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Map of the reaches and dams along the Snake River through Hells Canyon. Modified from Braatne et al. 2008.
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Riparian or streamside woodlands include obligate riparian trees and shrubs (obligates) that are restricted to streamside zones, and facultative riparian species that are abundant in, but not restricted to the riparian areas. Due to their distinctive life history requirements, it may be predicted that the ecological specialist obligates would be mo...
Contexts in source publication
Context 1
... Snake River through Hells Canyon defines the border between Oregon and Washington, and Idaho, USA (Figure 1, Braatne et al., 2008). Here, the Snake River has a fairly steep gradient and was developed for hydroelectric power generation with the implementation of three large dams, Brownlee, Oxbow and Hells Canyon, in 1958, 1961and 1967, respectively. ...
Context 2
... the HCC, Hells Canyon provides a relatively inaccessible landscape and this has limited other human impacts. Instream flows are almost entirely determined by water release from the HCC since contributions from local streams are minor above the Imnaha and Salmon River inflows (Figure 1). ...
Context 3
... of the 31 photograph points occurred along the unimpounded Hells Canyon reach of the Snake River, between the Hells Canyon Dam and the Salmon River inflow (Figure 1). Three of these photograph pairs are presented in Figure 2 and interpretations for all 12 pairs are provided in Table I, along with information from the land survey records. ...
Context 4
... river flow data are often represented and archived as daily mean discharges, hydroelectric dams are generally operated with diurnal flow pulsing as has occurred for the HCC (Figure 10). The pulsing shown for August 2006 was typical for the low flow period of mid-to late summer ( Figure 8). ...
Citations
... Floodplains are associated with riparian watercourses and contain woody shrubs and trees that are classified as being both "obligate-riparian" and "facultative riparian." Both categories play a significant role in stream bank stabilization, sediment and erosion control, assimilation of nutrients and pollutants, and provide a diverse habitat for specialized flora and fauna living within riparian habitats [15]. The ecological term 'obligate' suggests this category of woody shrubs and trees are restricted to wet soils in bottomland riparian zones. ...
... This suggests that there is no one species in the Denton Creek study area exerting influence over the other species of trees from this study and is another indicator of the rich biodiversity within this community [8]. [14][15][16][17][18][19][20][21][22]. The most abundant tree species are assigned rank 1, followed by the second most abundant species, and so on. ...
... The later construction of the apartments altered the natural floodplain topography, adding impervious surfaces such as asphalt and concrete pavement, and asphalt-shingled roofing. All of which increases surface runoff of rainwater, especially during unseasonal and abnormal flooding, which increases sediment loading into streams and rivers [4,15,18] like Denton Creek. The anthropogenic effect from loss of habitat contributes to negative impacts on native riparian plants and trees from deleterious modification of hydrogeomorphology and sedi-ment substrate [4,15,33]. ...
Data comprising the location, size, and frequency of occurrence of 1,300 bottomland riparian trees along a 4,300 ft (1,311 m) stretch of Denton Creek in Grapevine, Texas, was captured. Twenty-five separate species were determined from fourteen different families whose diameter at breast height (DBH) was three inches (7.62 cm) or greater. Elms were the most frequently occurring trees, with Hackberry and American Elm the predominant species. Most occurrences of trees were between 3-12 inches (7.62-30.48 cm) DBH. Brillouin's index of diversity (H) was 1.00 out of a maximum possible diversity (H max) of 1.29, indicating that this community has high species diversity, in spite of the fact that trees less than 3 inches DBH were not included in the survey. Relative diversity according to the evenness (J) ratio of H and H max was 0.78, suggesting that this community is nearly 80% at its maximum possible diversity. In terms of ecological importance, this riparian community is rich in habitat diversity and provides vegetative and protective cover for both flora and fauna, habitat niche, breeding sites and plant distribution. In terms of human importance, the site has economic importance, both as a source of crop and domestic animal production, erosion control, water conservation, and land value.
