Beaver Ponds Research Articles

A national scale floodplain model revealing channel gradient as a key determinant of beaver dam occurrence and inundation potential can anticipate land-use based opportunities and conflicts for river restoration

The Eurasian beaver (Castor fiber) has expanded its range considerably due to reintroduction and conservation efforts and the species is now found in more than 30 countries across Europe. This expansion brings with it opportunities for nature restoration, the provision of river ecosystem services and the return of naturally functioning floodplains. It also has the potential for conflict with existing human land-use through dam induced floodplain inundation and wetland development. To maximise restoration benefits and minimise conflict, modelling approaches are needed that can predict the likelihood of dam building and include scenarios for subsequent floodplain inundation. This study describes the first national-scale comprehensive study on the drivers of beaver dam occurrence and beaver floodplain inundation potential. This revealed that channel gradient was the overriding driver of both dam occurrence and potential land-use impact. Although widely considered to be a key constraint, channel width exhibited considerably lower explanatory power. The delineation of areas reflecting overall opportunities and conflict reveals that the reintroduction of Castor fiber into Switzerland implies a net benefit from a landscape restoration perspective, though outcomes scaled closely with catchment position. Given the rapidly expanding population range and popularity of continuing beaver reintroductions, this approach could help maximise landscape restoration goals whilst minimising undesirable land-use conflicts that may harm conservation efforts.

The Impacts of Beaver Dams on Groundwater Regime and Habitat 6510

Changes in land usage, increasing climatic uncertainty, and dynamic development of the rate of natural population growth of the Eurasian beaver will lead to increasing benefits and disadvantages from beaver activity. During three growing seasons from 2020 to 2022, four cross-sections were marked on unused sub-irrigation systems with the periodic occurrence of beaver dams, located on organic soils in parts of the facility protected by the Habitats Directive (natural habitat 6510) in Central Poland. Periodic water table measurements in wells, the beds of adjacent ditches, and the riverbed were carried out. Identification of the states and structures of plant communities was done using the botanical-weight analysis of several samples with an area of 1 m2. Beaver dams increased water levels in the river, ditches, and groundwater depth in over 78% of events in 2020–2022 years. A large impact of precipitation on the hydraulic conditions in the meadow was observed. In the studied area, since a moderately moist habitat (6510) is protected within the Natura 2000 network, phenomena increasing soil moisture, in the absence of mowing of meadows and the occurrence of expansive herbaceous vegetation that tolerates increased moisture, may lead to the disappearance of these habitats, especially in the zone near the riverbed.

Structure of Zooplanktocenoses of Water Bodies of Zoogenic Origin of Different Types in a Specially Protected Natural Territory

The features of the structure of zooplankton in beaver ponds and the course of successions in zooplanktocenoses have been studied in the territory of State Natural Reserve “Kologrivsky Les” named after M.G. Sinitsyn. Ponds are divided into groups according to the nature of the watercourse on which they are formed, the height of the floodplain, and the duration of existence. The seasonal succession of zooplankton for all types of ponds begins with the predominance of juvenile stages of Copepoda. In the summer, in newly formed ponds and ponds on rivers with high floodplains, a typical zoogenic transformation of communities is observed occurs with the development of large Cladocera. In long-term ponds on streams and rivers with low floodplains, the dominance of Rotifera and small Cladocera, characteristic of anthropogenic eutrophication, and the highest average values of abundance and biomass, indices of species diversity and evenness were noted.

Beaver dams in Mediterranean ecosystems: trait‐specific effects on macroinvertebrates

