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Aim: Freshwater invasions are a global conservation issue. Emerging tools for biogeographical analyses can provide critical information for their effective management and monitoring. Here, we propose a method to assess the distribution of environmental resistance of stream ecosystems to biological invasions by coupling multi‐stage habitat potential models for non‐native species. Location: Andean Patagonia (Chile and Argentina). Taxa: North American beaver (Castor canadensis), Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (O. kisutch). Methods: Environmental resistance to invasive species was mapped throughout a large region of Patagonia by stacking multi‐stage habitat relationships for each target species and assessing the complementation between critical habitats at multiple scales. We generated an environmental model of stream networks derived from high‐resolution topographic and climatic data representing 15,406 drainage basins (>1 km2) covering an area of 369,791 km2. We quantified the intrinsic potential of stream‐reaches (100‐m and 1000‐m) to sustain high‐quality habitats and assessed habitat complementation (i.e., abundance and proximity) at the sub‐basin scale as a proxy for environmental resistance. Results: Our model revealed high heterogeneity in the distribution of environmental resistance to invasions throughout the study region, providing case‐specific insights for the research and management of invaders. Main Conclusions: Environmental resistance modelling is a novel method to study the biogeography of riverine invasions. Our approach is compatible with additional sources of information about species and the environment and shows versatility to diverse invasion scenarios and data sources. This method can be useful in prioritising research and management of incipient and spreading invasions, especially for large and data‐poor regions. [ABSTRACT FROM AUTHOR]

River ecosystems in Himalaya are changing rapidly as glaciers continue to recede at a pace faster than rest of the globe. We delineate riverine ecotones along an elevational gradient in the western Himalaya by examining community turnover of freshwater macroinvertebrates. Using the Threshold Indicator Taxa Analysis (TITAN), we provide a set of indicator macroinvertebrate taxa that represent the altitudinal band of greatest community turnover. Out of a total of 31 taxa, 11 were identified as indicators, responding either positively (n = 2) or negatively (n = 9) to altitude. Further, assessments of community turnover points toward a potential ‘riverine ecotone’ for the western Himalayan streams at an altitudinal band of 1442–2447 m above sea level (asl). As ecotones are transitional bands that harbour communities most sensitive to climate change, we further compared them across different latitudes of Himalaya to ascertain the differences in climate sensitive zones across latitudes. Our comparisons reveal that as we move towards higher latitudes in the Himalaya, the climate sensitivity drops to a lower elevational range of 1442–2447 m above sea level at 31° 33′–31° 43′ N. In contrast, at lower latitudes (27° 51′–28° 23′ N) the riverine ecotones have been recorded at a much higher elevation of 2900–3500 m above sea level. Through our study, we delimit that lower elevations in western Himalaya warrant concentrated long-term monitoring efforts to track species responses to climate change. Our comparisons of riverine ecotones along latitudes unlock new insights to understand the macroecology of community turnovers in riverine ecosystems. [ABSTRACT FROM AUTHOR]

We aimed at assessing the role of ecological infrastructures (EI) in promoting ant biodiversity in floodplain Mediterranean agricultural crops. We examined and compared ant communities at the interface between EI (remnant vegetation patches) and adjoining agricultural matrix (maize, rice, others) in irrigated farmland. The study was conducted in 2019, in two agricultural landscapes in the valleys of the rivers Tagus and Sorraia, Central Portugal. We used the Akaike information criterion for model selection and to distinguish among a set of possible models describing the relationship between: the ant richness in the agricultural matrix and drivers associated with the surrounding landscape and crop type; the ant richness in EI and the habitat quality of EI patches, the characteristics of the surrounding landscape, and the presence of invasive ant species. We found that: EI patches supported a higher ant diversity and an overall specialized ant community, distinctive from the agricultural matrix; location but not vegetation physiognomy influenced ant diversity; ant richness within the agricultural matrix decreased with the distance to the EI, and that this relationship was influenced by the crop type; and that ant richness in the EI was associated with the absence of the invasive Argentine ant and the area of terrestrial EI in the surrounding landscape. [ABSTRACT FROM AUTHOR]

