USE OF NATIVE AND NONNATIVE NEST PLANTS BY RIPARIAN‐NESTING BIRDS ALONG TWO STREAMS IN NEW MEXICO

Nonnative plant invasions are a management concern, particularly in riparian forests, but little is known about mechanisms through which they influence vertebrate communities. In the American Southwest, native trees such as cottonwood (Populus spp.) are thought to provide better habitat for breeding birds than nonnative plants, which are more tolerant of human‐altered conditions. To evaluate effects of riparian forest composition on riparian‐nesting birds, we examined nest plant use along two rivers in New Mexico that differed in abundance of nonnative vegetation. Of the nests we observed, 49% along the Middle Rio Grande were constructed in nonnative plants, compared with 4% along the Gila River. Birds in the canopy and cavity‐nesting guilds constructed less than 5% of their nests in nonnative plants along either river. At the Middle Rio Grande, birds in the subcanopy/shrub guild constructed 67% of their nests in nonnative plants. Despite the relatively low availability of cottonwoods, they were used by greater numbers of species than any other woody plant at either river. Riparian obligates and species of conservation concern in the canopy and cavity guilds were especially dependent on cottonwood and Arizona sycamore (Platanus wrightii). Our results show that, although nonnative trees and shrubs support large numbers of nests for certain birds, cottonwoods and other large native trees are disproportionately important to riparian bird communities. Copyright © 2013 John Wiley & Sons, Ltd.     

The importance for birds of the riparian woodlands within the alluvial corridor of the river garonne,S.W. France

Communities of nesting birds were studied in four distinct biotopes within the alluvial corridor of the River Garonne: 50 terrace woodlands, 17 riparian woodlands, one poplar plantation, and one slope woodland. A total of 400 stations were investigated, consisting of eight distinct classes of forest size for the terrace woodlands and four for the riparian woodlands. The distribution of 64 species of birds, observed by means of 20 minute listening point surveys, was related to three main factors: forest size, site wetness, and the wooded space marginality (forests, woods, copses, hedges, trees). Indices of mean richness and of mean abundance show that the riparian woodlands were the richest and the most densely populated. The surface area of woodlands has a strong effect on the structure of the bird community on terraces but less in the riparian environment. Multivariate analysis contrasted the species from the open islands within closed environments with the species from the closed islands within an open environment. The effect upon the nesting bird communities of the fragmentation of the original forest within the alluvial corridor of the River Garonne is demonstrated by a grouping of two characteristics: the connectivity of the riparian woodlands and the insularity of the terrace woodlands. The conservation of a continuous ribbon of riparian woodlands is shown to be an important condition for maintaining a rich community of nesting birds.     

Anthropogenic Disturbance and Environmental Associations with Fish Assemblage Structure in Two Nonwadeable Rivers

Nonwadeable rivers are unique ecosystems that support high levels of aquatic biodiversity, yet they have been greatly altered by human activities. Although riverine fish assemblages have been studied in the past, we still have an incomplete understanding of how fish assemblages respond to both natural and anthropogenic influences in large rivers. The purpose of this study was to evaluate associations between fish assemblage structure and reach‐scale habitat, dam, and watershed land use characteristics. In the summers of 2011 and 2012, comprehensive fish and environmental data were collected from 33 reaches in the Iowa and Cedar rivers of eastern‐central Iowa. Canonical correspondence analysis (CCA) was used to evaluate environmental relationships with species relative abundance, functional trait abundance (e.g. catch rate of tolerant species), and functional trait composition (e.g. percentage of tolerant species). On the basis of partial CCAs, reach‐scale habitat, dam characteristics, and watershed land use features explained 25.0–81.1%, 6.2–25.1%, and 5.8–47.2% of fish assemblage variation, respectively. Although reach‐scale, dam, and land use factors contributed to overall assemblage structure, the majority of fish assemblage variation was constrained by reach‐scale habitat factors. Specifically, mean annual discharge was consistently selected in nine of the 11 CCA models and accounted for the majority of explained fish assemblage variance by reach‐scale habitat. This study provides important insight on the influence of anthropogenic disturbances across multiple spatial scales on fish assemblages in large river systems. Copyright © 2014 John Wiley & Sons, Ltd.     

