Abandoned Beaver Ponds Research Articles

The effects of beaver impoundments on montane stream fish communities

Abstract North American beavers (Castor canadensis) are ecosystem engineers that create novel habitats in stream ecosystems. Although driven to the edge of extinction by historical over‐exploitation, beavers are recolonizing much of their former range. In the Southern Appalachian Mountains beavers alter habitats occupied by diverse fish communities across a mosaic of changing forest cover and management priorities. Fishes were sampled from nine streams with active beaver ponds and from seven streams with inactive ponds in the Southern Appalachians during summer 2019. The status of beaver ponds was among the most important factors affecting fish communities; however, both active and inactive beaver ponds affected fish community structure, α‐diversity, and local contributions to β‐diversity (LCBD). Fish α‐diversity was lower in reaches from streams with active ponds and the magnitude of this reduction was dependent on the position relative to a pond. However, both active and abandoned beaver ponds and pond tail races had higher LCBD values compared with free‐flowing reaches. Arcsin‐transformed forest cover did not improve the model fit for any dependent variables. Indicator species analysis found that two species had an association with active beaver ponds, whereas eight species were associated with inactive beaver ponds or free‐flowing reaches. The effects of beaver impoundments on fish communities in Appalachian streams are dependent on the pond activity level and spatial context. Although diversity and species richness may be reduced in individual habitats, beaver ponds contribute to higher biodiversity at a regional spatial scale. An increased understanding of beaver effects on Southern Appalachian fish communities will enable stakeholders to make informed decisions regarding the management of sensitive or economically important fishes. Mitigating conflicts between sensitive resources and these ecosystem engineers will become an increasingly important management concern as beaver populations recover in the Southern Appalachians.

Rewilding wetlands: beaver as agents of within-habitat heterogeneity and the responses of contrasting biota.

Ecosystem engineers can increase biodiversity by creating novel habitat supporting species that would otherwise be absent. Their more routine activities further influence the biota occupying engineered habitats. Beavers are well-known for transforming ecosystems through dam building and are therefore increasingly being used for habitat restoration, adaptation to climate extremes and in long-term rewilding. Abandoned beaver ponds (BP) develop into meadows or forested wetlands that differ fundamentally from other terrestrial habitats and thus increase landscape diversity. Active BP, by contrast, are superficially similar to other non-engineered shallow wetlands, but ongoing use and maintenance might affect how BP contribute to aquatic biodiversity. We explored the 'within-habitat' effect of an ecosystem engineer by comparing active BP in southern Sweden with coexisting other wetlands (OW), using sedentary (plants) and mobile (water beetles) organisms as indicators. BP differed predictably from OW in environmental characteristics and were more heterogeneous. BP supported more plant species at plot (+15%) and site (+33%) scales, and plant beta diversity, based on turnover between plots, was 17% higher than in OW, contributing to a significantly larger species pool in BP (+17%). Beetles were not differentiated between BP and OW based on diversity measures but were 26% more abundant in BP. Independent of habitat creation beaver are thus significant agents of within-habitat heterogeneity that differentiates BP from other standing water habitat; as an integral component of the rewilding of wetlands re-establishing beaver should benefit aquatic biodiversity across multiple scales.This article is part of the theme issue 'Trophic rewilding: consequences for ecosystems under global change'.

Spatial and Temporal Variability of Channel Retention in a Lowland Temperate Forest Stream Settled by European Beaver (Castor fiber)

Beaver ponds remain a challenge for forest management in those countries where expansion of beaver (Castor fiber) is observed. Despite undoubted economic losses generated in forests by beaver, their influence on hydrology of forest streams especially in terms of increasing channel retention (amount of water stored in the river channel), is considered a positive aspect of their activity. In our study, we compared water storage capacities of a lowland forest stream settled by beaver in order to unravel the possible temporal variability of beaver’s influence on channel retention. We compared distribution, total damming height, volumes and areas of beaver ponds in the valley of Krzemianka (Northeast Poland) in the years 2006 (when a high construction activity of beaver was observed) and in 2013 (when the activity of beaver decreased significantly). The study revealed a significant decrease of channel retention of beaver ponds from over 15,000 m3 in 2006 to 7000 m3 in 2013. The total damming height of the cascade of beaver ponds decreased from 6.6 to 5.6 m. Abandoned beaver ponds that transferred into wetlands, where lost channel retention was replaced by soil and groundwater retention, were more constant over time and less vulnerable to the external disturbance means of water storage than channel retention. We concluded that abandoned beaver ponds played an active role in increasing channel retention of the river analyzed for approximately 5 years. We also concluded that if the construction activity of beaver was used as a tool (ecosystem service) in increasing channel retention of the river valley, the permanent presence of beaver in the riparian zone of forest streams should have been assured.