... Human management activity along rivers such as livestock grazing ( Holland et al. 2005 ;Batchelor et al. 2015 ;Nusslé et al. 2017 ), flow alterations ( Rood et al. 2010 ), and mining ( Cubley et al. 2022 ) can influence the cover and height of willow species in riparian areas, which can ultimately affect stream and riparian conditions ( Li et al. 1994 ;Saunders and Fausch 2007 ;Hough-Snee et al. 2015b ). As willow are generally considered shade intolerant species ( Humbert et al. 2007 ), their presence and cover will be more likely to influence the condition of riparian communities in areas where streamside overstory vegetation, such as coniferous forests and tall deciduous trees, are limited or absent ( Sarr and Hibbs 2007 ;Wohl 2011 ;Hough-Snee et al. 2015a ). ...
Willows are an important component of western riparian zones as their roots stabilize streambanks, their overstory mediates stream temperature, and aquatic biota use their stems and leaves as forage and build- ing material. We evaluated 1894 stream reaches in the Inland Pacific Northwest for the presence of wil- lows and detected one or more willow species at 1 247 (66%) of those reaches. Most stream reaches where willow was present had two or more willow species. We identified 23 unique species, of which 11 were found in 50 or more stream reaches. Across all sites, stream reaches with willow were more likely to be in the southern high-elevation portion of the study area. Distribution models constructed using random forests included a measure of spatial location (latitude, longitude, elevation) as one of the top predictors for 10 of the 11 common species. Only one species included a stream reach-scale attribute (bankfull stream width) as a top predictor, although two species had gradient or percent of the reach forested as a secondary predictor. While spatial location within the study area was a key factor in deter- mining species presence, differences among species resulted in willows being found across the range of landscape and stream reach conditions except where forest cover in the reach was high ( > 75%). Given that willows share characteristics such as rapid root growth, rhizomes, flexible stems, and vegetative re- production, in many situations different species may respond as functional equivalents when it comes to protecting streambanks, providing habitat for fish and wildlife, and promoting stream heterogeneity. Ongoing threats to willows near streams on public lands include grazing, water diversion, mining, and climate change. Each of these threats can be at least partially addressed by identifying stream reaches inhabited by willow and establishing reach-scale management objectives for this taxon.
... Freshwater ecosystems are typically fringed by riparian or waterside plant communities, composed of both obligate and facultative species (Rood et al. 2010). Rivers and their riparian zones are among the best examples of meta-ecosystems given their cross-ecosystem connectivity of materials and energy (Loreau et al. 2003, Abelho andDescals 2018). ...
Riparian zones are important for the maintenance of aquatic ecosystem functional integrity, yet are considered to be particularly vulnerable to plant invasions. The role of terrestrial riparian plant invasions in compromising aquatic ecosystem processes is, however, still poorly understood. This issue is particularly relevant for temporary rivers, which are understudied compared to permanent river systems, despite their ubiquity and largescale contributions to biogeochemical processes. Here we experimentally assessed leaf litter breakdown dynamics in situ in a temporary river in arid southeastern Botswana, Southern Africa. We contrasted aquatic leaching and microbial and invertebrate litter breakdown contributions to the native leadwood Combretum imberbe and invasive river red gum Eucalyptus camaldulensis in the Lotsane River. Fine-mesh (detritivore exclusion) and coarse-mesh (detritivore inclusion) bags were separately filled with leaf litter from each species and deployed in the river during a hydroperiod (wet phase), with decomposition measured over a 6-week period. E. camaldulensis shed significantly more leachate than the native C. imberbe. Significantly more microbial and detritivore breakdown was, however, observed in native than in invasive leaf litter. Overall, invertebrates contributed little to biological leaf litter breakdown processes compared to microbial breakdown contributions. Although significantly higher in native leaves, low invertebrate numbers were found in leaf litter in the study. This study highlights the role of microbial contributions to detrital decay in temporary arid zone rivers, whereas invertebrate contributions were relatively minor. The study further contributes to our understanding of how invasive riparian plant species alter aquatic detrital pool dynamics in invaded temporary wetland ecosystems.