Ecological strategies successfully predict the effects of river floodplain rehabilitation on breeding birds

To improve the ecological functioning of riverine ecosystems, large‐scale floodplain rehabilitation has been carried out in the Rhine–Meuse Delta since the 1990s. This paper evaluates changes in abundance of 93 breeding bird species over a period of 10 years in response to rehabilitation, by comparing population changes in 75 rehabilitated sites with 124 non‐rehabilitated reference sites. Such quantitative, multi‐species, large‐scale and long‐term evaluations of floodplain rehabilitation on biodiversity are still scarce, particularly studies that focus on the terrestrial component. We try to understand the effects by relating population trends to ecological and life‐history traits and strategies of breeding birds. More specifically, we try to answer the question whether rehabilitation of vegetation succession or hydro‐geomorphological river processes is the key driver behind recent population changes in rehabilitated sites. Populations of 35 species have significantly performed better in rehabilitated sites compared to non‐rehabilitated floodplains, whereas only 8 have responded negatively to rehabilitation. Differences in effects between species are best explained by the trait selection of nest location. Reproductive investment and migratory behaviour were less strong predictors. Based on these three traits we defined eight life‐history strategies that successfully captured a substantial amount of variation in rehabilitation effects. We conclude that spontaneous vegetation succession and initial excavations are currently more important drivers of population changes than rehabilitation of hydrodynamics. The latter are strongly constrained by river regulation. If rehabilitation of hydro‐geomorphological processes remains incomplete in future, artificial cyclic floodplain rejuvenation will be necessary for sustainable conservation of characteristic river birds. Copyright © 2010 John Wiley & Sons, Ltd.     

Colonisation of terrestrial vegetation in an intermittent river: Diversity responses to seasonal drying

Intermittent rivers are dynamic ecosystems that experience a predictable or unpredictable loss of surface water and are characterised by changing lotic, lentic (ponding) and dry habitats. Plant communities colonising dry channels during the desiccation stage can be diverse, abundant and differ in their tolerances to water availability and habitat conditions. This study examines the colonisation of terrestrial vegetation in two intermittent rivers in the United Kingdom, and whether terrestrial plant taxonomic richness and functional diversity increase during the dry phase. Six reaches were surveyed for terrestrial plants during the dry phase over a standard 100 m length every month from April to October 2021. We found the channel and bank taxonomic richness increased with drying duration. Functional traits of vegetation height, clonality, clonality richness and Ellenberg's value of light moisture also increased with stream desiccation. Bed sediment conditions (the proportion of sand and gravel) and the 12-month antecedent percentage of zero flow days were the key drivers of plant community composition. We believe plant propagules from the riparian zone and channel vegetation on topographic high points in the channel aided plant colonisation of the riverbed once flow ceased. Past research may have underestimated the biodiversity value of intermittent rivers by failing to include the ecological importance of plants during the dry phase. Information on plant diversity of the dry phase is important to determine the overall biodiversity of intermittent rivers for their long-term conservation and management.     

MORE EXOTIC AND FEWER NATIVE PLANT SPECIES: RIVERINE VEGETATION PATTERNS ASSOCIATED WITH ALTERED SEASONAL FLOW PATTERNS

Natural flow regimes are important for sustaining riverine vegetation. The regulation of river flows to provide water for agriculture often results in changes to flow timing. This study assesses the impact of altered seasonal flow patterns on riverine flora. Within temperate Australia, we surveyed the vegetation of five lowland rivers, three of which have large dams that alter their seasonal flow patterns; the other two are unregulated. From four to six sites were selected on each river, and these were classified into three levels of regulation based on the extent to which the timing of their seasonal flow patterns were altered. Sites were surveyed in winter and the following summer. Permanent quadrats were also established at a number of the surveyed sites and resurveyed every 3 months. Of the 267 plant taxa identified, 145 were exotic (non‐native). More exotic taxa and fewer native taxa were associated with increasing level of seasonal flow inversion (regulation). In particular, greater numbers of short‐lived exotic terrestrial taxa and fewer native woody taxa were associated with increasing level of regulation. Some exotic woody species (e.g. willows) were more common in the unregulated rivers and may have life‐history traits favoured by the natural seasonal flow patterns of study area. Multivariate analyses showed that level of regulation had a significant effect on the overall composition of the riverine vegetation. Our results provide support for the hypotheses that flow regulation adversely affects native species diversity and increases the vulnerability of riparian zones to invasion by exotic species; however, these effects are dependent on plant species' life‐history strategies. Our study highlights the importance of natural seasonal flow patterns for sustaining native riverine plant communities. Flow management aimed at maintaining or restoring ecological values should consider seasonal flow patterns. Winter/spring flow peaks may be particularly important for the recruitment of native riverine plants, especially trees and shrubs, and reducing the extent of exotic annuals and grasses. Copyright © 2012 John Wiley & Sons, Ltd.     