AbstractAfter centuries of extinction due to human persecution, Eurasian beavers Castor fiber L. have been released to Southern Europe in the last decades. Being ecosystem engineers, beavers have attracted great attention regarding restoration of aquatic and terrestrial ecosystems. Nonetheless, the effects of the species on aquatic invertebrates known to date are not univocal and mostly refer to central European riverine systems. Here, we evaluated the effects of beaver presence on aquatic macroinvertebrates for the first time in a Mediterranean riverine ecosystem, by applying a sound control‐impact sampling design and controlling for seasonal variation in macroinvertebrate assemblage composition. A significant variation in response to season was evident for macroinvertebrate communities, revealing distinct assemblages during spring and summer. Furthermore, the presence of beavers was also identified as a significant driver of species composition, as samples near the beaver dam showed significant variation from control sites. Macroinvertebrate community traits changed according to the relative position to the beaver dam, as control sites featured on average higher abundances of taxa with higher values of bioindication score, larger size, lower adaptation to drag, and were less frequently of introduced origins. Yet, these differences were strongly taxon‐ and season‐specific in their intensity and direction. Differences across sites were mainly driven by the relative abundances of few taxa—including both alien species and high environmental quality indicators—such as those from genera Potamopyrgus, Baetis, Habrophlebia, Ephemerella, Leuctra, and Radix, which explained about 70% of the observed divergence among conditions. Our results indicate that beavers and their engineering activity may induce highly variable species‐specific responses in macroinvertebrates, thus possibly representing a driver of environmental heterogeneity along Mediterranean rivers, and that both bioindicators and alien species may exploit such heterogeneity.

Comparing the Sources of Sediment Retained by Beaver Dams and Beaver Dam Analogs

AbstractBeavers modify riverine systems by building dams that alter downstream fluxes of water and sediment. Where beavers have been lost and stream channels degraded, beaver dam analogs (BDAs) are being used to mimic the effects of beaver engineering. Central to the success of these structures in accelerating stream recovery is creating similar ecosystem responses as beaver dams including sediment retention. Unknown is the relative importance of beaver actions versus erosion in the catchment in generating the retained sediment. This study tested the viability of sediment fingerprinting to determine the source of sediment retained by beaver dams and BDAs in a watershed in Alberta, Canada. Concentrations of 29 elements were measured as potential tracers from known sediment sources: upland, terrace, stream bank, and beaver canal. Virtual mixture tests, used to compare the computed source estimates with known source mixtures, revealed that sediment fingerprinting is a robust method for identifying sources of sediment retained by beaver ponds and BDAs. The un‐mixing model results indicate that on average 56% of the sediment retained by the beaver dams originated from terraces, 23% from uplands, and 13% from beaver canals. About 89% of sediment retained by the BDAs originated from eroding stream banks. We conclude that the geomorphic effects of beavers and their dams are more diverse, resulting in more diverse sources of sediment retained by their dams. This differentiates beaver dams from BDAs. The study has implications for informing management practices that involve beavers and beaver mimicry.

Post‐fire sediment attenuation in beaver ponds, Rocky Mountains, CO and WY, USA

AbstractWe evaluated the post‐fire sediment dynamics in beaver ponds to examine these ponds' contributions to sediment storage following disturbance. Beaver dams and beaver mimicry structures impound water and sediment, a function that is of growing interest in wildfire‐prone landscapes. Wildfires typically lead to high sediment loading into rivers in the years following fire, constituting a disturbance to aquatic ecosystems and a challenge to water resource managers. Previous work establishes that beaver dams trap substantial volumes of sediment, but sedimentation appears spatially and temporally heterogeneous and it remains unclear the extent to which short‐term pulses of sediment are attenuated by these structures. We examine the conditions under which beaver dams and beaver mimicry structures store post‐fire sediment by quantifying the sediment volume of 40 ponds, about half of which were burned in large wildfires in the Colorado and Wyoming Rocky Mountains in 2020. The median relative volume of burned ponds is 85%, which is greater than the median for unburned ponds (58%), meaning that burned ponds store higher relative volumes of sediment when pond size is accounted for. Furthermore, sediment accumulated at a median rate of 3.0 cm/year over the entire history of the pond. Post‐fire sedimentation rates, with a median of 20.4 cm/year, were an order of magnitude higher than pre‐fire rates with a median of 1.8 cm/year. In addition, vegetation and geomorphic characteristics correlated with sediment storage in ponds. Sediment surveys confirmed that ponds with greater surface areas contain higher volumes of sediment. Additionally, older ponds and ponds abandoned by beavers stored higher volumes of sediment compared to recently constructed ponds, ponds actively maintained by beaver, and beaver mimicry structures. These findings demonstrate that beaver ponds and mimicry structures may function as sediment sinks capable of attenuating post‐fire sediment. The biogeomorphic context, defined across multiple scales from the pond to the catchment, provides additional explanation for the wide range of sediment storage observed and remains an important consideration for beaver‐based restoration, catchment sediment management, and resilience evaluation.

