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Flood–recession cropping improves smallholder farmers' household food security. The objective of this study was to determine the fertility status of cultivated Zambezi Valley floodplain soils, in northern Zimbabwe. The study was conducted at three sites, along tributaries of Musengezi River. Soil samples were taken at 0.20 m depth increments to 0.60 m from hydromorphologically stratified fields, during the cropping season. Sampling points were replicated twice in each stratum at points equidistant from river edges. Relative elevations of sampling points were measured using levelling equipment. Soil was analysed using: core method for bulk density, hydrometer method for texture, loss on ignition for soil organic carbon (SOC), Kjeldahl procedure for total nitrogen (N), 0.01 M CaCl 2 for pH, and Inductively Coupled Plasma (ICP) for Mehlich 3 extractable elements. Data from soil analyses were subjected to One Way Analysis of Variance and Pearson's correlation analysis. Bulk density ranged from 1.2 to 1.4 g cm −3 and it was negatively related to distance from river; and positively related to elevation at two sites. Highest values for SOC and total N were 2.04% and 0.36% respectively. Soil pH ranged from 7.70 to 8.60. Soil organic carbon and N were positively related to distance from river but negatively related to elevation. Threshold concentrations for deficiency: < 12 ppm for K, and <39 ppm for Mg, were exceeded. Calcium, Na, and micronutrients in most cases exceeded concentrations reported for floodplains. Practices that slow down flowing water and fertilizer microdosing are among possible fertility management options. [ABSTRACT FROM AUTHOR]

Tamarisk ( Tamarix spp.) is an invasive plant species that is rapidly expanding along arid and semi-arid rivers in the western United States. A biocontrol agent, tamarisk beetle ( Diorhabda carinulata ), was released in 2001 in California, Colorado, Utah, and Texas. In 2009, the tamarisk beetle was found further south than anticipated in the Colorado River ecosystem within the Grand Canyon National Park and Glen Canyon National Recreation Area. Our objectives were to classify tamarisk stands along 412 km of the Colorado River from the Glen Canyon Dam through the Grand Canyon National Park using 2009 aerial, high spatial resolution multispectral imagery, and then quantify tamarisk beetle impacts by comparing the pre-beetle images from 2009 with 2013 post-beetle images. We classified tamarisk presence in 2009 using the Mahalanobis Distance method with a total of 2500 training samples, and assessed the classification accuracy with an independent set of 7858 samples across 49 image quads. A total of 214 ha of tamarisk were detected in 2009 along the Colorado River, where each image quad, on average, included an 8.4 km segment of the river. Tamarisk detection accuracies varied across the 49 image quads, but the combined overall accuracy across the entire study region was 74%. Using the Normalized Difference Vegetation Index (NDVI) from 2009 and 2013 with a region-specific ratio of >1.5 decline between the two image dates (2009NDVI/2013NDVI), we detected tamarisk defoliation due to beetle herbivory. The total beetle-impacted tamarisk area was 32 ha across the study region, where tamarisk defoliation ranged 1–86% at the local levels. Our tamarisk classification can aid long-term efforts to monitor the spread and impact of the beetle along the river and the eventual mortality of tamarisk due to beetle impacts. Identifying areas of tamarisk defoliation is a useful ecological indicator for managers to plan restoration and tamarisk removal efforts. [ABSTRACT FROM AUTHOR]

The pantropical genus Sesbania (Leguminosae) comprises approximately 85 species and 34 infraspecific taxa. This genus is unusual ecologically in its predilection for wetlands, and morphologically distinctive among legumes, yet has never been comprehensively investigated for the phylogenetic integrity of its subgeneric classification. We subjected a broad sampling of Sesbania species to phylogenetic analysis using both nuclear and plastid DNA sequence data. The resulting phylogenies support the monophyly of Sesbania and two constituent subclades, one represented by the New World endemic Sesbania sections Daubentonia, Daubentoniopsis and Glottidium, and the second comprising the pantropically distributed S. section Sesbania and former S. subgenera Pterosesbania and Agati. The species-rich S. section Sesbania is paraphyletic with respect to S. subg. Agati and Pterosesbania, while S. sect. Daubentonia is paraphyletic with respect to S. sect. Daubentoniopsis. Based on these results we revise the sectional classification of Sesbania. The genus is consistently thoughweakly supported as sister to tribe Loteae. Rate and age estimates suggest that the Sesbania crown clade has an estimated mean age of approximately 18.9 Ma. This implicates long-distance dispersal as causing the pantropical distribution of the genus. Regardless, the New World is optimized as the ancestral area for Sesbania. The prevalence of Sesbania in riparian, wetland, and coastal systems combined with low levels of geographic phylogenetic structure suggested that hydrochory and local extinction potentially explain present-day distributions. [ABSTRACT FROM AUTHOR]

Abstract: Over the past few decades, nitrate‐nitrogen (NO3‐N) concentrations have increased within streams of the central Rockies, a pattern linked to regional N deposition trends. As NO3‐N concentrations increase, in‐stream biological demand may become saturated and stream N export may increase. In mountain landscapes, streams generally flow through steep, narrow valleys with limited riparian area and strong stream‐hillslope connectivity. Interspersed between the narrow valleys are wide segments where substantial floodplain riparian areas can develop. Here, we coupled measures of stream reach NO3‐N flux balances with nutrient enrichment experiments along two stream reaches of contrasting valley morphology in Rocky Mountain National Park. The stream reaches were (1) a narrow valley segment with limited floodplain riparian area and (2) a longitudinally adjacent (directly downstream) wide valley segment with extensive floodplain riparian area. We found that in‐stream biological uptake of added NO3‐N was limited in both segments, presumably as a consequence of saturating conditions. Assessment of mass flux indicated that the narrow valley segment was a consistent source of water and NO3‐N across flow states, while the wide segment was a sink at high flow and a source at low flow. Due to low in‐stream biological retention, gross gains and losses of water and NO3‐N to and from the stream exerted primary constraint on segment mass balances. Our results suggest that the exchange of water and nutrients between the stream and adjacent landscape can exert strong control on reach‐scale nutrient export, particularly in streams experiencing or approaching N saturation. [ABSTRACT FROM AUTHOR]