The Riparian Ecological Infrastructure (REI) is defined by the ensemble of natural and semi-natural woody and herbaceous vegetation patches located contiguously to water courses. Freshwater environments and the associated REI provide habitat for many species, acting as corridors linking landscapes at a wider scale.Focusing on ants, a ubiquitous and diverse group of insects that provide a large number of ecosystem roles, we address the relative importance of REI-related local and landscape factors that drive the species and functional richness of ant communities.The study was conducted in 2019, at 100 sites in central Portugal, in Tagus and Sorraia irrigated valleys, comprising three landscape systems, namely, Forest production, Agroforestry and Irrigated cropland. Four major types of variables were used to characterize the sampling patches, including the landscape system, patch typology, spatial configuration and habitat quality. Ants were collected using pitfall traps and species composition was used to classify functional groups. Using an extensive survey, machine learning methods were used to identify the relative importance of REI-related variables in explaining ant specific and functional richness.Results indicated that ant biodiversity was primarily explained by the ‘Landscape system’ and the ‘Argentine ant abundance’. Nevertheless, ‘Shrub richness’ was selected as an important variable to enhance ‘Animal community regulation’ and ‘Plant community regulation’ functional groups, while herbaceous patches appeared to be relevant for the ‘Decomposition through scavenging’ group.The highest ant biodiversity was found in the Forest production ‘Landscape system’, where patches were larger, more complex and less fragmented, showing high habitat quality associated with a reduced abundance of the invasive Argentine ant. Contrarily, the lowest was expected in the Intensive cropland ‘Landscape system’, where the REI is highly fragmented, showing low habitat quality and suffering from a high Argentine ant invasion, as a result of high human pressure. The Agroforestry ‘Landscape system’ showed moderate ant biodiversity, mainly associated with patches characterized by low strata complexity and shrub cover densities, due to understory clearing and grazing activities.

Many salmonid‐bearing rivers exhibit thermal and hydrologic heterogeneity at multiple spatial and temporal scales, but how this translates into spatiotemporal patterns of fry emergence is poorly understood. Understanding this variability is important because emergence timing determines the biophysical conditions fish first experience (e.g., temperature, flow, and food supply), thereby influencing growth opportunities and survival during this critical life stage. We predicted spring Chinook Salmon (Oncorhynchus tshawytscha) emergence phenology across four northeastern Oregon subbasins over 5–9 years using empirical spawning and temperature data. We then related interannual emergence timing estimates to juvenile salmon size and growth rates at consistent sampling locations. There were clear longitudinal patterns of predicted emergence timing in each subbasin: The shape of these patterns was consistent among years, but not among subbasins. In two subbasins, emergence occurred progressively later with distance upstream, whereas in the other two subbasins emergence was earliest at upstream sites. Within each year, median emergence dates among sites within each subbasin ranged between 44 and 58 days. This spatial variation was comparable to interannual variation, with median emergence dates for a given location in each subbasin ranging between 47 and 74 days among years. Contrary to our expectations, juvenile salmon were not larger in years with earlier emergence, owing to slower estimated spring and summer growth rates compared to years with later emergence. Despite large interannual variation in estimated emergence dates, these results suggest that other factors (e.g., stream flow, temperature, and density‐dependence) were more important than growth duration in determining juvenile salmon growth rates and size among years. We demonstrated considerable spatial and interannual variation in emergence phenology within these subbasins. Understanding how this variation translates to spatiotemporal patterns of juvenile salmon habitat use, growth, and survival has important implications for guiding restoration efforts and understanding how climate change may impact these populations. [ABSTRACT FROM AUTHOR]

Lateral Hydrological Connectivity (LHC) has been extensively fragmented in river–floodplain ecosystems of the world. Uncertainties about how LHC affects fishes are great, impeding the design of effective rehabilitation strategies. Existing conceptual frameworks do not provide sufficient mechanistic detail to support the novel decision problems river managers face. We offer a framework of how LHC affects fishes in river–floodplain ecosystems that is, process‐based, integrates all life‐stages and is spatial; these features, we argue, are required to assess risks and opportunities associated with different LHC rehabilitation strategies. Within river–floodplain segments, LHC affects population processes through five 'effect‐classes': effects of floodplain habitat (1) and channel habitat (2); effects of material subsidies from the floodplain to the channel (3) and vice versa (4); and effects of connectivity on lateral dispersal (5). The relative influence of these effect‐classes on processes varies among species and life‐stages. At the scale of the drainage basin, inter‐segment variation in geomorphology generates a longitudinal source‐sink structure to habitat quality and quantity, pointing to a need to better understand fish metapopulation dynamics in river–floodplain ecosystems. Given the significant investment in trying to restore river–floodplain ecosystems, we highlight potentially costly and ineffective LHC management decisions. These include certain heavily engineered LHC rehabilitation strategies that do not promote critical population processes at a local scale, and at basin scales implementing strategies that do not facilitate the metapopulation processes that promote species' persistence. [ABSTRACT FROM AUTHOR]

Abstract Many salmonid‐bearing rivers exhibit thermal and hydrologic heterogeneity at multiple spatial and temporal scales, but how this translates into spatiotemporal patterns of fry emergence is poorly understood. Understanding this variability is important because emergence timing determines the biophysical conditions fish first experience (e.g., temperature, flow, and food supply), thereby influencing growth opportunities and survival during this critical life stage. We predicted spring Chinook Salmon (Oncorhynchus tshawytscha) emergence phenology across four northeastern Oregon subbasins over 5–9 years using empirical spawning and temperature data. We then related interannual emergence timing estimates to juvenile salmon size and growth rates at consistent sampling locations. There were clear longitudinal patterns of predicted emergence timing in each subbasin: The shape of these patterns was consistent among years, but not among subbasins. In two subbasins, emergence occurred progressively later with distance upstream, whereas in the other two subbasins emergence was earliest at upstream sites. Within each year, median emergence dates among sites within each subbasin ranged between 44 and 58 days. This spatial variation was comparable to interannual variation, with median emergence dates for a given location in each subbasin ranging between 47 and 74 days among years. Contrary to our expectations, juvenile salmon were not larger in years with earlier emergence, owing to slower estimated spring and summer growth rates compared to years with later emergence. Despite large interannual variation in estimated emergence dates, these results suggest that other factors (e.g., stream flow, temperature, and density‐dependence) were more important than growth duration in determining juvenile salmon growth rates and size among years. We demonstrated considerable spatial and interannual variation in emergence phenology within these subbasins. Understanding how this variation translates to spatiotemporal patterns of juvenile salmon habitat use, growth, and survival has important implications for guiding restoration efforts and understanding how climate change may impact these populations.

