), and German ivy (Senecio mikanioides). Three species, strawberry guava, fountain grass, and banana poka, were widely distributed throughout the study area, while the remaining three species were found on less than 2% of the stations sampled. Relatively xeric habitats (median annual rainfall 49 in. or < 1,250 mm) and low-elevation areas (1,640-4,265 ft or 500-1,300 m) were found to be consistently invaded by three or more of the species. Forty-six (72%) of the 64 vegetation types sampled contained at least one of the six alien plant species. Portions of the two largest vegetation units, `ohia (Metrosideros polymorpha) rain forest, andohia-koa (Acacia koa) rain forest, were colonized by five of the six species analyzed. Elevation and median annual rainfall ranges were used to predict the potential geographical distribution of each species in the study area, assuming no restriction in plant invasion over time. Four of the six species (banana poka, German ivy, strawberry guava, and yellow Himalayan raspberry) showed great potential for expansion of their ranges if they continue to invade areas with environmental conditions similar to those where they were found during this survey.
What is the most appropriate sampling scheme to estimate event-based average throughfall? A satisfactory answer to this seemingly simple question has yet to be found, a failure which we attribute to previous efforts' dependence on empirical studies. Here we try to answer this question by simulating stochastic throughfall fields based on parameters for statistical models of large monitoring data sets. We subsequently sampled these fields with different sampling designs and variable sample supports. We evaluated the performance of a particular sampling scheme with respect to the uncertainty of possible estimated means of throughfall volumes. Even for a relative error limit of 20%, an impractically large number of small, funnel-type collectors would be required to estimate mean throughfall, particularly for small events. While stratification of the target area is not superior to simple random sampling, cluster random sampling involves the risk of being less efficient. A larger sample support, e.g., the use of trough-type collectors, considerably reduces the necessary sample sizes and eliminates the sensitivity of the mean to outliers. Since the gain in time associated with the manual handling of troughs versus funnels depends on the local precipitation regime, the employment of automatically recording clusters of long troughs emerges as the most promising sampling scheme. Even so, a relative error of less than 5% appears out of reach for throughfall under heterogeneous canopies. We therefore suspect a considerable uncertainty of input parameters for interception models derived from measured throughfall, in particular, for those requiring data of small throughfall events.
Nutrient fluxes in stemflow and throughfall were compared among three successional stages of an upper montane rain forest and related to structural characteristics of the stands (stem density, leaf area, epiphyte abundance). An old-growth forest stand, an early successional (10-y-old) forest stand and a mid-successional (40-y-old) forest stand were studied in the Cordillera Talamanca, Costa Rica. All three sites were dominated by Quercus
copeyensis with a variable admixture of other tree species. There was no difference in the average stand leaf area index between the old-growth forest and the early successional forest. A significantly higher leaf area was found in the mid-successional forest. There were large differences in litterfall from non-vascular epiphytes (mosses, liverworts and lichens) which reflected differences in epiphyte abundance, with highest values in the old-growth forest. Total nutrient transfer via stemflow and throughfall from the canopy to the soil showed only minor differences among the stands. The stands differed widely in the ratio of nutrient transport via stemflow to the total nutrient flux by water below the canopy. The K flux with stemflow accounted for 5% of the total in the old-growth forest but it accounted for 17% (early successional forest) and 26% (mid-successional forest) in the secondary forests. It is concluded that differences in canopy structure and epiphyte abundance in old-growth and secondary forests resulted in large differences in the partitioning of nutrient transport into stemflow and throughfall components although total nutrient transfers via water reaching the soil were similar.
Over small-scale topography in windy areas, precipitation tends to be redistributed by wind through the modification of precipitation inclination. The latter is often derived from wind speed and conventional rain gauge records by application of relations—derived mainly for convective rainfall conditions—between (1) precipitation intensity and drop diameter, and (2) drop diameter and terminal fall velocity. However, it remains to be seen whether such relationships give valid results for the typically low precipitation intensities prevailing in tropical montane cloud forests. On the basis of the assumption that the total amount of near-surface atmospheric liquid water, defined hereafter as the ‘potential precipitation’, is most likely to be identical over small distances, this paper introduces a device to measure amounts of potential precipitation. The gauge captures both the vertical and horizontal component of precipitation, and this allows derivation of precipitation inclination using simple trigonometry. Results on precipitation inclinations obtained with the ‘potential precipitation gauge’ on a wet and windy site in northern Costa Rica suggest the droplets to be smaller than those predicted by the commonly used relationships referred to above. The current gauge is also shown to be more effective in catching inclined precipitation than two different types of spherical gauges. In addition, ‘effective’ fall velocities were determined for each precipitation event using derivated precipitation inclination and wind speed. The assumption of spatially similar potential precipitation amounts and effective fall velocities throughout a small catchment allows the catchment-wide determination of precipitation inclination and therefore of hydrologically effective precipitation from a single-point measurement of potential precipitation and wind speed in combination with modelled spatial wind speed pattern. This approach is believed to yield appreciably better estimates of spatial precipitation inputs compared to reliance on conventional rain gauges and derivation of terminal fall velocities from precipitation intensity records. Copyright © 2010 John Wiley & Sons, Ltd.
This article reviews the hydrologic importance of fog in its various forms. Meteorologically, fog is defined as a ground-touching cloud with a visibility in the horizontal of less than 1000 m. The most widely occurring fog types include radiation fog, sea fog and steam fog, and advection fog, but often fog is also referred to by its location of occurrence (coastal, valley, or mountain fog). The physical processes underlying the various types of fog are described briefly. The use, advantages, and limitations of the most common types of fog collectors, fog detectors, and fog droplet spectrometers are dealt with before embarking on a discussion of techniques for the measurement and modeling of fog deposition on forest vegetation. Results of fog deposition measurements made at selected locations (representing coastal vs. inland, lowland vs. montane, and temperate vs. tropical conditions) are compared. The data confirm the importance of fog interception at many coastal and montane sites across the tropical to mediterranean and warm-temperate climatic spectrum. Under more continental conditions, contributions by fog are usually more modest except on windy mountain ridges and summits. Finally, the paper indicates the chief gaps in knowledge regarding the measurement and importance of fog as a hydrologic input.