Abstract: Accurate maps of wetlands and riparian areas are critical for targeting conservation and monitoring efforts. However, detailed inventories in mountain regions are largely non‐existent, as conventional mapping approaches are hindered by high costs, remoteness, and landscape variability. Contemporary modeling techniques can circumvent many of these issues, but are often difficult to interpret and tend to rely on specialized datasets that prevent their wider application. In this study, we used machine learning, Landsat 8 imagery and geomorphometric indices to map the distribution of wetlands and riparian areas in the Cache la Poudre River watershed, Colorado, USA. We used a presence‐background approach to develop and compare predictions from three popular algorithms: boosted regression trees, MaxEnt and random forests. In addition, we developed the models within three elevation‐based life zones to account for altitudinal changes in ecohydrology and land use. Our results showed strong predictive performance, with top‐performing models achieving area under the curve values as high as 0.98 and correctly classifying up to 95% of test data. Model performance varied by elevation zone, and no algorithm consistently outperformed the others. The boosted regression trees approach was uniquely able to differentiate wetlands from irrigated agriculture and residential areas in lower elevations. Multi‐seasonal greenness and wetness indices were highly influential predictors in all models, underscoring the importance of capturing local phenological characteristics and hydrological regimes. Dissection and roughness terrain metrics were key predictors for identifying valley bottom meadows and emergent wetlands in high‐elevation forests. We demonstrate how integrating ecological interpretation into the modeling workflow can inform conventional accuracy statistics and help bridge field‐based and remote sensing perspectives. We also show how continuous model outputs can facilitate this process by depicting nuances of the wetland‐upland continuum. Our approach requires only public data that are widely available, and can be easily adapted to other heterogeneous mountain settings. [ABSTRACT FROM AUTHOR]

Abstract: The effects of disturbance on communities have been a focus of both theoretical and empirical inquiries for many years. Food web stability is hypothesized to be affected by disturbance and the nature of the energy pathways (i.e. allochthonous or autochthonous) of a community. In this study, we investigated whether food webs at paired sites, one in forest and the other in grassland, in ten New Zealand streams along a disturbance gradient differ in their topological structure and robustness. Food web robustness (an indicator of web resistance) assesses the ease with which secondary extinctions permeate the food web following an initial random extinction (disturbance). We found that neither the nature of the energy source nor physical disturbance affected structural metrics or web robustness. As stream systems, particularly in New Zealand, are exposed to regular, unpredictable and dramatic physical disturbance from flooding, it may simply be that the floods result in generalist species dominating and increasing robustness irrespective of the energy source. [ABSTRACT FROM AUTHOR]

Biomonitoring is a common method to monitor environmental change in river ecosystems, a key advantage of biomonitoring over snap-shot physicochemical monitoring is that it provides a more stable, long-term insight into change that is also effects-based. In New Zealand, the main biomonitoring method is a macroinvertebrate sensitivity scoring index, with little established methods available for biomonitoring of fish. This study models the contemporary distribution of common freshwater fish and then uses those models to predict freshwater fish assemblages for each river reach under reference conditions. Comparison of current fish assemblages with those predicted in reference conditions (as observed/ expected (O/E) ratios) may provide a suitable option for freshwater fish biomonitoring. Most of the fish communities throughout the central North Island and lower reaches show substantial deviation from the modelled reference community. Most of this deviation is explained by nutrient enrichment, followed by downstream barriers (i.e. dams) and loss of riparian vegetation. The presence of modelled introduced species had relatively little impact on the presence of the modelled native fish. The maps of O/E fish assemblage may provide a rapid way to identify potential restoration sites. [ABSTRACT FROM AUTHOR]

Abstract: The transition area between rivers and their adjacent riparian aquifers, which may comprise the hyporheic zone, hosts important biochemical reactions, which control water quality. The rates of these reactions and metabolic processes are temperature dependent. Yet the thermal dynamics of riparian aquifers, especially during flooding and dynamic groundwater flow conditions, has seldom been studied. Thus, we investigated heat transport in riparian aquifers during 3 flood events of different magnitudes at 2 sites along the same river. River and riparian aquifer temperature and water‐level data along the Lower Colorado River in Central Texas, USA, were monitored across 2‐dimensional vertical sections perpendicular to the bank. At the downstream site, preflood temperature penetration distance into the bank suggested that advective heat transport from lateral hyporheic exchange of river water into the riparian aquifer was occurring during relatively steady low‐flow river conditions. Although a small (20‐cm stage increase) dam‐controlled flood pulse had no observable influence on groundwater temperature, larger floods (40‐cm and >3‐m stage increases) caused lateral movement of distinct heat plumes away from the river during flood stage, which then retreated back towards the river after flood recession. These plumes result from advective heat transport caused by flood waters being forced into the riparian aquifer. These flood‐induced temperature responses were controlled by the size of the flood, river water temperature during the flood, and local factors at the study sites, such as topography and local ambient water table configuration. For the intermediate and large floods, the thermal disturbance in the riparian aquifer lasted days after flood waters receded. Large floods therefore have impacts on the temperature regime of riparian aquifers lasting long beyond the flood's timescale. These persistent thermal disturbances may have a significant impact on biochemical reaction rates, nutrient cycling, and ecological niches in the river corridor. [ABSTRACT FROM AUTHOR]

