Thesis (M.S.)--University of Montana, 2006. / Title from PDF t.p. (viewed on Feb. 26, 2007). Includes bibliographical references.

Dynamic exchange of water across the stream-riparian zone interface is important in increasing stream water transit time through basins and enhancing redox-sensitive biogeochemical reactions that influence downstream water quality and ecosystem health. Such exchange may be enhanced by beaver dams, which are common throughout low order streams in North America, Europe, and Argentina. Lateral exchanges of water and nitrogen (N) were observed along a beaver dammed, third-order stream draining a 1.3 km2 Canadian Rocky Mountain valley bottom capped in peat. Measurements of hydraulic heads and chloride concentrations from a network of 80 water table wells were used to identify areas of stream water and groundwater mixing in the riparian area, and their spatiotemporal dynamics in summer 2008. Beaver were found to be the greatest factor affecting lateral movement of channel water into the riparian area. Channel water flowed laterally into the riparian area upstream of the dams and back to the channel downstream of the dams. The hyporheic zone expanded by ¡Ü1.5 m in the un-dammed reaches, but upwards of 7.5 m or more when dams were present. High contributions of stream water were found far out in the riparian area where dams were not immediately present within the stream reach, suggesting that upstream dams directed stream water into the riparian area where it travelled down valley before returning to the stream. This suggests that multiple dams create hyporheic flow paths at multiple scales. Potential mass flux calculations show the riparian area immediately downstream of the beaver dam was a source of N and dissolved organic carbon (DOC) to the stream, and a sink along the rest of the reach. Cold spots of N and DOC availability were also found along the beaver-driven flow paths in the riparian area adjacent to the dam. This pattern likely developed due to flushing of nutrients along the beaver driven hyporheic flow vectors. This work enhances our understanding of stream-aquifer exchange and N dynamics in riparian areas, and the effects of beaver on these processes.

Dynamic exchange of water across the stream-riparian zone interface is important in increasing stream water transit time through basins and enhancing redox-sensitive biogeochemical reactions that influence downstream water quality and ecosystem health. Such exchange may be enhanced by beaver dams, which are common throughout low order streams in North America, Europe, and Argentina. Lateral exchanges of water and nitrogen (N) were observed along a beaver dammed, third-order stream draining a 1.3 km2 Canadian Rocky Mountain valley bottom capped in peat. Measurements of hydraulic heads and chloride concentrations from a network of 80 water table wells were used to identify areas of stream water and groundwater mixing in the riparian area, and their spatiotemporal dynamics in summer 2008. Beaver were found to be the greatest factor affecting lateral movement of channel water into the riparian area. Channel water flowed laterally into the riparian area upstream of the dams and back to the channel downstream of the dams. The hyporheic zone expanded by ¡Ü1.5 m in the un-dammed reaches, but upwards of 7.5 m or more when dams were present. High contributions of stream water were found far out in the riparian area where dams were not immediately present within the stream reach, suggesting that upstream dams directed stream water into the riparian area where it travelled down valley before returning to the stream. This suggests that multiple dams create hyporheic flow paths at multiple scales. Potential mass flux calculations show the riparian area immediately downstream of the beaver dam was a source of N and dissolved organic carbon (DOC) to the stream, and a sink along the rest of the reach. Cold spots of N and DOC availability were also found along the beaver-driven flow paths in the riparian area adjacent to the dam. This pattern likely developed due to flushing of nutrients along the beaver driven hyporheic flow vectors. This work enhances our understanding of stream-aquifer exchange and N dynamics in riparian areas, and the effects of beaver on these processes.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains v, 391 p. : maps. Includes abstract. Includes bibliographical references (p. 374-389).