Riparian zones are critical for functional integrity of riverscapes and conservation of riverscape biodiversity. The synergism of intermediate flood-induced disturbances, moist microclimates, constant nutrient influx, high productivity, and resource heterogeneity make riparian zones disproportionately rich in biodiversity. Riparian vegetation intercepts surface-runoff, filters pollutants, and supplies woody debris as well as coarse particulate organic matter (e.g., leaf litter) to the stream channel. Riparian zones provide critical habitat and climatic refugia for wildlife. Numerous conservation applications have been implemented for riparian-buffer conservation. Although fixed-width buffers have been widely applied as a conservation measure, the effectiveness of these fixed buffer widths is debatable. As an alternative to fixed-width buffers, we suggest adoption of variable buffer widths, which include multiple tiers that vary in habitat structure and ecological function, with each tier subjected to variable management interventions and land-use restrictions. The riparian-buffer design we proposed can be delineated throughout the watershed, harmonizes with the riverscape concept, thus, a prudent approach to preserve biodiversity and ecosystem functions at variable spatial extents. We posit remodeling existing conservation policies to include riparian buffers into a broader conservation framework as a keystone structure of the riverscape. Watershed-scale riparian conservation is compatible with landscape-scale conservation of fluvial systems, freshwater protected-area networks, and aligns with enhancing environmental resilience to global change. Sustainable multiple-use strategies can be retrofitted into watershed-scale buffer reservations and may harmonize socio-economic goals with those of biodiversity conservation. [ABSTRACT FROM AUTHOR]

To better understand the fish fauna of Amazonian streams, we assessed small streams in a landscape of forest fragments and savannah in the region of the lower Tapajós River, Brazil. We sampled the fish fauna using a well-tested active capture method during two dry seasons (October 2006 and 2018) and one rainy season (March to May 2018). Species richness was calculated using an abundance matrix and first-order jackknife estimator. Using qualitative and quantitative data, we present a cluster analysis in which each stream corresponds to a sampling unit. We collected 6,094 individuals of 43 species distributed in six orders. The sampling effort represents 73% of the estimated richness (58.69 ± 7.65). The most abundant species were Copella nattereri, Iguanodectes variatus and Laimosemion dibaphus that together represent almost half of the total sample (48.7%). The most frequent species were Aequidens epae, Helogenes marmoratus and Laimosemion dibaphus, which were collected in 11 of the 13 sampled streams. This is the first fish fauna list for small-order streams of savannah and forest fragments landscape in Amazonian Brazil. The richness of fish and the presence of many rare species underscore the contribution of small streams to the regional fish fauna composition, even in dynamic and spatially restricted landscapes. [ABSTRACT FROM AUTHOR]

Changes in biophysical conditions through time generate spatial and temporal variability in habitat quality across landscapes. For river ecosystems, researchers are increasingly able to characterize spatial and temporal patterns in habitat conditions, referred to as shifting habitat mosaics, yet rarely demonstrate how this translates into corresponding biological processes such as organism growth and production.We assessed spatial patterns and processes determining seasonal changes in juvenile Chinook Salmon Oncorhynchus tshawytscha size, growth and production over 30–40 km in two NE Oregon subbasins.We quantified seasonal patterns of growth by combining estimated emergence dates and body size distributions in July and September. We then used analysis of bioenergetics, empirical fish diets and spatial models incorporating temperature, habitat and population density to evaluate mechanisms driving spatiotemporal patterns of growth. Lastly, we quantified seasonal contributions to individual fish growth and to total production as a function of position within the stream network.Spatial heterogeneity in incubation temperatures corresponded to later estimated emergence timing with distance upstream in both subbasins. During spring, estimated growth rates decreased with distance upstream, and coupled with emergence patterns, resulted in pronounced longitudinal gradients in body size by July. During summer, spatial patterns of growth reversed, with greater diet ration sizes and growth efficiencies upstream than downstream. These opposing spatiotemporal patterns of emergence timing and seasonal growth rates produced longitudinal gradients in the proportion of fish growth achieved in spring versus summer, with up to 80% of an individual's growth occurring in spring at downstream sites but as low as 10% at upstream sites. Coupling longitudinal patterns of fish density and growth revealed that in one subbasin the majority (65%) of total production occurred in spring, while in the other, in which fish were concentrated in headwaters, the majority (60%) of production occurred in summer.While recent work has emphasized inter‐annual shifts in fish production across large spatial scales, this study demonstrates that longitudinal gradients of fish growth and production can reverse across seasons, and reveals important contributions of warmer, downstream habitats to overall production that occurred during cooler times of the year. [ABSTRACT FROM AUTHOR]