Denitrification is the anaerobic, microbial transformation of nitrate (NO3-,) into inert, atmospheric nitrogen (N) under ideal conditions. It is a critical process in the management of anthropogenic NO3-, and has been shown to respond to elevated N concentrations within the soil of urban riparian zones. We investigated the relationship between land use / land cover (LULC) classifications on soil denitrification and associated biogeochemistry within coastal, sub-tropical riparian zones. Soil samples were collected from low-order streams throughout Tampa. FL at distances of 0 m, 5 m, and 10 m from the streambank. Results from factorial analysis indicate that LULC classification (p = 0.005, F = 4.406) was significant in predicting denitrification enzyme activity (DEA) potential, with high density residential sites showing the greatest average DEA potential at 2.439 mg N kg-1 h-1. Variables showing significant difference based on LULC classifications were pH and soil carbon to N ratio, and showing that these factors likely had the most influence over riparian zone soil DEA potential based on LULC classification. These findings suggest that urban riparian zones are responding to elevated N loads when they are present; however, high residential areas showed lower carbon to nitrogen ratios than other sites, suggesting that some of the most urbanized areas could be improved to act as better NO3- sinks. [ABSTRACT FROM AUTHOR]

Abstract: Streams, riparian areas, floodplains, alluvial aquifers, and downstream waters (e.g., large rivers, lakes, and oceans) are interconnected by longitudinal, lateral, and vertical fluxes of water, other materials, and energy. Collectively, these interconnected waters are called fluvial hydrosystems. Physical and chemical connectivity within fluvial hydrosystems is created by the transport of nonliving materials (e.g., water, sediment, nutrients, and contaminants) which either do or do not chemically change (chemical and physical connections, respectively). A substantial body of evidence unequivocally demonstrates physical and chemical connectivity between streams and riparian wetlands and downstream waters. Streams and riparian wetlands are structurally connected to downstream waters through the network of continuous channels and floodplain form that make these systems physically contiguous, and the very existence of these structures provides strong geomorphologic evidence for connectivity. Functional connections between streams and riparian wetlands and their downstream waters vary geographically and over time, based on proximity, relative size, environmental setting, material disparity, and intervening units. Because of the complexity and dynamic nature of connections among fluvial hydrosystem units, a complete accounting of the physical and chemical connections and their consequences to downstream waters should aggregate over multiple years to decades. [ABSTRACT FROM AUTHOR]

Land use alteration is recognized as a threat for many aquatic species, but demographic drivers of land use associated declines are poorly studied. We examined hellbender, Cryptobranchus alleganiensis, demography in six stream reaches stratified across a land use gradient to understand how land use might influence a long-lived species. We used robust-design surveys (2014–2015) to estimate abundance and demographic structure, and all captures recorded between 2007 and 2015 to estimate demographic rates. Catchment-wide riparian (CWR) forest predicted demography better than catchment or local riparian forest. Across space, sub-adult/adult abundance declined and demographic structure became increasingly skewed towards older adults as CWR forest declined. Demographic rates indicated sub-adults/adults were being lost from each reach at a similar rate and most populations remained stable over the period for which data were available (1–8 years per reach). Our findings suggest recruitment (via births, juvenile survival and/or immigration) of young age classes facilitated stability of high-density populations when CWR forest was relatively high. When CWR forest was lower, survivorship and longevity of old adults facilitated persistence of low-density populations for multiple years while recruitment of young age classes suffered. Fine sediment was not correlated with land use but water temperature, conductivity and pH declined as CWR forest increased, highlighting water quality as a possible mechanism linking forest cover to hellbender demography. Our findings suggest maintaining forest in upstream riparian areas is critical for conserving downstream biota, and emphasize the difficulty of detecting declines in long-lived species when environmental alterations act specifically on recruitment of young age classes. [ABSTRACT FROM AUTHOR]

Headwater stream networks expand and contract in response to changes in stream discharge. The changes in the extent of the stream network are also controlled by geologic or geomorphic setting – some reaches go dry even under relatively wet conditions, other reaches remain flowing under relatively dry conditions. While such patterns are well recognized, we currently lack tools to predict the extent of the stream network and the times and locations where the network is dry within large river networks. Here, we develop a perceptual model of the river corridor in a headwater mountainous catchment, translate this into a reduced-complexity mechanistic model, and implement the model to examine connectivity and network extent over an entire water year. Our model agreed reasonably well with our observations, showing that the extent and connectivity of the river network was most sensitive to hydrologic forcing under the lowest discharges ( Q gauge  < 1 L s −1 ), that at intermediate discharges (1 L s − 1  <  Q gauge  < 10 L s −1 ) the extent of the network changed dramatically with changes in discharge, and that under wet conditions ( Q gauge > 10 L s −1 ) the extent of the network was relatively insensitive to hydrologic forcing and was instead determined by the network topology. We do not expect that the specific thresholds observed in this study would be transferable to other catchments with different geology, topology, or hydrologic forcing. However, we expect that the general pattern should be robust: the dominant controls will shift from hydrologic forcing to geologic setting as discharge increases. Furthermore, our method is readily transferable as the model can be applied with minimal data requirements (a single stream gauge, a digital terrain model, and estimates of hydrogeologic properties) to estimate flow duration or connectivity along the river corridor in unstudied catchments. As the available information increases, the model could be better calibrated to match site-specific observations of network extent, locations of dry reaches, or solute break through curves as demonstrated in this study. Based on the low initial data requirements and ability to later tune the model to a specific site, we suggest example applications of this parsimonious model that may prove useful to both researchers and managers. [ABSTRACT FROM AUTHOR]

