Theses and Dissertations at Montana State University (MSU)
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Item Long-term response of willow to beaver reintroduction and moose browsing in the southern Absaroka-Beartooth Wilderness(Montana State University - Bozeman, College of Agriculture, 2022) Dines, Rachael Helen; Chairperson, Graduate Committee: Bok SowellWillow is an important component in the southern Absaroka Beartooth Wilderness (ABW) riparian areas because it provides critical beaver habitat and is an essential food source for moose populations. Forest Service managers have monitored long-term trends in willow condition and herbivore populations in the southern ABW. Beavers were extirpated in the mid-1900's and then reintroduced beginning in 1986. Moose numbers increased in the early 1900's and willow over-browsing followed until the population declined after habitat loss from the 1988 Yellowstone fires. The objective of this study was to examine willow condition in response to changes in beaver and moose populations in the southern ABW. I used annual stream-side surveys to record the number and location of beaver colonies from 1986 to 2021 and aerial imagery to describe changes in willow canopy cover. I used a binomial regression to evaluate the relationship between willow canopy cover and beaver colony density and longevity to estimate if long-term beaver presence increased willow canopy cover. I used linear regression to analyze indices of moose relative abundance, willow plots recording height and browsing, and a long-term browsing exclosure to evaluate the effect of moose population trends on willow height. Beaver have remained at carrying capacity over the last 20 years, and average willow canopy cover increased from 16% in 1981 to 37% in 2019. The probability of willow occurrence increased the longer beaver occupied an area and with colony density (colonies/km). Moose relative abundance declined from 1987 to 2021, while average willow height increased from 113cm in 1988 to 190cm in 2021 and browsing decreased from 53% in 1989 to 3% in 2021. Browsing was an important factor limiting willow height. Moose abundance had a positive linear relationship with average browsing pressure and negative linear relationship with average willow height. This study shows that the southern ABW was able to recover from historic over-browsing and beaver extirpation. The long-term effects of beaver reintroduction and reduced moose numbers in a historically degraded environment enhanced willow, indicating that under the right circumstances, willow communities have the potential to recover from a previously degraded state.Item The response of parafluvial soils to beaver mimicry restoration in a Montane stream(Montana State University - Bozeman, College of Agriculture, 2020) Whitehead, Briana Katherine; Chairperson, Graduate Committee: Tracy M. Sterling and William Kleindl (co-chair); Paul Stoy, William Kleindl, Martin Rabenhorst, Rob Payn, David Wood and Anthony Hartshorn were co-authors of the article, 'Parafluvial soil response to beaver mimicry restoration in a montane stream' submitted to the journal 'Restoration ecology' which is contained within this thesis.Beaver Mimicry Restoration (BMR) is a relatively new aquatic restoration practice that seeks to improve deteriorated stream ecological functions. BMR is designed to rejoin hydrologically disconnected streams with their adjacent floodplains via the installation of small-scale, stream-spanning structures derived from natural materials and inspired by the influence of natural beaver (Castor spp.) dams. These structures capture sediment, elevate stream stage and groundwater tables, create thermal refugia, and re-establish riparian vegetation. Most research on BMR has focused on the hydrological or botanical results, but little is known about the response of parafluvial soils. I report measurements of soil water content, soil temperature, soil biogeochemical reduction, and vegetation responses at paired BMR-influenced treatment and non-BMR-influenced control locations from June through September of 2018 and 2019 in a montane stream in southwestern Montana (USA). In comparison to soils at control sites, soils adjacent to BMR activity experienced an extended period of higher water contents (0.23 m 3/m 3 higher), increased anoxic conditions (on average 27% more during the field season), a less variable and cooler soil temperature range (on average 5 °C cooler), and supported longer durations of vegetation greenness (additional 20 days) during the dry months. Results demonstrate how BMR produces conducive conditions for the development of new and/or the reestablish of historic hydric soils.Item Biotic and physical responses to biomimicry structures in a Rocky Mountain incised stream(Montana State University - Bozeman, College of Letters & Science, 2020) Reinert, James Holden; Chairperson, Graduate Committee: Lindsey Albertson; Lindsey K. Albertson and James R. Junker were co-authors of the article, 'Biotic and physical responses to biomimicry structures in a Rocky Mountain incised stream' submitted to the journal 'River research and applications' which is contained within this thesis.An increase in stream degradation resulting from land use change has motivated an increase in restoration efforts across the globe. Post-restoration monitoring is still lacking, however, and