Tropical montane cloud forests (TMCF) typically experience conditions of frequent to persistent fog. On the basis of the altitudinal limits between which TMCF generally occur (800–3500 m.a.s.l. depending on mountain size and distance to coast) their current areal extent is estimated at ∼215 000 km2 or 6·6% of all montane tropical forests. Alternatively, on the basis of remotely sensed frequencies of cloud occurrence, fog-affected forest may occupy as much as 2·21 Mkm2. Four hydrologically distinct montane forest types may be distinguished, viz. lower montane rain forest below the cloud belt (LMRF), tall lower montane cloud forest (LMCF), upper montane cloud forest (UMCF) of intermediate stature and a group that combines stunted sub-alpine cloud forest (SACF) and ‘elfin’ cloud forest (ECF). Average throughfall to precipitation ratios increase from 0·72 ± 0·07 in LMRF (n = 15) to 0·81 ± 0·11 in LMCF (n = 23), to 1·0 ± 0·27 (n = 18) and 1·04 ± 0·25 (n = 8) in UMCF and SACF–ECF, respectively. Average stemflow fractions increase from LMRF to UMCF and ECF, whereas leaf area index (LAI) and annual evapotranspiration (ET) decrease along the same sequence. Although the data sets for UMCF (n = 3) and ECF (n = 2) are very limited, the ET from UMCF (783 ± 112 mm) and ECF (547 ± 25 mm) is distinctly lower than that from LMCF (1188 ± 239 mm, n = 9) and LMRF (1280 ± 72 mm; n = 7). Field-measured annual ‘cloud-water’ interception (CWI) totals determined with the wet-canopy water budget method (WCWB) vary widely between locations and range between 22 and 1990 mm (n = 15). Field measured values also tend to be much larger than modelled amounts of fog interception, particularly at exposed sites. This is thought to reflect a combination of potential model limitations, a mismatch between the scale at which the model was applied (1 × 1 km) and the scale of the measurements (small plots), as well as the inclusion of near-horizontal wind-driven precipitation in the WCWB-based estimate of CWI. Regional maps of modelled amounts of fog interception across the tropics are presented, showing major spatial variability. Modelled contributions by CWI make up less than 5% of total precipitation in wet areas to more than 75% in low-rainfall areas. Catchment water yields typically increase from LMRF to UMCF and SACF–ECF reflecting concurrent increases in incident precipitation and decreases in evaporative losses. The conversion of LMCF (or LMRF) to pasture likely results in substantial increases in water yield. Changes in water yield after UMCF conversion are probably modest due to trade-offs between concurrent changes in ET and CWI. General circulation model (GCM)-projected rates of climatic drying under SRES greenhouse gas scenarios to the year 2050 are considered to have a profound effect on TMCF hydrological functioning and ecology, although different GCMs produce different and sometimes opposing results. Whilst there have been substantial increases in our understanding of the hydrological processes operating in TMCF, additional research is needed to improve the quantification of occult precipitation inputs (CWI and wind-driven precipitation), and to better understand the hydrological impacts of climate- and land-use change. Copyright © 2010 John Wiley & Sons, Ltd.
The deposition of fog to a wind-exposed 3 m tall Puerto Rican cloud forest at 1010 m elevation was studied using the water budget and eddy covariance methods. Fog deposition was calculated from the water budget as throughfall plus stemflow plus interception loss minus rainfall corrected for wind-induced loss and effect of slope. The eddy covariance method was used to calculate the turbulent liquid cloud water flux from instantaneous turbulent deviations of the surface-normal wind component and cloud liquid water content as measured at 4 m above the forest canopy. Fog deposition rates according to the water budget under rain-free conditions (0Ð11 š 0Ð05 mm h 1) and rainy conditions (0Ð24 š 0Ð13 mm h 1) were about three to six times the eddy-covariance-based estimate (0Ð04 š 0Ð002 mm h 1). Under rain-free conditions, water-budget-based fog deposition rates were positively correlated with horizontal fluxes of liquid cloud water (as calculated from wind speed and liquid water content data). Under rainy conditions, the correlation became very poor, presumably because of errors in the corrected rainfall amounts and very high spatial variability in throughfall. It was demonstrated that the turbulent liquid cloud water fluxes as measured at 4 m above the forest could be only ¾40% of the fluxes at the canopy level itself due to condensation of moisture in air moving upslope. Other factors, which may have contributed to the discrepancy in results obtained with the two methods, were related to effects of footprint mismatch and methodological problems with rainfall measurements under the prevailing windy conditions. Best estimates of annual fog deposition amounted to ¾770 mm year 1 for the summit cloud forest just below the ridge top (according to the water budget method) and ¾785 mm year 1 for the cloud forest on the lower windward slope (using the eddy-covariance-based deposition rate corrected for estimated vertical flux divergence).
Photosynthesis was limited by low-intensity photosynthetically active radiation (PAR) and leaf wetness in a lower montane cloud forest (LMCF) of Cauca, Colombia. Mean PAR intensity remained below the saturation level for leaf-scale net photosynthesis (P n) throughout the solar day during the wet season and for most of the solar day during the dry season. PAR represented a smaller fraction of total solar radiation (K↓) in LMCF than in lowland rain forest (LRF). In LMCF trees and shrubs, mean PAR-saturated P n ranged from 4.3–10.6 µmol C m −2 s −1 at 1450 m, and from 3.5–10.2 µmol C m −2 s −1 at 2150 m. P n was reduced by abaxial wetness in leaves of some trees and shrubs, and eliminated in others. This study indicates that persistent cloudiness and interception of cloud water by leaves limit LMCF productivity.
Island tropical montane cloud forests may be among the most sensitive of the world's ecosystems to global climate change. Measurements in and above a montane cloud forest on East Maui, Hawaii, document steep microclimatic gradients. Relatively small climate-driven shifts in patterns of atmospheric circulation are likely to trigger major local changes in rainfall, cloud cover, and humidity. Increased interannual variability in precipitation and hurricane incidence would provide additional stresses on island biota that are highly vulnerable to disturbance-related invasion of non-native species. Because of the exceptional sensitivity of these microclimates and forests to change, they may provide valuable listening posts for detecting the onset of human-induced global climate change.
