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Importance of Organic Debris Dams in the Structure and Function of Stream Ecosystems
Abstract
Removal of all organic debris dams from a 175-m stretch of second-order stream at the Hubbard Brook Experimental Forest in New Hampshire led to a dramatic increase in the export of organic carbon from this ecosystem. Output of dissolved organic carbon (<0.50 @mm) increased 18%. Fine particulate organic carbon (0.50 @mm-1 mm) export increased 632% and coarse particulate organic matter (>1 mm) export increased 138%. Measurement of the standing stock of coarse particulate organic matter on streambeds of the Hubbard Brook Valley revealed that organic debris dams were very important in accumulating this material. In first-order streams, debris dams contain nearly 75% of the standing stock of organic matter. The proportion of organic matter held by dams drops to 58% in second-order streams and to 20% in third-order streams. Organic debris dams, therefore, are extremely important components of the small stream ecosystem. They retain organic matter within the system, thereby allowing it to be processed into finer size fractions in headwater tributaries rather than transported downstream in a coarse particulate form.
... If organic material is to be used by aquatic biota it needs to be retained within a stream, as does inorganic matter to form physical habitats . High retentiveness allows organic matter to accumulate and to be processed to small particles and dissolved organic carbon (DOC) before it is transported downstream (Bilby and Likens, 1980;Bilby, 1981;Naiman, 1982;Allan, 1995). "Shredders", who feed on CPOM, appear in greater abundance in streams or reaches which are retentive, ...
... High geomorphological complexity has been shown to increase retention of organic matter, (e.g. Sheldon and Thorns, 2006), as have various strictures such as wood jams (Bilby and Likens, 1980;Daniels, 2006), trees and large rocks (Harmon et al., 1986), shallow areas of channel over bars, and narrow sections of channel (Braudrick et al., 1997). Braudrick et al. (1997) propose that a stream's ability to retain wood of a given size is a function of its 'debris roughness,' (or 'wood roughness') which varies with the ratios of wood diameter/channel depth and wood length/channel width. ...
... (1989) found that wood jams were very important for reducing the distance travelled by leaves: 99% of leaves were retained in a section of the Buzzards Branch stream, southeastern USA, which had wood jams, whereas only 11 % were retained in a section with no jams (see Table 3.7). Wood jams therefore increase retention of CPOM (Bilby and Likens, 1980;Bilby, 1981), and hence increase the potential for nutrient cycling and detritus processing (Winterbourn and Townsend, 1980). Low velocity areas associated with large wood provide sites for propagule colonisation which may create islands of riparian vegetation (Fetherston et ai., 1995). ...
p>This thesis investigates geomorphological processes within the forested floodplain of the Highland Water, a small, lowland river in the New Forest, southern England. Geomorphological processes were monitored (a) before restoration, in order to define reference conditions, and (b) after restoration, in order to monitor the performance of the restoration against the reference conditions.
The results demonstrate that the restoration was successful at moving the restored system towards target reference conditions by re-connecting the channel and floodplain, and consequently floodplain geomorphological dynamics were increased after restoration. However, the restored floodplain was considerably more connected and more dynamic than an upstream semi-natural reference reach, indicating that the restored channel was perhaps undersized.
Floodplain channels were an important geomorphological feature observed on semi-natural floodplains, particularly in association with hydraulically effective wood jams. Experiments into sedimentation and erosion showed that overbank flow scoured the surface and distributed sediment, and rates of erosion and deposition were higher within floodplain channels than elsewhere on the floodplain surface. These channels were therefore a major control over the spatial distribution of energy and materials on the floodplain at the patch, feature and reach scale (10<sup>-1</sup> to 10<sup>2</sup> m).
The formation of in-channel wood jams, which force flow overbank, relies on the accumulation of wood. Experiments to investigate transport of small wood recorded travel distances ranging from 0 to over 1000 m. Shorter travel distances were associated with higher in-channel geomorphological diversity, particularly the presence of in-channel wood jams.
This thesis therefore provides a greater understanding of the geomorphological processes operating on a forested floodplain in conjunction with monitoring the performance of a river restoration project that incorporated a forested floodplain.</p
... The active channel and its margins can be a significant source or sink of fine-grained, organic-rich sediment (Skalak & Pizzuto, 2010). Although initially assumed to move rapidly downstream as washload (Garcia, 2007), fine-grained sediment is now recognized to move in a series of discrete steps (Bilby & Likens, 1980;Bonniwell et al., 1999) separated by periods of storage on channel margins that can approach 10 3 years for coarse suspended load (Pizzuto et al., 2014). Here, the channel margins are defined as those parts of the bankfull channel below the floodplain where fine sediment can collect. ...
... By this definition, channel margin areas include, but are not restricted to, the edges of the channel between the water's edge and the floodplain. Importantly, however, channel margin areas also include in-channel areas where fine sediment can collect, such as behind debris dams and large woody debris (Bilby & Likens, 1980;Skalak & Pizzuto, 2010). Subsequently, we refer to any fine sediment deposited within the channel as channel margin deposits. ...
... While sediment undoubtedly exchanges in both directions, the net transfer of sediment from the channel to the margins indicates that, in simplest terms, the channel cross section can be partitioned into two regions, an erosional region in the central channel and a depositional region in the channel margins. As noted earlier, especially in headwater systems, the depositional margins may also include in-channel areas where fine sediment collects such as behind debris dams (Bilby & Likens, 1980;Skalak & Pizzuto, 2010). However, to simplify the analysis, we conceptualize the stream as a central thalweg region where erosion dominates and a depositional region along the lateral edges ( Figure 1). ...
Input of organic matter into stream channels is the primary energy source for headwater ecosystems and ultimately carbon to the oceans and hence is an important component of the global carbon cycle. Here, we quantify organic‐rich fine sediment mobilization, transport, and storage in a Strahler fourth‐order stream during individual intermediate‐sized storm events. By combining measurements of fallout radionuclides (FRNs) ⁷Be and ²¹⁰Pb and stable water isotopes with a conceptual model of suspended load trapping by channel margins, we find that the channel bed was consistently a source of suspended load to the channel margins. Relative to storage on the channel margins, suspended load export increased through the spring and summer, perhaps related to the in‐channel decomposition of organic debris as indicated by its FRN exposure age and changing bulk δ¹³C composition. Trapping of suspended load by riparian margins limits sediment transport distances, which, given sufficient discharge to fully suspend the load, is nearly independent of stream discharge for sub‐bankfull discharges. Limited data indicate that the fractional size of the channel margins where trapping occurs decreases with increasing watershed area. Increasing transport length and decreasing fractional margin area with increasing watershed area results in a systematic downstream decoupling of the channel from local terrestrial organic matter exchange. These findings provide a framework for understanding suspended load dynamics in formerly glaciated regions where sediment production and fluxes are generally low and thus the annual input of organic debris is a major component of suspended load budget.
... Here, we define CPOM as organic matter 1-100 mm in diameter that does not meet the criteria of small wood, as defined by Galia et al. (2018). Freshwater ecosystems in headwater streams are highly dependent on stored CPOM as a food and energy source (Fisher and Likens, 1973;Bilby and Likens, 1980;Vannote et al., 1980). In many headwater streams, the majority of CPOM is terrestrial in origin; therefore, CPOM represents an important subsidy of organic matter and carbon to aquatic systems (Wallace et al., 1995;Turowski et al., 2016). ...
... When comparing CPOM yields at Como Creek and Gordon Gulch to CPOM yields at other sites from previous studies, there is not a clear pattern in CPOM yield between climate regions (Table 3). Annual CPOM yields for the 2022 water year at our study sites, calculated using our CPOM transport rate-discharge rating curves, were lower than those estimated elsewhere in previous studies (Table 3) (Bilby and Likens, 1980;Bunte et al., 2016;Turowski et al., 2016;Iroumé et al., 2020). Although the 2022 water year CPOM yield was lower than published estimates from other studies, the multi-year average CPOM transport rates for our study reaches were similar to previous studies, with the exception of lower average yield calculated for the Hi-ret reach ( Table 3). ...
Coarse particulate organic matter (CPOM; organic matter 1–100 mm in diameter, excluding small wood) stored in streams provides an important energy source for aquatic ecosystems, and CPOM transport provides downstream energy subsidies and is a pathway for watershed carbon export. However, we lack understanding of the magnitude of and processes influencing CPOM storage and transport in headwater streams. We assessed how geomorphic complexity and hydrologic regime influence CPOM transport and storage in the Colorado Front Range, USA. We compared CPOM transport during snowmelt in a stream reach with high retentive feature (e.g., wood, cobbles, and other features) frequency to a reach with low retentive feature frequency, assessing how within-a-reach geomorphic context influences CPOM transport. We also compared CPOM transport in reaches with differing valley geometry (two confined reaches versus a wide, multi-thread river bead) to assess the influence of geomorphic variations occurring over larger spatial extents. Additionally, we compared CPOM storage in accumulations in reaches ( n = 14) with flowing water or dry conditions in late summer and investigated how small pieces of organic matter [e.g., woody CPOM and small wood (>1 min length and 0.05–1 min diameter or 0.5–1 min length and >0.1 min diameter)] influence CPOM storage. We found that within-a-reach retentive feature frequency did not influence CPOM transport. However, valley geometry influenced CPOM transport, with a higher CPOM transport rate (median: 1.53 g min ⁻¹ ) downstream of a confined stream reach and a lower CPOM transport rate (median: 0.13 g min ⁻¹ ) downstream of a low gradient, multi-thread river bead. Additionally, we found that particulate organic carbon (POC) export (0.063 Mg C) in the form of CPOM was substantially lower than dissolved organic carbon (DOC) export (12.3 Mg C) in one of these headwater streams during the 2022 water year. Dry reaches stored a higher volume of CPOM (mean = 29.18 m ³ ha ⁻¹ ) compared to reaches with flowing water (15.75 m ³ ha ⁻¹ ), and woody CPOM pieces trapped 37% of CPOM accumulations. Our results demonstrate that the influence of geomorphic context on CPOM transport depends on the scale and type of geomorphic complexity, POC may be lower than DOC export in some headwater streams, and small woody organic material is important for trapping CPOM small streams.