Populations of stream organisms across trophic levels, including microbial taxa, are adapted to physical and biotic stream features, and are sentinels of geological and hydrological landscape processes and anthropogenic disturbance. Stream bacterial diversity and composition can have profound effects on resident and migratory species in Great Lakes tributaries. Study objectives were to characterize and compare the taxonomic composition and diversity of bacterial communities in 18 rivers of the Lake Michigan basin during April and June 2019 and to quantify associations with stream and watershed physical features and dominant landuse practices. River water was filtered, and genomic DNA was extracted from filtrate using antiseptic techniques. We performed high-throughput amplicon sequencing using the highly variable V4 region of the 16S rRNA gene to characterize microbial community composition and diversity. Effects of landscape-scale landuse, environmental variables and dispersal predictors (e.g., inter-stream distance) on community compositional differences were quantified. Greater than 90% of variation in bacterial relative abundance between rivers and time were attributed to 11 phyla representing 10,800 operational taxonomic units. Inter-stream geographic distance, stream hydrology, and variation in stream properties that were tied to patterns of watershed landuse were significantly associated with differences in bacterial community composition among streams at both sampling time periods. based on Bray-Curtis distances. Understanding how environmental characteristics and watershed-scale landuse influence lower trophic level stream communities such as bacteria will inform managers as biological indicators of ecosystem health, sources of disturbance, and current and future bottom-up trophic changes in coupled tributary-Great Lakes ecosystems. [ABSTRACT FROM AUTHOR]

Riparian zones are critical for functional integrity of riverscapes and conservation of riverscape biodiversity. The synergism of intermediate flood-induced disturbances, moist microclimates, constant nutrient influx, high productivity, and resource heterogeneity make riparian zones disproportionately rich in biodiversity. Riparian vegetation intercepts surface-runoff, filters pollutants, and supplies woody debris as well as coarse particulate organic matter (e.g., leaf litter) to the stream channel. Riparian zones provide critical habitat and climatic refugia for wildlife. Numerous conservation applications have been implemented for riparian-buffer conservation. Although fixed-width buffers have been widely applied as a conservation measure, the effectiveness of these fixed buffer widths is debatable. As an alternative to fixed-width buffers, we suggest adoption of variable buffer widths, which include multiple tiers that vary in habitat structure and ecological function, with each tier subjected to variable management interventions and land-use restrictions. The riparian-buffer design we proposed can be delineated throughout the watershed, harmonizes with the riverscape concept, thus, a prudent approach to preserve biodiversity and ecosystem functions at variable spatial extents. We posit remodeling existing conservation policies to include riparian buffers into a broader conservation framework as a keystone structure of the riverscape. Watershed-scale riparian conservation is compatible with landscape-scale conservation of fluvial systems, freshwater protected-area networks, and aligns with enhancing environmental resilience to global change. Sustainable multiple-use strategies can be retrofitted into watershed-scale buffer reservations and may harmonize socio-economic goals with those of biodiversity conservation.

The structure and development of river corridors are controlled by an interplay of hydrological, geomorphological and ecological processes over a range of spatial and temporal scales. The majority of existing studies on fluvial biogeomorphology focus either on conceptual development or on investigations on the scales of single geomorphic units or study reaches. With this study, we extend the view on biogeomorphology beyond the reach scale using satellite time series. We take the Naryn River in Kyrgyzstan as an example for demonstrating our approach to biogeomorphological analysis of river corridors. The Naryn is still in a natural state on an entire flow length of more than 600 km with full longitudinal and lateral connectivity. Along the central part of the catchment, the Naryn is a highly dynamic braided river system. This makes this river ideal to study large scale biogeomorphological dynamics. In our study, we follow the well-established concept of biogeomorphological succession. We mapped the different succession stages in the field and used the results to derive spectral-temporal indices characterizing the different biogeomorphological succession stages. Monthly time series of the modified difference water index as well as the normalized difference vegetation index derived from the Landsat archive have been used to compute statistical trends and changepoints by means of a Bayesian time series decomposition algorithm. The results are then evaluated regarding biogeomorphological succession and disturbance events. The results show that dense satellite time series are well suited to derive indicators of biogeomorphological interactions on large spatial scale. The temporally continuous nature of this kind of observations allows an observation of processes and an interpretation for instance against the background of the theory of adaptive cycles and panarchy. In conclusion, the suggested approach has the potential to give new insights in the structure and functioning of entire river corridors or networks. [Display omitted] • Satellite time series reveal biogeomorphic dynamics of braided rivers. • Spatially and temporally continuous analysis of biogeomorphology for entire rivers. • Extending the idea of riverscapes to the temporal domain. • Satellite remote sensing complements other methods to multiscale analysis of rivers. [ABSTRACT FROM AUTHOR]