Riverine Landscape Patches Influence Trophic Dynamics of Riparian Ants

Food webs in riparian corridors are increasingly viewed as embedded in complex riverine landscapes characterized by an amalgam of aquatic, semi‐aquatic, and terrestrial habitats. However, the influence of riverine landscape pattern on trophic dynamics of riparian consumers remains largely unknown. We used naturally abundant stable isotope ratios (δ¹⁵N) to compare trophic structure of ants (Formica subsericea) among riparian patch types (crop, grass/herbaceous, gravel bar, lawn, mudflat, shrub, swamp, and woody vegetation) at 12 riverine landscapes distributed along an urban‐rural landscape gradient of the Scioto River, Ohio, USA. We expected that the diet of F. subsericea, a common generalist consumer, would reflect local prey availability and thus differences in trophic dynamics among patch types. Mean ant δ¹⁵N was higher in crop patches than in any other patch type, and was lowest in grass/herbaceous, lawn, shrub, and woody vegetation patches, suggesting that patch type was associated with trophic position of F. subsericea. We also found that the range of δ¹⁵N, and thus trophic breadth, was significantly different by patch type, with woody vegetation exhibiting the greatest spread. Variability in canopy, tree and shrub cover, and the degree of urban development was positively correlated with δ¹⁵N range (R² = 0.78), pointing to the role of habitat structure in mediating trophic breadth of riparian ants. These findings provide evidence that riverine landscape pattern can strongly influence trophic dynamics of riparian arthropods. Copyright © 2016 John Wiley & Sons, Ltd.     

Occupancy Patterns of Mammals and Lentic Amphibians in the Elwha River Riparian Zone Before Dam Removal

The downstream transport of sediments and organics and upstream migration of anadromous fishes are key ecological processes in unregulated riverine ecosystems of the North Pacific coast, but their influence on wildlife habitats and populations is poorly documented. Removal of two large hydroelectric dams in Washington's Elwha Valley provides an unprecedented opportunity to study long‐term responses of wildlife populations to dam removal and restoration of these key ecological processes. We compared pre‐dam removal patterns in the relative abundance and occupancy of mesocarnivores, small mammals and lentic amphibians of the Elwha River riparian zone above, between and below the dams. Occupancy of riparian habitats by three mesocarnivore species diminished upriver but did not appear to be closely linked with the absence of salmon in the upper river. Although the importance of salmon in the lower river cannot be discounted, other gradients in food resources also likely contributed to observed distribution patterns of mesocarnivores. Abundance and occupancy patterns within congeneric pairs of new world mice (Peromyscus spp.) and shrews (Sorex spp.) indicated that closely related species were negatively associated with each other and responded to habitat gradients in the riparian zone. The availability of lentic habitats of amphibians was highly variable, and occupancy was low as a result of rapidly changing flows during the larval development period. We speculate that long‐term changes in habitat conditions and salmon availability following dam removal will elicit long‐term changes in distribution of mesocarnivores, small mammals and amphibians. Long‐term monitoring will enhance understanding of the role of fish and restored ecosystem processes on wildlife communities along salmon‐bearing rivers in the region. Copyright © 2013 John Wiley & Sons, Ltd.     