Understanding the relationship between heterogeneity, biodiversity and ecosystem function is an active focus of ecological research that has direct applications to the formulation of sustainable, science-based, watershed conservation plans. Here, I applied ecological theory on heterogeneity to the expansion of North American beaver to test hypotheses about physical habitat and fish biodiversity at a riverscape scale. To test these hypotheses (Chapter 4), I first addressed two methodological issues (Chapter 2, 3). By evaluating three types of gear at three levels of effort in a randomized block design over 4 replicate days, I show that 10 minnow traps, 2 hoop nets and 20 m of electrofishing captured most fish species within a 30-m sampling area (Chapter 2). Multiple statistical measures provided similar information, therefore I used general indices (richness, diversity), ecological guilds (flow based), and select multivariate analyses (DCA) to summarize fish communities (Chapter 3). I used these methodological insights to test ecological hypotheses by collecting habitat and fish data at all beaver dams (n = 15) and select control sites (n = 9) in Fish Brook, a coastal watershed in northeastern Massachusetts. From these data, I gained six basic and applied insights. First, beaver dams were distributed throughout the stream network. Second, at a local scale, beaver dams created more habitat heterogeneity than control sites. Specifically, beaver dams created four types of habitat alterations based on upstream-downstream differences in stream width, depth, velocity, and substrate. Third, richness and diversity of fish species around beaver dams were linked to habitat heterogeneity. Fourth, the mechanisms by which beaver dams altered fish biodiversity were mediated through habitat changes at the beaver dam patch boundary. Upstream of the dam macrohabitat guilds occupied the lentic areas, while below dams, fluvial fish guilds used shallow, faster water. Fifth, fluvial species responded the most dramatically to these habitat changes. Finally, in a system depauperate of lotic habitat, fluvial habitats created below beaver dams provided an important refuge for native stream fish. These source areas can increase resiliency and maintaining them may be useful for sustainable watershed conservation plans in these types of systems.

Movement is a core mechanism through which animals interact with their environment. A popular approach for investigating animal movement involves the use of GPS telemetry, which provides insights into both the spatial and temporal patterns exhibited by an individual or population. While many approaches for evaluating movement data have often analyzed intensity of use, most studies focused on a single property of use: the total duration an animal spent in a location. While this can provide insight into which landscape and habitat characteristics an individual may be selecting for, it does not fully account for how that space is being used. Therefore, it could be beneficial to combine more than one aspect of intensity of use to evaluate the behavioral mechanisms leading to patterns in space use, and by extension the drivers of home range structuring. As a territorial, central-place forager, the North American beaver (Castor canadensis) presents an ideal system for investigating drivers of home range structuring. However, while some species are easily tracked through traditional GPS attachment methods (such as GPS collars or backpacks), other species such as beavers present unique challenges given their fusiform shape and tapered neck. The overall objective of my thesis was to better understand fine-scale movement of beavers and the drivers of home range structuring. To do so, in chapter 1, I first developed and tested three different GPS transmitter attachment methods to determine which was most effective in terms of retention time (RT, total number of days a transmitter remains attached) and GPS fix success rate (FSR, % of successful fixes vs. attempted) and investigated to what degree various factors (season, sex, and age class) affected these results. In chapter 2, I analyzed space use in relation to four intensity of use metrics with machine learning to define homogenous types of space use. These metrics included the total number of visits, total and mean duration of visits, and mean interval between visits. GPS transmitters glued to the lower back of beavers provided up to two months of fine-scale data, as well as producing the highest FSR. In addition, longer retention times were found for transmitters attached to males versus females, and for transmitters deployed in the fall versus the spring. Using these data, I was able to capture five distinct population level intensity of use types including, low use – irregular, low use – regular, medium use – short duration, medium use – long duration, and lodge use. These types of use were all generally observed towards the core of the home range. In addition, all types of use were characterized by low intervals between visits except for the low use – irregular cluster. These results suggest highly structured, regular movements occurring in the core of beaver home ranges related primarily to shelter, foraging patches, and the movement paths used to link these locations. Overall, this approach allowed me to delineate between two distinct low use and medium use types and provided insight into the different behavioral mechanisms that may be driving these similar types of use. Capturing these different types of use was only possible by specifically combining multiple movement metrics at once to evaluate space use, as opposed to strictly using the number of GPS fixes to evaluate a location.

No description available.

No description available.

Thesis (Ph. D.)--University of Oregon, 2003. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 634-646). Also available for download via the World Wide Web; free to University of Oregon users.

The importance of spatial variation in abundance for the assessment of climate change impacts was examined using the North American beaver ( Castor canadensis) in Quebec as a model species. A preliminary characterization of the beavers' range edge improved the core-sampling bias and revealed that beavers are present at low densities, in shrubby riparian habitats as far north as the communities of Tasiujaq and Umiujaq. Spatial variation in beaver abundance across the province follows a roughly logistic pattern, with abundance peaking in southern Quebec, declining steeply around 49°N, and remaining uniformly low as far as 58°N. Although climate sensitivity of beaver abundance and the greatest changes in future beaver density are predicted to occur near the middle of their range, beavers are expected to occupy most of the province by 2055. These results highlight the value of incorporating density estimates from across a species' range into climate envelope models.