Urbanization is thought to decrease riparian tree canopy cover, but this outcome may vary depending on geographic context. We examined changes in land cover and riparian tree canopy near Sacramento, California, a Mediterranean climate region impacted by agriculture before urbanization. We used aerial imagery to quantify changes in land cover and the area, width, and density of riparian tree canopy between 1937 and 2014 for the 85-km 2 Arcade Creek watershed. While watershed land cover shifted almost entirely from pasture and crops to urban development, riparian forested area increased by 38 percent. The median width of riparian tree canopy more than doubled, and the density along smaller streams increased significantly ( p <  0.0001). We used multiple data sources to examine potential drivers of these changes. Stream gage data and field observations indicated that the formerly intermittent Arcade Creek stream network receives spatially and temporally variable dry-season flow subsidies from urban runoff, but widespread channel incision may limit the impact of subsidies on riparian vegetation. Accordingly, sampling of riparian woody plants showed few hydrophilic species growing along these streams. Instead we found evidence of native oak regeneration and a high density of escaped horticultural species. The increase in riparian forest cover was thus likely due to changes in vegetation management and species composition from land use conversion, possibly augmented by increased dry-season water availability. The changes in canopy cover we quantified stand in contrast to the accepted pattern of riparian forest decline with urbanization, and are expected to affect ecosystem services. [ABSTRACT FROM AUTHOR]

After decades of fire suppression in eastern North America, land managers now are prioritizing prescribed fire as a management tool to restore or maintain fire-adapted vegetation communities. However, in long-fire-suppressed landscapes, such as the central and southern Appalachians, it is unknown how bats will respond to prescribed fire in both riparian and upland forest habitats. To address these concerns, we conducted zero-crossing acoustic surveys of bat activity in burned, unburned, riparian, and non-riparian areas in the central Appalachians, Virginia, USA. Burn and riparian variables had model support (ΔAICc < 4) to explain activity of all bat species. Nonetheless, parameter estimates for these conditions were small and confidence intervals overlapped zero for all species, indicating effect sizes were marginal. Our results suggest that bats respond to fire differently between upland and riparian forest habitats, but overall, large landscape-level prescribed fire has a slightly positive to neutral impact on all bats species identified at our study site post-fire application. [ABSTRACT FROM AUTHOR]

The longitudinal influences of dam removal on river ecosystems are increasingly well described, but impacts to aquatic-terrestrial connectivity are largely unknown. Before and four successive years after dam removal, we quantified density and trophic metrics of nearshore tetragnathid spiders and riparian swallows and their potential emergent-aquatic insect prey at two experimental reaches located within the former impoundment (one unrestored, one with channel restoration) and one control reach above an intact lowhead dam. We observed substantial annual variability in response variables; however, few patterns appear to be strongly linked to dam removal. We found negligible changes in emergent-insect biomass or community structure, although there were slight changes in the relative abundance of feeding modes (e.g., increased predators, decreased collector-gatherers). The most pronounced response was a ~9.9 times average decline in spider densities after dam removal at the restored reach. Stable-isotope analysis (13C, 15N) indicated that changes in aquatically-derived energy (i.e., nutritional subsidies derived from aquatic primary producers) to riparian consumers generally showed comparable patterns system-wide; swallow aquatically-derived energy declined more in the restored vs. control reach by the final year of the study. Trophic position (TP) of spiders showed little change post-dam removal, while swallow TP converged slightly between control and experimental reaches after dam removal. Collectively, we interpret our results as evidence that lowhead dam removal can prompt relatively nuanced shifts in aquatic-terrestrial trophic dynamics, regardless of intensive channel-restoration activities. In contrast, we found that broader-scale forcings (e.g., discharge, regional temperature) may be more influential in governing crossboundary trophic interactions than the perturbations related to lowhead dam removal. This study furthers current understanding of the effects of dam removal on integrative, food-web metrics of ecosystem structure and function. [ABSTRACT FROM AUTHOR]

Understanding how factors that vary in spatial scale relate to population abundance is vital to forecasting species responses to environmental change. Stream and river ecosystems are inherently hierarchical, potentially resulting in organismal responses to fine-scale changes in patch characteristics that are conditional on the watershed context. Here, we address how populations of two salamander species are affected by interactions among hierarchical processes operating at different scales within a rapidly changing landscape of the southern Appalachian Mountains. We modeled reach-level occupancy of larval and adult black-bellied salamanders (Desmognathus quadramaculatus) and larval Blue Ridge two-lined salamanders (Eurycea wilderae) as a function of 17 different terrestrial and aquatic predictor variables that varied in spatial extent. We found that salamander occurrence varied widely among streams within fully forested catchments, but also exhibited species-specific responses to changes in local conditions. While D. quadramaculatus declined predictably in relation to losses in forest cover, larval occupancy exhibited the strongest negative response to forest loss as well as decreases in elevation. Conversely, occupancy of E. wilderae was unassociated with watershed conditions, only responding negatively to higher proportions of fast-flowing stream habitat types. Evaluation of hierarchical relationships demonstrated that most fine-scale variables were closely correlated with broad watershed-scale variables, suggesting that local reach-scale factors have relatively smaller effects within the context of the larger landscape. Our results imply that effective management of southern Appalachian stream salamanders must first focus on the larger scale condition of watersheds before management of local-scale conditions should proceed. Our findings confirm the results of some studies while refuting the results of others, which may indicate that prescriptive recommendations for range-wide management of species or the application of a single management focus across large geographic areas is inappropriate. [ABSTRACT FROM AUTHOR]

Beavers (Castor canadensis) disappeared from drainages north of Yellowstone National Park in the mid-1900s because of trapping, a potential tularemia outbreak, and willow ( Salix spp.) stand degradation by ungulates. Beavers were reintroduced in 1986 after a 40-yr absence with inventories of active-beaver structures completed each fall after reintroduction for 24 consecutive yr. We used this inventory to evaluate the expansion of beaver populations in a riparian environment recovering from past overuse by ungulates. Specifically, we investigated the density of active-beaver colonies and dams, the change in willow cover, and habitats associated with beaver expansion since reintroduction. Successful establishment and expansion of beavers indicate that sufficient resources were available to the population despite the suboptimal condition of riparian vegetation. Carrying capacity on third-order streams was reached approximately 14 yr after reintroduction (2000) with an average annual density of 1.33 (95th percentile = 1.23 -1.44 active colonies/stream km) between 2000 and 2010. The average annual density of beaver dams during this time was 2.37 (2.04 - 2.71 active dams/stream km). Despite the beaver population being at carrying capacity in meadows since 2000, willow cover increased by 16% between 1981 and 2011. We speculate that beaver activities, together with reduced ungulate browsing from predation and habitat loss, combined to increase willow cover. Willow cover and height were positively associated with colony longevity, but numerous other influencing variables included secondary channels, sinuosity, stream depth, and sandbar width. Our results provide evidence that beaver reintroduction can be successful in riparian areas where willow stand condition is less than optimal and that beavers might ultimately improve willow condition. We suggest that reducing ungulate use of overgrazed riparian environments will facilitate the reestablishment of beaver populations. We also provide managers with habitats that should be identified in an environment targeted for reintroduction. [ABSTRACT FROM AUTHOR]