Assessing controls on sedimentation rates and sediment organic carbon accretion in beaver ponds

Beaver dams trap sediment, promote channel-floodplain connectivity, modify biogeochemical cycling and organic carbon (OC) storage, and influence geomorphic form. Beaver-related sediment accumulation has been investigated at longer timescales (e.g., > 1000 years) and shorter timescales (< 10 years), but we lack information on sedimentation and sediment-associated OC accretion rates over multiple decades in relatively persistent beaver ponds (10–100 years old). We coupled field surveys of 45 beaver ponds with historical aerial imagery and radiometric dating with 7Be, 210Pb, and 14C to calculate sedimentation rates, mean sediment depth, and sediment OC content at two study sites in the southern Rocky Mountains, USA. Sedimentation rates in beaver ponds (median = 5.7 cm yr−1, mean = 11.6 cm yr−1) decreased with pond age. Incised, single threaded reaches had greater variability in mean sediment depth compared to less incised reaches. In less incised reaches, mean sediment depth and beaver dam height increased with pond age, indicating more stable dams and depositional environments. Sediment OC content within beaver ponds (median = 0.8 %, mean = 1.7 %) increased with finer sediment grain size distributions. Sediment OC accretion rates in ponds ranged between 0.13 and 23 Mg C ha −1 per year. We used Monte Carlo simulations to estimate it would take ∼100 years or more of uninhibited beaver activity for deposition to laterally reconnect adjacent terraces in the incised study reaches, a common objective within many stream restoration projects. Our findings show that beaver ponds in complex, multi-threaded reaches better retain fine sediment over longer timescales, highlighting the need to incorporate geomorphic context when considering whether beaver can help restore incised river channels and floodplain connectivity, retain fine sediment, and store OC on the landscape.

Persistence, changes and robustness of nest webs along a latitudinal gradient in the Canadian boreal forest

IntroductionIn eastern Canada, the boreal forest is associated with an important latitudinal shift in forest composition and structure, which occurs in the transition between the mixed southern boreal forest and the coniferous northern boreal forest. Along this transition, upland mixedwood stands with large deciduous trees (important for cavity-dependent vertebrate species) are gradually replaced by forests with smaller conifer trees, primarily black spruce (Picea mariana). Concomitantly, the availability of lowland forests flooded by the American beaver (Castor canadensis), which can provide adequate conditions for tree-cavity users, is also decreasing.MethodsWe hypothesized that this latitudinal gradient would bring important changes in the functional diversity and network structure of vertebrate cavity-using communities. Along this latitudinal gradient we used a nest web approach to analyze the structure and robustness of networks of cavity users in upland forests and in lowland forests flooded by beavers.ResultsDespite their low availability in the northern forest region, we found that mixedwood stands persisted throughout the boreal forest in being the main drivers of nest webs network structure of upland forests whereas old black spruce stands contribution was low. In lowland forests, beaver ponds harbored nest webs with a rich and complex structure in both forest regions. Species removal simulations revealed that across our latitudinal gradient upland and lowland forest nest webs responded differently. In upland forests, the removal of trembling aspen and the Pileated Woodpecker (Dryocopus pileatus) caused the highest proportions of secondary extinctions, showing low robustness of nest webs given that these two species were highly connected to the other species. Contrastingly, nest webs in beaver ponds were more robust mainly because excavator species used a higher diversity of tree species despite the removal of the Northern Flicker (Colaptes auratus) which induced numerous secondary extinctions. The Pileated Woodpecker remained the pivotal species across the two forest regions in upland forests whereas the Northern Flicker became the main large cavity provider in beaver ponds across the latitudinal gradient.DiscussionWe discuss how mixedwood forests and beaver ponds, which are key habitat types for the cavity-using vertebrate community across our latitudinal gradient, should be maintained and protected in landscapes under industrial timber harvesting.