does not always incorporate biotic responses to changes in the physical template. Beaver mimicry structures (BMS) are becoming a popular tool to restore degraded streams throughout the American west, but relatively little is known about how these installations influence both biotic and abiotic factors, with consequences for ecosystem functioning. We monitored basal resource deposition and macroinvertebrate density, biomass, and production to quantify functional responses to BMS installations. We compared conditions at BMS sites to naturally occurring beaver dam and reference riffle sites in a low-gradient stream in southwest Montana. Thermal ranges were contracted, and daily maximum temperatures increased at BMS sites compared to reference riffle sites. Deposition of fine sediment and basal resources was similar at beaver and BMS sites, and both were higher than reference riffles. Densities and production of macroinvertebrates were higher at the BMS sites compared to reference sites and similar to beaver sites due to changes in physical habitat and basal resource availability, reflected by increases in production of shredders (beaver) and collector-gatherers (BMS). In this study site, changes to the physical template using BMS appear to have strong impacts on biotic functional responses, creating habitats similar to target conditions of natural beaver dams. Future research should consider the extent of degradation and temporal limitations of monitoring schemes to incorporate BMS into standard restoration practice. Functional response metrics provide an important and mechanistic approach to determine the efficacy of process-based stream restoration practices.Item Ecosystem pioneers: beaver dispersal and settlement site selection in the context of habitat restoration(Montana State University - Bozeman, College of Agriculture, 2018) Ritter, Torrey Daniel; Chairperson, Graduate Committee: Lance McNewThe activities of beavers (Castor canadensis) provide a variety of benefits to stream systems by capturing and storing water and sediment, expanding riparian areas, and increasing habitat heterogeneity. Understandably, land and wildlife managers are interested in using beavers as a habitat restoration tool. However, streams targeted for restoration are often degraded and lack recent beaver activity, and therefore represent suboptimal habitat. The habitat selection process for beavers in suboptimal and unmodified habitats provides a natural analogue to beaver restoration, but the process is not well-understood. I radio-marked juvenile beavers and conducted beaver-use surveys in tributary streams of the Gallatin and Madison River drainages in southwest Montana to investigate dispersal, survival, and settlement site selection by beavers colonizing novel areas. My objective was to study beaver ecology in the context of beaver restoration to improve identification of suitable project locations. Beaver colony densities in the study area were low or average, though colony densities in suitable habitat were generally high. There was evidence of delayed dispersal, and as the density of active beaver colonies increased the probability of dispersal decreased. Radio-marked beavers that dispersed settled quickly and dispersal distances were highly variable. Most beavers settled in active colonies or other beaver-modified habitats, and colonization of unmodified stream segments was rare. My top habitat selection models indicated new settlement sites were located in stream segments characterized by low gradients, dense woody riparian vegetation close to the stream, and relatively narrow stream channels. Stream channels at new settlement sites were more variable both in cross-sectional and longitudinal depth and were more heavily influenced by secondary channels than unsettled sites. My results suggest beavers select for pre-engineered habitat over unoccupied stream segments, and in novel areas habitat conditions that facilitate stable dam construction appear most important. When choosing project locations, restoration practitioners should consider local beaver colony locations and densities to assess the potential for dispersers to reach the restoration site. Stream segments that provide dam resiliency and hiding cover should be targeted for initial restoration efforts, and pre-engineering of habitat prior to beaver occupancy may increase the probability of successful colony establishment.Item A study of beaver-waterfowl relations in the mountainous area of Beaverhead County, Montana(Montana State University - Bozeman, College of Letters & Science, 1955) Casagranda, LloydItem A study in beaver ecology in western Montana with special reference to movements(Montana State University - Bozeman, College of Letters & Science, 1952) Townsend, Joseph E.Item Effects of beaver reintroduction and ungulate browsing on aspen recovery in the Eagle Creek drainage of the northern Yellowstone winter range(Montana State University - Bozeman, College of Agriculture, 2013) Runyon, Molly Jean; Chairperson, Graduate Committee: Bok SowellUngulate browsing and lack of overstory disturbance have historically prevented aspen regeneration on the Northern Yellowstone Winter Range (NYWR). Aspen clones regenerate if sprouts are produced that grow into recruitment stems (>2 m tall) and replace the mature overstory. Beaver were reintroduced to the Eagle Creek drainage on