... Densities of Arizona walnut (Juglans major), both elm species (Ulmus americana and Ulmus crassifolia), anacua (Ehretia anacua), and roughleaf dogwood (Cornus drummondii) were highest in the riparian zone. All are facultative species, which are generalists well-suited to a transitional area such as the riparian zone (Rood et al., 2010). ...
... These changes in riparian vegetation are frequently associated with disturbance (the opening of agricultural fields, highways and roads and overgrazing), and when they co-occur with other processes, such as groundwater decline or soil salinization, the probability of invasion by exotic species (e.g., Tamarix spp.), or replacement by native facultative riparian species (e.g., Prosopis sp.) can increase [68,[98][99][100]. Some studies have registered how fragmentation of the riparian landscape can negatively affect biodiversity by limiting aquatic species dispersion [101]. ...
Natural vegetation in arid and semi-arid environments of Northwestern Mexico has been subject to transformation due to extensive and intensive human occupation related mostly to primary activities. Keystone habitats such as riparian ecosystems are extremely sensitive to land use changes that occur in their surrounding landscape. In this study, we developed remote sensing-based land cover classifications and post-classification fragmentation analysis, by using data from Landsat's moderate resolution sensors Thematic Mapper and Operational Land Imager (TM and OLI) to assess land use changes and the shift in landscape configuration in a riparian corridor of a dynamic watershed in central Sonora during the last 30 years. In addition, we derived a high spatial resolution classification (using PlanetScope-PS2 imagery) to assess the "recent state" of the riparian corridor. According to our results, riparian vegetation has increased by 40%, although only 9% of this coverage corresponds to obligate riparian species. Scrub area shows a declining trend, with a loss of more than 17,000 ha due to the expansion of mesquite and buffelgrass-dominated areas. The use of moderate resolution Landsat data was essential to register changes in vegetation cover through time, however, higher resolution PlanetScope data were fundamental for the detection of limited aerial extent classes such as obligate riparian vegetation. The unregulated development of anthropogenic activities is suggested to be the main driver of land cover change processes for arid ecosystems in this region. These results highlight the urgent need for alternative management and restoration projects in an area where there is almost a total lack of protection regulations or conservation efforts.
... This approach is widely used to describe successional stages or changes in their distribution (86% of such studies). Indeed, RGB/GS aerial images have been available since before the 1950s (Gonz� alez et al., 2010;Rood et al., 2010;Varga et al., 2013;Wan et al., 2015). However, manual interpretation of images is time-consuming, and the discriminating power of RGB/GS aerial images Fig. 8. Results of the multiple correspondence analysis (see section 2.3. ...
Riparian vegetation is a central component of the hydrosystem. As such, it is often subject to management practices that aim to influence its ecological, hydraulic or hydrological functions. Remote sensing has the potential to improve knowledge and management of riparian vegetation by providing cost-effective and spatially continuous data over wide extents. The objectives of this review were twofold: to provide an overview of the use of remote sensing in riparian vegetation studies and to discuss the transferability of remote sensing tools from scientists to managers. We systematically reviewed the scientific literature (428 articles) to identify the objectives and remote sensing data used to characterize riparian vegetation. Overall, results highlight a strong relationship between the tools used, the features of riparian vegetation extracted and the mapping extent. Very high-resolution data are rarely used for rivers longer than 100 km, especially when mapping species composition. Multi-temporality is central in remote sensing riparian studies, but authors use only aerial photographs and relatively coarse resolution satellite images for diachronic analyses. Some remote sensing approaches have reached an operational level and are now used for management purposes. Overall, new opportunities will arise with the increased availability of very high-resolution data in understudied or data-scarce regions, for large extents and as time series. To transfer remote sensing approaches to riparian managers, we suggest mutualizing achievements by producting open-access and robust tools. These tools will then have to be adapted to each specific project, in collaboration with managers.