... When large wood enters a stream and lodges, it forms a dam retaining additional organic matter such as smaller wood and leaves (Bilby & Likens, 1980). Woody debris increases the time available for biological processing of organic matter (Evans et al., 1993), significant for leaf litter processing (Bilby & Likens, 1980). ...
... When large wood enters a stream and lodges, it forms a dam retaining additional organic matter such as smaller wood and leaves (Bilby & Likens, 1980). Woody debris increases the time available for biological processing of organic matter (Evans et al., 1993), significant for leaf litter processing (Bilby & Likens, 1980). Wood dams can also create backwater pools with low water velocity, accumulating and controlling the movement of sediment (M. ...
... This conclusion might be extended to mountain streams in temperate climates, where major floods shortly follow autumn litterfall and winter temperatures limit litter breakdown. In fact, expressed in units of the forested catchment area, the transport rate of CPOM in the Leysse River (1.25 t yr −1 km −2 of forested catchment area) compares well with that (1.0 t yr −1 km −2 ) obtained by Bilby and Likens [57] in 0.1 km 2 catchments of the Hubbard Brook Forest (USA). In addition, CPOM yield was 2.4 times higher when debris dams were removed from this stream [57]. ...
... In fact, expressed in units of the forested catchment area, the transport rate of CPOM in the Leysse River (1.25 t yr −1 km −2 of forested catchment area) compares well with that (1.0 t yr −1 km −2 ) obtained by Bilby and Likens [57] in 0.1 km 2 catchments of the Hubbard Brook Forest (USA). In addition, CPOM yield was 2.4 times higher when debris dams were removed from this stream [57]. For two mountain streams draining 10 km 2 coniferous catchments, Bunte et al. [46] computed a ten-year average export of 2.1 t yr −1 km −2 of the forested catchment. ...
Transport of coarse particulate organic matter (CPOM) derived from forest litterfall has been hardly studied in rivers, unlike fine particulate organic matter (FPOM) or dissolved organic matter (DOM). Yet, many rivers are dammed or run into lakes, and there is growing evidence that CPOM accumulation in river delta participates substantially in ecological processes such as greenhouse gas emissions of lakes and reservoirs. We investigated the transport of CPOM and FPOM by the Leysse River (discharge from 0.2 to 106 m3 s−1) to Lake Bourget (France) in relation to aerial litter deposition, river network length, and discharge. Over a 19-month study period, the volume-weighted mean CPOM and FPOM concentrations were 1.3 and 7.7 g m−3, respectively. Most CPOM and FPOM transport occurred during major flood events, and there were power relationships between maximum discharge and particulate organic matter (POM) transport during these events. The annual export of CPOM (190 t AFDM) was 85% of the litter accumulation in autumn on permanent sections of the riverbed (224 t AFDM), which suggests that export is a major process compared to breakdown. Export of CPOM was 1.25 t yr−1 km−2 of the forested catchment area. This study highlights the need to account for long-range CPOM transport to describe the fate of litter inputs to streams and to quantify the organic matter input and processing in lakes and reservoirs.
... Our changes in stream water DOM during drought were only reflected in the soil solution (26-cm depth) in the case of DOC:DON, but not for DOC concentrations or DOM aromaticity. Thus, decreases in DOC concentrations and increases in DOC aromaticity in stream water during drought may be due to the altered in-stream processing of organic matter under drought (Bilby and Likens 1980). However, our measurements of soil solution were conducted only during the wet season (December-May); concentrations of DOM in soil solution might be lower at the beginning of a water year during drought, and this mechanism might also be responsible for the reduction in stream DOC during these climatic periods. ...
... Positive correlations between DOC concentrations in stream water and drainage density ( Figure 6B) were presumably due to increased transport of DOC from the uplands to streams under increased drainage density (Hope and others 1994), as upland is the main source of DOC in these low order streams (Moeller and others 1979;Hongve 1999). And the negative correlation (in WY 2009 only) between DOC concentrations in stream water and stream channel length may reflect the greater consumption of DOC during its transport within the stream (Bilby and Likens 1980;Kalé n 2007). ...
Understanding the transport of dissolved organic carbon (DOC) and nitrogen (N) as water flows through headwater basins is important for predicting downstream water quality. With increased recognition of climatic impact on nutrient transport, more studies are needed in headwater basins experiencing a Mediterranean-type climate, such as those of the Sierra Nevada, California. We analyzed water samples collected over 5 years from eight low-order and mixed-conifer watersheds to elucidate the temporal variation of water chemistry and evaluate their responses to prolonged drought and low-intensity forest thinning. We observed higher stream DOC concentrations in October compared to other months within water years prior to drought and thinning, suggesting the importance of antecedent moisture conditions on seasonal C export. In unthinned watersheds, stream DOC concentrations were lower (62%) and DOC aromaticity was higher (68 and 92%, depending on the index used) during drought compared to non-drought years. In thinned watersheds during drought years, stream water had higher DOC concentrations (66–94% in three consecutive years following thinning) and dissolved inorganic N (24%, in the third year following thinning) compared to unthinned watersheds during drought. Additionally, lower stream DOC concentrations were found in watersheds with higher elevations and lower drainage densities in the year with near-average precipitation; however, these correlations were not significant in years with greater or extremely low precipitation. Taken together, our results suggest that stream concentrations of DOC and dissolved N in Mediterranean headwater basins are extremely variable over time due to the high temporal climatic variabilities and periodic management practices.
... The influx of organic matter of all sizes resulting from floods may favor the development of several specific trophic groups, for example, filtering and gathering collectors, which feed on fine particulate organic matter (FPOM) (Cummins and Klug, 1979;Ward and Cummins, 1979), shredders, preference of which is coarse particulate organic matter (CPOM) with associated colonizing fungal-bacterial systems (Kostalos and Seymour, 1976), and scrapers (grazers), feeding on periphyton that grows on submerged large woody debris (LWD) (Merritt et al., 2017), as well as predators that benefit from the abundance of their potential preys (Czarnecka and Miler, 2018). Moreover, the decomposition of large organic particles, especially LWD, provides a continuous supply of organic matter of smaller sizes (Scherer, 2004), which increase structural complexity of habitats, or resource availability (i.e., niches) (O'Connor, 1991), and also act as a continuous food source for macroinvertebrate communities, though the food source derived from LWD is often ignored by ecologists (Booth and Fox, 2004;Lassettre and Harris, 2000). Due to the long decay times of LWD, which range from decades to hundreds of years (Hyatt and Naiman, 2001;Lloyd et al., 1991;Murphy and Koski, 1989;Swanson et al., 1984), LWD and its effects on food supply and habitat can persist for a considerable length of time unless it is removed from streams. ...
... Benke et al., 1984;Johnson et al., 2003;Lyon et al., 2009;Ogren and King, 2008;Pitt and Batzer, 2010;Rinella and Feminella, 2005) seems to corroborate this hypothesis. Macroinvertebrate abundance and richness generally increase with the introduction of CWD and LWD, owing to the high structural complexity of this habitat, the food it supplies, and its capacity for retaining particulate organic matter (Bilby and Likens, 1980;Flores et al., 2011;Lassettre and Harris, 2000;Lemly and Hilderbrand, 2000;O'Connor, 1991;Scholz and Boon, 1993;Schulze and Walker, 1997). Several authors have found that the highest abundance and richness of macroinvertebrates occurs at the intermediate stage of decomposition of woody debris, with a dominance of filteringgathering collectors, shredders, and scrapers (grazers) at various stages of decay (e.g. ...
We describe the multi-decadal delayed effects of flood on macroinvertebrate community structure using 33 years of monitoring data on macroinvertebrates, water quality, and climate, and 51 years of hydrological data, spanning 2300 km of the Murray River, Australia. We used distributed lag nonlinear models in a four-step analytical process, including 1) modelling macroinvertebrate community structure, represented as a set of principle coordinate axes, as a function of a lagged hydrologic index and other environmental variables using distance-based redundancy analysis 2) visualizing the patterns of delayed effects of flows on the PCO axes, 3) modelling the abundances of groups of taxa along individual PCO axes, and 4) combining the two sets of models in a counterfactual analysis to predict the community structure under flood and no-flood scenarios to describe the multi-decadal trajectory of the community following a flood. Our findings show an increase in abundance of most taxa of filtering-gathering collectors, scrapers, and shredders in the long term that implicates an influx of organic matter of all sizes, from particulate organic matter to coarse and large woody debris, that serves directly or indirectly as a food resource and/or habitat. Our approach enabled the isolation of a flood impact from the confounding effects of other flow events and environmental variables, overcoming a substantial challenge in ecohydrological studies.
... Woody debris in streams influences a wide array of abiotic features as well as biotic community structure and function (Harmon et al. 1986). These include (1) rapid dissipation of stream energy in high-gradient systems (Heede 1972, Bilby and Likens 1980, Smith et al. 1993a, (2) reduced current velocities (Trotter 1990), (3) increased retention of particulate organic matter, which may also provide food for invertebrates (e.g., Bilby and Likens 1980, Speaker et al. 1984, Smock et al 1989, Trotter 1990, Wallace et al. 1995a), (4) substrate for invertebrates (Nilson and Larimore 1973, Benke et al. 1984, Smock et al. 1989, and (5) modification of stream habitat and benthic community structure (Molles 1982, Huryn and Wallace 1987a, Smock et al. 1989, Wallace et al. 1995a). ...