In this study, we designed and built an automated system of collection and measurement of throughfall and stemflow, developing a new sampling methodology. Throughfall was measured by trough-type system of collectors, each collector with sampling area of 5 cm × 6 m, connected every six troughs to a large tipping bucket raingauge. Our throughfall measurement system covered a larger surface area than do most commonly used randomly relocated gauges, reducing the spatial variability. Temporal resolution was high (5 min), allowing the study of the short-term dynamics of the interception process. Stemflow was collected from 65 trees and also measured by large tipping bucket raingauges. Water vapor exchange at the forest–atmosphere interface was derived from eddy covariance data from a flux tower in the same area as the interception study. During the study period (November 2002–October 2004) a mild El Niño year developed and total annual rainfall was considerably lower than the average for the region. The interception loss in the year with normal rainfall was 13.3%, compared to 22.6% of gross precipitation in the dry year. The interception difference is explained by the comparison of mean intensity and duration of events in the normal year (8.77 mm/h and 1.88 h) versus the driest year (5.36 mm/h and 2.32 h). Interception loss for the whole period represented 16.5% of the gross rainfall, with throughfall 82.9% and stemflow 0.6%. We used the analytical Gash model to estimate the interception loss. The model succeeded in capturing the variability associated to the variability in the characteristics of precipitation. This is the first study to show the variability of interception in relation to rainfall (seasonally and between years).
During a one-year period, the variability of throughfall and the standard errors of the means associated with different gauge arrangements were studied in a lower montane rain forest in Puerto Rico. The following gauge arrangements were used: (1) 60 fixed gauges, (2) 30 fixed gauges, and (3) 30 roving gauges. Stemflow was measured on 22 trees of four different species. An ANOVA indicated that mean relative throughfall measured by arrangements 1 (77%), 2 (74%), and 3 (73%) were not significantly different at the 0.05 level. However, the variability of the total throughfall estimate was about half as high for roving gauges (23%) as for fixed gauges (48–49%). The variability of stemflow ranged from 36% to 67% within tree species and was 144% for all sampled trees. Total stemflow was estimated at 4.1% of rainfall, of which palms contributed about 66%. Comparative analysis indicated that while fixed and roving gauge arrangements can give similar mean values, least 100 fixed gauges are required to have an error at the 95% confidence level comparable to that obtained by 30 roving gauges.
The partitioning of gross rainfall into throughfall, stemflow and evaporation of intercepted rainfall was studied in four forest ecosystems in the Middle Caquetá, Colombian Amazonia. Data on climate was collected automatically on an hourly basis during a five-year period. Weekly measurements of rainfall, throughfall and stemflow were carried out during a period of two years, while daily measurements, on an event basis, were carried out during two subsequent years. Throughfall, stemflow and evaporation in each forest were checked for correlations with gross rainfall characteristics, canopy gap fraction, tree crown area and bark texture. Canopy gap fraction differed between forests, ranging from 9% on the flood plain to 17% on the Tertiary sedimentary plain. Rainfall was rather evenly distributed over the year, with one dry period from December to February. 92% of the rain fell in single showers of less than 30 mm and most of the storms (56%) fell in less than one hour, during the afternoon or early night. Throughfall ranged from 82 to 87% of gross rainfall in the forests studied and varied with gross rainfall in all forests. It depended on the amounts and characteristics of rainfall, but differences in throughfall among forests, when comparing similar rainfall events, clearly indicated that throughfall also depends on forest structure. Stemflow contributed little to net precipitation (on average 1.1% of gross rainfall in all forests) and showed a power relation with gross rainfall. Correlations between stemflow per tree, projected crown area and bark texture were very poor as indicated by the low coefficients of determination. Evaporation during rainfall events exhibited a linear relation with rainfall duration and the ratio of evaporation over gross rainfall increased with forest cover (1-gap fraction) in the forests studied. The structure of the forests seemed to vary considerably and given its influence on rainfall partitioning it may explain both differences and similarities between results from this study and those from most other studies within Amazonia.
Recent surveys of tropical forest water use suggest that rainfall interception by the canopy is largest in wet maritime locations. To investigate the underlying processes at one such location—the Luquillo Experimental Forest in eastern Puerto Rico—66 days of detailed throughfall and above-canopy climatic data were collected in 1996 and analysed using the Rutter and Gash models of rainfall interception. Throughfall occurred on 80% of the days distributed over 80 rainfall events. Measured interception loss was 50% of gross precipitation. When Penman–Monteith based estimates for the wet canopy evaporation rate (0.11 mm h−1 on average) and a canopy storage of 1.15 mm were used, both models severely underestimated measured interception loss. A detailed analysis of four storms using the Rutter model showed that optimizing the model for the wet canopy evaporation component yielded much better results than increasing the canopy storage capacity. However, the Rutter model failed to properly estimate throughfall amounts during an exceptionally large event. The analytical model, on the other hand, was capable of representing interception during the extreme event, but once again optimizing wet canopy evaporation rates produced a much better fit than optimizing the canopy storage capacity. As such, the present results support the idea that it is primarily a high rate of evaporation from a wet canopy that is responsible for the observed high interception losses.
Within the topo-climatically complex tropical mountains of Hawai’i, there are four distinctive montane forest zones where the direct canopy interception of wind-driven cloud water (also referred to as “fog drip”) plays a significant role in forest ecology and hydrology. Not all of these four zones can be characterized as classic tropical montane cloud forest (TMCF), but to varying degrees each is influenced by ground-level, orographic cloud.
Based on field measurements made at dry (Auwahi) and wet (Waikamoi) cloud forest sites on the island of Maui, a preliminary analysis of fog gage measurements and wet-canopy water balance estimates was made. Accounting for effects of wind-blown rainfall and varying wind direction, estimates of cloud water flux were derived based on fog gage observations. Throughfall (TF) measurements, incident rainfall estimates, and calculated amounts of wet-canopy evaporation were used to estimate event totals of cloud water interception (CWI) by the vegetation at each site. Measured TF was about 37% of incident rainfall at Auwahi, and 119% at Waikamoi. At both sites TF was dominated by rainfall, but was significantly influenced by fog at Waikamoi only. Fog contributed at an average frequency of once every two days at Auwahi and about twice in three days at Waikamoi. Derived CWI totals were equivalent to 151 mm year–1 at Auwahi and 1073 mm year–1 at Waikamoi. At Auwahi, however, the majority of intercepted water was re-evaporated from the wet vegetation, and never reached the ground. Total CWI was related to fog screen catch and cloud water flux at Waikamoi, but not at Auwahi.