1. Information on the dietary niches of adult odonates is sparse, as they are highly mobile and evasive animals, which makes them difficult to observe in their natural habitat. Moreover, there is a lack of knowledge on how varying behavioural traits of odonates relate to phenomena like niche partitioning. 2. This study investigated niche partitioning amongst odonate species, foraging guilds and size classes in a riverine system in the Eastern Cape province of South Africa. A combination of stable isotope and fatty acid-based niches was used to infer odonate feeding. 3. Both fatty acid and stable isotope-based niches showed that there was niche separation amongst odonates that forage in flight (fliers) and those that forage from a perch (perchers), amongst odonates of different size classes (damselflies, medium- and large-sized dragonflies), and amongst species, although varying levels of niche overlap were observed in each case. 4. Niche sizes of odonates varied between an upstream and a downstream site. Generally greater niche overlap was recorded at the narrow upstream site (associated with low insect emergence rates) than the wider downstream site (associated with high insect emergence rates), indicating that a greater degree of resource sharing occurred at the upstream site where aquatic food was less abundant. 5. The findings of this study suggest that dietary niches of odonates can be influenced by foraging guild, body size, and/or environmental conditions, and additional study in a variety of regions is recommended to determine the greater applicability of these findings. [ABSTRACT FROM AUTHOR]

1. Insects that emerge from rivers provide nutritional subsidies to local riparian predators. Adult damselflies and dragonflies often benefit from aquatic resources, but their high mobility and evasiveness have made it difficult to monitor their diets. 2. A dual fatty acid and stable isotope analysis approach was used to investigate the links between Odonata size and behaviour with proportions of their aquatically derived nutritional sources. Additionally, the study investigated the variation in dietary contributions of aquatic food sources to Odonata between two sections of a river, each with different aquatic productivity rates. 3. Variations in body size and foraging method of Odonata in the Kowie River ( South Africa) contributed to differences in the contributions of aquatic food sources to their diets. Large Odonata that consumed prey in flight had smaller proportions of aquatic indicator fatty acids and stable isotope-generated proportions of aquatic food sources than did the smaller Odonata that consumed prey from perches. 4. There was a considerable amount of interspecific variation in indicators of aquatic feeding, but Odonata at an upstream site had smaller proportions of aquatic indicators than those at a downstream site which had higher insect emergence rates. 5. The findings of this study contribute information on the dynamics of feeding ecology among adult Odonata, and the substantial contributions of aquatic prey (>80% of total diet in some cases) indicated that cross-boundary trophic linkages via odonates are strong in the Kowie River. [ABSTRACT FROM AUTHOR]

Abstract: This study examines the occurrence of invasive American mink Neovison vison and native water voles Arvicola amphibius along the shorelines of eutrophic lakes and at small midfield ponds in the Mazurian Lakeland, north‐east (NE) Poland. The main hypothesis tested in this study is that built‐up areas and small midfield ponds are avoided by mink; therefore, they can serve as refuges that protect water voles from mink predation. Floating rafts were used to monitor mink and water vole distribution. Mink presence was negatively associated with urbanization at lake shorelines and midfield ponds, and these two characteristics positively correlated with occurrence of water voles in the study area. The probability of occurrence of water voles was significantly lower at sites where mink occurred. The occupancy rates for mink at lakes and at midfield ponds were higher in autumn than in spring and conversely the occupancy rates for water voles were higher in spring and lower in autumn. Our study shows that within a postglacial landscape, urban areas and midfield ponds distant from lakes are avoided by the American mink and thus these areas may function as refuge habitats for water voles and may maintain populations of this rodent at the landscape scale despite the presence of mink. [ABSTRACT FROM AUTHOR]

Tree root exudation (TRE) of water soluble organic carbon (WSOC) is an important but under-assessed component of net primary production, and is thought to strongly influence rhizosphere biogeochemistry. Riparian systems in particular are often viewed as biogeochemical hot spots fueled partially by root exudate WSOC. However, TRE rates have not been previously reported for these systems. The δC signatures of exudates may provide important insights into plant physiology and inform isotope-based methods to identify sources of soil CO fluxes, but this information is also generally lacking. In the present study, root exudate WSOC was collected in situ to assess both net exudation rates and exudate δC values in a temperate riparian forest. Net TRE rates were found to be most strongly related to a combination of tree species, root characteristics and net ecosystem exchange (Adj. R = 0.73; p < 0.001). In contrast, exudate δC values were correlated to time-lagged vapor pressure deficit (Adj. R = 0.21; p < 0.05) and air temperature (Adj. R = 0.43; p < 0.05), suggesting a rapid transfer of photosynthate from the canopy to the rhizosphere. Extrapolation of mean net TRE rates (13 µmol C g root day) from a root mass basis to the entire sampling area suggests that TRE may account for as much as 3% of net annual C uptake and represents an important input of organic matter to riparian soils. Our findings of predictable TRE rates and exudate δC values in the present study suggest that future studies examining δC values of different plant components, soil organic matter and respired soil CO would benefit by accounting for the impact of root exudates. [ABSTRACT FROM AUTHOR]