Zooplankton and macrozoobenthos of small reservoirs of the State Natural Reserve «Kologrivsky Les» named after M.G. Sinitsyn

The article presents the results of studies of zooplankton and macrozoobenthos of small reservoirs on the territory of the State Natural Reserve «Kologrivsky Les» named after M.G. Sinitsyn. The hydrochemical and hydrophysical parameters of small reservoirs are given. In summer, the highest biomass and abundance of zooplankton were observed for long-existing beaver ponds on streams. In autumn, among the studied small reservoirs, the highest biomass and abundance of zooplankton are characteristic of oxbow lakes. The highest biomass of benthos was noted in oxbow lakes, and its abundance was found in beaver ponds. An analysis of the ecological groups of zooplankton and benthos by type of nutrition was carried out. In autumn, the composition of zooplankton was marked by a predominance of vertical feeders and primary filter feeders in beaver ponds, primary filter feeders and predatory forms in ditches, primary filter feeders and vertical feeders in oxbow lakes, and secondary filter feeders, scrapers, detritivores and stand feeders in hollows in wetlands. The benthos of beaver ponds and oxbow lakes contains all six ecological groups of benthos based on feeding type. There are no collectors, obligate filter feeders or active predators in the ditches. Only soil ingesters were noted in the hollows. A number of indices have been calculated to characterize the structure of zooplankton.

Multiyear trajectories of stream and riparian responses to beaver dam analogs on a low‐gradient channel lacking woody riparian vegetation

Beaver‐based restoration techniques seek to assist with the recovery of stream systems that have been damaged, degraded, or destroyed. In addition to reintroducing beaver, restoration practitioners have sought to mimic the influence of beaver dams on stream processes by building beaver dam analogs (BDAs). Stream restoration has been criticized for a lack of extended monitoring and a dearth of empirical evidence for the efficacy of BDAs. Here, we extend early and previously reported 1‐ to 2‐year monitoring of five BDAs on a low‐gradient stream lacking woody riparian vegetation to 3–6 years, depending on the parameter examined. BDAs raised groundwater near the stream and did not affect water temperatures during the duration of monitoring. Consistent with elevated groundwater levels, riparian willow cuttings grew 2.8–9.6 times more when planted near BDAs than far from BDAs, which was more than the 1.3‐ to 1.4‐fold difference after the first growing season. In contrast, a short‐term association between BDAs and willow survival disappeared in the long term. Likewise, sediment aggradation above the upstream BDA 1 year after construction reversed completely 4 years later, probably due to structural damage during high flows that could not be repaired until flows abated. Annual peak flow levels explained over 80% of the variation in the number of structures requiring annual repair. Our results suggest that BDA‐based restoration should account for both the costs of structure maintenance during project planning and the importance of long‐term monitoring during project assessment.

Multi‐method sampling increases detectability and assessment of spatio‐temporal interactions of mammals and birds in wetland habitats

Abstract Freshwater habitats support high levels of biodiversity and provide important habitat for wetland‐dependent taxa; however, impairment of aquatic connectivity through wetland loss, stream alterations and light pollution impacts species persistence and community resilience. Quantifying occupancy of these habitats to assess their use by mammals and birds can be challenging, especially for cryptic species. This study examines wetland habitat use by mammals and birds, and their spatial and temporal relationships within the Beaver Hills Biosphere in Alberta, Canada. As part of a multi‐method detection approach, camera boxes, cameras on beaver dams, and camera rafts allowed for multivariate analyses to determine temporal and spatial patterns of habitat use and species associations, while field sampling and environmental DNA (eDNA) provided data on site occupancy by a subset of semi‐aquatic mammals. From ~50,000 images, over 84 species were detected, including 52 species of birds and 25 species of mammals. Several species were spatially associated, and although most species of mammals exhibited temporal overlap, there were distinct differences, especially on beaver dams where predators such as coyotes and white‐tailed deer shared the same space. Temporally, birds were detected most often during the day and mammals at night. During new moon phases, use of beaver dams by beavers decreased dramatically, and use of camera rafts by muskrats increased. Winter field surveys allowed for a broad overview of wetland occupancy and abundance of some species, particularly by beavers and muskrats, and occasionally winter use by other semi‐aquatic mammals. Where there was limited detection of more cryptic species of semi‐aquatic mammals, eDNA analysis successfully detected American water shrew, American mink, North American river otter and northern bog lemming more often than camera and field methods. Applying a multi‐method monitoring approach for mammals and birds in wetland habitats is critical at a time when freshwater systems are experiencing dramatic declines in relative abundance of monitored wildlife populations, with many of these species underrepresented in conventional surveys.