Research on fog climatology and cloud water interception (CWI) in the montane cloud forests of Hawai'i spans nearly 50 years, from the pioneering work of Wendell Mordy and Paul Ekern on Lâna'i in the 1950s, through the continuing efforts of James Juvik since 1972. This work has helped to improve understanding of the spatial patterns of fog occurrence and to quantify CWI in forests and other vegetation. Reported CWI or fog incidence estimates are as high as 4982 mm year-1 at particularly exposed locations, although most windward sites within the cloud zone are in the range between 280 and 1130 mm year-1, with leeward sites receiving between 100 and 500 mm year-1, and less than 250 mm year-1 in high-elevation areas above the trade-wind inversion. Most of the early work was based on mechanical fog gage measurements whose well-known limitations make accurate estimation of actual CWI by a forest canopy difficult. Advancing the current level of understanding will have to come from studies incorporating other methods, such as the wet-canopy water budget and stable isotope mass balance approaches, in addition to the continued use of recording fog and throughfall gages.
This paper reviews current knowledge of the effect of forest type, ground cover and climate on rainfall partitioning into throughfall, stemflow and interception. It considers the variety and reliability of measurement techniques that have been used and interprets the results of interception studies in relation to methodological, vegetational and climatic factors. The review illustrates that it is difficult to draw general conclusions about interception losses by particular forest types because they almost always depend on the type of rainfall and other meteorological conditions during the study period. Characteristics of a forest that affect interception are not always easy to identify and quantify. Characteristics such as trees/ha, branch angle, the uniformity or lack of uniformity in crown height, the nature and thickness of the bark layer, leaf shape and inclination, and leaf area index will all influence interception. The major difficulty is reliable estimation of throughfall. It is not unusual for measured throughfall to exceed the rainfall value, causing interception to be negative. The difficulty in estimation of throughfall is discussed. while also addressing the need for accurate measurement of rainfall. In forests where stemflow volumes are large enough to significantly influence the interception values, the methodological approach is even more difficult. Measurement of interception on a periodic basis presents fewer problems than estimation on an individual event basis because the variables that affect the values of throughfall and stemflow can change over very short periods, for example the intensity and angle of rainfall, and wind speed and direction. However, carefully conducted event-based studies can quantify the influence of a number of the variables. Copyright (C) 2000 John Wiley & Sons, Ltd.
Myrica faya, an introduced nitrogen-fixing tree, is rapidly invading volcanically disturbed forests in Hawaii Volcanoes National Park on the island of Hawai'i. We investigated the direct effects of Myrica on the establishment and growth of the native tree, Metrosideros polymorpha, in a forest that is recovering from burial under a 10-200 cm deep layer of volcanic cinder. The number of Metrosideros seedlings found under Metrosideros trees, in the open, and under Myrica trees was 0.12/m^2, and 0.01/m^2, and zero, respectively. Myrica litter inhibited Metrosideros germination in field experiments; germination occurred only when Myrica litter was removed. In open sites, the addition of nitrogen-rich Myrica soils increased dry mass accumulation of transplanted Metrosideros seedlings. Shade from Myrica canopies (or shade cloth) increased survivorship and height growth but not dry mass accumulation of Metrosideros seedlings. Isolated Metrosideros trees increased diameter growth in response to nitrogen fertilizer but not in response to the presence of adjacent Myrica trees, despite previous findings that Myrica trees elevate available nitrogen in the soil. Myrica basal diameter and height growth were consistently greater than that of Metrosideros in all size classes. Although Myrica does not readily invade closed, late-successional Metrosideros forests, on young, volcanically disturbed soils it is rapidly establishing dense, monospecific stands under which Metrosideros does not regenerate.
The atmospheric deposition of N and base cations in fog, precipitation,
and dry deposition was measured over 5-7 years at the Hawaii Volcanoes
National Park, Hawaii. Precipitation deposition was measured for 1.5
years at the Kokee State Park/Na Pali Kona Forest Reserve, Kauai. Fog
interception on Hawaii was 158 +61/-32, 148 +69/-36, 251 +85/-51, 251
+91/-51, 243 +96/-59, and 181 +56/-38 cm per year for the years 1995 to
2000 respectively. This represents an average of 46% of the total water
input and 83% of precipitation. An analysis of the lowest uncertainty
that could realistically be achieved using our water balance method
yielded a minimum uncertainty of +16% and -14% for annual fog
interception values and +54% and -53% for individual fog events. At the
Thurston Lava Tube site, fog interception was by far the largest
deposition pathway for K+, Mg2+, Ca2+,
and N. Sea salt contributes the majority of cations, while local biomass
burning on Hawaii and Asian dust are significant sources for some years.
Fog N deposition at Thurston averaged 20 kg N ha-1
yr-1. Organic N was on average 16% and 12% of the N in rain
and fog. Several methods were used to determine whether volcanically
produced N significantly impacted the Thurston site. Back trajectory
analysis showed that air can blow from the volcano to our sampling site
when there is an interruption in the northeasterly trade winds.
Collected fog during one such episode had measurable
NO2-, indicating very high atmospheric
concentration of atmospheric NO2. NH4+
concentrations were higher for fog events with back trajectories that
indicated volcanic influence than for those without, indicating that the
volcano is also a reduced N source. Enough fog events were sampled from
1998 to 2000 to statistically show higher concentrations of
NO3- , NH4+, and organic N
in events with volcanic influence versus those without. Lower deposition
of NO3 - in precipitation on Kauai also argues
that volcanic N is significant at Thurston.