Context: Given the importance of spatial heterogeneity in altering dispersal, interspecific interactions, and population persistence, high rates of habitat homogenisation across the globe are a concern. In river ecosystems, confluences likely act as heterogeneity 'hotspots' by creating discontinuities in longitudinal processes and influences that are propagated both up and down stream networks.Objectives: We predicted the layout of abiotic conditions around confluences would influence the presence and configuration of spatial heterogeneity, and strongly influence spatial patterns in fish abundance and evenness.Methods: Twelve replicate mainstem and tributary stream combinations in Canterbury, New Zealand, were electrofished to evaluate how the configuration of flow disturbance (i.e. flooding) characteristics around a confluence (i.e. stable mainstem and disturbed tributary versus disturbed mainstem and stable tributary) influenced fish communities.Results: The configuration of abiotic conditions around confluences, and position of a sampled reach with respect to the confluence, significantly interacted to create configuration-specific patterns in fish abundance and evenness. Fish abundances were particularly high in disturbed tributaries juxtaposed with stable mainstems, suggesting certain confluence configurations are disproportionately ecologically important. Evenness scores differed significantly downstream of confluences, depending on configuration, with highest fish evenness in reaches downstream of confluences between a stable and a disturbed stream.Conclusions: These results reveal strongly context-dependent spatial patterns in communities and demonstrate the role of spatially transferred influence in river systems. Understanding importance of not just the presence of heterogeneity, but its configuration and context-dependence in the landscape will assist in identifying sites of ecological significance for management and conservation purposes. [ABSTRACT FROM AUTHOR]

Nested structures of species assemblages have been frequently associated with patch size and isolation, leading to the conclusion that colonization–extinction dynamics drives nestedness. The 'passive sampling' model states that the regional abundance of species randomly determines their occurrence in patches. The 'habitat amount hypothesis' also challenges patch size and isolation effects, arguing that they occur because of a 'sample area effect'. Here, we (a) ask whether the structure of the mammal assemblages of fluvial islands shows a nested pattern, (b) test whether species' regional abundance predicts species' occurrence on islands, and (c) ask whether habitat amount in the landscape and matrix resistance to biological flow predict the islands' species composition. We quantified nestedness and tested its significance using null models. We used a regression model to analyze whether a species' relative regional abundance predicts its incidence on islands. We accessed islands' species composition by an NMDS ordination and used multiple regression to evaluate how species composition responds to habitat amount and matrix resistance. The degree of nestedness did not differ from that expected by the passive sampling hypothesis. Likewise, species' regional abundance predicted its occurrence on islands. Habitat amount successfully predicted the species composition on islands, whereas matrix resistance did not. We suggest the application of habitat amount hypothesis for predicting species composition in other patchy systems. Although the island biogeography perspective has dominated the literature, we suggest that the passive sampling perspective is more appropriate for explaining the assemblages' structure in this and other non‐equilibrium patch systems. Abstract in Portuguese is available with online material. [ABSTRACT FROM AUTHOR]

• This paper uses a 'braided knowledge' approach to explore Aboriginal ancestral narratives, geomorphological interpretations and archaeological evidence relating to the Murray River (Rinta) in South Australia's Riverland region. • Commonalities between Aboriginal and Western knowledge systems are outlined through a number of key threads relating to the geographic directionality of peopling in the region, river dynamism (particularly in relation to the deglacial transformations from 15 ka) and more. • Differences between knowledge systems are also explored and include descriptions of 'Indigenous frameworks' which embed multiple levels of meaning, as well as Aboriginal interpretations of the subsurface. This paper uses a 'braided knowledge' approach to explore Aboriginal ancestral narratives, geomorphological interpretations and archaeological evidence relating to the Murray River (Rinta) in South Australia's Riverland region. The 'knowledge carriers' of ancestral narratives are honoured and complexities regarding the ways in which their wisdom was recorded by Europeans are considered. Commonalities between Aboriginal and Western knowledge systems are outlined through a number of key threads relating to the geographic directionality of peopling in the region, river dynamism (particularly in relation to the deglacial transformations from 15 ka) and more. Differences between knowledge systems are also explored and include descriptions of 'Indigenous frameworks' which embed multiple levels of meaning, as well as Aboriginal interpretations of the subsurface. The paper shows that through a collaborative exchange of ideas, together with the conscious positioning of Aboriginal knowledges, normally disparate systems may be explored to amplify our understandings of Indigenous riverscapes. [ABSTRACT FROM AUTHOR]