PERSISTING EFFECTS OF RIVER REGULATION ON EMERGENT AQUATIC INSECTS AND TERRESTRIAL INVERTEBRATES IN UPLAND FORESTS

River regulation can alter the structural complexity and natural dynamics of river ecosystems substantially with negative consequences for aquatic insects. However, there have been few studies of regulation effects on the export of emergent insects into terrestrial ecosystems. In northern Scandinavia, we compared emerged aquatic insect and terrestrial invertebrate biomass between four strongly regulated and four free‐flowing rivers using fortnightly measurements at three upland‐forest blocks in each over one summer. The biomass of emerged aquatic insects was significantly lower along regulated rivers than free‐flowing rivers. Biomass in Linyphiidae, Opiliones, Staphylinidae, total Coleoptera, Formicidae and total terrestrial invertebrates was also lower along regulated rivers. Aquatic insect biomass did not explain the entire regulation effect on terrestrial invertebrates but did explain significant variations among Linyphiidae, total Coleoptera, Formicidae and total terrestrial biomass. Variations in Formicidae also explained significant variance among several terrestrial taxa, suggesting some keystone role in this group. Overall, our results suggest that river regulation affects upland‐forest invertebrate communities, with at least some of these effects arising from links between aquatic emergence and terrestrial predators. The data highlight the need to consider areas beyond the riparian zone when assessing the effects of river regulation. Copyright © 2012 John Wiley & Sons, Ltd.     

Impact of Incision of Gravel‐bed Rivers on Ground Beetle Assemblages

The impact of river incision induced by channelization and gravel mining on the structure of ground beetle assemblages in riparian habitats was investigated on three montane rivers in southern Poland. Ground beetles were collected on three benches of different elevation in 11 incised and 14 vertically stable cross sections of the rivers. In total, 5821 individuals representing 106 species were collected. The effect of river incision on the diversity and abundance of ground beetles depended on bench height. Only on the lowest bench, inundated about once per year on average, species richness of the assemblages was significantly reduced in incised river cross sections. On this bench, the abundance of the specialists of exposed riverine sediments, i.e. small and medium‐sized predators with high dispersal power and spring breeding strategy, was highly negatively affected by river incision. On the highest bench, large, brachypterous species with spring and autumn breeding strategy, typical of undisturbed habitats, were more abundant in incised cross sections. As this bench is practically not subjected to flooding even in vertically stable cross sections, these species probably benefited from the occurrence of riparian forest along most incised river sections, whereas the riparian areas along vertically stable sections are subjected to higher agricultural pressure. This study shows that in the mountain region where high precipitation helps to maintain moisture of the riparian habitats, river incision has a negative impact only on the specialists of exposed riverine sediments. Copyright © 2016 John Wiley & Sons, Ltd.     

VEGETATION–LANDFORM ASSEMBLAGES ALONG SELECTED RIVERS IN THE CZECH REPUBLIC,A DECADE AFTER A 500‐YEAR FLOOD EVENT

Rivers with a natural flow regime strongly influence the dynamics of riparian plant communities through hydrological and geomorphological processes. In this study, associations between fluvial landforms and vegetation are investigated on three near‐natural rivers in the Czech Republic a decade after a 500‐year return period flood in July 1997. This extreme disturbance destroyed the anthropogenically modified river channels and created suitable conditions for a range of ecosystems with high diversity and ecological stability. Field surveys were conducted on fluvial landforms (bars, islands, banks, floodplains and terraces) along three ‘renaturalized’ rivers, where no technical modifications had subsequently been made to their channels outside urban areas and the floodplains had been left in a post‐flood state. Vegetation species abundance and 13 environmental variables (topographical, hydrological and soil) were investigated in summer 2007, 10 years after the extreme flood disturbance. The results suggest that the recently created fluvial geomorphic forms are key environmental determinants of riparian vegetation distribution patterns. A range of statistical analyses illustrate that some plant species show predictable patterns of occurrence that correspond with the fluvial forms, supporting a fourfold grouping of herbaceous and woody species and the identification of typical plant communities associated with gravel bars, islands, banks, floodplains and terraces. An investigation of the species richness found on different fluvial landforms showed that the highest number of species occurred on the floodplain and decreased gradually towards the channel bed and towards terraces. Investigation of existing conditions in reaches of rivers with natural dynamics of fluvial processes provides valuable information that can be used as an effective tool for planning restoration strategies and precise management. However, the most important finding of this study is the remarkable establishment of complex river corridor vegetation–landform associations within 10 years of a 500‐year flood that removed the heavily cultivated landscape that had existed before the event. Copyright © 2011 John Wiley & Sons, Ltd.     