the NYWR in 1991 in an attempt to facilitate recovery of riparian aspen communities by removing aspen overstory and increasing sprouting. However, intense ungulate browsing, primarily from the Northern Yellowstone elk herd, was preventing aspen recruitment in Eagle Creek in 2005. Wolf predation has contributed to a 56% decrease in this elk herd from 2005 to 2012. I investigated the effects of beaver reintroduction and ungulate herbivory on aspen recovery in the Eagle Creek drainage in 2012. Aerial photos taken of Eagle Creek in 1990, 2005, and 2011 showed that although beaver activity stimulated aspen sprouting, the mature overstory of many aspen stands has not been replaced 21 years after beaver reintroduction (p>0.05). Sprouting and recruitment were investigated using 4-m radius circular vegetation plots (n=31) established in aspen stands throughout Eagle Creek in 1997 and monitored annually until 2012. Beaver activity stimulated increased sprouting in 71% of these plots, and 77% of the plots had > or = 1 recruitment stem in 2012. Prolonged flooding and high browsing levels contributed to lack of recruitment in 23% of the plots (p<0.05). In 2012, 75% of the paired plots associated with aspen exclosures had unfenced aspen stems with an average stem height > or = 2 m. Recent increases in aspen recruitment in Eagle Creek indicate that aspen communities are regenerating. This is likely the result of decreased browsing pressure on aspen saplings from 2005 to 2012. These findings are consistent with the predictions of a density-mediated trophic cascade following wolf reintroduction.Item Habitat selection of a reintroduced beaver population in the Absaroka-Beartooth Wilderness(Montana State University - Bozeman, College of Agriculture, 2011) Scrafford, Matthew Allan; Chairperson, Graduate Committee: Duncan T. Patten; Geoffrey Poole (co-chair)In 1986, a beaver reintroduction program was initiated in the Absaroka-Beartooth Wilderness (AB), Montana, in an effort to restore this species to the landscape after a nearly 40 year absence. Since reintroduction, the AB has been inventoried yearly by the U.S.F.S. Gardiner Ranger District to document the location of active beaver structures. This study utilized the beaver structure inventory to report habitat characteristics associated with successful beaver colonies in the AB over a 24 year period. In meadows along 3rd order streams, colonies beaver established early (1986 - 1993) were more successful through 2010 than those established later (1994 - 2006), likely because habitat selected early was of higher quality. Odds of beaver colony success increased with greater stream sinuosity and depth, less distance to secondary channels, and less area of point/gravel bars. The amount of willow, although abundant at all locations, was not significantly different for beaver colony locations with varying levels of success. The best habitat for beaver colonies in meadows along 3rd order streams appeared to be on or within close proximity of secondary channels (e.g., sloughs, tributaries) because these locations were sheltered from destructive main stem flooding such that colonies and their structures were more permanent. Locations with evidence of historic use by beaver in meadows along 3rd order streams had less area of point/gravel bars, greater stream depth, and more willow than locations which had never been used by beaver. Successful beaver colonies were also found in smaller meadows on 1st and 2nd order streams although there was less available willow and streams could be intermittent in flow. After 24 years, the beaver population appears to be at carrying capacity, although there is no evidence that willow harvest rates are excessive or even negative. The success of reintroduced beaver populations in the AB is in contrast to conditions on the nearby northern Yellowstone winter range, where colony density is lower, likely because riparian woody vegetation shows more evidence of suppression from ungulate browsing, site potential for willow growth may be less, and negative anthropogenic effects persist.Item Restoring aspen riparian stands with beaver on the northern Yellowstone winter range(Montana State University - Bozeman, College of Agriculture, 2007) McColley, Samuel David; Chairperson, Graduate Committee: Bok F. Sowell.Aspen (Populus tremuloides) on the Gardiner Ranger District, Gallatin National Forest, have declined over the last half-century. In an attempt to reverse this trend, beaver (Castor canadensis) were reintroduced in Eagle Creek in 1991. Beaver promote aspen suckering through their dam and lodge building activities. In 2005, I assessed the long-term effects of beaver on aspen stands and the associated riparian area in the Eagle Creek Drainage. Aerial photographs taken in 1990 and 2005 were used to compare changes in riparian area vegetation where beaver were reintroduced. Aspen canopy cover decreased (P<0.05) from 43% to 25% on Eagle Creek (29 ha) between 1990 and 2005. Willow (Salix spp.) cover increased (P<0.05) from 10% to 14% and alder (Alnus incana) cover and water surface area doubled during the same period. Aspen recovery was estimated by comparing vegetative changes among control sites with <10% beaver use (n = 5), active beaver sites (n = 6), sites abandoned for 1-3 years (n = 7), sites abandoned for 4-6 years (n = 4), and sites abandoned for 7-11 years (n = 5).