Eager about beavers? Understanding opposition to species reintroduction, and its implications for conservation

Abstract The range of keystone species is increasing in some parts of the world, particularly Europe, through a combination of natural recolonization, government‐sanctioned and covert reintroductions. Reintroductions are an important conservation tool, particularly in the increasingly popular approach of rewilding. There is relatively little understanding of the politics, broadly conceived, of species reintroduction, particularly around how people who live alongside these newly introduced species might react, and what underpins this reaction, and how the method of reintroduction affects reactions. Here, we explore these issues through a case of beavers in central Scotland, which were covertly reintroduced. We explore opposition to reintroduction as manifest in beaver killing and dam destruction by land managers, quantifying these using the sensitive ‘bean count’ method. We also explore what underpins land managers' reactions, particularly their views and values around land and land management. We found considerable resistance. We found that beaver killing and dam destruction were widespread, both before and after beavers became a protected species. Nevertheless, beaver populations and ranges in Scotland continue to grow. We found attitudes were grounded in a strong set of relational values around land custodianship. We find a range of views towards beavers, including widespread opposition, particularly regarding the covert nature of beaver introduction, the challenge beavers and beaver protection provide to ideas of proper land management and custodianship, and a lack of trust in formal methods of beaver governance. We argue that species reintroductions policies and research should give careful consideration to potential opposition, its material impacts on reintroduction projects and how it is grounded in wider environmental values and politics. Read the free Plain Language Summary for this article on the Journal blog.

Bull Trout Passage at Beaver Dams in Two Montana Streams

Bull Trout Passage at Beaver Dams in Two Montana Streams

Landscape characteristics govern the impacts of beaver ponds on surface water methylmercury concentrations in boreal watersheds

Studies in boreal regions concerning the bioaccumulative neurotoxin methylmercury (MeHg) in natural wetlands and experimental reservoirs have shown that these waterbodies contribute to high MeHg levels in underlying sediments, inundated vegetation, and aquatic organisms. Beaver ponds are natural reservoirs that are ubiquitous in the Canadian boreal region and have been reported to increase downstream MeHg concentrations. However, the reported impacts of beaver ponds on stream MeHg vary widely across a limited number of studies, and factors influencing this variation are not well understood. To quantify the effect of beaver ponds on stream mercury concentrations, water samples were taken upstream and downstream of 10 in-channel beaver impoundments in northwestern Ontario, Canada. The downstream:upstream MeHg concentration ratios were related to pond and landscape characteristics to examine potential factors that play a role in determining the effect of beaver ponds on stream MeHg concentrations. Overall, MeHg concentrations were 1.6 times greater downstream of the beaver ponds, though this increase was not consistent; downstream concentrations up to 12 times greater and up to 5 times less were also observed. Landscape characteristics that can be readily obtained from existing spatial datasets or quantified using remote sensing techniques emerged as better predictors of downstream:upstream MeHg concentrations than site-specific stream chemistry parameters or pond characteristics that are more difficult to ascertain, with drier landscapes indicative of lower background MeHg export being more likely to exhibit greater increases in MeHg downstream of a beaver pond. These results suggest that the effects of beaver ponds on surface water MeHg concentrations are generally small but highly variable, and that the magnitude of the pond’s influence on stream MeHg are lessened in landscapes already conducive to higher MeHg concentrations.