... Dams are responsible for modifying the timing and quantity of river flows (e.g., Williams and Wolman, 1984;Rood and Mahoney, 1990;Maheshwari et al., 1995;Ward and Stanford, 1995;Maingi and Marsh, 2002;FitzHugh and Vogel, 2010), influencing the temperature of the water (e.g., Nilsson and Renöfält, 2008;Bae et al., 2016), interfering with nutrient loads (e.g., Nilsson and Renöfält, 2008;Maavara et al., 2014;Maavara et al., 2015;Zmijewski and Wörman, 2015), trapping sediments (e.g., Kondolf, 1997;Walling and Fang, 2003;Kondolf et al., 2014;Asaeda et al., 2015), blocking fish migrations and disturbing aquatic communities (e.g., Freeman et al., 2003;Kocovsky et al., 2009;Freedman et al., 2014;Cooper et al., 2017), and affecting floodplain ecosystems (e.g., Kingsford, 2000;Nilsson and Svedmark, 2002;Shafroth et al., 2002;Naiman et al., 2005;Gordon and Meentemeyer, 2006;Braatne et al., 2007;Braatne et al., 2008;New and Xie, 2008;Benjankar, 2009;Egger et al., 2009a;Egger et al., 2009b;Rood et al., 2010;Benjankar et al., 2012;Johnson and Waller, 2012). Flow regime alterations can thus have numerous impacts, namely, geomorphological (Lloyd et al., 2004), ecological (Poff and Zimmerman, 2010) and biological (Stromberg et al., 2010a). ...
... are pioneer species that are adapted to disturbance. The former is a phreatophyte with restricted intervals of seed release and viability (Rood et al., 2010), and the latter a facultative phreatophyte species with a longer seed dispersal period and greater drought tolerance (Glenn and Nagler, 2005). On the other hand, the ash tree is a non-obligate phreatophyte that usually vegetates in silty soils, ranging from mesic to mesic and wet (Dufour and Piégay, 2008), and takes up water from unsaturated ground. ...
This thesis composes an assessment of the flow regime effects on the structure and functioning of riparian vegetation, as well as, the influence of the respective vegetation changes back on the aquatic communities and fluvial processes. The expected flow regimes driven by climate change originate amendments in riparian vegetation, characterized mainly by a general area reduction and a greater menace to the younger and water dependent succession phases. In the European context, the Mediterranean rivers are the ones most threatened. The fluvial disturbance has different effects on the location and shape of the vegetation patches, being groundwater hydrology the main driver of patch location, which exposes a predominant zonation of succession phases over the natural ecologic succession. The potential natural riparian patch mosaic was determined in regulated rivers, allowing for the establishment of reference conditions for environmental flows. The riparian maintenance flows are able to restore the dynamics of riparian vegetation and reduce the effects of regulation in these communities. The safeguarding of a minimum discharge during the summer period allows for the prevention of channel invasion and encroachment by vegetation. The changes in the riparian patch mosaic have influence in the hydraulic characteristics of the river channel, changing the habitat availability of the local fish species according to the magnitude of the changes. Environmental flows that disregard riparian vegetation requirements become obsolete in few years due to the modification of the habitat premises for which they were based, revealing therefore to be unsustainable in the long term and failing to achieve the desired effects on aquatic communities to which those were proposed in the first place. Accounting for the requirements of riparian vegetation into environmental flows poses an essential measure to assure the effectiveness of environmental flow regimes in the long-term perspective of the fluvial ecosystem.