The forest landscape across the Nordic and Baltic regions hosts numerous lakes and watercourses, which must be included in forest management. In this study, national policy designs regarding protection zones for surface waters on forest land were reviewed and compared for the Nordic countries, Estonia and Latvia. The focus was how each country regulates protection zones, whether they are voluntary or mandatory, and the rationale behind adopting a low or high degree of prescriptiveness. Iceland and Denmark had a low degree of policy prescriptiveness, whereas Norway, Estonia and Latvia had a high degree of prescriptiveness. Sweden and Finland relied to a large extent on voluntary commitments. The prescribed zone widths within the region ranged from 1 m to 5 km. The results indicated that land-use distribution, forest ownership structure and historical and political legacies have influenced the varying degrees of prescriptiveness in the region. [ABSTRACT FROM AUTHOR]

Converting riparian buffers in agricultural areas from annual row crops to short rotation woody crops (SRWCs) grown for biofuel can provide both water quality benefits and a financial incentive for buffer adoption among agricultural producers. A randomized complete block design was used to determine water quality changes resulting from converting plots previously cultivated in corn to SRWC willow ( Salix . spp ) adjacent to a stream in Storrs, CT. Both overland flow and ground water samples were analyzed for total nitrogen (TN) and total phosphorus (TP). Additionally, overland flow was analyzed for suspended solids concentration (SSC) and ground water samples were analyzed for nitrate + nitrite (NO 2 +NO 3 -N). Lower (p = 0.05) concentrations of TN (41%) and TP (53%) were observed in overland flow from willow plots than from corn plots. Shallow ground water concentrations at the edge of willow plots were lower in TN (56%) and NO 3 +NO 2 -N (64%), but 35% higher in TP, than at the edge of corn plots. SSC was also lower (71%) in overland flow associated with willow compared to corn. The treatment had no effect on the depth or volume of overland flow or mass export. The changes in concentrations resulting from conversion of corn to SRWC in a riparian buffer are similar to those observed in restored and established buffers. [ABSTRACT FROM AUTHOR]

Riparian areas are often the only green areas left in urban and suburban landscapes, providing opportunities for conservation and connectivity of both aquatic and terrestrial organisms. While city planners and land managers often tout the importance of riparian networks for these uses, it is not well established if urban riparian plant communities are actually functioning as connected assemblages. Furthermore, urban riparian zones are well known to be highly invaded by non-native plant species and may be functioning to increase the spread of non-native species across the landscape. Here we examine connectivity of plant assemblages in riparian networks within an extensively urbanized landscape. We sampled riparian plant communities at 13 sites along three second-order streams of the Rahway River watershed, New Jersey. We also characterized propagule dispersal at each site by sampling litter packs on the river banks five times between March-October 2011 and identifying germinants from litter packs after cold stratification. Species turnover of both riparian and litter vegetation was more strongly associated with flow distance, particularly for native species, indicating that riverine systems are important for promoting connectivity of native plant assemblages in urban landscapes. However, non-native germinants significantly dominated propagule dispersal along the stream reaches, particularly early in the growing season, suggesting spread utilizing the river system and preemption may be an important mechanism for invasion success in this system. Our data show that management of invasive species should be planned and implemented at the watershed scale to reduce spread via the river system. [ABSTRACT FROM AUTHOR]

This paper describes a method of mapping riparian vegetation in semi-arid to arid environments using the Landsat normalized difference vegetation index (NDVI). The method successfully identified a range of riparian community types across the entire state of Nevada, USA, which spans 7 degrees of latitude and almost 4000 m of elevation. The landscape was stratified into units of similar elevation and solar exposure, and riparian areas were identified as having anomalously high NDVI within a local neighborhood. Thousands of calibration points were used in a simplex optimization to select the spatial neighborhood, the elevation and insolation strata, the minimum NDVI to be considered as potentially riparian, the number of standard deviations from the mean for an anomaly to be classified as riparian, and a limit on upslope position. Mapping of subpixel riparian corridors was improved by applying a directional high-pass filter to the NDVI data. Irrigated areas in agricultural and urban areas were removed based on land ownership maps and manual editing. The final map was tested with 400 independent test points: producer’s accuracy was 84.6% and user’s accuracy was 93.5%. This method should be broadly useful for mapping riparian features across large and complex regions with arid to semi-arid environments.

This study is about the classification and syntaxonomic allocation of the riparian vegetation of the Porsuk River (Eskişehir- Kütahya, western part of Central Anatolia). The Porsuk is part of the Sakarya River basin and is the longest tributary of the Sakarya River. The data were collected using the phytosociological method of Braun-Blanquet and analyzed using TWINSPAN classification and NMDS ordination. Ten syntaxa were identified, all of which are more or less widespread in the nemoral and meridional zone. The woody alluvial vegetation of the study area comprises the associations Salicetum albae, Populetum albae, and Elymo-Rubetum caesii. The riparian reed bed vegetation is represented by the associations Phragmitetum australis, Schoenoplectetum tabernaemontani, Typhetum latifoliae, Typhetum angustifoliae, Cyperetum longi, Caricetum gracilis, and Galio palustris-Juncetum inflexi. The community composition, though of azonal character, suggests marked influence of biogeographical and climatic sub-Mediterranean conditions. [ABSTRACT FROM AUTHOR]

Riparian forests exhibit levels of ecological disturbance that leave them especially prone to biological invasions. Japanese knotweed (Fallopia japonica) is particularly suited to these habitats and is an aggressive invader along watercourses throughout its now-global range as an exotic invader. Using one of the few Silver Maple Floodplain Forest communities that has not been invaded by F. japonica in the West Branch Susquehanna River valley (Pennsylvania, USA) as a baseline, this study examines whether and how this primarily intact riparian forest community differs from nearby invaded communities in terms of 1) native species richness, 2) native species density, and 3) riparian forest tree recruitment. Defining a baseline (intact) community composition will inform restoration plans for local riparian forests where knotweed might be eradicated or reduced. Invaded and non-invaded sites differed statistically across species richness, species density, and tree recruitment. Our results suggest that F. japonica has reduced the diversity and abundance of native understory riparian plant species. The species also appears to have suppressed long-term tree recruitment, setting up a trajectory whereby the eventual decline of trees currently in the canopy could shift this community from a tree-dominated riparian forest to a knotweeddominated herbaceous shrubland. [ABSTRACT FROM AUTHOR]