Instream large wood (LW) is widely perceived as a source of hazard that should be avoided. This is also the case of Spain, where wood has been systematically removed from rivers for decades. Consequently, people are accustomed to rivers with minimal or no LW at all. However, the presence and transport of wood is natural and has positive ecological effects. Previous studies reported that the general negative perception towards LW in rivers is related to the lack of background knowledge about stream ecology or fluvial dynamics. However, we hypothesize here that recent flooding experience has an influence on the perception of LW as well. To test this hypothesis, we surveyed groups of individuals living in different areas of Spain that have been affected more or less frequently by floods. In addition, we surveyed a group of scientists to test whether their perception towards LW differs from that of the general public. We observe that flooding experience is not the main controlling factor of how LW is perceived. Instead, we observe that respondents, independently of the time passed since the last flood, perceived watercourses with LW as less aesthetically, more dangerous, and with a larger need to improve channels than in watercourses without LW. Regional differences were detected, potentially related to differences in environmental attitudes. We confirm the existence of a gap in perception between scientific communities and the general public regarding natural river systems with wood; thereby highlighting the need to transfer knowledge, training, and education to bridge this gap. The generalized negative perception towards LW could have important consequences on the implementation of river management measures, such as LW augmentation for restoration purposes. This study underlines that wood removal should be more balanced in post-flood works and that public information is needed to implement a balanced LW management policy. [ABSTRACT FROM AUTHOR]

Spatial variation in fish densities across river networks suggests that the influence of food and habitat resources on assemblages varies greatly throughout watersheds. Conceptual models predict that in situ primary production should vary with river characteristics, but the influence of autochthonous resource availability on the capacity for river reaches to support fish is poorly understood. We estimated primary production throughout the South Fork and Middle Fork of the John Day River, Oregon, by measuring diel cycles in dissolved oxygen (DO) during July 2013. Using these data, we (1) evaluated the extent to which juvenile salmonid abundance and resource limitation correlated with areas of high gross primary production (GPP), (2) developed models to predict GPP from both site-level measurements and remotely sensed data, and (3) made predictions of GPP across the entirety of theMiddle Fork John Day River (MFJD) network and assessed the utility of these spatially continuous predictions for describing variation fish densities at broad scales. We produced reliable estimates of GPP at sites where DO loggers were deployed using measurements of solar exposure, water temperature, and conductivity measured at each site, as well as surrogates for these data estimated from remote sensing data sources. Estimates of GPP across fish sampling sites explained, on average, 58-63% of the variation in juvenile salmonid densities during the summer sampling period, and 51-83% during the fall sampling period, while continuous network predictions of GPP explained 44% of the variation in fish densities across 29 km of the MFJD. Further, GPP explained nearly half of the variation in juvenile steelhead dietary resource limitation, as inferred from bioenergetics modeling results. These results comprise a first effort at quantifying variation in autochthonous production across an entire river network and, importantly, provide a much-needed food-web context for guiding more effective fish and habitat management. [ABSTRACT FROM AUTHOR]

Shigeru Nakano was a Japanese ecologist whose work crossed boundaries among subdisciplines in ecology, between aquatic and terrestrial habitats, and between different languages and cultures. He published his first paper in 1985 while still an undergraduate, and is well known for his early research on the individual behavior of stream salmonids in dominance hierarchies. Shortly after completing his Master's degree in 1987 he began collaborating with many graduate students and other scientists, including those from the US, and expanded his research to include factors controlling stream salmonid distribution and abundance across spatial scales ranging from local to landscape levels. In 1995 he moved to a research station in southwestern Hokkaido and began new collaborative research on interactions between forest and stream food webs. Nakano pioneered large-scale field experiments using greenhouses to sever the reciprocal fluxes of invertebrate prey between stream and riparian food webs. The strong direct and indirect effects of isolating these food webs from each other on organisms ranging from stream algae to fish, riparian spiders, and bats have revealed new linkages and explained phenomena that were previously unexplained. When combined with similar results from other investigators, they have created a paradigm shift in ecology. Shigeru Nakano was lost at sea in Baja California on March 27, 2000 at the age of 37, but key papers from his 15-year career set new standards for rigor, detail, and synthesis. They continue to be highly cited and inspire new research, and to foster new collaborations among Japanese and western scientists. [ABSTRACT FROM AUTHOR]

Waterways of the USA are protected under the public trust doctrine, placing responsibility on the state to safeguard public resources for the benefit of current and future generations. This responsibility has led to the development of management standards for lands adjacent to streams. In the state of Oregon, policy protection for riparian areas varies by ownership (e.g., federal, state, or private), land use (e.g., forest, agriculture, rural residential, or urban) and stream attributes, creating varying standards for riparian land-management practices along the stream corridor. Here, we compare state and federal riparian land-management standards in four major policies that apply to private and public lands in the Oregon Coast Range. We use a standard template to categorize elements of policy protection: (1) the regulatory approach, (2) policy goals, (3) stream attributes, and (4) management standards. All four policies have similar goals for achieving water-quality standards, but differ in their regulatory approach. Plans for agricultural lands rely on outcome-based standards to treat pollution, in contrast with the prescriptive policy approaches for federal, state, and private forest lands, which set specific standards with the intent of preventing pollution. Policies also differ regarding the stream attributes considered when specifying management standards. Across all policies, 25 categories of unique standards are identified. Buffer widths vary from 0 to ∼152 m, with no buffer requirements for streams in agricultural areas or small, non-fish-bearing, seasonal streams on private forest land; narrow buffer requirements for small, non-fish-bearing perennial streams on private forest land (3 m); and the widest buffer requirements for fish-bearing streams on federal land (two site-potential tree-heights, up to an estimated 152 m). Results provide insight into how ecosystem concerns are addressed by variable policy approaches in multi-ownership landscapes, an important consideration to recovery-planning efforts for threatened species. [ABSTRACT FROM AUTHOR]