... Woody debris in streams influences a wide array of abiotic features as well as biotic community structure and function (Harmon et al. 1986). These include (1) rapid dissipation of stream energy in high-gradient systems (Heede 1972, Bilby and Likens 1980, Smith et al. 1993a, (2) reduced current velocities (Trotter 1990), (3) increased retention of particulate organic matter, which may also provide food for invertebrates (e.g., Bilby and Likens 1980, Speaker et al. 1984, Smock et al 1989, Trotter 1990, Wallace et al. 1995a), (4) substrate for invertebrates (Nilson and Larimore 1973, Benke et al. 1984, Smock et al. 1989, and (5) modification of stream habitat and benthic community structure (Molles 1982, Huryn and Wallace 1987a, Smock et al. 1989, Wallace et al. 1995a). ...
... Allochthonous coarse particulate organic matter (CPOM), commonly in the form of autumn-shed leaves, supplies most of the energy to first order streams in eastern US deciduous forests [12,13]. Retention of this energy in headwaters is often driven by large woody debris from riparian forests that trap CPOM and sediments, creating wood jams that operate as bioenergetic hotspots [8,11,14] and influence nutrient cycling, microbial populations, and macroinvertebrate densities locally and downstream [15][16][17][18][19][20]. Retained CPOM can be transformed into dissolved organic matter (DOM) by leaching [21] or broken down into fine particulate organic matter (FPOM) by mechanical or biological processes. ...
The forested landscape of New England (USA) was dramatically altered by logging during the nineteenth and early twentieth centuries. Although the northern temperate forests of the region have largely regenerated, the streams and rivers remain impacted. The loss of terrestrial wood, organic material, and nutrient inputs during the forest regeneration period has affected habitat quality and biotic communities, most notably in small headwater streams. The same waterways are further impacted by now undersized stream crossings, mostly culverts associated with old infrastructure that alter hydrology and sediment transport; moreover, these culverts have created barriers to the movement of riverine organisms. We synthesize literature on headwater stream wood additions and culvert removal in North America and discuss observed patterns in organic matter, benthic macroinvertebrates, and Brook Trout (Salvelinus fontinalis) from before and after wood additions and stream-crossing enhancements in a previously logged watershed in New England. There were minimal changes to habitat and substrate two years after restoration efforts. However, streams with wood additions retained a higher density of rafted organic matter and had significantly higher benthic macroinvertebrate density. Additionally, two years after restoration, one year-old Brook Trout were significantly longer in restored streams than prior to restoration. Collectively, these results document a relatively rapid increase in organic matter retention, macroinvertebrates, and Brook Trout size, soon after restoration efforts.
... As integral elements of instream structure, stream pools and large woody debris contributed to explaining all aspects of otter habitat selection and were particularly relevant for breeding site selection. Large woody debris is a recognised key component of river aquatic habitats since it promotes stepped-channel profiles, pool habitats, energy flow dissipation and organic matter accumulation, and overall provides high levels of physical diversity (Bilby and Likens 1980;Brooks et al. 2004;Roni et al. 2015), and are associated to increases in river fish, amphibian and invertebrate populations (Thevenet and Statzner 1999;Dolloff and Warren 2003;Kail et al. 2007;Schneider and Winemiller 2008;Thompson et al. 2017;Dalbeck et al. 2020), which are the main prey for otters (Mason and Macdonald 1986;Krawczyk et al. 2016). The link between otters and large woody debris could be particularly relevant in low and medium-flow river reaches, where this feature has an even greater role in shaping habitat structure and local ecosystem functioning (Dominguez and Cederholm 2000;Anlanger et al. 2022). ...
Assessing habitat selection is essential to protecting threatened species but also to understand what factors influence species that, although globally not currently in decline, act as flagships of their ecosystems and remain highly vulnerable to human impacts, such as the Eurasian otter. This paper examines otter habitat selection at the river reach scale in two heavily anthropized river basins. Both river basins encompass a wide spectrum of human pressures and biogeographic units, which offers an excellent opportunity to assess otter responses to anthropogenic activities in different scenarios. Through two modelling approaches (structure-agnostic way and a priori hypothesized habitat factors) we demonstrate that otters currently inhabiting these human-dominated landscapes show a trade-off between a preference for highly productive areas and for well-structured and safe areas. We suggest that habitat simplification and human disturbance, which were of minor relevance to the dramatic decline of otter populations in the 20th century, are emerging as potential threats in the context of worldwide increasing land use intensification. Furthermore, we found that otter habitat requirements were remarkably more stringent for breeding site selection than for occurrence, particularly concerning variables related to human disturbance. The results of this work provide tools for integrating ecological criteria oriented to effective otter conservation into river management in human-dominated landscapes, as well as serving as methodological support for lowland river restorations. Our results suggest that long-term otter conservation in anthropized rivers will depend on ensuring the availability of habitat patches that maintain sufficient structural complexity away from intensely outdoor recreational activities.
... Individuals undergoing metamorphosis (i.e., adult recruitment) may also be particularly vulnerable to floods because they undergo abrupt and major physiological and physical transformations (King-solver et al. 2011;Rose et al. 2021), all while they are not able to leave the stream to escape flooding. In addition to direct physical effects on individuals, flooding and associated shear stresses can mobilize instream wood and remove allochthonous material from the stream channel, reducing secondary production (i.e., in-stream prey resources; Bilby and Likens 1980;Wallace et al. 1997;Wohl 2010). This reduction in prey resources may exacerbate intraspecific competition and predation in the nutrientlimited headwater streams of Hubbard Brook (Hall et al. 2001;McGuire et al. 2014), ultimately reducing survival rates, particularly in G. porphyriticus larvae (Resetarits 1995). ...
... et al. 2016). About four-fifths of the original protocol has been used, supplemented by measuring woody debris jams (WDJ) in the channel, which strongly influence hydromorphological features (Bilby, R.E. and Likens, G.E. 1980;Dahlström, N. and Nilsson, C. 2004;Galia, T. and Hradecky, J. 2014). Following the original protocol's logic, the WDJ parameters survey was structured to collect the data detailed below. ...
Small catchments in mountainous regions affect downstream rivers as a primary source of sediment supply and also generate flash swasfloods, especially during extreme events. These floods have significantly shaped the catchments of small streams in the Mecsek Hills and some rural areas over the past two decades. However, there has been no previous study examining the hydromorphology of headwater catchments in low mountain environments in Hungary. The present study was meant to investigate the fundamental hydrogeomorphological properties of a first-order catchment. A customary and detailed GIS survey of 50-metre sections was aimed at deciphering flash flood vulnerability and geomorphic interrelations within a micro watershed. We found moderate susceptibility to flash floods compared to the whole Mecsek Hills. Stable large woody debris jams were identified during the field survey as major geomorphic channel features functioning as natural barriers which drive channel evolution and reduce flood hazards.
... These processes are important for the formation of in-stream fish habitat (Brierley, Fryirs 2022;Beechie et al. 2010;Biron et al. 2014;Choné and Biron 2016), including the formation and maintenance of pools, riffles, bars, and side channels (Allan 2004; Williams et al. 2020). Riparian zones, sediment, and debris transported from upstream contribute to woody debris, gravel patches, and a diverse range of sediment sizes (Frissell et al. 1986), which provide numerous benefits: shelter (Bjornn et al. 1991;Culp (Sweka and Hartman 2006) and fish food (source of invertebrates) (Inoue and Nakano 1998;Kratzer 2018); create pools (Berg et al. 1998) and habitat diversity (Bilby and Likens 1980;Roni 2001); and, increase bank stability (Keller and Swanson 1979) and nutrient input (Johnson et al. 2005). ...
Habitat degradation is one of the major reasons for freshwater species decline. Hydrogeomorphological processes (such as sediment transport, bank erosion, and flooding) operate at the catchment scale and determine habitat features in river reaches. However, habitat quality indices and restoration for freshwater fish species are often implemented at small spatial scales of a few hundred metres. The Morphological Quality Index (MQI) considers fluvial processes at larger scales as well as channel forms, human impacts, and historical changes, but few studies have assessed its relevance for ecosystem health. We investigated relationships between the MQI, habitat quality (using the Qualitative Habitat Evaluation Index, QHEI), land cover, and fish metrics (number of fish species, index of biotic integrity (IBI), and trout biomass) in 26 salmonid streams in Aotearoa New Zealand and Southern Ontario, Canada. We found a significant correlation between the MQI and QHEI, and both metrics were correlated with urban and native forest proportion in the catchment. However, we found no relation between the MQI and the proportion of agricultural land in the catchment, while the QHEI was correlated with agricultural land in the riparian zone, highlighting the importance of vegetated riparian buffers in providing fish habitat. Establishing a strong correlation with fish metrics remains challenging. Nevertheless, a modified MQI targeting ecological health could be used as an effective management tool for aquatic conservation.
... Early studies focused on wood loading and the geomorphic effects of wood on channel form and hydraulics (Hicken, 1984;Lienkaemper and Swanson, 1987;Gregory and Gurnell, 1988). Soon after, ecologists began to examine the influence of wood on fish populations, organic matter storage, macroinvertebrates (Anderson et al., 1978;Bilby and Likens, 1980;Bisson et al., 1987); and since the 1990s, research expanded to include the importance of dead wood for terrestrial invertebrate, bird, and mammal communities in riparian areas along stream margins (Maser and Sedell, 1994;Trevarrow and Arismendi, 2022). ...