PREFACE TO THE SECOND EDITION LIST OF SYMBOLS 1. SCOPE OF ENVIRONMENTAL PHYSICS 2. GAS LAWS Pressure, volume and temperature Specific heats Lapse rate Water and water vapour Other gases 3. TRANSPORT LAWS General transfer equation Molecular transfer processes Diffusion coefficients Radiation laws 4. RADIATION ENVIRONMENT Solar radiation Terrestrial radiation Net radiation 5. MICROCLIMATOLOGY OF RADIATION (i) Interception Direct solar radiation Diffuse radiation Radiation in crop canopies 6. MICROCLIMATOLOGY OF RADIATION (ii) Absorption and reflection Radiative properties of natural materials Net radiation 7. MOMENTUM TRANSFER Boundary layers Wind profiles and drag on uniform surfaces Lodging and windthrow 8. HEAT TRANSFER Convection Non-dimensional groups Measurements of convection Conduction Insulation of animals 9. MASS TRANSFER (i) Gases and water vapour Non-dimensional groups Measurement of mass transfer Ventilation Mass transfer through pores Coats and clothing 10.MASS TRANSFER (ii) Particles Steady motion 11.STEADY STATE HEAT BALANCE (i) Water surfaces and vegetation Heat balance equation Heat balance of thermometers Heat balance of surfaces Developments from the Penman Equation 12.STEADY STATE HEAT BALANCE (ii) Animals Heat balance components The thermo-neutral diagram Specification of the environment Case studies 13.TRANSIENT HEAT BALANCE Time constant General cases Heat flow in soil 14.CROP MICROMETEOROLOGY (i) Profiles and fluxes Profiles Profile equations and stability Measurement of flux above the canopy 15.CROP MICROMETEOROLOGY (ii) Interpretation of measurements Resistance analogues Case studies: Water vapour and transpiration Carbon dioxide and growth Sulphur dioxide and pollutant fluxes to crops Transport within canopies APPENDIX BIBLIOGRAPHY REFERENCES INDEX
This paper reviews current knowledge of the effect of forest type,
ground cover and climate on rainfall partitioning into throughfall,
stemflow and interception. It considers the variety and reliability of
measurement techniques that have been used and interprets the results of
interception studies in relation to methodological, vegetational and
climatic factors. The review illustrates that it is difficult to draw
general conclusions about interception losses by particular forest types
because they almost always depend on the type of rainfall and other
meteorological conditions during the study period. Characteristics of a
forest that affect interception are not always easy to identify and
quantify. Characteristics such as trees/ha, branch angle, the uniformity
or lack of uniformity in crown height, the nature and thickness of the
bark layer, leaf shape and inclination, and leaf area index will all
influence interception. The major difficulty is reliable estimation of
throughfall. It is not unusual for measured throughfall to exceed the
rainfall value, causing interception to be negative. The difficulty in
estimation of throughfall is discussed, while also addressing the need
for accurate measurement of rainfall. In forests where stemflow volumes
are large enough to significantly influence the interception values, the
methodological approach is even more difficult. Measurement of
interception on a periodic basis presents fewer problems than estimation
on an individual event basis because the variables that affect the
values of throughfall and stemflow can change over very short periods,
for example the intensity and angle of rainfall, and wind speed and
direction. However, carefully conducted event-based studies can quantify
the influence of a number of the variables.
A novel design of gauge for measuring net rainfall beneath a forest canopy is described. The advantages of this system, based on the use of a large plastic sheet, over conventional throughfall and stemflow measuring systems is discussed.
Recent studies of the water balance of tropical rainforests in northern Queensland have revealed that large fractions of rainfall, up to 30%, are intercepted by the canopy and lost as evaporation. These loss rates are much higher than those reported for continental rainforests, for example, in the Amazon basin, where interception is around 9% of rainfall. Higher interception losses have been found in coastal and mountain rainforests and substantial advection of energy during rainfall is proposed to account for these results. This paper uses a process based model of interception to analyse the interception losses at Oliver Creek, a lowland coastal rainforest site in northern Queensland with a mean annual rainfall of 3952 mm. The observed interception loss of 25% of rainfall for the period August 2001 to January 2004 can be reproduced by the model with a suitable choice of the three key controlling variables, the canopy storage capacity, mean rainfall rate and mean wet canopy evaporation rate. Our analyses suggest that the canopy storage capacity of the Oliver Creek rainforest is between 3.0 and 3.5 mm, higher than reported for most other rainforests. Despite the high canopy capacity at our site, the interception losses can only be accounted for with energy advection during rainfall in the range 40 70% of the incident energy.
Although floristic lists for a large sample of U.S. reserves have 5-25% introduced species, most introductions are confined to drastically disturbed areas and pose little or no threat to native ecosystems. A survey of Biosphere Reserves of the United States suggests that many reserves have only very minor problems or no problems at all with introduced plant species. Problems with invasive introduced species are most severe on oceanic islands, but serious problems occur in some continental areas as well. In some U.S. parks and reserves, the primary concern for introduced plant species is that they pose economic threats to adjacent agricultural lands. In extreme situations, however, introduced plants may inhibit and entirely prevent reproduction of native plant species, degrade habitat for native animal species, and/or alter otherwise natural habitats through changing nutrient, fire, or water regimes. At the highly disruptive end of the spectrum, native ecosystems may become so totally transformed by invaders that they are scarcely recognizable, although this condition is rare within U.S. parks and reserves.
The Galapagos Archipelago is nearly devoid of freshwater resources, but during six months of the year, a fog layer covers the windward slopes of the main islands. In order to investigate the hydrological importance of this phenomenon, a monitoring network was set up on Santa Cruz Island, at the center of the archipelago. Meteorological parameters were monitored together with throughfall and stemflow at two stations: a first in a secondary forest at the lowest fringe of the fog layer (400 m a.s.l.), and a second in shrub lands of the Galapagos National Park, at the center of the fog layer (650 m a.s.l.). Cloud water interception was quantified from the wet canopy water budget, based on a modified Rutter-type canopy interception model. This methodology allowed the estimation of fog interception for short time intervals (15 min) and avoided the subjective separation into individual rainfall events. Fog was found to be a negligible water input at the lower site, but was estimated at 26 ± 16% of incident rainfall at the higher site. Wind was shown to enhance fog interception, but this alone could not explain the difference in fog catch between the two sites. Higher liquid water content and more frequent fog occurrence contributed to the difference as well. This study highlights that the presence of fog may induce a marked increase of net precipitation, but this effect is restricted to the summit areas exposed to winds, located in the center of the cloud belt.
This book introduces an interdisciplinary framework to understand the interaction between terrestrial ecosystems and climate change. It reviews basic meteorological, hydrological and ecological concepts to examine the physical, chemical and biological processes by which terrestrial ecosystems affect and are affected by climate. The textbook is written for advanced undergraduate and graduate students studying ecology, environmental science, atmospheric science and geography. The central argument is that terrestrial ecosystems become important determinants of climate through their cycling of energy, water, chemical elements and trace gases. This coupling between climate and vegetation is explored at spatial scales from plant cells to global vegetation geography and at timescales of near instantaneous to millennia. The text also considers how human alterations to land become important for climate change. This restructured edition, with updated science and references, chapter summaries and review questions, and over 400 illustrations, including many in colour, serves as an essential student guide.