EFFECTS OF FLOW DYNAMICS ON THE AQUATIC‐TERRESTRIAL TRANSITION ZONE (ATTZ) OF LOWER MISSOURI RIVER SANDBARS WITH IMPLICATIONS FOR SELECTED BIOTA

Sandbars are an important aquatic terrestrial transition zone (ATTZ) in the active channel of rivers that provide a variety of habitat conditions for riverine biota. Channelization and flow regulation in many large rivers have diminished sandbar habitats and their rehabilitation is a priority. We developed sandbar‐specific models of discharge‐area relationships to determine how changes in flow regime affect the area of different habitat types within the submerged sandbar ATTZ (depth) and exposed sandbar ATTZ (elevation) for a representative sample of Lower Missouri River sandbars. We defined six different structural habitat types within the sandbar ATTZ based on depth or exposed elevation ranges that are important to different biota during at least part of their annual cycle for either survival or reproduction. Scenarios included the modelled natural flow regime, current managed flow regime and two environmental flow options, all modelled within the contemporary river active channel. Thirteen point and wing‐dike sandbars were evaluated under four different flow scenarios to explore the effects of flow regime on seasonal habitat availability for foraging of migratory shorebirds and wading birds, nesting of softshell turtles and nursery of riverine fishes. Managed flows provided more foraging habitat for shorebirds and wading birds and more nursery habitat for riverine fishes within the channelized reach sandbar ATTZ than the natural flow regime or modelled environmental flows. Reduced summer flows occurring under natural and environmental flow alternatives increased exposed sandbar nesting habitat for softshell turtle hatchling emergence. Results reveal how management of channelized and flow regulated large rivers could benefit from a modelling framework that couples hydrologic and geomorphic characteristics to predict habitat conditions for a variety of biota. Published in 2011 by John Wiley & Sons, Ltd.     

Changes in riparian vegetation communities below a large dam in a monsoonal region: Futase Dam,Japan

This paper examines the effects of a dam reservoir flood control on riparian plant communities in an Asian monsoon area subjected to large summer floods under natural conditions. We compared riparian plant communities downstream of the Futase Dam located on the Arakawa River, with communities on the Nakatsu River, a tributary of the Arakawa River with no dam. Historical changes in spatial distribution of riparian vegetation communities were analysed using aerial photographs. Stand ages and flood history were also examined to analyse the likelihood of tree erosion in scenarios with and without flood control. Comparison of the two reaches shows that the reduced flood peaks below the Futase Dam led to the expansion of riparian forest area and an increase in species diversity. Reduction in the flood peaks below the dam means that the toppling moment of the trees is no longer exceeded. The result is that the riparian forest below the dam is able to develop into later successional stages. Copyright © 2004 John Wiley & Sons, Ltd.     

How do instream flow increase and gravel augmentation impact biological communities in large rivers: A case study on the Upper Rhine River

Actions are being developed to address the adverse consequences of engineering works on large European rivers by developing and implementing restoration activities in order to enhance the functionality and biodiversity of fluvial hydrosystems. However, as has frequently been mentioned in the scientific literature, quantitative and qualitative evaluation of the project benefits, if any, and their sustainability are hindered by the difficulty in assessing the responses of aquatic and riparian communities to the methods employed. A case study was conducted on a by‐passed section of the Upper Rhine River (France and Germany) to investigate the effects of instream flow increase and gravel augmentation on selected aquatic and riparian communities (macroinvertebrates, macrophytes, and riparian plants). This paper presents the results of a 6‐year interdisciplinary, before‐after control‐impact design monitoring study. The complexity of the study lies in carrying out a separate assessment of the cumulative effects on a site‐based, project‐specific basis. The results showed that (a) the instream flow increase resulted in greater richness of macrophyte species in the newly created backwaters, (b) the artificial gravel bar favoured the recruitment of pioneer species, including invasive species, although gravel redistribution by floods prevented their development, and (c) gravel augmentation tended to promote the taxonomic richness of macroinvertebrate communities with the appearance of species adapted to the new substrate areas. These findings should help to fill the knowledge gaps in large‐scale restoration and contribute key responses to the most frequently arising issues in this area, especially those concerning the efficiency and sustainability of river restoration projects.     