Disruption of longitudinal connectivity is a major concern in most of the world´s rivers. Approaches based on graph theory have proven to be a suitable tool for analysing functional connectivity. However, previous applications of graph-based connectivity methods to river systems have been oversimplified in that they have treated potential barriers as binary features and rivers as symmetric networks. We here apply a network analytical approach in which (a) upstream and downstream connectivity are considered so that fish passability values across dams are asymmetrical, and (b) it is possible to consider a continuous range of passability values for every dam. We build on previous and widely used connectivity metrics (Probability of Connectivity, PC), which here are generalised and adapted toward that end. We compare the results of our approach with those that would be obtained under the more simplified assumptions of symmetric movement and of barriers as binary features. We want to prove if there are substantial differences between considering or not the asymmetry in river networks. The application of symmetrical and asymmetrical PC highlights major differences between the upstream connectivity versus the downstream connectivity. We provide our methods in a free software package so that they can be used in any other application to riverscapes. We expect to provide a better graph-based approach for the prioritisation of the removal or permeabilization of artificial obstacles as well as for the preservation of target river segments for connectivity conservation and restoration. [ABSTRACT FROM AUTHOR]

The microchemical composition of a fish's calcified structure, such as an otolith, fin ray, or scale, is a 'biological tag' that reflects the use of different habitats throughout its life history. Hard-part microchemistry has the potential to address many fish conservation, management, and behavior questions. In order to use hard-part microchemistry to address fisheries research questions, elemental signatures of water must be distinct at the spatial scale of interest and ideally temporally stable. The goal of this study was to assess whether spatial differences existed in the concentrations of five elements [barium (137Ba), magnesium (24Mg), manganese (55Mn), sodium (23Na), and strontium (88Sr)] between and within eight Missouri River tributaries and whether those signatures were temporally stable. All elemental concentrations were converted to molar ratios (mmol mol-1) using calcium (43Ca) concentrations as the base. Canonical correspondence analysis showed distinct differences in Mg:Ca, Na:Ca, and Sr:Ca concentrations between the eight tributaries. Cochran-Mantel-Haenszel tests showed that sites within a tributary were distinguished using Mg:Ca and Na:Ca concentrations. However, only Mg:Ca concentrations were temporally stable. Results from this study demonstrate the potential for using hard-part microchemistry to address various questions at multiple spatial scales in the Missouri River riverscape but also highlight the importance of evaluating water microelemental signatures prior or simultaneous to any hard-part microchemistry study. [ABSTRACT FROM AUTHOR]

• Land use was the main driver of ant richness in riparian ecological infrastructures. • Shrub richness promoted animal and plant community regulation services. • Proximity to urban areas affected scavenger ant species in woody patches. • Forest production system had the highest capacity to provide ant-mediated functions. • Argentine ant impacted native ant species in Agroforestry and Irrigated cropland. [Display omitted] The Riparian Ecological Infrastructure (REI) is defined by the ensemble of natural and semi-natural woody and herbaceous vegetation patches located contiguously to water courses. Freshwater environments and the associated REI provide habitat for many species, acting as corridors linking landscapes at a wider scale. Focusing on ants, a ubiquitous and diverse group of insects that provide a large number of ecosystem roles, we address the relative importance of REI-related local and landscape factors that drive the species and functional richness of ant communities. The study was conducted in 2019, at 100 sites in central Portugal, in Tagus and Sorraia irrigated valleys, comprising three landscape systems, namely, Forest production, Agroforestry and Irrigated cropland. Four major types of variables were used to characterize the sampling patches, including the landscape system, patch typology, spatial configuration and habitat quality. Ants were collected using pitfall traps and species composition was used to classify functional groups. Using an extensive survey, machine learning methods were used to identify the relative importance of REI-related variables in explaining ant specific and functional richness. Results indicated that ant biodiversity was primarily explained by the 'Landscape system' and the 'Argentine ant abundance'. Nevertheless, 'Shrub richness' was selected as an important variable to enhance 'Animal community regulation' and 'Plant community regulation' functional groups, while herbaceous patches appeared to be relevant for the 'Decomposition through scavenging' group. The highest ant biodiversity was found in the Forest production 'Landscape system', where patches were larger, more complex and less fragmented, showing high habitat quality associated with a reduced abundance of the invasive Argentine ant. Contrarily, the lowest was expected in the Intensive cropland 'Landscape system', where the REI is highly fragmented, showing low habitat quality and suffering from a high Argentine ant invasion, as a result of high human pressure. The Agroforestry 'Landscape system' showed moderate ant biodiversity, mainly associated with patches characterized by low strata complexity and shrub cover densities, due to understory clearing and grazing activities. [ABSTRACT FROM AUTHOR]