Estimating Increased Transient Water Storage with Increases in Beaver Dam Activity

Dam building by beaver (Castor spp.) slows water movement through montane valleys, increasing transient water storage and the diversity of residence times. In some cases, water storage created by beaver dam construction is correlated to changes in streamflow magnitude and timing. However, the total amount of additional surface and groundwater storage that beaver dams may create (and, thus, their maximum potential impact on streamflow) has not been contextualized in the water balance of larger river basins. We estimate the potential transient water storage increases that could be created at 5, 25, 50, and 100% of maximum modeled beaver dam capacity in the Bear River basin, USA, by adapting the height above nearest drainage (HAND) algorithm to spatially estimate surface water storage. Surface water storage estimates were combined with the MODFLOW groundwater model to estimate potential increases in groundwater storage throughout the basin. We tested four scenarios to estimate potential transient water storage increases resulting from the construction of 1179 to 34,897 beaver dams, and estimated surface water storage to range from 57.5 to 72.8 m3 per dam and groundwater storage to range from 182.2 to 313.3 m3 per dam. Overall, we estimate that beaver dam construction could increase transient water storage by up to 10.38 million m3 in the Bear River basin. We further contextualize beaver dam-related water storage increases with streamflow, reservoir, and snowpack volumes.

The Impact of Beaver Dams on the Dynamic of Groundwater Levels at Łąki Soleckie

Areas excluded from agricultural production are susceptible to the presence of beaver families. The most significant changes occur during the initial period, when agricultural utilization is abandoned and beavers establish their presence on the land. During this period, some parcels remain uncultivated, while agricultural activities persist in neighboring areas. This situation is accompanied by the destruction of beaver dams, especially during periods of abundant water resources, and notably during intensive fieldwork. The article presents field studies aimed at determining the extent to which constructed and operational beaver dams contribute to changes in groundwater levels in drained peatland areas. In order to protect and sustainably use peat soils, it is necessary to maintain their high moisture content by ensuring a high groundwater level elevation. This can be achieved through the use of existing damming structures in the area (levees, weirs). Beaver dams can also serve a similar function, blocking the outflow of water from peat lands by raising the water level and consequently retaining it naturally. The specific objective was to develop principles for verifying factors influencing the effects of beaver dam construction on groundwater levels in fields within their range of influence. The water table levels within the study area during rainless periods were influenced by water levels in ditches, dependent on beaver activity in the nearby river. Beaver activities, manifested through dam construction, were influenced by periodic water resources in the river, defined by the cumulative monthly precipitation. Factors affecting groundwater levels in rainless periods on the plots also included the distance from the river cross-section and the permeability of soils expressed by the filtration coefficient of the active layer. Beaver dams had the greatest impact on stabilizing the water table in the soil profile closest to the river.

Effects of a beaver dam on the benthic copepod assemblage of a Mediterranean river

As known “ecosystem engineers”, beavers influence river hydrology, geomorphology, biochemistry, and biological assemblages. However, there is a lack of research regarding the effects of beaver activities on freshwater meiofauna. In this study, we investigated the taxonomic and functional composition of the benthic copepod assemblage of a segment of the Tiber River (Italy) where a beaver dam, created about 7 weeks before our survey, had formed a semi-lentic habitat upstream and a lotic habitat downstream of the dam. We also analyzed the copepod assemblage before and after a flood event that destroyed the beaver dam, providing a unique opportunity to observe changes in a naturally reversing scenario. Our analyses revealed that, while the taxonomic composition and functional traits of the copepod assemblage remained largely unchanged across the recently formed semi-lentic and lotic habitats, substantial differences were evident between the dammed and undammed states. The dammed state showed lower copepod abundances, biomass, and functionality than the undammed one. These results highlight the role of beaver dams in changing the composition and functionality of meiofaunal assemblages offering insights into the dynamic interactions within aquatic ecosystems.

Full floodplain connectivity: Realising opportunities for ‘Stage 0’ river restoration

AbstractContinued declines in freshwater biodiversity and the challenges of climate change are creating greater interest in river restoration projects. Increasing recognition of the interaction between biological, geomorphological and hydrological processes has led to the development of ‘Stage 0’ river restoration. Stage 0 reaches are typically multi‐thread anabranching systems connected to the floodplain and its ecosystems. It is suggested that the defining characteristic of Stage 0 conditions is that of connectivity (longitudinal, lateral and vertical) at base flows. The methods or mechanisms that can re‐create such reaches are described, namely valley floor reset, beaver activity, beaver dam analogues and the use of large wood in the channel and floodplain. The scope for wider adoption of Stage 0 is then discussed and recommendations for expanding this approach across temperate regions with a long history of river modification and higher population densities are presented.

