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Item Community composition analysis of altered vegetation communities following the release of grazing pressure(Montana State University - Bozeman, College of Agriculture, 2015) Buckmaster, Joshua; Chairperson, Graduate Committee: Clayton B. MarlowDetermining community composition and recognizing successional gradients of community recovery following release from disturbance is vital in determining proper land management techniques. Successful native plant recovery depends on biotic and abiotic factors and the type and degree of anthropogenic disturbance. Degraded vegetation communities need initial survey efforts to determine the extent of degradation followed by consistent standardized monitoring to determine transition along successional gradients. The aim of this study was to determine community composition and successional gradients following release from livestock grazing. To this end, initial surveys were completed at the Lost Trail National Wildlife Refuge during the summers of 2013 and 2014, with the aim of evaluating the composition of each previously mapped community type and making recommendations for future management practices. Prior to any fieldwork, various vegetation sampling methods were compared including, Daubenmire percent canopy cover (DPCC), point-intercept and modified Whittaker plots. The DPCC method was determined to be the most efficient for current and future sampling efforts, balancing the quality of data and the time needed for collection. Using this method, a minimum of 60 Daubenmire frames were sampled from 16 vegetation communities. The USFWS project objectives were to (1) determine if each of the premapped community types were named correctly, and (2) collect enough vegetation data to determine a 20% change in the five most common species with an accuracy of 80%. Species area curves were plotted, and sample adequacy calculated to determine if each community was adequately sampled. It was found that a minimum of 24 to 180 sample frames are necessary to sufficiently describe all communities. However, this number may increase as the communities transition to native-dominated stands. Litter depth was found to be the only statistically significant abiotic factor related to community composition (P = 0.03): litter depth is highly correlated with non-native species (r = 0.904), and the lack of litter is correlated with the presence of three climax species (r = 0.736). The intermontane grasslands in this refuge were found to be part of the Northern Fescue Grasslands rather than part of the Palouse Prairie.Item Pioneer plant communities five years after the 1988 Yellowstone fires(Montana State University - Bozeman, College of Letters & Science, 1995) Ament, Robert J.The Yellowstone fires of 1988 burned many different types of vegetation. This initiated secondary succession in environments from valley bottoms to alpine tundra. Five years after fire, plant communities were measured. Species presence was recorded in 100 m^2 macroplots and cover was sampled in twenty 1000 cm^2 quadrats. Pioneer community composition after severe fire in late-seral vegetation was compared across the elevational gradient in nine environmental types with three replications in each. In two of the subalpine fir environments, communities arising from four different pre-fire serai stages were sampled to test the hypothesis that pioneer community compostion differs when early-seral versus late-seral forests burn in one environmental type. Plant cover tends to decrease with increasing elevation. Along the elevational gradient, the wet grasslands had the strongest recovery from fire (plant cover averaged 97%), while the lowest cover was in the subalpine zone near treeline (39% average cover). Species richness was between 32 and 42 species per 0.01 hectare in the seven lowest environmental types. Diversity in the two highest elevational environmental types was distinctly low (19 and 20 species/0.01 hectare, respectively). Forty-two of the 262 species identified occurred in nearly all environments. Many of the others were concentrated in various portions of the gradient (i.e. grasslands, montane forests, subalpine fir forests). Each species and its distribution was tabulated. To test the hypothesis that pioneer communties were influenced by previous vegetation, ordinations (principal component analysis and principal coordinate analysis) were conducted on postfire communities representing four pre-fire serai stages. Neither method indicated communities arising from any pre-fire serai stages were distinct from any others. Chi-square goodness-of-fit to random distribution and Monte Carlo randomizations of individual species in these environmental types identified only three species that were significantly non-randomly distributed among postfire communities from pre-fire serai stages. All three were more strongly represented