It is widely recognized that physical landscapes can shape genetic variation within and between populations. However, it is not well understood how riverscapes, with their complex architectures, affect patterns of neutral genetic diversity. Using a spatially explicit agent-based modeling (ABM) approach, we evaluate the genetic consequences of dendritic river shapes on local population structure. We disentangle the relative contribution of specific river properties to observed patterns of genetic variation by evaluating how different branching architectures and downstream flow regimes affect the genetic structure of populations situated within river networks. Irrespective of the river length, our results illustrate that the extent of river branching, confluence position, and levels of asymmetric downstream migration dictate patterns of genetic variation in riverine populations. Comparisons between simple and highly branched rivers show a 20-fold increase in the overall genetic diversity and a sevenfold increase in the genetic differentiation between local populations. Given that most rivers have complex architectures, these results highlight the importance of incorporating riverscape information into evolutionary models of aquatic species and could help explain why riverine fishes represent a disproportionately large amount of global vertebrate diversity per unit of habitable area. [ABSTRACT FROM AUTHOR]

Modeling habitat connectivity for conservation of semi-aquatic vertebrates is a particularly challenging task, due to the fine-scale and linear distribution of riverine habitats and to the capacity of species to move both on freshwater and terrestrial realms. We showed how the integrated analytical framework provided by the habitat availability (reachability) metrics and their fractions can be used to effectively evaluate the distinctive roles and contributions of both habitat patches (aquatic and riparian) and linkage areas (permeable land matrix) to the connectivity and functioning of a complex system composed of multiple river catchments. Analysis focused on the Eurasian otter ( Lutra lutra L.), one of the most endangered mammals in Italy. We developed a network connectivity model based on suitable otter habitats and multiple least-cost paths between catchments. A graph analytical approach was used to identify critical nodes and links for the potential expansion and long-term viability of the species in the region. Our results showed that few basins concentrate most of the importance for sustaining the overall habitat connectivity, due to the extension of suitable habitats they contain, their strong connections with other basins, and their importance as stepping stones that uphold ecological fluxes between otherwise weakly connected habitats. The potential contribution of each basin to enhance the dispersal and expansion of otters in the area strongly depended on the key functional paths (sequences of links and nodes) among the catchments. We identified vacant basins that could be colonized by otters in the near future, and connecting areas in the intermediate matrix that might be preferentially used to conduct and promote dispersal movements and gene flow in the area. The novel approach here adopted could be easily extended to other semiaquatic species and catchment systems, offering a management strategy to preserve the hydrographic network as an integrated system, as well as a joint evaluation of the role of both the river courses and the matrix in between in a single landscape model. [ABSTRACT FROM AUTHOR]

Estimating genetic connectivity in disturbed riverine landscapes is of key importance for river restoration. However, few species of the disturbed riverine fauna may provide a detailed and basin-wide picture of the human impact on the population genetics of riverine organisms. Here we used the most abundant native fish, the three-spined stickleback ( Gasterosteus aculeatus L.), to detect the geographical determinants of genetic connectivity in the eastern part of the Scheldt basin in Belgium. Anthropogenic structures came out as the strongest determinant of population structure, when evaluated against a geographically well-documented baseline model accounting for natural effects. These barriers not only affected genetic diversity, but they also controlled the balance between gene flow and genetic drift, and therefore may crucially disrupt the population structure of sticklebacks. Landscape models explained a high percentage of variation (allelic richness: adjusted R2 = 0.78; pairwise FST: adjusted R2 = 0.60), and likely apply to other species as well. River restoration and conservation genetics may highly benefit from riverine landscape genetics, including model building, the detection of outlier populations, and a specific test for the geographical factors controlling the balance between gene flow and genetic drift. [ABSTRACT FROM AUTHOR]

In this study, we assess the potential of ants as bioindicators of riparian ecological health in two river types (upland and lowland type) located in the Catalonian region. We proposed to understand to what extent do metrics based on ant responses provide useful information that cannot be presented by traditional biophysical assessments while attempting an approach to creating an ant-based multimetric index (ant-based MMI) of the riparian ecological health. A total of 22 ant species were identified, and 42 metrics related to ant foraging activity, species richness, and functional traits were evaluated as potential core metrics of the index. Riparian features and proximal land use land cover (LULC) were used to distinguish disturbed from less disturbed sites. We found that ant communities strongly responded to human disturbance. When compared with an exclusively physical-based index for the assessment of the riparian health, the ant-based MMI was more sensitive to human disturbance, by also reacting to the effects of the surrounding LULC pressure. This study provides a preliminary approach for an ant-based assessment tool to evaluate the health of riparian corridors although additional research is required to include other river types and a wider stressor gradient before a wider application. [ABSTRACT FROM AUTHOR]