... Conversely, facultative riparian species are ecological generalists that occur across a broader range of environmental conditions including upland zones, but are typically promoted by the additional moisture present in the riparian zone (Auble et al. 1994). Accordingly, obligate riparian trees and shrubs are more likely to be negatively affected by river damming and flow regulation while facultative species may be less vulnerable (Rood et al. 2010b). Some patterns of flow regulation could even be beneficial to these facultative plants, particularly operational patterns that augment flows during the warm and dry period of mid-to late summer when drought stress is most likely (Doody et al. 2014;Hillman et al. 2016). ...
... These augmented flows may be delivered over periods of days or weeks, or through the shorter pulses associated with hydropeaking. Increasing flows and correspondingly elevated river stage could provide diurnal recharge of the riparian fringe and root zones, and this beneficial influence may be regarded as the 'irrigation effect' (Rood et al. 2010b). We previously proposed that netleaf hackberry (Celtis reticulata), a predominant facultative riparian shrub along the Snake River through Hells Canyon has been promoted by an irrigation effect, while the obligate riparian shrub, sandbar willow (Salix exigua), was more vulnerable to river regulation and sediment depletion following damming (Rood et al. 2010b(Rood et al. , 2011b. ...
... Increasing flows and correspondingly elevated river stage could provide diurnal recharge of the riparian fringe and root zones, and this beneficial influence may be regarded as the 'irrigation effect' (Rood et al. 2010b). We previously proposed that netleaf hackberry (Celtis reticulata), a predominant facultative riparian shrub along the Snake River through Hells Canyon has been promoted by an irrigation effect, while the obligate riparian shrub, sandbar willow (Salix exigua), was more vulnerable to river regulation and sediment depletion following damming (Rood et al. 2010b(Rood et al. , 2011b. This study was undertaken to explore the distributions and abundances of hackberry along the Hells Canyon corridor and to investigate possible benefit due to the irrigation effect. ...
River regulation impacts riparian ecosystems by altering the hydrogeomorphic conditions that support streamside vegetation. Obligate riparian plants are often negatively impacted since they are ecological specialists with particular instream flow requirements. Conversely, facultative riparian plants are generalists and may be less vulnerable to river regulation, and could benefit from augmented flows that reduce drought stress during hot and dry periods. To consider this ‘irrigation effect’ we studied the facultative shrub, netleaf hackberry (Celtis reticulata), the predominant riparian plant along the Hells Canyon corridor of the Snake River, Idaho, USA, where dams produce hydropeaking, diurnal flow variation. Inventories of 235 cross-sectional transects revealed that hackberry was uncommon upstream from the reservoirs, sparse along the reservoir with seasonal draw-down and common along two reservoirs with stabilized water levels. Along the Snake River downstream, hackberry occurred in fairly continuous, dense bands along the high water line. In contrast, hackberry was sparsely scattered along the free-flowing Salmon River, where sandbar willow (Salix exigua), an obligate riparian shrub, was abundant. Below the confluence of the Snake and Salmon rivers, the abundance and distribution of hackberry were intermediate between the two upstream reaches. Thus, river regulation apparently benefited hackberry along the Snake River through Hells Canyon, probably due to diurnal pulsing that wets the riparian margin. We predict similar benefits for some other facultative riparian plants along other regulated rivers with hydropeaking during warm and dry intervals. To analyze the ecological impacts of hydropeaking we recommend assessing daily maxima, as well as daily mean river flows.
... Many responses of riparian communities to regulation of flows and water levels have been identified world-wide (Greet, Cousens, & Webb, 2012;Johnson & Waller, 2013;Nilsson & Berggren, 2000), including vegetation encroachment, interruptions of natural regeneration, senescence of forests, increasing stress and disease-induced mortality, reduced growth rate, altered recruitment, failure of seedling establishment, longitudinal and lateral fragmentation (Belmar, Bruno, Martínez-Capel, Barquín, & Velasco, 2013;Garófano-Gómez et al., 2013;González, González-Sanchís, Cabezas, Comín, & Muller, 2010;González, González-Sanchis, Comín, & Muller, 2012), and shifts in the composition and diversity of riparian vegetation (Bejarano, Nilsson, González del Tánago, & Marchamalo, 2011;Rood, Braatne, & Goater, 2010;Webb et al., 2013). The responses to altered flows of the riparian ecosystems remain a long-standing challenge in Mediterranean regions (Belmar et al., 2013;Dallas, 2013;Garófano-Gómez et al., 2013), likely a result of the multiple external pressures that influence these ecosystems, either directly or indirectly. ...