Application and assessment of a dynamic riparian vegetation model to predict the spatial distribution of vegetation in two Japanese river systems

Riparian ecosystems which are highly sensitive for hydrological processes are being altered worldwide, largely because of anthropogenic activities that include the construction of dams, the afforestation of river basins and the mining of river gravel. During last 60 years, many of the Japanese rivers have been severely forested, and the gravel habitats that were dominant before the 1950s no longer exist. The restoration of these habitats to their former condition to conserve the diversity associated with undisturbed gravel habitats is a growing concern. Therefore, the influences that alter these riparian habitats must be recognized, and the development of a management tool to predict possible changes and evaluate causes and effects is emerged. In this context the numerical models used to describe the riparian vegetation dynamics is important. Therefore, the objective of this study was to evaluate the application of a recently developed dynamic riparian model (DRIPVEM) under Japanese river conditions to predict the spatial distribution of riparian vegetation. The model simulation was conducted for two Japanese river reaches, and the compatibility of the model was verified with observations on the distribution of vegetation. Based on these visual observations, the simulated results showed reasonable agreement with the observations. Furthermore, the compatibility of the model was evaluated with the help of a GIS tool. The model compatibility was greater than 70% for the simulation of both tree and herb distributions; however, for the bare areas, the compatibility was approximately 50%. The accuracy of the model was greater than 0.85 and based on the Kappa coefficient of agreement, the performance of the model was moderate to substantial for the conditions of the two river systems. Although mimicking complex ecosystem processes is a challenging task for any type of dynamic model; the DRIPVEM has great potential to predict the distribution of riparian vegetation.     

Evaluating the Framework of a New River Bird Survey Method

River bird assemblages can serve as beacons of environmental change associated with restoration or degradation. River birds regularly rely on riverine resources at some point in their life cycle, vary in the scale of temporal and spatial of use and forage at multiple levels of the food web (e.g. fish, aquatic plants, aquatic or emergent insects). We present a novel river bird survey method that is more easily employed and less intrusive than riverbank transect or boat surveys and encompasses a wide suite of species and a year‐round time frame. We evaluate the relative efficacy of different levels of survey duration (20, 15, 10 or 5 min), number of surveys (every 2 weeks in spring and fall and every 3 weeks in summer and winter) and number of sites on the survey's ability to document species richness and bird abundance. We used two statistical approaches, species accumulation curves (for duration, number of surveys and number of sites) and first‐order Jackknifes (for duration). We conclude that a biweekly or triweekly survey, 25 sites in the focal river, and a survey duration of at least 15 min are sufficient to meet our objectives. This logistically efficient survey approach facilitates monitoring complex and long‐term change such as that associated with river restoration and dam removal. Copyright © 2017 John Wiley & Sons, Ltd.     

Dynamic vegetation model as a tool for ecological impact assessments of dam operation

This study presented the results of an application of a floodplain dynamic model to the Nakdong River, South Korea. At the Nakdong River, high flows are reduced by dams and the river bed is degraded. Both changes contribute toward the same result: the floodplain is hydraulically disconnected from the main channel and the morphology of the river has been modified. Such changes brought also to a deep modification in the riparian vegetation distribution, abundance and composition. The focus of the study is on the relationship between the hydrology alterations induced by dams and the successional changes in riparian vegetation. More in detail, the study attempts to adapt an existing dynamic floodplain vegetation model to the Nakdong ecosystem characteristics in order to single out what were the effects of the dam operations that led to a change in the riparian landscape. The dynamic model is targeted on Monsoon floodplain vegetation, it is developed upon a custom developed geoprocessing framework and supported by a standalone user interface. It simulates dynamics of floodplain vegetation communities based on different physical parameters. The general concept of the model is that a vegetation community will either undergo toward a maturation stage or will be destroyed (recycling or retrogression) if the magnitude of key physical parameters is greater than the threshold value for a specific community. The model has been calibrated using hydraulic data spanning the time period 1952–2007. The calibration results have been also used to investigate the impacts on the riparian vegetation given by dams operations. The findings of the research highlight that consecutive years of reduced maximum discharge allowed consistent vegetation colonization of riverine areas that were bare before the dam construction.     

Regulation leads to increases in riparian vegetation,but not direct allochthonous inputs,along the Colorado River in Grand Canyon,Arizona