We quantified temporal dynamics of wood storage, input, and transport in a third-order stream over a 23-year period in adjacent old-growth and second-growth forested reaches in the Cascade Mountains of Oregon. Numbers and volumes of large wood (i.e., standing stock) in the old growth reach were more than double and triple, respectively, than those in the second growth. Annual inputs of large wood were highly variable. Wood numbers delivered into the old-growth reach were 3X higher and wood volume 10X greater than that of the second growth. Movement of number and volume of logs did not differ significantly between the two reaches. Less than 3% of the logs moved in most years, and the highest proportion moved in the year of the 1996 flood (9% in old growth and 17% in second growth). The majority of wood occurred in accumulations (i.e., jams) in both reaches. The second-growth reach lacked major jams, but 29% of the logs in the old growth were in full-channel spanning jams. Long-term observations of annual storage, input, and movement best reveal the dynamics of wood rather than static representations of the characteristics of wood. Input events and transport of wood in Mack Creek were episodic and varied greatly over the 23-yr study, which illustrates one of the major challenges and opportunities for understanding the cumulative dynamics of wood in streams.
... The debate concerning deadwood availability outside conservation areas has largely been limited to its shortage caused by over-harvesting (Arnold 1978, Anderson & Fishwick 1984, Bembridge & Tarlton 1990, Shackleton 1993b, and its exploitation reported as leading to habitat destruction for woodinhabiting organisms and deforestation (Mainguet 1991). Little attention, however, has been given to the ecological effects of deadwood harvesting or the role of deadwood in maintaining ecological integrity and biodiversity (Banerjee 1967, Bilby 1981, Bilby & Likens 1980). This oversight is despite the well-recognised fact that the presence of wood-inhabiting organisms in deadwood attracts other organisms that are either predators of these organisms or their larvae (Fager 1968, Harmon et al. 1993. ...
... The debate concerning deadwood availability outside conservation areas has largely been limited to its shortage caused by over-harvesting (Arnold 1978, Anderson & Fishwick 1984, Bembridge & Tarlton 1990, Shackleton 1993b, and its exploitation reported as leading to habitat destruction for woodinhabiting organisms and deforestation (Mainguet 1991). Little attention, however, has been given to the ecological effects of deadwood harvesting or the role of deadwood in maintaining ecological integrity and biodiversity (Banerjee 1967, Bilby 1981, Bilby & Likens 1980). This oversight is despite the well-recognised fact that the presence of wood-inhabiting organisms in deadwood attracts other organisms that are either predators of these organisms or their larvae (Fager 1968, Harmon et al. 1993. ...
... In fact, the pace of increase in water demand is many times that of population growth, necessitating the construction of massive hydraulic structures, which cause significant non-uniformity in flow. 'High Dams' and 'Constricted Bridges' should be followed by efficient management and downstream river flow restoration; because these structures are mainly responsible to degrade the ecological status of river systems (Bilby and Likens 1980;Jansson et al. 2000;Kingsford 2000;Baird and Barney 2017;Bhaumik et al. 2017). The current consensus is that minor hydraulic structures should be used to restore the river flow if large hydraulic structures disrupt it. ...
... Forest canopy adjacent to single-threaded headwaters may mediate temperatures and provide allochthonous inputs that support detrital-based food webs (Meyer & Wallace, 2001). On the other hand, legacy effects in the form of simplified habitat with reduced capacity to retain forest litter inputs (Bilby & Likens, 1980;Muotka Webster et al., 1994) can alter the biological structure and function of channelized streams (Lepori et al., 2005;Pilotto et al., 2018) regardless of canopy cover from reforested riparian zones (Harding et al., 1998). ...
Legacies of past land use persist today in the form of incised, single-threaded stream channels with dramatically different hydrologic functions of pre-colonial stream valleys. Restoration practices that aim to return lost hydrologic functions by re-establishing floodplain and groundwater connections should result in stream habitat and biological assemblages that differ from modern, single-threaded channels. The aim of this case study was to identify attributes of macroinvertebrate assemblages that might serve as biological indicators of improved hydrologic functions following the restoration of a stream-wetland complex, similar to a Stage 0 restoration, of a headwater valley in the Western Allegheny region of the USA. We monitored hydrologic functions and macroinvertebrate assemblages from stream reaches of a restored and unrestored site over multiple years during the early years following restoration. Reduced bed mobility and increased flow duration indicated improved hydrologic functions from the restored site. Aggregate metrics that capture functional attributes of macroinvertebrate assemblage (i.e., density and biomass) were consistently greater from the restored site. EPT biomass from restored pools was 3–4 × greater than amounts from the unrestored site as a result of consistently greater mayfly abundance. Restored pools also supported a subassemblage of taxa with life history attributes that are aligned with habitat conditions created from improved hydrologic functions. Results from this case study demonstrate the importance of habitat-specific sampling designs that report the absolute abundance of potential biological indicators. Findings from this case study should help guide the development of rapid biological indicators of improved hydrologic functions.
... Stream restoration is implemented to create habitat, improve water quality, reduce flood impacts downstream, and in some cases stabilize channels and banks (Bernhardt et al., 2005;Mondal & Patel, 2018). Stream restoration practices can be grouped into three main categories: channel alterations, floodplain reconnection, and Stage 0. Channel alterations (e.g., construction of weirs, cross-vanes, pool-riffle sequences, meanders) induce exchange into channel beds and banks (Hester & Doyle, 2008), stabilize the bed, and create specific habitat types (Bilby & Likens, 1980;Diez et al., 2000;Roni et al., 2006;USDA, 2007). Floodplain reconnection aims to reestablish the hydraulic function of floodplains by allowing increased access of water for conveyance and temporary storage during larger storm events (Opperman et al., 2009), traditionally accomplished by lowering channel banks, removing or breaching levees, raising the channel bed, and/or creating riparian wetlands (McMahon et al., 2021;Opperman et al., 2009;Orr et al., 2007). ...
River flooding impacts human life and infrastructure, yet provides habitat and ecosystem services. Traditional flood control (e.g., levees, dams) reduces habitat and ecosystem services, and exacerbates flooding elsewhere. Floodplain restoration (i.e., bankfull floodplain reconnection and Stage 0) can also provide flood management, but has not been sufficiently evaluated for small frequent storms. We used 1D unsteady Hydrologic Engineering Center's River Analysis System to simulate small storms in a 5 km‐long, second‐order generic stream from the Chesapeake Bay watershed, and varied % channel restored (starting at the upstream end), restoration location, restoration bank height (distinguishes bankfull from Stage 0 restoration), and floodplain width/Manning's n. Stream restoration decreased (attenuated) peak flow up to 37% and increased floodplain exchange by up to 46%. Floodplain width and % channel restored had the largest impact on flood attenuation. The incremental effects of new restoration projects on flood attenuation were greatest when little prior restoration had occurred. By contrast, incremental effects on floodplain exchange were greatest in the presence of substantial prior restoration, setting up a tradeoff. A similar tradeoff was revealed between attenuation and exchange for project location, but not bank height or floodplain width. In particular, attenuation and exchange were always greater for Stage 0 than for bankfull floodplain restoration. Stage 0 thus may counteract human impacts such as urbanization.
... Previous work on riparian forest harvesting by Kreutzweiser et al. (2004) showed that riparian forest composition did not alter leaf litter accumulations in streams, which they attributed to continuous drifting input from upstream sources. Downstream transport of leaf litter can outweigh direct inputs from adjacent riparian zones, especially as stream order increases along a watershed continuum (Bilby and Likens 1980;Vannote et al. 1980;Bretschko 1990). Therefore, a lack of correlation between aquatic leaf litter and adjacent riparian trees may simply reflect a greater impact of downstream transport of leaf litter rather than immediate lateral inputs from the banks. ...
Emerald ash borer (EAB), has killed millions of ash trees in the United States and Canada, yet impacts on terrestrial-aquatic linkages are largely unknown. Ash tree death along streams creates canopy gaps, increasing light to riparian plants and potentially affecting organic matter subsidies. Six EAB-related canopy gaps along streams across a gradient of timing of EAB invasion in Michigan were characterized for characterized coarse woody debris (CWM), terrestrial and aquatic leaf litter and their associated bacterial communities, and macroinvertebrates upstream, downstream, and at the center of the gap. Stream sites downstream of EAB-related canopy gaps had significantly lower dissolved oxygen and macroinvertebrate diversity than sites upstream and at the gaps. Yet there was no difference in CWM or aquatic leaf litter, likely due to downstream movement of organic matter from upstream riparian sources. Low abundance bacterial amplicon sequence variants unique to gap or forest were detected in leaves and leaf litter, suggesting EAB-related canopy gaps altered leaf associated bacterial communities. Overall, EAB invasion indirectly impacted some variables, while organic matter dynamics were resistant to change.
... In larger streams the wood or wood-created habitat fell to some 12%. Bilby & Likens (1980) also showed that debris dams contained 75% of the standing stock of organic matter in the first order streams of the Hubbard Brook system in the USA. This fell to 58% and 20% in second and third order streams respectively. ...
p>A detailed study of forested streams in the New Forest in southern England has shown that the accumulation of coarse woody debris (CWD) in channels affects the within-reach structure of the stream channel and the abundance, diversity and community structure of the fish fauna. Samples in a priori selected habitat units, namely 43 riffles, 80 pools and 39 CWD accumulations showed significantly higher densities of fish in the riffles than in the other habitat units and significantly higher biomass in the CWD accumulations. Effects on each of the six species present differed. There was a significant correlation between maximum size of salmonids and abundance of CWD in a habitat unit.