Beavers (Castor fiber) increase habitat availability, heterogeneity and connectivity for common frogs (Rana temporaria)

Beavers (Castor fiber), as typical ecosystem engineers, alter living conditions especially for amphibians through the building of dams and felling of trees, thereby changing the hydroperiod and substantially affecting forest succession stages. In this study we quantify the effects of beavers on the availability of amphibian breeding waters in the Hürtgenwald, a woodland area in the Central European Rhenish Massif, its colonisation by common frogs (Rana temporaria) and the effects of age and succession stage of beaver ponds on ovipositional site selection. In 2013, beaver ponds comprised about half (49%) of all lentic water bodies but contained 82.5% of all common frog egg masses. Mature beaver ponds (>6 years old) harboured approximately half of the egg masses (), but new beaver ponds (1-3 years old) can also be home to large breeding aggregations. Abandoned beaver ponds are of minor importance as ovipositional sites for common frogs. High egg mass counts were also found in artificially-dammed ponds (). We believe that common frogs prefer occupied beaver ponds as ovipositional sites because of high insolation and a permanent hydroperiod, which lead to rapid tadpole emergence. Beaver ponds are generally located in close proximity to each other, facilitating movement and rapid colonisation by common frogs. Our research provides additional evidence to show that beavers enhance habitat availability, heterogeneity and connectivity, thereby fostering amphibian populations at a landscape level. As natural elements of small streams, beaver ponds must be taken into account in the context of the EU Water Framework Directive.

Engineering by an invasive species alters landscape‐level ecosystem function, but does not affect biodiversity in freshwater systems

AbstractAimEcological theory predicts that invasive ecosystem engineers like the American beaver (Castor canadensis) in Tierra del Fuego (TDF) affect landscape‐level biodiversity and ecosystem function (BEF) when engineered habitats are novel or extensive. We tested these hypotheses on freshwater BEF, sampling benthic habitat and macroinvertebrates in natural lotic (forest and grassland streams) and natural lentic habitats (bogs, lakes) and beaver‐modified lentic ecosystems (active and abandoned ponds).LocationTierra del Fuego Archipelago (Chile and Argentina).MethodsTo determine effects on patch‐scale BEF, we assessed two drivers: substrate diversity (H′) and benthic organic matter standing crop (BOM, g m−2). Extent of impact was estimated as relative stream length (%) for each patch type in four 1000 ha images.ResultsThe freshwater landscape was 56% free‐flowing streams (natural lotic), 13% bogs and lakes (natural lentic) and 31% active and abandoned beaver ponds (beaver lentic). While engineering significantly modified lotic habitats (converting them to ponds), the beaver ponds were largely similar to natural lentic systems, but engineered lentic patches retained more BOM. While benthic biodiversity in beaver ponds was less than streams, the assemblage contained no habitat‐specific taxa and was a subset of the natural lentic community.Main conclusionsInvasive beavers engineer habitats whose biodiversity is similar to the landscape's natural lentic habitats, but by increasing the surface area and unit area retention of BOM via its impoundments, this invasion augments carbon standing stock approximately 72% in watersheds. While this invasion is considered the largest alteration to TDF's forested biome in the Holocene, here we discover that its impact is to ecosystem function, rather than biodiversity in the aquatic landscape.

Downstream effects of beaver ponds on the water quality of New England first‐ and second‐order streams

AbstractBeaver, as allogenic ecosystem engineers, are capable of extensively altering surrounding habitats resulting in significant effects on stream water quality. This paper presents insight into downstream effects of beaver impoundments (both actively maintained and abandoned by beaver) and accumulated sediments on water quality, especially in protected watersheds serving as a drinking water supply. In a tributary un‐inhabited by beaver compared to those with active beaver ponds, we found significantly (p < 0·001) lower concentrations of NO3N (respectively: mean (standard error)) without beaver 0·11 (0·005) mg/l and with beaver 0·14 (0·002) mg/l), NH4N (0·007 (0·002) and 0·24 (0·002) mg/l), dissolved organic carbon (DOC) (3·47 (0·081) and 8·37 (0·203) mg/l), chlorophyll (2·38 (0·066) and 6·96 (0·203) µg/l), and temperature (16·43 (0·101) and 19·85 (0·123) °C), but higher pH (7·17 (0·02) and 6·72 (0·022)), PO4 (0·20 (0·01) and 0·17 (0·014) mg/l) concentration, and dissolved oxygen (DO) saturation (100·8 (0·708) and 67·6 (1·74)%). Within the beaver ponds, we observed a high abundance of predatory zooplankton, which help to control algae and feed on detritus within the pond ecosystem. We intentionally breached an abandoned beaver dam in the field and conducted a sediment resuspension experiment in the laboratory to assess the potential for increases in turbidity and nutrients from beaver pond sediments as would be expected in the event of a catastrophic dam breach. We found that abandoned beaver ponds have a stronger influence on downstream water quality than actively maintained ponds owing to higher turbidity with finer sediments and sharply increased stream water temperature during a dam failure. Copyright © 2010 John Wiley & Sons, Ltd.