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Active revegetation is an essential component of biodiversity conservation for fragmented ecosystems and the species that depend on them. However, key knowledge gaps exist around the most cost-effective revegetation strategies to employ in different contexts. This article reports on a revegetation trial undertaken in the Capertee Valley of New South Wales, Australia, to assist the conservation of the critically endangered bird, the Regent Honeyeater ( Anthochaera phrygia). Seven treatments were compared to assess their cost-effectiveness for enhancing plant survival at a floodplain site with a history of grazing on introduced pastures. While overall survival rates were low, treatments involving tree guards had higher survival rates and were more cost-effective than treatments without guards. Weed growth, animal activity and water stress all appeared to play a role in the low survival rates at this site, with enhanced weed control emerging as a priority for future trials at similar sites. [ABSTRACT FROM AUTHOR]

Spatial welfare heterogeneity is frequently modeled within stated preference analysis as a function of discrete or continuous distance between households and affected resources. A common example is distance-decay analysis. Although distance-based models such as these are easily estimated, the ubiquity of this paradigm can lead to analyses that overlook other forms of analysis with equal or greater relevance. This paper develops an alternative approach to spatial heterogeneity in stated preference willingness to pay (WTP) based on the quantity or area of an affected resource surrounding each respondent at an optimized distance band or radius, with distance bands optimized using a grid-search algorithm that maximizes model likelihood. Methods and results are illustrated using a choice experiment on riparian land restoration in Maine, USA. The resulting quantity-within-distance model identifies systematic spatial patterns that are undetectable using distance-based analysis and directly relevant for welfare analysis. [ABSTRACT FROM AUTHOR]

The transport of water and sediment from rivers to adjacent floodplains helps generate complex floodplain, wetland, and riparian ecosystems. However, riverside levees restrict lateral connectivity of water and sediment during flood pulses, making the re-introduction of floodplain hydrogeomorphic processes through intentional levee breaching and removal an emerging floodplain restoration practice. Repeated topographic observations from levee breach sites along the lower Cosumnes River (USA) indicated that breach architecture influences floodplain and channel hydrogeomorphic processes. Where narrow breaches (<75 m) open onto graded floodplains, archetypal crevasse splays developed along a single dominant flowpath, with floodplain erosion in near-bank areas and lobate splay deposition in distal floodplain regions. Narrow breaches opening into excavated floodplain channels promoted both transverse advection and turbulent diffusion of sediment into the floodplain channel, facilitating near-bank deposition and potential breach closure. Wide breaches (>250 m) enabled multiple modes of water and sediment transport onto graded floodplains. Advective sediment transport along multiple flow paths generated overlapping crevasse splays, while turbulent diffusion promoted the formation of lateral levees through large wood and sediment accumulation in near-bank areas. Channel incision (>2 m) upstream from a wide levee breach suggests that large flow diversions through such breaches can generate water surface drawdown during flooding, resulting in localized flow acceleration and upstream channel incision. Understanding variable hydrogeomorphic responses to levee breach architecture will help restoration managers design breaches that maximize desired floodplain topographic change while also minimizing potential undesirable consequences such as levee breach closure or channel incision. [ABSTRACT FROM AUTHOR]

Human communities from the Okavango Delta benefit from the services and goods provided by the wetland ecosystem through its riparian vegetation. These include food and timber products used for the construction of shelter and canoes. Despite the importance of riparian tree species in the Delta, their regeneration structure is currently unknown. For riparian trees to be managed sustainably, information on the current regeneration status of the trees under different land uses is needed. The Moremi game reserve (protected area) and Seronga (communal area) were selected for this study on the regeneration of riparian tree species of Croton megalobotrys Müll. Arg, Philenoptera violacea (Klotzsch) Schrire, Senegalia nigrescens ( Acacia nigrescens) Oliv and Diospyros mespiliformis Hochst. ex A. Dc. The height of each individual tree was estimated in randomly selected 30 plots (15 from each site) of 20 × 50 m for assignment to five regeneration classes: 0-0.5, 0.5-1, 1-2, 2-4 and >4 m. Linear regression was used to infer regeneration status of each species. An independent-sample Student's t test was used to determine any significance differences in seedling density/ha and sapling density/ha between different sites at p < 0.05. Diospyros mespiliformis populations had an unstable regeneration structure in both sites, while P. violacea regeneration was stable regardless of land-use type. Croton megalobotrys and S. nigrescens had an unstable regeneration pattern in Seronga, while in Moremi it was stable; thus, the regeneration structure of C. megalobotrys and S. nigrescens is affected by land-use. This result implies that intervention is needed to conserve the two species in Seronga where the current land-use appears to be incompatible with regeneration; D. mespiliformis also needs to be conserved in both Moremi and Seronga. [ABSTRACT FROM AUTHOR]

Comparisons of community-level functional traits across environmental gradients have potential for identifying links among plant characteristics, adaptations to stress and disturbance, and community assembly. We investigated community-level variation in specific leaf area (SLA), plant mature height, seed mass, stem specific gravity (SSG), relative cover of C4 species, and total plant cover over hydrologic zones and gradients in years 2013 and 2014 in the riparian plant community along the Colorado River in the Grand Canyon. Vegetation cover was lowest in the frequently inundated active channel zone, indicating constraints on plant establishment and production by flood disturbance and anaerobic stress. Changes in trait values over hydrologic zones and inundation gradients indicate that frequently inundated plots exhibit a community-level ruderal strategy with adaptation to submergence (high SLA and low SSG, height, seed mass, C4 relative cover), whereas less frequently inundated plots exhibit adaptation to drought and infrequent flood disturbance (low SLA and high SSG, height, seed mass, C4 relative cover). Variation in traits not associated with inundation suggests niche differentiation and multiple modes of community assembly. The results enhance understanding of future responses of riparian communities of the Grand Canyon to anticipated drying and changes in hydrologic regime. [ABSTRACT FROM AUTHOR]