The spatial distribution of throughfall in a tropical rainforest in Peninsular Malaysia was evaluated using 100 bucket raingauges placed along a line as well as two large raingauges (collection areas of 9.58 and 7.08m2). Throughfall was clearly large in a treefall gap although it was not significantly different between a typical old-growth area with big trees and another area without big trees. A cyclic variation, the scale of which was 10–15m, was detected in the entire forest through Fourier analysis, and this scale roughly corresponded to the index of canopy cover openness. The observations gave the spatial mean value of throughfall with enough accuracy considering that the distribution of throughfall in the forest was controlled by different scale effects consisting of the size of disturbance areas such as gaps as well as the size of individual canopies.
Mixed tree-heath/beech forest is a type of subtropical montane cloud forest found on wind- and fog-exposed ridges in the Canary Islands. With a dry season of 5 months and an annual precipitation of 600–700 mm, the extra water inputs through fog interception assume particular importance in this environment. Measurements were made of rainfall, fog occurrence, wind speed and direction as well as of throughfall (TF) in a ridge top cloud forest located near the centre of the National Park of Garajonay on the island of La Gomera. Measured amounts of incident rainfall were corrected for wind-induced losses around the gauge and for topographic effects. Amounts of fog water as collected by a 0·25-m2 fog screen were corrected for changes in effective screen surface collection area depending on wind direction. No such corrections were taken into account in most if not all previous studies of rainfall and fog water inputs in the Canary Islands. TF fractions differed between events with rain-only (87% of wind-corrected rainfall), fog-only (∼6% of wind-corrected fog) and mixed precipitation (110%). It is concluded that the fog screen was more efficient at capturing fog water than the forest canopy, whereas previous wetting of the canopy and bryophytes by rain may have caused the higher TF fraction found on days with rainfall and fog. Copyright © 2010 John Wiley & Sons, Ltd.
This article presents a comprehensive study of canopy interception in six rainforests in Australia's Wet Tropics for periods ranging between 2 and 3·5 years. Measurements of rainfall, throughfall, stemflow and cloud interception were made at sites characterized by different forest types, canopy structure, altitude, rainfall and exposure to prevailing winds. Throughfall at these sites ranged between 64 and 83% of total precipitation inputs, while stemflow ranged between 2 and 11%. At sites higher than 1000 m, cloud interception was found to contribute up to 66% of the monthly water input to the forest, more than twice the rainfall at these times. Over the entire study period, cloud interception accounted for between 4 and 30% of total precipitation inputs, and was related more to the exposure of sites to prevailing winds than to altitudinal differences alone.
Over the duration of the study period, interception losses ranged between 22 and 29% of total water input (rainfall and cloud interception) at all sites except the highest altitude site on Bellenden Ker, where interception was 6% of total water input. This smaller interception loss was the result of extremely high rainfall, prolonged immersion in cloud and a sparser canopy. On a monthly basis, interception losses from the six sites varied between 10 and 88% of rainfall. All sites had much higher interception losses during the dry season than in the wet season because of the differences in storm size and rainfall intensity. The link between rainfall conditions and interception losses has important implications for how evaporative losses from forests may respond to altered rainfall regimes under climate change and/or large‐scale atmospheric circulation variations such as El Niño. Copyright © 2007 John Wiley & Sons, Ltd.
Methods for measuring throughfall, stemflow and, hence, interception in the tropical rainforests of the Wet Tropics region of North Queensland, Australia, were tested at three sites for between 581 and 787 days. The throughfall system design was based on long troughs mounted beneath the canopy and worked successfully under a range of rainfall conditions. Comparison of replicated systems demonstrated that the methodology is capable of capturing the variability in throughfall exhibited beneath our tropical rainforest canopies. Similarly, the stemflow system design which used spiral collars attached to sample trees worked well under a range of rainfall conditions and also produced similar estimates of stemflow in replicated systems.
Higher altitude rainforests (>1000 m) in North Queensland can receive significant extra inputs of water as the canopy intercepts passing cloud droplets. This additional source of water is referred to as ‘cloud interception’ and an instrument for detecting this is described. The results obtained from this gauge are compared with cloud interception estimates made using a canopy water balance method. This method is based on stemflow and throughfall measurements and provides an alternative means to fog or cloud interception gauge calibration techniques used in the literature. Copyright
The stemflow of 30 sample trees belonging to six different species was quantified in the laurel forest of Agua Garcı́a, Tenerife, Canary Islands, during a complete year. Different methods described in the literature, for scaling up the stemflow values from tree level to stand level were applied. The best for this type of forest is based on the application of annual regressions between basal area and stemflow in each species, giving a total annual stand stemflow of 42.86 l m−2. This represents 6.85% of annual gross precipitation. This is not a very high value but important to be taken into account in the determination of the water balance of the forest. An antecedent precipitation of 2 mm was necessary for the initiation of the stand stemflow. Stemflow attained 10% of gross precipitation during big rain events, being positively correlated with the mean hourly rain intensity.Differences among trees and species were also studied resulting that trees with the biggest crown area, not dominated by their neighbours, and with the smoothest bark collected the largest volumes of stemflow in the stand. Bark roughness, divergence angle of the branches with respect to the trunk and also the size of the leaves, were responsible for the differences between species.As a consequence of the stemflow the rain can be concentrated up to 12.8 times in the infiltration areas of the trees which could produce better soil conditions for tree growth. The results obtained in the Agua Garcı́a laurel forest stand are the first stemflow data obtained for the Canarian laurel forest and they are in the range found in other types of forests.