in pioneer communities from early prefire serai stages. Eighteen species in each environmental type possibly had non-random distributions (P=0.06 to 0.15) indicating they may deserve further study.Item Relationship between spotted knapweed and indigenous plant assemblages and prediction of plant community response to picloram(Montana State University - Bozeman, College of Agriculture, 1999) Kedzie-Webb, SusanItem Directing succession by altering nutrient availability(Montana State University - Bozeman, College of Agriculture, 1999) Herron, Gretchen J.Item Succession in riparian communities of the lower Yellowstone River, Montana(Montana State University - Bozeman, College of Letters & Science, 1984) Boggs, Keith WebsterItem Relationships between benthic communities, land use, chemical dynamics, and trophic state in Georgetown Lake(Montana State University - Bozeman, College of Agriculture, 1983) Garrett, Paul AllenItem Biogeochemical and plant functional group response to long-term snow manipulation in a subalpine grassland(Montana State University - Bozeman, College of Agriculture, 2013) Holsinger, Jordan Paul; Chairperson, Graduate Committee: Jack BrookshireSnow represents an important control over plant communities in seasonally snow-covered ecosystems. It constrains the growing season and affects the availability of important resources including water, nitrogen (N) and phosphorus (P). Snow depth, distribution and duration have been affected by global climate change making it increasingly important to understand the effects of changing snow regimes on terrestrial ecosystems. Here we leverage a 43-year snow manipulation experiment to examine the effects of long-term changes in snow depth on plant community structure, resource availability and interactions therein in a common grassland type of the northern Rocky Mountains in western North America. Long-term experimental doubling and quadrupling of snowpack was associated with a significant shift in plant functional group distribution to a more forb rich community. Snow addition has resulted in a two to three-fold increase in forb to grass biomass ratios over time. Forbs consistently had greater N and P contents and lower nutrient use efficiencies compared to grasses. Forbs also displayed higher rates of net photosynthesis relative to grasses and sustained positive carbon (C) fixation rates late into the growing season after grasses had ceased. Though there is evidence that water exerts considerable control over ecosystem processes, increased snow depth did not have affect soil water availability through the growing season. However, snow depth was associated with significant differences in plant-available phosphate across the entire growing season with approximate 15% and 31% increases in pools of available P relative to ambient snowpack depth for doubled and quadrupled snowpacks respectively. Estimates of direct P inputs via dust and the ratio of available P to total P in the soil suggest that internal cycling was largely responsible for the observed differences in pools of available P. However, growing season net mineralization rates do not differ across treatments. This may suggest that winter processes make significant contributions to nutrient cycles. It is possible that the increased availability of P favors the shift to a forb-rich community under deeper snow because of their increased productivity under dry conditions and that the increased litter quality of forbs likewise promotes increased litter decomposition and mineralization, especially of P.Item Quantifying non-native plant impacts : Centaurea stoebe L. (spotted knapweed) and Bromus tectorum L. (downy brome) in sagebrush-grasslands of the greater Yellowstone ecosystem(Montana State University - Bozeman, College of Agriculture, 2012) Skurski, Tanya Christine; Chairperson, Graduate Committee: Bruce D. Maxwell; Lisa J. Rew (co-chair); Bruce D. Maxwell and Lisa J. Rew were co-authors of the article, 'Quantifying non-native plant impacts for natural areas management: a review of experimental research' in the journal 'Journal of applied ecology' which is contained within this thesis.; Lisa J. Rew and Bruce D. Maxwell were co-authors of the article, 'Mechanisms underlying non-native plant impacts: a review of recent experimental research' in the journal 'Biological invasions' which is contained within this thesis.; Bruce D. Maxwell and Lisa J. Rew were co-authors of the article, 'Ecological tradeoffs in non-native plant management' in the journal 'Biological conservation' which is contained within this thesis.; Lisa J. Rew and Bruce D. Maxwell were co-authors of the article, 'Abundance-impact relationships of non-native plants: an examination of Bromus tectorum L. in Southwest Montana sagebrush-grassland plant communities' in the journal 'Biological invasions' which is contained within this thesis.Non-native plant species (NIS) are considered a significant