Dams and associated river regulation have led to the expansion of riparian vegetation, especially nonnative species, along downstream ecosystems. Nonnative saltcedar is one of the dominant riparian plants along virtually every major river system in the arid western United States, but allochthonous inputs have never been quantified along a segment of a large river that is dominated by saltcedar. We developed a novel method for estimating direct allochthonous inputs along the 387 km‐long reach of the Colorado River downstream of Glen Canyon Dam that utilized a GIS vegetation map developed from aerial photographs, empirical and literature‐derived litter production data for the dominant vegetation types, and virtual shorelines of annual peak discharge (566 m³ s^?1 stage elevation). Using this method, we estimate that direct allochthonous inputs from riparian vegetation for the entire reach studied total 186 metric tons year^?1, which represents mean inputs of 470 gAFDM m^?1 year^?1 of shoreline or 5.17 gAFDM m^?2 year^?1 of river surface. These values are comparable to allochthonous inputs for other large rivers and systems that also have sparse riparian vegetation. Nonnative saltcedar represents a significant component of annual allochthonous inputs (36% of total direct inputs) in the Colorado River. We also estimated direct allochthonous inputs for 46.8 km of the Colorado River prior to closure of Glen Canyon Dam using a vegetation map that was developed from historical photographs. Regulation has led to significant increases in riparian vegetation (270–319% increase in cover, depending on stage elevation), but annual allochthonous inputs appear unaffected by regulation because of the lower flood peaks on the post‐dam river. Published in 2010 by John Wiley & Sons, Ltd.     

Increasing River Flow Expands Riparian Habitat: Influences of Flow Augmentation on Channel Form,Riparian Vegetation and Birds Along the Little Bow River,Alberta

With river regulation, water withdrawal is common, reducing instream flows. The opposite alteration, flow augmentation, is less common and could reveal a mechanistic coordination between flow regime, channel form, and riparian ecosystems. The Little Bow River, a naturally intermittent prairie stream in Southern Alberta, has experienced flow augmentation since the late 1890s, and the Little Bow/Highwood Project of 2004 enabled a tripling of diversion flows from 2.9 to 8.5 m³/s. We investigated the subsequent responses by assessing the channel form and riparian vegetation based on aerial photographs taken in 2000 versus 2010, and riparian birds were assessed between 2005 and 2013 to investigate associations with riparian vegetation. Following recent flow augmentation, the mean channel width increased from 12.2 to 13.5 m, while sinuosity was relatively unchanged. Streamside zones with true willows (especially Salix exigua and Salix bebbiana) increased from 7 to 11% of the river corridor, and the facultative riparian wolf willow (Elaeagnus commutata) zones increased from 16 to 20%, while grassy zones decreased from 64 to 52%. Avian species richness and Shannon–Wiener index increased, while species evenness was relatively unaltered, suggesting an increase of rarer bird species in response to the increased habitat structure and diversity following the expansion of riparian shrubs and woodland. This study revealed responses to the recent flow augmentation over the first decade of implementation, and alterations following flow augmentation would likely continue for decades until the river and riparian zones adjust to the new flow regime. Copyright © 2016 John Wiley & Sons, Ltd.     

GEOMORPHOLOGICAL CONTROLS ON VEGETATION RESPONSES TO FLOW ALTERATIONS IN A MEDITERRANEAN STREAM (CENTRAL‐WESTERN SPAIN)

The expected recovery of the natural conditions of large regulated rivers over the distance downstream from a dam is limited by relative tributary size according to the Serial Discontinuity Concept; however, geomorphology may also influence the recovery process. We examined the woody vegetation of the riparian zone in seven river segments distributed along the regulated reach of the Tiétar River in central‐western Spain, which flows through two distinct geomorphic templates. Whereas the annual runoff has decreased by 30% on average along the entire studied reach following the construction of the Rosarito Dam and the initiation of field irrigation in the region, the magnitude and frequency of the peak flows decreased by 30% immediately downstream from the dam but recovered the natural values with the distance downstream. We evaluated the recovery patterns toward the natural riparian conditions by comparing woody species composition, diversity and distribution of vegetation patches established prior to and after dam completion. Our results did not indicate a recovery gradient of any of the analysed vegetation attributes downstream from the dam. Instead, we found that the difference in the slope of the stream channel and banks, the width of the valley and the size of substratum particles among the surveyed patches were factors that significantly mediated dam and tributary effects on vegetation and influenced the degree of vegetation recovery. Hence, the maintenance of the intensity of the flow alteration scheme by the numerous water withdrawals and the low tributary contributions, coupled with differential geomorphological characteristics along the reach, overwhelmed the natural tendency for the river to restore its natural conditions with distance downstream. Improving water management and, particularly, restoring endangered riparian ecosystems require a detailed understanding of existing and potential woody species behaviour across the geomorphological settings of rivers. Copyright © 2012 John Wiley & Sons, Ltd.