Simple but effective models are needed for the prediction of rainfall interception under a full range of environmental and management conditions. The Liu model was validated using data published in the literature and was compared with two leading models in the literature: the Rutter and the Gash models. The Liu model was tested against the Rutter model on a single-storm basis with interception measurements observed from an old-growth Douglas fir (Pseudotsuga menziesii) forest in Oregon, USA. Simulated results by the Liu model were close to the measurements and comparable to those predicted by the Rutter model. The Liu model was further tested against the Gash model on a multistorm basis. The Gash and Liu models successfully predicted long-term interception losses from a broad range of 20 forests around the world. Results also indicated that both the Gash and the Liu models could be used to predict rainfall interception using daily rainfall data, although it was assumed in both models that there is only one storm per rain day. The sensitivity of the Liu model to stand storage capacity, canopy gap fraction and evaporation rate from wet canopy surface during rainfall was investigated. Results indicate that the Liu model has the simplest form, least data requirements and comparable accuracy for predicting rainfall interception as compared with the Rutter and the Gash models. Copyright © 2001 John Wiley & Sons, Ltd.
The description of the evaporation of rainfall intercepted by forests in terms of a regression of evaporation loss on incident rainfall is discussed and some of the assumptions implicit in that method are re-examined. The two major factors which control the evaporation of intercepted rainfall are identified. These are: (i) the amount of time that the canopy spends saturated during rainfall and the evaporation rate applicable under these conditions; and (ii) the canopy saturation capacity and the number of times this store is emptied, by drying out after the cessation of rainfall. A model is then constructed which is conceptually similar to the Rutter model, but which replaces that model's numerical approach with an analysis by storm events. The evaporation from a saturated canopy during rainfall is estimated from the Penman-Monteith equation; the evaporation after rain has ceased, the effect of small storms insufficient to saturate the canopy, wetting-up the canopy and evaporation from the trunks are added as separate terms. The model has been tested against data from Thetford Forest in East Anglia, with satisfactory agreement between observation and estimation. It is suggested that the model may be capable of making useful estimates of the evaporation of intercepted rainfall, solely from rainfall measurements.
Leaf surface wetness that occurs frequently in natural environments has a significant impact on leaf photosynthesis. However, the physiological mechanisms for the photosynthetic responses to wetness are not well understood. The responses of leaf CO2 assimilation rate (A) to 72 h of artificial mist of a wettable (bean; Phaseolus vulgaris) and a non-wettable species (pea; Pisum sativum) were compared. Stomatal and non-stomatal limitations to A were investigated. A 28% inhibition of A was observed in the bean leaves as a result of a 16% decrease in stomatal conductance and a 55% reduction in the amount of Rubisco. The decrease of Rubisco was mainly due to its partial degradation. In contrast to the bean leaves, a 22% stimulation of A was obtained in the 72 h mist-treated pea leaves. Mist treatment increased stomatal conductance by 12.5% and had no effect on the amount of Rubisco. These results indicated that a positive photosynthetic response to wetness occurred only in non-wettable species and is due to the change in stomatal regulation.
Rainfall partitioning into throughfall and stemflow was studied in a diverse and in a mono specific stand of secondary vegetation
in Eastern Amazonia. The nutrient concentrations in the water were analysed in order to quantify the related hydrochemical
fluxes. Secondary vegetation forms the fallow in the local shifting cultivation system and is usually dominated by shrubs
and trees. Phenakospermum guyannense (Strelitziaceae), a banana-like herb, is one of the predominant non-woody species. The study was conducted during an 18-month
period in a 2.5-year-old relatively species-rich stand and a 10-year-old stand dominated by P. guyannense. In a year with 1956 mm of rainfall 65% (1281 mm) of this quantity reached the soil as throughfall in the diverse stand and
38% (743 mm) in the mono specific stand. Stemflow was estimated to be 23% and 41% respectively. P. guyannense and Banara guianensis (Flacourtiaceae), a tree species, were causing these high funnelling effects. In the young diverse stand B. guianensis had a stemflow of more than 200 l year−1 and P. guyannense had a median flux of 77 l year−1 per pseudostem. In the older stand the taller plants of P.␣guyannense collected 644 l year−1 per pseudostem on the median. The reason for these high values could be the banana-like growth form of P. guyannense and the crown morphology of B. guianensis, which has inclined branches. The low proportion of throughfall and the high stemflow values differ from all previous studies
in Amazonian primary forests. The proximity to the Atlantic Ocean strongly influenced the nutrient fluxes via rainfall at
our study site. This becomes obvious from the high Na and Cl fluxes with rainfall (19.7 kg Na ha−1 year−1, 37.2 kg Cl ha−1 year−1) which were approximately equal to the Na and Cl fluxes with the sum of throughfall and stemflow for both stands. K fluxes
in throughfall and stemflow in both stands were higher than in rainfall by a factor of 8. The high K enrichment during the
crown passage is assumed to be caused by a␣high K concentration in the leaf tissue resulting in enhanced leaching from the
leaves. In months with low␣rainfall the concentrations of Ca, Mg, S and Cl in throughfall of the diverse stand were significantly
higher than in months with high rainfall. This was mainly due to vegetation burns in the dry period, which resulted in ash
deposition on the canopy and subsequent wash-off and solution of ash particles.
Stemflow is a spatially localized point input of precipitation and solutes at the plant stem and is of hydrological and ecological significance in forested and agricultural ecosystems. The purpose of this review is to: (1) critically evaluate our current understanding of stemflow; (2) identify gaps in our present knowledge of stemflow; and (3) stimulate further research in areas where present knowledge is weak. The review begins by analyzing stemflow drainage and nutrient inputs under diverse vegetal cover. Stemflow inputs are then examined as a function of meteorological conditions, seasonality, interspecific and intraspecific differences among and within species, canopy structure, spatiality, and atmospheric pollutants in urban environments. Stemflow modeling studies are also reviewed and evaluated. Stemflow yield and chemistry are the result of the interaction of the many complex variables listed. By analyzing each separately, it may be possible to isolate their individual affects on stemflow production and chemistry. A comprehensive understanding of each influencing factor would enable the accurate modeling of stemflow water and nutrient inputs into agricultural and forest soils which may result in the optimization of timber and crop harvests.Some areas where present knowledge is particularly weak are: (1) stemflow production and nutrient transfers in northern boreal forests (aspen, birch, conifers) and desert cacti; (2) chemical enrichment of stemflow from live trees charred by forest fires; (3) stemflow yield and nutrient inputs during the winter season; (4) intraspecific variation in stemflow production and chemistry; (5) stemflow chemistry from standing dead trees; (6) influence of canopy structure on stemflow chemistry; (7) understory stemflow generation and nutrient transfer; and (8) stemflow enrichment associated with insect infestations.