Habitat diversity and fish diversity were lowest in riffles and dense CWD accumulations and highest in habitats with moderate amounts of CWD present. Communities of habitat units could not be separated clearly based on the a priori selection, but both the physical structure and fish communities showed a gradient of change from an erosional to a depositional condition with riffles and the deepest CWD habitats as the opposing extremities of the gradient. On the reach scale habitat diversity was related to the abundance of CWD but overall fish diversity and abundance were not. Salmonid density was negatively correlated with CWD abundance on the reach scale. The fish community of the forested streams was highly structured and characteristic of a deterministic community relatively undisturbed by human influences. A simple, partly hypothetical model is proposed to predict the effects of varying abundance of CWD on the fish communities of the forested streams. Future stream habitat management is discussed and potential applied and fundamental topics for research outlined.</p
... (a) Function (i) geomorphological processes; (e.g. Bilby and Likens, 1980;Fetherston et al., 1995;Hogan, 1986 andHogan et al., 1995;Hupp, 1999;Osterkamp, 1985 andKeller and Swanson, 1979;Piegay and Gumell, 1997;; ...
p>Previously published research has not explicitly investigated lateral and vertical accretion on lowland wooded floodplains. This thesis describes how these lacunae were addressed with three field campaigns undertaken along the Highland Water, a small lowland stream that is surrounded by one of the largest areas of uncleared woodland in England.
Firstly, a catchment-scale survey identified the geomorphology of this lowland forested floodplain. Visual observations were made of floodplain features and channel characteristics; and the width of the channel, the area most recently flooded, and the maximum extent of the floodplain were measured. This survey provides the first inventory of geomorphological features found on a wooded lowland floodplain. The channel and floodplain were split into reaches that were observed to be geomorphologically homogeneous. The outcomes from this survey were that management and in-channel accumulations of woody debris appeared to be primarily responsible for changes in floodplain formation.
A second survey, similar to the first but more focused upon lateral channel change, provided evidence to suggest that lateral accretion was frequently determined by vegetation. Rates of channel change were found to be extremely low, except in the vicinity of in-channel accumulation of debris, which caused change at the reach scale (10<sup>1</sup>-10<sup>2</sup>m). In contrast with cleared floodplains, lateral river accretion was not focused at meander apices, but instead within zones of discrete floodplain activity directly caused by in-channel blockages of woody debris. This debris also caused significant areas of overbank flow to occur.
Thirdly, reach-scale experiments into floodplain sedimentation determined that vertical accretion did occur, but the pattern and amount of sediment deposited was a direct result of floodplain vegetation, particularly trees and LWD.
These controls of vegetation upon fluvial and floodplain processes also have implications for long-term landscape development and may explain the palaeoenvironmental history of many lowland floodplains. The findings from this thesis could also be used to design and implement sustainable forest floodplain management practices.</p
... In the Pacific Northwest, headwater streams receive most of their energy from organic matter inputs (Cummins et al. 1983;Bilby and Bisson 1992) as shading from riparian vegetation generally limits autotrophic production (Richardson and Danehy 2007). Macroinvertebrate assemblages typically consist of those specialized in shredding and collecting particulate organic matter, which is retained in depositional areas upstream of wood dams (Bilby and Likens 1980;Bilby 1981;. Timber harvest has the potential to shift the energy balance of these streams through a reduction in organic matter inputs and increase in insolation and primary production (Bilby and Bisson 1992;Richardson and Danehy 2007;Warren et al. 2016). ...
... However, questions remain about the types and magnitudes of disturbances required to cause significant LW deposition onto floodplains. In-channel CPOM dynamics have been well-studied (Bilby & Likens, 1980;Iroumé et al., 2020;Quinn et al., 2007;Wallace et al., 1995;Wohl et al., 2019), but we lack understanding of CPOM deposition onto floodplains during disturbances. ...
Organic matter dynamics (entrainment, transport, deposition) can influence ecogeomorphic complexity in rivers. However, the depositional controls on downed, large wood (LW) and coarse particulate organic matter (CPOM) on floodplains have rarely been assessed. We investigate the influence of different disturbance histories, as well as geomorphology and forest stand density, on the deposition of LW and CPOM accumulations, or jams, between two adjacent drainages (West Creek, North Fork Big Thompson) in the semi-arid Colorado Front Range, USA. Both basins recently experienced an extreme flood, but West Creek experienced a larger flood peak as well as a recent upstream fire. We also analyse jam fabric (LW piece orientation) between floodplain and in-channel jam types. We measured LW and CPOM jams on the North Fork to compute jam frequencies (jams ha⁻¹) and loads (volume per area; m³ ha⁻¹), and we compare these data to a previously published dataset from West Creek. Average floodplain LW jam frequencies (70.4 jams ha⁻¹) and loads (678.6 m³ ha⁻¹) on West Creek were significantly higher than on the North Fork (frequency: 14.8 jams ha⁻¹; load: 94.3 m³ ha⁻¹). Average floodplain CPOM jam frequencies (West Creek: 19.0 jams ha⁻¹; North Fork: 15.1 jams ha⁻¹) and loads (West Creek: 10.70 m³ ha⁻¹; North Fork: 9.98 m³ ha⁻¹) were not significantly different between basins. A larger flood peak, likely enhanced by a recent upstream fire and a more confined valley bottom, resulted in greater deposition of LW jams on West Creek compared to the North Fork. Geomorphic characteristics, such as valley confinement and slope, also influence jam frequencies and loads. Floodplain jam types oriented parallel to the stream were significantly different than other jam types. This work will inform river restoration efforts using wood and organic matter and provide insight on the transport and depositional processes influencing floodplain LW jam formation.
... Prior research has shown that trees with root wads display much lower levels of mobility due to their increased roughness, the substantially larger size (diameter) of the root wad relative to the trunk, and the subsequent necessity for deeper flows in order to mobilize them (Bertoldi et al., 2014;Curran, 2010;Davidson et al., 2015). This observation could have important implications for future recovery/reestablishment of pre-flood LW load dynamics such that jam frequency (and subsequently relative wood volume) could increase in the years following an extreme flood such as this due to the increased abundance of root wads in the channel, which are less likely to mobilize in subsequent, lower-intensity events, and which often serve as the key members upon which larger jams form Bilby & Likens, 1980;Braudrick & Grant, 2000). However, the fate of the newly deposited LW pieces, including those with root wads present, and whether or not they will remain stable enough to form jams during subsequent events is in large part dependent on the transport capacity of the channel. ...
This research investigates impacts of an extreme flood on recruitment and transport of large wood (LW) in sub-basins of the North Fork River, Missouri. Data collection took place two months after a >500 year flood to characterize LW conditions before natural recovery processes could obscure impacts. We used sites from previous LW studies in the region as reference to help identify flood impacts. Results showed 1) LW load volumes were no different than reference sites, but individual LW pieces comprised a greater percentage of the total load, 2) a high proportion of pieces at flood-impacted sites contained root wads, 3) transport capacity of the flood-impacted sites was high compared to reference sites, and 4) LW recruitment increased exponentially with flood magnitude. These results suggest that extreme floods have a significant impact on the composition of the LW load, and that geomorphic impacts of such floods may result in enhanced transport capacities. Based on these findings, we present two possible post-flood LW response/recovery scenarios; one in which elevated transport capacity serves to speed system recovery to the pre-flood LW regime, and one in which the enhanced LW piece composition results in a new post-flood LW regime with an enhanced load.
... Removal of vegetation in the catchment creates flashier stream conditions, marked by more intense moments of high flow and velocity and lower base flow (Bradshaw et al., 2007;Recha et al, 2012). The loss of large wood leads to increased stream velocity and fewer debris dams (Bilby & Likens, 1980;Wantzen, 2006). Increased sediment loads and more frequent moments of high stream velocity scour substrates of periphyton, damage the roots of aquatic vegetation (Wantzen, 1998), and increase the rate that organic material is flushed downstream, further decreasing availability of organic material to biota. ...
Recent waves of illegal deforestation for cattle pasture are damaging the Indio Maíz Biological Reserve and Rama-Kriol Territory of Nicaragua, with negative consequences to aquatic ecosystems and the people they support. This study creates a framework for how deforestation from cattle ranching causes shifts in stream community structure, mediated by changes in stream habitat over time. It integrates temporally explicit land use information with stream habitat, macroinvertebrate, freshwater shrimp, and fish community data to assess impacts of cattle ranching on 15 headwater streams. The deforestation history measure (DHM), a product of deforestation amount and time since deforestation for each catchment, strongly predicted stream habitat and biotic responses. Delayed effects of land-use change such as decreased allochthonous inputs (large wood, debris) and increased bank destabilization, sedimentation, flashiness, and the scouring effect were apparent in longer deforested catchments, causing lower richness and density and higher evenness of macroinvertebrates; lower shrimp abundance; and distinct changes in fish and invertebrate community composition. Both recently and longer deforested catchments had degraded riparia and smaller sized game fish. Otherwise, recently deforested catchments were more similar to forested catchments. Nicaragua’s understudied primary rainforest ecosystems should be high priority for research and conservation before they are lost.
... The natural input of coarse woody debris (CWD) from the surrounding catchment influences stream ecosystems in a variety of ways (Harmon and others 1986). CWD dams can shape channel morphology (by altering water velocity and streambed erosion patterns, and dissipating energy), increase hydrological heterogeneity (by creating backwaters and eddies), facilitate the deposition and retention of organic matter (Naiman and Sedell 1979;Bilby and Likens 1980;Smock and others 1989), and provide habitat surfaces for biofilm algae and microbes and larger organisms (Gregory and others 2003). Nutrient uptake rates (retention) tend to be higher in association with CWD than other stream habitats (Munn and Meyer 1990;Hoellein and others 2009) and increase after experimental wood additions (Wallace and others 1995;Roberts and others 2007b) but not in all cases (for example, Hoellein and others 2012). ...