Crayfish communities converge over succession in beaver pond metacommunities

Abstract Metacommunity theory predicts that the relative importance of regional and local processes structuring communities will change over ecological succession. Determining effects of these processes on taxonomic and evolutionary diversity in spatially structured freshwater habitats of different successional stages may greatly improve understanding of the maintenance of diversity across temporal and spatial scales. In this study, we evaluated crayfish diversity at local and regional scales in pond metacommunities undergoing secondary succession from beaver (Castor canadensis) disturbance. Following theoretical predictions from metacommunity ecology of the increasing importance of local processes over succession, we hypothesised a decline in crayfish local and β diversity over succession from stronger local structuring as the older ponds may provide less suitable habitat than streams. Crayfish species and phylogenetic diversity were evaluated in beaver pond metacommunities and reference headwater streams located in three catchment regions. DNA sequences from the mitochondrial cytochrome oxidase I gene were used to assign crayfish to species for community and phylogenetic diversity tests. Local and β diversity were contrasted across beaver ponds ranging in age from 24 to 70 years and as a function of metacommunity processes. Counter to predictions, local species diversity among streams and the successional stages of ponds categorised by age class (24–39 years; 42–57 years; 60–70 years) did not differ, but community and phylogenetic convergence occurred in the oldest pond ecosystems. Crayfish community composition differed between the youngest and oldest ponds, resulting from higher abundance in the youngest ponds and community convergence in the oldest ponds. The association between community composition and the environment was strongest in streams and decoupled with pond age. In contrast, the correlation between intraspecific haplotype composition and the environment increased over succession. Among the three metacommunities, the regional crayfish species diversity arose from a combination of the temporal and environmental drivers from beaver‐constructed ecosystems and dispersal limitation within catchments. This study represents the first investigation of the taxonomic and phylogenetic diversity response to the successional stages of beaver pond metacommunities. The detection of differential crayfish composition and haplotype sorting to pond age suggests a role for local structuring and further indicates that future studies should acknowledge succession in shaping species diversity at local and regional scales. Dispersal limitation within catchment regions probably contributes to the evolution of crayfish species diversity in metacommunities and the overall maintenance of biodiversity. The results support a transition in community and freshwater ecology from a recent emphasis on spatial processes towards the integration of temporal drivers to better identify regulators of taxonomic and phylogenetic diversity across scales.

Features of the Distribution of Beaver Dams and Ponds along Small Rivers: The Volga-Kama Region, European Russia

In this paper, by using GNSS technologies, some features of the distribution and some morphometric parameters of dams and ponds created by the Eurasian beaver (Castor fiber L.) along ten rivers of the Volga-Kama region of European Russia were identified. Detected features depend on the geomorphological, lithological, and landscape features of these rivers and their basins. The significant role of river slopes, as well as landscape zoning, in the distribution of beaver dams and ponds along small rivers in the study region is shown. In the rivers under study, almost all beaver constructions are located on riverbed slopes of less than 3% (most often, less than 2%). In the south of the forest zone (the southern taiga of the Vyatka River basin), the majority of dams and ponds (about 90%) are located on slopes of less than 1%, while, within the uplands of the forest-steppe zone, this location varies depending on the length of the rivers. In general, the greater the average slope of the river (the greater the average elevation of the river basin), the lower, other things being equal, the degree of beaver transformation of such rivers. This feature is better expressed in the rivers of the forest landscape zone and less expressed in the rivers flowing in the forest-steppe zone. Analysis of the morphometric parameters of beaver dams shows statistically significant trends towards an increase in their average height, as the channel slopes increase. Statistically significant trends were also identified towards a decrease in the length of dams and the length of associated ponds, with an increase in channel slopes. It is noteworthy that the critical values of the slope for a statistically significant and relatively sharp change in these parameters are 1.45%, 1.07 (or 0.54)%, and 0.65 (or 0.47)%, respectively. The greatest average heights of beaver dams are confined to those rivers where their basins are composed of loamy rocks/soils (especially those that are poorly plowed), compared with “sandy” river basins. This may be due to the peculiarities of the ratio of surface and underground water runoff in these basins and, as a consequence, different intensities of snowmelt- and rainfall-induced flood flow. We assume that the above-mentioned features reflect the early stages of beaver expansion (population growth) in the studied rivers.