Management activities alter the structure of many tropical forest stands which can be expected to influence the magnitude of canopy water fluxes. The objectives of this study were to determine throughfall, stemflow and rainfall interception in differently managed forest stands, and to relate the observed pattern of rainfall partitioning to stand structural characteristics. The study was conducted in a lower montane rainforest region (800–1140 m asl) in Central Sulawesi, Indonesia. Stands of four management types (natural forest, forest subject to small-diameter timber extraction, forest subject to selective logging of large-diameter timber, and cacao agroforest under trees remaining from the natural forest) were analyzed with three replicates per use type. The tree basal area decreased from the natural forest (52.5 m2 ha−1) to the agroforest (19.4 m2 ha−1) which was paralleled by a reduction in mean tree height (trees ≥ 10 cm dbh) from 21.3 to 17.5 m. The estimated leaf area index (LAI), as derived from hemispherical photos, averaged 6.2 m2 m−2 in the natural forest, 5.3 in forests with small timber extraction, 5.0 in forests with large timber extraction, and 5.3 in the agroforest. The annual gross precipitation close to our different study plots varied locally between 2437 and 3424 mm during the time of the study. Throughfall was measured on 15–17 rain days per plot with a median of 70% of gross precipitation over all the natural forest plots, 79 and 80% in forest with small and large timber extraction respectively, and 81% in the agroforest. Stemflow was less than 1% in all studied use types. Thus, rainfall interception was highest in the natural forest where 30% (median) of the gross precipitation was re-evaporated back into the atmosphere, and much lower in the three other use types (18–20%). Variability in structure and rainfall partitioning was high even within the same forest use types, thus further analysis focused on gradual changes rather than categories. In the 12 stands, LAI alone did not correlate significantly with the pattern of rainfall partitioning, the throughfall percentage increased significantly with decreasing tree height (r2 = 0.63). In a multiple linear regression with tree height and LAI as influencing factors, 81% of the variation in throughfall percentage is explained. A possible reason for this tree height-LAI-throughfall relationship is that under the conditions prevailing in our study region the canopy may not completely dry up between subsequent rainfall events. Therefore, the actual water storage at the start of a rainfall event would be below its potential. We hypothesize that tall trees increase the vertical distribution of foliage and other canopy components contributing to the canopy water storage, resulting in a higher canopy roughness and a more effective energy exchange with the atmosphere. This would consequently lead to an increased re-evaporation of intercepted water, larger available water storage and, thus, a reduced throughfall in stands with tall trees.
The spatial variability of throughfall and stemflow in Amazonian tropical rainforest is analysed. Statistical tests are used to assess the minimum sampling size and number of gauges required. Random relocation of throughfall gauges is shown to be better than fixed position gauges and random relocation of gauges on a transect line is better than over an area. During the study period, throughfall and stemflow, calculated as percentages of gross rainfall, were 91(± 2) and 1.8(± 1)%, respectively. No attempt was made in this study to investigate storm size dependency of these figures.
Measurements of transpiration and interception loss were made from a region of secondary lowland tropical rain forest located in the Janlappa nature reserve, West Java, using soil physical and water-balance methods. For the period of observation, the mean daily transpiration rate was 2.6 mm day−1, (soil-moisture tensions were < 1 bar), a rate which would be obtained with a constant surface resistance of 120 s m−1. Interception models of the Rutter type, in which net-rainfall rate is uniquely related to canopy storage, were found to be unsatisfactory; better results were obtained with models using a stochastic wetting function. Measurements of rain and net rainfall indicated that interception losses were 21% of the gross rainfall. The calculated total evaporation from the site for the year from August 1980 to July 1981 was 1481 mm (886 mm transpiration and 595 mm interception), a value for which the latent heat requirement is identical to the measured net radiational input to the site.
Throughfall determined by stationary and mobile methods in a disturbed evergreen-dominated forest stand in northern Thailand was 82% of rainfall (1134 mm) during a 4-month study period in the monsoon rain season of 2002. Associated coefficients of variation and standard errors were ≤10% and 2%, respectively, for both methods. Agreement between four stationary trough collectors and 20 mobile standard gauge collectors was achieved only after 35 sampling occasions, having a total rainfall depth >700 mm, and included one storm event >100 mm. Several canopy trees contributed to points with throughfall > rainfall by channeling stemflow to common drip points on the trunk and large limbs. However, no significant correlation was observed between throughfall point measurements and corresponding canopy cover. Although 180-point measurements of throughfall provided a realistic representation of the spatial variability within the 500-m2 forest stand, it is questionable that they duplicated the basin-scale variability, which would be affected both by tree gaps and variable topographically related rain shadow effects.
Evapotranspiration (ET) and energy balance were observed, using eddy covariance and other micrometeorological measurements, at a native Metrosideros polymorpha forest site in Hawai‘i. Total rainfall for the 12-month study period (2401 mm) was close to the long-term mean (2500 mm year−1), but was highly variable from month to month with distinct dry periods in February, May, and December 2005. Measured annual ET of 996 mm year−1 was slightly higher than previous estimates for similar locations in Hawai‘i. However, the energy closure ratio was 0.784, leading us to adjust turbulent energy fluxes upward by 27.6%. The resulting adjusted annual ET of 1232 mm is significantly higher than previous forest ET estimates for Hawai‘i. Variations in canopy conductivity suggest that midday stomatal closure is occurring and/or that evaporation is high in the morning because of frequent wet canopy conditions early in the day. The daily fraction of turbulent energy flux used for ET was observed to be lower for days with high net radiation, indicating that transpiration is being limited under conditions of high evaporative demand. ET was generally higher during rainy periods than dry periods. After controlling for differences in available energy, ET is, on average, 29% higher on days with rain than days without rain. The fraction of energy used for ET follows a distinct annual pattern, roughly corresponding to the observed cycle in leaf area at the site, with a minimum in mid-April and a maximum in mid-October. Variations in rainfall appear to be the cause of deviations from the annual cycle of the fraction of energy used for ET. This suggests that ET is strongly controlled by variations in canopy wetness at this wet forest site.
The process of rainfall interception by vegetation is discussed. Using data from an East African experiment, relationships between interception and various rainfall parameters are analysed and the reliability of predictive equations assessed. Simple relationships appeared to be as valid for prediction as more complex ones, although in general the results were rather unsatisfactory.