We evaluated the ecological effectiveness of an in-stream restoration project involving coarse woody debris (CWD) additions to streams along an upland soil and vegetation disturbance gradient at the Fort Benning Military Installation near Columbus, GA. We examined short-term (immediate effectiveness) and longer-term (sustainability) responses to CWD additions by measuring ecosystem metabolism rates in 8 streams quarterly over a 6-year period, including 3 years before (2001–2003) and 3 years after (2004–2006) CWD additions that were made to half of the streams. Ecosystem respiration (ER) rates in most CWD addition streams increased relative to control streams from spring 2004 through autumn 2005, suggesting heterotrophic bacteria were the initial responders to CWD additions. Gross primary production (GPP) rates remained low (typically < 0.3 g O2 m−2 d−1) but increased in some CWD addition streams relative to control streams in spring 2004 and 2005. The magnitude of ER increases in CWD addition streams during the first two years post-addition increased with catchment disturbance intensity, indicating that more heavily disturbed streams responded most strongly to restorations—an important consideration when targeting future restoration locations. Because restorations did not address actual upland disturbance, continued high erosion rates resulted in 32–77% of the added CWD being buried by year two and a corresponding return of GPP and ER rates to pre-CWD addition levels by year three. If restoration projects do not adequately address the source of catchment disturbances, CWD additions will provide only short-term increases in streambed structure and stability, hydrodynamic complexity, and nutrient and organic matter processing and retention.
... The primary mechanisms of change are: 1) altering the proximal forest canopy that provides OM inputs to the stream (Fig. 4d); 2) increasing sunlight on the stream allowing greater algal growth, and 3) altering dissolved organic carbon inputs from runoff and shallow groundwater inputs from adjacent forests. Direct removal of vegetation adjacent to stream channels will substantially reduce particulate OM until vegetation regrows (Webster et al., 1992), with an even longer delay for large wood inputs (Bilby and Likens, 1980;Verry et al., 1999). Log jams may become century-scale legacies of past riparian harvest on large OM (Wohl and Goode, 2008). ...
Forest management guidelines are designed to protect water quality from unintended effects of land use changes such as timber harvest, mining, or forest road construction. Although streams that periodically cease to flow (nonperennial) drain the majority of forested areas, these streams are not consistently included in forest management guidelines. This paper reviews management guidelines for nonperennial (intermittent and ephemeral) streams draining temperate forests in the continental U.S., evaluates potential impacts of land use activities on ecosystem services provided by these streams, and identifies information needed to incorporate nonperennial streams into water quality protection practices. For federally administered lands, national management guidance is deliberately nonprescriptive, deferring to regional and forest-level recommendations for both perennial and nonperennial streams. Most state guidelines recommend riparian management zone (RMZ) protection for perennial streams (48/50 states) and intermittent streams (45/50 states), but only Alaska and West Virginia require RMZs around ephemeral streams. Based on the National Hydrography Dataset, an average of 58% of forested land area in the U.S. drains to nonperennial headwater streams, making these stream types the most common connectors between forested lands and the aquatic system. Land uses that modify flow regimes in these streams can affect sediment and organic matter transport and distribution, stream temperature dynamics, and biogeochemical processing. Nonperennial streams also provide material subsidies to downstream waters and serve as temporary habitats for some aquatic species. However, limited research has examined how forest land uses affect ecosystem services and biota in these streams. Therefore we highlight a set of key questions about nonperennial streams in forests, not the least of which is simply understanding where headwater stream channels are located and associated patterns of flow duration. Although many questions remain, we also note where recent advances in data collection, modeling and process-level research provide opportunties to resolve uncertainties around nonperennial streams in forested landscapes of the continental U.S.
... Wood also acts as an important surface for the development of stream biofilms (e.g., Hax & Golladay, 1993;Tank & Winterbourn, 1996;Vaz et al., 2014;Hellal et al., 2016), as an attachment site and refuge for macroinvertebrates (e.g., Benke & Wallace, 2003;Schneider & Winemiller, 2008;Molokwu et al., 2014;Dossi et al., 2020), and as an important component of habitat complexity for stream salamanders (e.g., Mackey et al., 2014;Rizzo et al., 2016). At the ecosystem level, wood is important to the retention of sediment (Nakamura & Swanson, 1993;Osei et al., 2015;Wohl & Scott, 2016;Schalko, 2020) and organic matter (Bilby & Likens, 1980;Osei et al., 2015) within stream channels. Wood can also influence channel morphology and dynamics, such as through pool formation (e.g., Bilby, 1984;Abbe & Montgomery, 2003). ...
In streams and rivers, wood from riparian vegetation contributes to habitat complexity and substrates for stream biota, influences channel geomorphology, alters flow, retains sediment and organic matter, and enhances nutrient uptake. A few studies have shown that wood amounts in urban streams may be lower than in rural streams or that wood amounts in streams are inversely related to watershed impervious surface cover (ISC). To determine if these patterns occur more broadly, we compared wood amounts in urban and non-urban streams in the South Carolina Piedmont and Blue Ridge Provinces. We measured wood abundance in 20 streams draining urbanized (15–68% ISC) or non-urbanized (≤ 2.5% ISC) watersheds. Our results did not support the hypothesis that urban streams would have less wood than rural streams, and we found no relationship between wood amounts and watershed ISC. Indeed, one urban stream bordered by large riparian trees had the greatest wood volume of all streams in our study. Instead, large wood amounts were best explained by tree canopy cover and length of unobstructed tree-lined channel upstream. These results suggest that the presence of numerous riparian trees influences wood amounts positively even in urban streams where wood amounts might be expected to be low.
... Whether moving in contact with the stream bed or in suspension, CPOM is typically of lower density than mineral sediment and is therefore more readily transported. Physical complexity, such as large wood (LW, defined here as downed, instream wood ≥1 m in length, and ≥10 cm in diameter) or other boundary irregularities that create sites of lower velocity and shear stress, promotes storage and retention zones that can extend the residence time of CPOM during downstream transport (Beckman & Wohl, 2014;Bilby & Likens, 1980;Jochner et al., 2015;Lautz & Fanelli, 2008;Livers & Wohl, 2016;Livers, Wohl, Jackson, & Sutfin, 2018;Raikow, Grubbs, & Cummins, 1995). Streams with lower wood loads (volume of wood per area) are significantly less retentive of CPOM and less physically complex than streams with abundant wood loads (Beckman & Wohl, 2014;Livers et al., 2018;Livers & Wohl, 2016). ...
We measured coarse particulate organic matter (CPOM) transport along a wood‐rich, pool‐riffle mountain stream in the Southern Rockies of Colorado, USA, to examine how spatial variations in storage features and temporal variations in discharge influence the transport of CPOM. Ecologists have found that the majority of annual CPOM export occurs during periods of high discharge. More recently, geomorphologists have begun to examine the transport of CPOM as bedload. There has been, however, little direct sampling of CPOM to evaluate how shorter (diurnal) and longer (seasonal peak flow) variations in discharge affect CPOM transport, and no examination of where CPOM is transported in the water column (primarily in suspension or as bedload). We collected CPOM moving as bedload, in suspension (at 0.6 of the flow depth) and at the surface to evaluate CPOM transport processes. Samples were collected at three sites: (1) in the backwater pool upstream from a channel‐spanning logjam; (2) immediately downstream from the logjam; and (3) in a riffle about 10 bankfull‐channel‐widths downstream from any channel‐spanning logjams. During sample sets, we collected samples over 15‐min increments at approximately 4‐hr intervals over a 24‐hr period. Seven sample sets were distributed over a period of 2 months that spanned the rise, peak, and recession of the annual snowmelt flood. We found that the majority of CPOM is transported in suspension following a clockwise hysteresis loop in which CPOM peaks prior to discharge during the seasonal hydrograph.
... Such events also occur in unburned, geologically unstable landscapes. Inputs of fineparticulate carbon and large woody debris (LWD) are critical for aquatic ecosystems; LWD provides essential channel structure, habitat diversity, nutrient retention, and carbon to streams (Bilby and Likens 1980;Bilby 1981;Seo et al. 2008;Martin and Benda 2001), and fine organic carbon forms the basis of aquatic food webs for primary and secondary consumers (Mulholland and Watts 1982). ...
The Chinese government adopted an “ecological civilization”
(or promoting ecological progress – 生态文明 ) national strategy to change the land development patterns, promote resource conservation and utilization, protect natural ecosystems and the environment, and improve quality of life in China.
... Landslide dam stability further promotes diverse aquatic habitats and ecological complexity in mountain streams (Baillie et al., 2008;Beeson et al., 2018;Mackey et al., 2011;May et al., 2013). These factors, in addition to the contribution of landslide dams to surface processes that act over timescales pertinent to landscape evolution (Korup, 2004;Korup, Strom, & Weidinger, 2006) and potentially to carbon sequestration (Bilby & Likens, 1980;Scott & Wohl, 2020), necessitates future detailed examination of this important geomorphic process. ...