The Antillean manatee ( Trichechus manatus manatus) is a species at risk of extinction. Its diet in freshwater environments has been scarcely studied in Mexico, despite its significance for managing populations and habitat., The diet of Antillean manatees inhabiting the Natural Protected Area of Laguna de las Ilusiones, in Villahermosa, Tabasco, Mexico, was studied during the rainy season., A microhistological analysis was conducted on 51 manatee faecal samples. The cuticle and epidermis of 35 plant species present in vegetation patches used as foraging grounds by the Antillean manatee were described., In total, 223 plant fragments belonging to 11 families and 25 vascular plant taxa were identified. Echinochloa polystachya had the highest frequency (70.6%). Plant richness per faecal sample varied between one and eight plant species., This manatee population feeds mainly on grass. The plant species found coincide with those reported in other studies on sirenian diets. However, 11 new plant species consumed by manatees were recorded. This is the most comprehensive study to date in river systems in Mexico on the botanical richness of manatee faeces. The information provided here can be applied to decision-making on the conservation of the Antillean manatee and its critical habitat. [ABSTRACT FROM AUTHOR]

Riparian invertebrate communities occupy a dynamic ecotone where hydrogeomorphological (e.g. river flows) and ecological (e.g. succession) processes may govern assemblage structure by filtering species according to their traits (e.g. dispersal capacity, niche)., We surveyed terrestrial invertebrate assemblages (millipedes, carabid beetles, spiders) in 28 river islands across four river catchments over 2 years. We predicted that distinct ecological niches would produce taxon-specific responses of abundance and species richness to: (i) disturbance from episodic floods, (ii) island area, (iii) island vegetation structure, and (iv) landscape structure. We also predicted that responses would differ according to species' dispersal ability (aerial vs. terrestrial only), indicating migration was sustaining community structure., Invertebrate abundance and richness was affected by different combinations of vegetation structure, island area, and flood disturbance according to species' dispersal capacity. Carabid abundance related negatively to episodic floods, particularly for flightless species, but the other taxa were insensitive to this disturbance. Larger islands supported greater abundance of carabids and all invertebrates able to disperse aerially. Vegetation structure, particularly tree canopy density and plant richness, related positively to invertebrate abundance across all taxa and aerial dispersers, whereas terrestrial disperser richness related positively to tree cover. Landscape structure did not influence richness or abundance., Multiple ecological processes govern riparian invertebrate assemblages. Overall insensitivity to flood disturbance and responses contingent on dispersal mode imply that spatial dynamics subsidise the communities through immigration. Particular habitat features (e.g. trees, speciose vegetation) may provide refuges from disturbance and concentration of niches and food resources. [ABSTRACT FROM AUTHOR]

Nutrient dynamics in streambanks may impact nutrient movement to water, and may be influenced by cattle activity, river water level fluctuations, and time. Our objective was to determine the influence of these factors on nutrient (NO3-N, P, S, Fe, Mn, Cu, Zn, Ca, Mg) dynamics in streambanks along the Lower Little Bow River in southern Alberta using Plant Root Simulator or PRS® probes. Three experiments were conducted from 2012 to 2015. In the first experiment, few significant (P≤ 0.05) effects were found among three reaches varying in cattle impact except for Fe and Mn, which generally increased with increasing cattle impact. In the second experiment (probe placement), adsorption of P, Fe, Mn, S, Ca, and Mg was significantly greater for submerged than exposed streambanks, and the opposite trend occurred for Cu and Zn. In the third experiment on the influence of probe burial periods from 0.2 to 14 days, maximum nutrient adsorption generally occurred within 1 to 7 days, and S adsorption showed an exponential increase with time. Overall, few cattle impact effects were found on nutrient dynamics, certain nutrients were greater in submerged than exposed banks, and 7-day burial of PRS probes was sufficient to assess nutrient dynamics. [ABSTRACT FROM AUTHOR]

Floodplain and riparian ecosystems have cooler, wetter microclimatic conditions, higher water availability and greater vegetation biomass than adjacent terrestrial zones. Given these conditions, we investigated whether floodplain ecosystems allow terrestrial bird species to extend into more arid regions than they otherwise would be expected to occupy. We evaluated associations between aridity and the occurrence of 130 species using bird survey data from 2998 sites along the two major river corridors in the Murray-Darling Basin, Australia. We compared the effects of aridity on species occurrence in non-floodplain and floodplain ecosystems to test whether floodplains moderate the effect of aridity. Aridity had a negative effect on the occurrence of 58 species (45%) in non-floodplain ecosystems, especially species dependent on forest and woodland habitats. Of these 58 species, the negative effects of aridity were moderated in floodplain ecosystems for 22 (38%) species: 12 showed no association with aridity in floodplain ecosystems and the adverse effects of aridity on species occurrence were less pronounced in floodplain ecosystems compared to non-floodplain ecosystems for ten species. Greater vegetation greenness indicated that floodplain vegetation was more productive than vegetation in non-floodplain ecosystems. Floodplain ecosystems allow many terrestrial species to occur in more arid regions than they otherwise would be expected to occupy. This may be due to higher vegetation productivity, cooler microclimates or connectivity of floodplain vegetation. Although floodplain and riparian ecosystems will become increasingly important for terrestrial species persistence as climate change increases drying in many parts of the world, many are also likely to be highly affected by reduced water availability. [ABSTRACT FROM AUTHOR]