threat to individual species, communities, and ecosystems; thus, NIS management is mandated in most natural areas (i.e. non-crop). Controlling NIS in natural areas should, ideally, not only reduce target NIS abundance, but also benefit broader management objectives such as conserving native species and improving wildlife habitat. In this context, the benefits of NIS control must be weighed against the impacts of NIS themselves. This dissertation examines ecological impacts of NIS through a synthesis of previous experimental research and field-based manipulative experiments. In a review and synthesis of experimental research, we found that NIS caused significant impacts in approximately half of all experiments. Negative impacts were most frequent on community structure, followed in descending order by individual species, ecosystem properties, and ecosystem processes. Contrary to common assumptions, NIS typically caused impacts by modifying the abiotic environment rather than outcompeting native species for resources. NIS impacts were also examined through experiments conducted in sagebrush-grasslands of the GYE. The first study compared plant community impacts of Centaurea stoebe L. and common herbicide treatment for C. stoebe. The broadleaf herbicide, picloram, was highly effective at reducing C. stoebe, but also significantly reduced native forb cover and significantly increased non-native grass cover. Native forb cover increased with manual removal of C. stoebe, suggesting C. stoebe had been suppressing native forbs. However, there was an equivalent increase with no treatment. In these communities, C. stoebe appears to have a negligible effect on native forb and grass cover and richness. The final study examined plant community impacts of the non-native annual grass, Bromus tectorum L, and relationships between impacts and NIS abundance. In a four-year field experiment, we did not detect significant impacts of B. tectorum on native plant cover and richness. Environmental factors, particularly climate variability, are likely more important determinants of current vegetation patterns in these communities rather than the presence of B. tectorum. Overall, the research shows NIS often do not have significant detectable impacts on native species and communities, and that the negative non-target effects of herbicide treatments may outweigh the benefits of NIS control.Item Riparian vegetation and forest structure of two unregulated tributaries, compared to the regulated Snake River, Grand Teton NP, WY(Montana State University - Bozeman, College of Letters & Science, 2008) Foy, Elizabeth Christina; Chairperson, Graduate Committee: David RobertsThe dynamic nature of rivers shapes riparian plant communities, and changes to the flow regime can have profound effects on these diverse ecosystems. To examine how riparian plant communities of the dam-regulated Snake River in Grand Teton National Park, WY respond to hydro-geomorphological factors, I studied the vegetation of two unregulated tributaries, Pacific Creek and Buffalo Fork, in relation to the main river. I considered three perspectives in this analysis. In chapter 2, I examined hydro-geomorphological processes shaping riparian vegetation in naturally flowing systems, by evaluating 15 environmental variables, and determining which were most related to vegetation. Using cluster analysis, I identified six distinct communities. I described environmental conditions associated with each community, using the unconstrained ordination technique NMDS, coupled with generalized additive models (GAMs). Community types occur on characteristic geomorphologic landforms. Depth to gravel, soil texture, pH, distance to bankfull channel, and elevation above water are all related to vegetation, and interact to determine where community types occur. In my third chapter, I compared the vegetation of the unregulated tributaries to the Snake River, as a means of assessing dam effects. Species richness per plot is higher on the tributaries, despite higher overall richness on the Snake River. Through the use of NMDS ordination and clustering techniques, I found the composition of the upper section of the Snake River, immediately below the dam, to be distinct. However, this section is naturally more incised, and the lower sections of the river do not seem to be influenced, suggesting dam impacts on vegetation are minimal. Environmental variables related to vegetation composition include elevation above water, depth to gravel, and geomorphological landform. In chapter 4, I compared age class distributions of spruce and cottonwoods across river sections, and found no evidence for a late-successional trend on the regulated river, versus unregulated tributaries. Age distribution is related to geomorphological landform, and browing also influences forest structure through root coppicing. Forest understory communities are structured by cottonwood age.