Bedrock landsliding, including the formation of landslide dams, is a predominant geomorphic process in steep landscapes. Clarifying the importance of hydrologic and seismic mechanisms for triggering deep-seated landslides remains an ongoing effort, and formulation of geomorphic metrics that predict dam preservation is crucial for quantifying secondary landslide hazards. Here, we identify >200 landslide-dammed lakes in western Oregon and utilize dendrochronology and enhanced ¹⁴C dating (“wiggle matching”) of “ghost forests” to establish slope failure timing at 20 sites. Our dated landslide dataset reveals bedrock landsliding has been common since the last Cascadia Subduction Zone earthquake in January 1700 AD. Our study does not reveal landslides that date to 1700 AD. Rather, we observe temporal clustering of at least four landslides in the winter of 1889/1890 AD, coincident with a series of atmospheric rivers that generated one of the largest regionally recorded floods. We use topographic and field analyses to assess the relation between dam preservation and topographic characteristics of the impounded valleys. In contrast to previous studies, we do not observe systematic scaling between dam size and upstream drainage area, though dam stability indices for our sites correspond with “stable” dams elsewhere. Notably, we observe that dams are preferentially preserved at drainage areas of ∼1.5 to 13 km² and valley widths of ∼25 to 80 m, which may reflect the reduced downstream influence of debris flows and the accumulation of mature conifer trees upstream from landslide-dammed lake outlets. We suggest that wood accumulation upstream of landslide dams tempers large stream discharges, thus inhibiting dam incision.
... Research on the geomorphic and ecological effects of large wood was initially largely confined to the Pacific Northwest region of the United States as part of an increasing focus on old-growth forest ecosystems (e.g., Keller & Swanson, 1979;Swanson et al., 1976), although important precursors of this work were pioneering studies of interactions between forest and river dynamics (Hack & Goodlett, 1960) and the influence of vegetation on channel forms in small streams (Zimmerman et al., 1967). Simultaneous with the work in the Pacific Northwest, ecologists started to emphasize the role of large wood in creating structure, habitat diversity, and transient storage in smaller streams in the eastern United States (e.g., Bilby & Likens, 1980). The long history of deforestation and wood removal from river corridors in most of the world (Erskine & Webb, 2003;Harmon et al., 1986;Montgomery et al., 2003;Wohl, 2014) initially limited recognition of the historical importance of large wood in rivers. ...
... Mosley (1981) found that LW accumulations may function as zones of sediment deposition, storing mainly coarse sediments. Other studies have reported the significant storage potential of LW accumulations in steep mountain streams (Bilby and Likens, 1980;Harmon et al., 1986), which can hold material of up to 15 times of the yearly sediment freight (Megahan and Nowlin, 1976;Swanson and Lienkaemper, 1978). LW can affect sediment connectivity, an ecologically important process that is not well understood. ...
Large wood (LW) commonly forms log jams, influencing bed composition and biota via complex flow-sediment-wood interactions. A LW blockage, often induced by river-crossing infrastructure, can strongly alter channel hydraulics and sediment transport patterns, thus inducing a ‘forced’ channel morphology. For studying the deposition of bedload gravel fractions in the presence of a rigid LW jam, a novel experimental setup is presented. Using a mobile bed stream table, the effects of a channel-spanning blockage (a ‘dam jam’), resting at a bridge pier, on sediment transport and scour dynamics are examined. Changes in channel morphology were measured using Structure from Motion (SfM) photogrammetry and manually obtained bedload measurements. For the experiment without LW accumulation in place, natural bedload transport was observed over the entire channel length - about 20% of fed colour gravel was recovered from the sediment trap at the outlet, while a total bedload interruption occurred in presence of the LW accumulation, resulting in trapping all fed gravel material upstream of the obstructed cross-section. The volumetric deviation between SfM and manual measurements was less than 0,4%. The porosity characteristics of the LW accumulation were analysed using volumetric meshing techniques. With our experiments, we demonstrated that a relatively high log jam porosity has significant impact on channel morphology. By interrupting the hydraulic energy gradient, the movement of coarse sediment transport is damped, forcing deposition and initiating the development of a sediment wedge upstream of the infrastructure. Our quantitative results provide new insights into how LW can force channel morphology (particularly sediment storage) through the alteration of channel hydraulics. We further elaborate on how novel laboratory-based SfM techniques can be used to enhance the current understanding of complex flow-sediment-wood interaction processes at engineered in-stream structures.
... Kaufmann & Faustini, 2012;Livers & Wohl, 2016) removed from the site (e.g. Bilby & Likens, 1980;Mellina & Hinch, 2009). Wood can also induce more persistent morphologic features, such as formation of secondary channels that can persist after the wood is removed (Wohl & Scamardo, 2021 showing relationships between bulk skew and wood load. ...
We use four stream segments along a wood‐rich, pool‐riffle mountain stream in the Southern Rockies of Colorado, USA to examine how spatial variations in wood load and variations in discharge during and after the snowmelt peak flow influence the magnitude of surface and subsurface transient storage. Segments range in complexity from a single channel with no large wood to an anabranching channel with closely spaced, channel‐spanning logjams. Discharges at which transient storage was assessed range from base flow to snowmelt peak flow. To explore these relations, we used ten geomorphic variables representing channel morphology and bed substrate, four wood‐related variables representing wood load and associated backwater storage, and two measures of skewness from instream and bulk electrical conductivity breakthrough curves during tracer tests. Instream curves reflect surface and subsurface transient storage whereas bulk curves primarily represent subsurface transient storage. Higher values of skewness indicate greater retention, and we used the values here as a metric of increased transient storage. Although limited sample size restricts the power of our results, our findings suggest that stream segments with greater instream large wood loads have more and larger pools, greater storage of fine sediment and particulate organic matter, and higher values of skew from instream conductivity. The results also suggest that the presence of instream wood, rather than changes in channel morphology associated with wood, is the most important driver of transient storage. This implies that river management designed to foster transient storage should focus on retaining instream large wood. We did not find significant correlations between geomorphic or wood‐related variables and the skew estimated from bulk conductivity, which may reflect the relatively thin alluvium present in the field area and the prevalence of surface transient storage in this system.
... Leaf litter enters streams mainly in a large burst during the period of leaf abscission (autumn in most temperate regions) and can either be trapped in the reach and thus become available for heterotrophs or transported downstream. Therefore, the capacity of a stream reach to retain materials (retentiveness) is important for the productivity and ecosystem efficiency of streams (Bilby and Likens 1980;Pozo et al. 1997). ...
Food webs in forested streams are largely fuelled by plant litter of terrestrial origin. Litter enters streams directly from the canopy (vertical inputs), laterally as material initially fallen on the ground (lateral inputs) and as material transported longitudinally from upstream. This chapter describes how to estimate these three components of input in small streams. The last pathway is the most difficult to quantify, as it is highly variable over time, depending on rates of litter fall and on discharge. Litter traps are constructed from 1 mm-mesh on a wooden or metallic frame and deployed over the stream channel, along the banks and in the channel upstream of a selected reach to collect vertical and lateral inputs as well as litter transported downstream. The collected litter is regularly retrieved, sorted into categories such as leaves, wood, etc., and dried and weighed. Subsamples are ashed and re-weighed to determine ash-free dry mass. Longitudinal transport traps can only be deployed for short periods. Therefore, transport during periods without traps in the channel needs to be estimated based on transport-discharge relationships computed from multiple short-term measurements. This requires continuous discharge records. The collected input data provide essential information to construct energy budgets for streams.
... Large woody debris (LWD) plays a key role in controlling the ecology and geomorphology of streams. Woody debris traps coarse particulate organic matter and sediments (Andersen and Sedell, 1979;Bilby and Likens, 1980;Marston, 1982); provides habitat for aquatic insects (Angermeier and Karr, 1984;Benke et a/., 1985); and provides cover in pools and slow water areas (Bisson et a/., 1982(Bisson et a/., , 1987Tschaplinski and Hartman, 1983;Fausch and Northcote, 1992). The role of wood in affecting stream morphology is dependent on the size of the stream (Bilby and Ward, 1989). ...
Large woody debris (LWD) plays a key role in controlling the ecology and geomorphology of streams. Woody debris traps coarse particulate organic matter and sediments (Andersen and Sedell, 1979; Bilby and Likens, 1980; Marston, 1982); provides habitat for aquatic insects (Angermeier and Karr, 1984; Benke et al., 1985); and provides cover in pools and slow water areas (Bisson et al., 1982, 1987; Tschaplinski and Hartman, 1983; Fausch and Northcote, 1992). The role of wood in affecting stream morphology is dependent on the size of the stream (Bilby and Ward, 1989). In smaller streams, woody debris can create step pool sequences (Heede, 1972, 1985; Marston, 1982), increase pool area (Murphy and Hall, 1981; Ralph et al., 1994), and reduce sediment transport (Bilby, 1984). Nakamura and Swanson (1993) noted that the importance of woody debris to the morphology of first order streams can be limited by the size of the debris, which is often large enough to bridge the channel and not interact with the flow. Woody debris plays a larger role when it enters the channel bottom, where it can divert flow and affect erosion and deposition. The scale issues raised by Bilby and Ward (1989) and Nakamura and Swanson (1993) are critical to understanding the role of woody debris. To date, LWD has not been adequately studied at watershed scales in larger rivers. In fact, there is little understanding of the relationship between LWD and the geomorphic pattern of the river channel (Piegay and Marston, 1998; Piegay and Gumell, 1997; Piegay, 1993). The purpose of this study is to document the distribution of LWD jams on the Snake River in Grand Teton National Park, Wyoming in order to understand the effects of LWD on channel morphology in large river systems.
Background
Cocoa is an important tropical tree crop that is mainly cultivated in agroforestry systems (AFS). This system, known as cabruca in northeastern Brazil, holds promise to reconcile biodiversity conservation and economic development. However, since cocoa AFS alters forest structure composition, it can affect litter dynamics in riparian zones and streams. Thus, our objective was to determine litter inputs and standing stocks in riparian zones and streams under three types of forest: managed cocoa AFS, abandoned cocoa AFS, and secondary forest.