Habitat dynamics of beaver Castor canadensis at two spatial scales

Abstract We studied habitat dynamics of the Canadian beaver Castor canadensis in a boreal forest landscape in southern Finland at two scales: the beaver pond level and the landscape level. To explore the changes in tree species composition due to beaver browsing and flooding, six abandoned beaver ponds were sampled (537 sample plots altogether). For habitat dynamics at the landscape scale, the variation in the flooded area and the number of active beaver colonies were recorded during 18 years (1980–1998). At the pond level, flooding appeared to effect more rapid and more pronounced changes in woody growth production than browsing. Coniferous trees were particularly susceptible to flooding, and deciduous trees were more susceptible to browsing. Deciduous trees dominated during succession following a flooding. At the landscape level, mean occupation time of a colony site was found to be short (2.6 years), and the mean area of beaver impoundments was small (0.14% of the total area). Recolonisation of habitat...

Building for the future: Abandoned beaver ponds promote bird diversity

We examined beaver (Castor canadensis) pond dynamics and associated riparian bird communities, based on call- response surveys. Following water disappearance, abandoned beaver ponds were invaded by grassy areas and alder shrubs and supported higher bird species numbers than nearby riparian areas. We detected a total of 49 species. At abandoned beaver ponds, the mean number of species was 6.4, whereas it ranged between 2.4 and 3.1 species for active beaver ponds, rivers, and lakes. Density of deciduous shrubs and graminoid cover, higher in abandoned beaver ponds, was positively associated to the number of species of birds. However, riparian avian diversity was lower near clearcuts and large water areas. Beaver population control or geographic confinement may suppress both spatial and temporal dynamics of beaver pond creation and abandonment, and could impact riparian vegetation and birds.

Hydrologic, geomorphic and climatic processes controlling willow establishment in a montane ecosystem

Willow communities dominate mid-elevation riparian areas throughout the Rocky Mountains of North America. However, many willow stands are rapidly declining in aerial cover and individual plants in stature. A poor understanding of the processes that control willow establishment hinders identifying the causes of this decline. We analysed the processes that have facilitated or limited willow establishment over the last half of the 20th century on two large floodplains in Rocky Mountain National Park in Colorado by addressing two questions: (1) How does hydrologic regime control willow establishment on different fluvial landforms? (2) How might climate-driven variations in hydrologic regime affect future willow establishment? We precisely aged willows on the three most common fluvial landforms, stream point bars, drained beaver ponds, and abandoned channels, and statistically related establishment dates to patterns of annual stream peak flow. The role of peak flow on willow establishment varied significantly by landform. Willow recruitment had occurred nearly every year on point bars. In former beaver complexes, most willows had established following dam breaches, whereas willows had established on abandoned channels for several years following channel avulsion. Establishment on point bars and abandoned channels was driven by peak flows of 2- to 5-year return intervals, whereas in abandoned beaver ponds most establishment was associated with flow events of >5-year return interval. Models of climate change suggest that temperatures will increase and precipitation seasonality will shift over the coming decades in the Rocky Mountains, leading to earlier spring runoff, lower summer and fall flows, decreased snowpack and decreased soil moisture. Such changes are likely to diminish opportunities for willow establishment. Copyright © 2005 John Wiley & Sons, Ltd.

Life budgets for a population of Tipula sacra (Diptera; Tipulidae)

Abstract. A population of Tipula sacra was studied intensively from 1969 to 1974 in a series of abandoned beaver ponds. Beavers recolonized the ponds from 1974 to 1976 and again in 1978. The basic life‐cycle is of 2 years duration, but cohort‐splitting occurs in the autumn as a result of some larvae growing faster and completing the life‐cycle in 1 year. Some periods are more favourable for growth than others and the size of the fast‐growing cohort varies from year to year. This insight allows some anomalies in the estimates of population size to be explained and life budgets have been produced for three year‐classes. The short‐fall in realization of egg potential is massive, apparently due to heavy female mortality by predation and the prevention of oviposition by inclement weather. Mortality rate is relatively low and constant from stage II larvae until pupation, but increases to adult emergence. There is a correlation between larval density and mortality rate. Certain aspects of the life‐history (e.g. high fecundity, variability in growth rate) appear to fit the species to life in a temporally unstable habitat.