Many riparian ecosystems in Mediterranean Europe are affected by land use and flow alteration by dams. We focused on understanding how these stressors and their components affect riparian forests in the region. We asked the following questions: (1) Are there well‐defined, responsive riparian guilds? (2) Do dam‐induced streamflows determine abundance and distribution of riparian guilds? (3) What are the main drivers governing composition and cover of riparian guilds in regulated rivers?
We inventoried the cover of riparian woody species in free‐flowing rivers and downstream of dams. We performed a cluster analysis and ordination to derive riparian guilds, using abundance data from 66 riparian woody species and 26 functional plant traits. We used a reduced set of principal components for the environment, land use and hydrology, and general linear modelling to explore the effect of these factors (separately and combined) on riparian guilds.
We found that: (1) four dominant guilds are responsive to disturbance in southwestern European streams, namely the obligate riparian, water‐stress tolerant, deciduous competitive and Mediterranean evergreen guilds; (2) a set of land use and hydrological variables differentially affect the diverse co‐occurring riparian guilds; (3) frequency and duration of high flow pulses and the low‐flow conditions were major drivers of change in landscapes dominated by intensive agriculture and forestry; (4) storage reservoirs reduced the cover of obligate riparian and Mediterranean evergreen guilds, and increased the abundance of water‐stress tolerant and deciduous competitive guilds, while run‐of‐river dams, having limited water storage, reduced both obligate and deciduous competitive guilds.
Synthesis and applications . Future research in southwestern Europe should address the resilience of riparian guilds and the effects of interacting landscape factors and stressors on guild distribution. Streamflow regulations downstream of reservoirs should focus on specific flow components, namely the magnitude of flows, and frequency and duration of extreme flow events. For successful mitigation of the dam‐induced effects on riparian vegetation, river management plans must incorporate the environmental and land use site‐specific contexts.
... The mean litter production estimate for the LRZ in which tamarisk dominates is 299 g AFDM/m 2 per year. Both substrate and associated plant composition resulting from historic and presentday fluvial processes affect associated biotic assemblages found along regulated rivers (Greenwood et al. 2004, Durst et al. 2008, Rood et al. 2009). ...
The disturbance history, plant species composition, productivity, and structural complexity of a site can exert bottom-up controls on arthropod diversity, abundance, and trophic structure. Regulation alters the hydrology and disturbance regimes of rivers and affects riparian habitats by changing plant quality parameters. Fifty years of regulation along the Colorado River downstream of Glen Canyon Dam has created a no-analog, postdam "lower" riparian zone close to the water's edge that includes tamarisk (Tamarix sp.), a nonnative riparian shrub. At the same time, the predam "upper" facultative riparian zone has persisted several meters above the current flood stage. In summer 2009, we used pitfall traps within these 2 riparian zones that differ in plant composition, productivity, and disturbance frequency to test for differences in arthropod community (Hymenoptera, Arachnida, and Coleoptera) structure. Arthropod community structure differed substantially between the 2 zones. Arthropod abundance and species richness was highest in the predam upper riparian zone, even though there was a greater amount of standing plant biomass in the postdam lower riparian zone. Omnivore abundance was proportionately greater in the upper riparian zone and was associated with lower estimated productivity values. Predators and detritivores were proportionately greater in the postdam lower riparian zone. In this case, river regulation may create habitats that support species of spiders and carabid beetles, but few other species that are exclusive to this zone. The combined richness found in both zones suggests a small increase in total richness and functional diversity for the Glen Canyon reach of the Colorado River.