Methods
We determined terrestrial litter fall (TI), vertical (VI) and lateral (LI) litter inputs to streams, and litter standing stocks on streambeds (BS) in the Atlantic Forest of northeastern Brazil. Litter was collected every 30 days from August 2018 to July 2019 using custom-made traps. The litter was dried, separated into four fractions (leaves, branches, reproductive organs, and miscellaneous material) and weighed.
Results
Terrestrial litter fall was similar in all forests, ranging from 89 g m ⁻² month ⁻¹ in secondary forest (SF) to 96 g m ⁻² month ⁻¹ in abandoned cocoa AFS (AC). Vertical input were higher in AC (82 g m ⁻² month ⁻¹ ) and MC (69 g m ⁻² month ⁻¹ ) than in SF (40 g m ⁻² month ⁻¹ ), whereas lateral input were higher in MC (43 g m ⁻² month ⁻¹ ) than in AC (15 g m ⁻² month ⁻¹ ) and SF (24 g m ⁻² month ⁻¹ ). Standing stocks followed the order SF > AC > MC, corresponding to 425, 299 and 152 g m ⁻² . Leaves contributed most to all litter fractions in all forests. Reproductive plant parts accounted for a larger proportion in managed AFS. Branches and miscellaneous litter were also similar in all forests, except for higher benthic standing stocks of miscellaneous litter in the SF. Despite differences in the amounts of litter inputs and standing stocks among the forests, seasonal patterns in the abandoned AFS (AC) were more similar to those of the secondary forest (SF) than the managed AFS, suggesting potential of abandoned AFS to restore litter dynamics resembling those of secondary forests.
Popularnonaukowa monigrafia zagadnień związanych z bilansem, rolą i ochroną martwych drzew w w ekosystemach, głównie (ale nie tylko) leśnych. Przedstawia m. in. zagadnienia:
Co to jest drewno. Jakich rozmiarów dorastają i jak długo żyją drzewa?
Pochodzenie, bilans i cechy martwego drewna, w lasach, poza lasem: w parkach, zadrzewieniach i innych środowiskach; w wodach. Martwe drewno na żywym drzewie – Mikrosiedliska nadrzewne. Znikający krajobraz ekotonów leśnych i lasów pastwiskowych.
Etapy i konsekwencje zamierania drzew. Jak martwe drzewa „ożywają”: kolonizacja martwych drzew i martwego drewna
Zamierające i martwe drewno jako środowisko życia. Organizmy zwiąane z martwym drewnem.
Funkcje ekosystemowe martwego drewna: Leśne „paliwo”, magazynowanie materii organicznej, akumulacja węgla i azotu, magazynowanie wody, rola martwych drzew w odnowieniu lasu, ochrona przed erozją, rola w procesach glebowych, rola w ciekach.
Rola martwego drewna w ochronie lasu i ochronie przyrody. Rola w leśnictwie i świadomość leśników. Martwe drewno jako składnik chronionych ekosystemów i wskaźnik ich stanu. Ochrona gatunkowa zwiążanych z martwym drewnem zwierząt, roślin i grzybów, w tym gatunków reliktowych.
Rozległe zaburzenia – niechciany dar przyrody?
Martwe drewno a zagadnienia bezpieczeństwa.
Martwe drewno w nauce i gospodarce.
Metody jakościowej i ilościowej oceny martwego drewna.
„Drugie Zycie Drzewa”, autorstwa J.M. Gutowskiego, A. Bobca, P. Pawlaczyka i K. Zuba ukazało się po raz pierwszy w 2004 r. Obecne II wydanie (2022 r.) jest znacznie zmienione i rozbudowane, stosownie do obecnej wiedzy na temat ekologicznej roli martwych drzew. Wiedza ta przez 18 lat jakie minęły od I wydania, wzrosła niepomiernie: w 2021 r. internetowe wyszukiwarki literatury naukowej znajdowały ok. 40 tys. publikacji na ten temat. Blisko połowa z nich pochodzi z ostatniego dziesięciolecia.
Do autorów II wydania dołączyli: Michał Ciach i Anna Kujawa. W szczególności szeroko zostały opisane zagadnienia związane z rolą tzw. drzew biocenotycznych i mikrosiedlisk nadrzewnych w lasach. Zupełnie nową treść i jakość uzyskały rozdziały opisujące grzyby, porosty i śluzowce oraz ich związki z martwym drewnem. O nowe zagadnienia i treści został rozszerzony rozdział „Martwe drewno w ochronie lasu i ochronie przyrody”, który zaktualizowano też do obecnego stanu prawnego. Znacznie szerzej przedstawiono rolę martwego drewna w wodach. Zaktualizowano oraz uzupełniono, przede wszystkim o nową literaturę, również pozostałe rozdziały publikacji. Znacznie rozbudowano materiał ilustracyjny. Nowe wydanie liczy ponad 340 stron, dodatkowo na większym formacie, co oznacza ok. dwukrotnie większą objętość od wydania I.
Książka w wersji elektronicznej (pdf) jest dostępna także na stronach wydawcy (The book is available at the publisher website): https://www.wwf.pl/sites/default/files/2022-03/drugie-zycie-drzewa-03-2022.pdf
Forest management in riparian ecosystems can significantly alter biotic and abiotic processes in streams. Forest harvest without the retention of buffers along small streams can affect organic matter dynamics, and drive instream characteristics like trophic food webs. To investigate the extent to which differing levels of tree retention adjacent to the channel mitigated changes in organic matter dynamics, we examined coarse particulate organic matter delivery, transport, and retention, as well as canopy cover, along small streams with four harvest treatments, both before and after harvest. Our research was part of a larger effort of the Trask River Watershed Study (TRWS) in the northern Oregon Coast Range, which examined the long-term physical, chemical, and biological effects of forest management on aquatic ecosystems at multiple spatial scales. Canopy cover at reference and treatment sites prior to harvest was approximately 91%, but following harvest, mean canopy cover at treatment sites decreased with increasing harvest intensity: 3% decrease after clearcut with buffer, 14% after clearcut with leave trees, and 57% after complete clearcut. Organic matter delivery (i.e., the amount of leaf, needle, wood, reproductive, or miscellaneous litter material) to streams was dominated by leaves and varied seasonally but decreased overall after harvest with complete clearcut. Organic matter transport (i.e., the amount of material netted during a sampling period at the end of each stream reach) values fell within the observed range of reference values at all harvested sites. Organic matter retention (i.e., the amount of material sampled in plots systematically placed along the stream reach) post-harvest was dominated by woody material and was consistent with pre-harvest measurements and reference sites for all the harvested streams. The number of log jams, and the total weight of log jams, increased for all treatments after harvest, although the most dramatic increase in log jam weight (140% increase) was observed for the complete clearcut and clearcut with leave tree sites. On these five sites, our results indicated that while complete clearcutting reduced organic matter delivery, retention of even a small number of trees along these streams appeared to support litter delivery rates after harvesting comparable to before harvest. We acknowledge the limitations of results from single treatment sites; however, our results were generally consistent with studies that had full replication. As part of the Trask River Watershed study, our research adds to the comprehensive effort to understand the ecological significance of riparian buffers and forest harvest in headwater streams.
The decomposition of organic carbon provides key energy inputs to most food webs, and this is especially true in fluvial ecosystems. These energy pathways are referred to as detrital or detritus-based, and the immediate consumers of this material are decomposers and detritivores.
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and the animals in tunnels inside the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to piscivorous fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
Substantial amounts of dead wood in the intertidal zone of mature mangrove forests are tunnelled by teredinid bivalves. When the tunnels are exposed, animals are able to use tunnels as refuges. In this study, the effect of teredinid tunnelling upon mangrove forest faunal diversity was investigated. Mangrove wood not containing teredinid tunnels had very few species and abundance of animals. However, with a greater cross-sectional surface area of teredinid tunnels, the numbers of species and abundance of animals was significantly higher. Temperatures within teredinid-attacked wood were significantly cooler compared with air temperatures, and the animals in tunnels inside the wood may avoid desiccation by escaping the higher temperatures. Animals co-existing in teredinid tunnelled wood ranged from animals found in terrestrial ecosystems including centipedes, crickets and spiders, and animals found in subtidal marine ecosystems such as fish, octopods and polychaetes. There was also evidence of breeding within teredinid-attacked wood, as many juvenile individuals were found, and they may also benefit from the cooler wood temperatures. Teredinid tunnelled wood is a key low-tide refuge for cryptic animals, which would otherwise be exposed to piscivorous fishes and birds, and higher external temperatures. This study provides evidence that teredinids are ecosystem engineers and also provides an example of a mechanism whereby mangrove forests support intertidal biodiversity and nurseries through the wood-boring activity of teredinids.
Plant litter of terrestrial origin is a key food resource in forested streams, but leaves entering stream channels tend to be moved downstream by water flow. Therefore, the capacity of stream channels to retain leaf litter (retentiveness) is an important factor affecting stream secondary productivity. Retentiveness depends on channel size and form, discharge, and the presence of structures such as logs or branches. Leaf retention can be estimated in short-term release experiments with leaves or leaf proxies showing similar floating behaviour. This chapter describes a method to measure stream retentiveness by releasing leaves of Ginkgo biloba, a tree producing bright yellow leaf litter that is readily spotted and is uncommon in most areas of the world. A stop-net is set at the lowermost end of a selected stream reach to prevent the loss of any leaves released at the head of the reach. All leaves trapped along the study reach are recovered and the distance travelled noted to the nearest metre. The average distance is calculated based on a negative exponential retention model. The method is best used in wadeable streams under low to medium discharge, but can be adapted to other situations.
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