Growth and development of larvae and adults of Tipula sacra Alexander (Insecta: Diptera) in a series of abandoned beaver ponds

Collections of all stages of the crane fly, Tipula sacra have been made over a period of years from a series of abandoned beaver ponds in the Kananaskis Valley, Alberta. The growth of larvae was followed by head-capsule measurements and weights. Eggs hatch within a month; first-instar larvae grow rapidly and enter the second instar after a few weeks. The second instar may last for 3 months and the third instar usually lasts for 6 months, including the first winter. Most larvae spend almost a full year in the fourth instar and overwinter for a second time. However, there was much variation in growth rate within the population. Adult emergence curves were consistent in form in 4 years. Each spanned a period of just over 2 months, although individual adults lived for only a few days. These curves snowed two peaks, the second of which contained 15–20% of the year's emergents. These two groups may represent different cohorts that have grown at different rates, suggesting that the life history may be semivoltine or univoltine. The sex ratio changes from about 1:1 in the third instar to 2:1 in favor of males in the late fourth instar, pupa, and adult.

The Food of Larvae of Tipula sacra Alexander in a Series of Abandoned Beaver Ponds (Diptera: Tipulidae)

The work described here forms part of a study of the ecology of a series of abandoned beaver ponds in the Kananaskis Forest Reserve of Alberta. Pritchard & Hall (1971) should be consulted for details of the study site and for a description of the study organism, the aquatic cranefly Tipula sacra Alexander. The thesis of this particular investigation was that sex, instar, season, and location of habitat were all factors capable of influencing the food of larvae of T. sacra, and quantitative investigations of larval gut contents with reference to these factors were carried out. The relationship between the availability of suitable food in the habitat and the quantities of this food ingested by the larvae was also investigated. Previous work on the food of aquatic herbivorous insects has generally shown little or no selectivity in ingestion. Mecom & Cummins (1964), for example, determined that Trichoptera larvae in five streams ingested algal cells in densities proportional to those in the environment. Brown (1960), however, investigating the algal food of Chloeon dipterum (L.) (Ephemeroptera), showed some selectivity in the food habits on the basis of size of larvae; large larvae ingested large species of algae with greater frequency than did small larvae. Brown also showed (1961) there were changes in the diet with seasonal changes in the environment, and also gave a useful review of methods used in the study of food habits. The importance of such studies and the current problems are reviewed by Cummins (1973).

The life history and feeding habits of Sialis cornuta Ross in a series of abandoned beaver ponds (Insecta; Megaloptera)

Sialis cornuta is being studied in a series of abandoned beaver ponds in the Rocky Mountains 80 km west of Calgary, Alberta. The species has a 2-year life cycle in this area. Eggs are laid mainly on the undersides of uprooted trees; each egg mass contains a mean of 585 eggs which are susceptible to heavy parasitism by Trichogramma semblidis. Most eggs are laid during late June, they hatch in 7 to 21 days, and most larvae attain the fifth or sixth instar by the first winter. In the laboratory there are between 7 and 10 instars before pupation, but in the field the number appears to be more constant at 10. Sexual dimorphism and possibly a larval diapause complicate the separation of instars and the translation of laboratory data to the field. Between May and mid-June of their second year larvae leave the water and pupate in the soil a short distance from the water's edge and adults emerge through June and the first half of July.Larvae feed on benthic invertebrates in approximate proportion to their abundance provided they are not too large. Chironomid larvae, tubificid worms, and ostracods form the bulk of the food.Information is given on mating, oviposition, and feeding behavior, and comparisons are made with the life history features of S. californica and S. rotunda in Oregon.

An introduction to the biology of craneflies in a series of abandoned beaver ponds, with an account of the life cycle of Tipula sacra Alexander (Diptera; Tipulidae)

A series of five beaver ponds that have been abandoned for about 10 years is described, and an introduction to the ecology of the area is given. The life cycle of the cranefly Tipula sacra is described. This is the commonest cranefly in the area and the larvae are important grazers on the microflora in benthic sediments. There are four larval instars, which can be separated by a combination of the presence or absence of setae on the spiracular lobes and the size of the spiracles. Larvae in instars III and IV can be sexed by examination of the gonads, while the presence of growth lamellae on the lateral sclerites of the head capsule shows promise as a means of aging larvae in all instars.