Theses and Dissertations at Montana State University (MSU)
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Item Responses of riparian and stream ecosystems to varying timing and intensity of livestock grazing in central Montana(Montana State University - Bozeman, College of Letters & Science, 1996) Endicott, Carol LeighItem Exploring linkages between floodplains and riparian vegetation in small mountain watersheds(Montana State University - Bozeman, College of Agriculture, 2003) Schmitz, Denine MichelleItem The decline of a riparian gallery forest in Devils Tower, Wyoming : causation and management techniques for restoration(Montana State University - Bozeman, College of Agriculture, 2013) Anderson, Jacob Michael; Chairperson, Graduate Committee: Clayton B. MarlowDevils Tower National Monument, Wyoming, (DT) has experienced a decline in cottonwood recruitment along the Belle Fourche River, leaving the remaining riverine forest in danger of disappearing. The National Park Service has requested information about the mechanisms behind this decline and possible management methods that could be used to restore forests to the Belle Fourche riparian corridor. Previous research has indicated that cottonwood seedlings require flood-deposited sediments and high initial groundwater for survival. A dam located 12 miles upstream of Devils Tower could be impacting the recruitment success of cottonwoods because of a decrease in seasonal flooding. If this decline is due to factors that managers have little control over, other methods should be explored to increase the success of future restoration efforts. This case study examined the physical attributes of the Devils Tower riparian area in comparison to a healthy, functioning, riparian gallery forest located on the nearby Powder River (PR) to learn the complex mechanisms that help support and sustain these healthy riparian ecosystems. Soil field tests, cottonwood surveys, and measurements of local groundwater patterns were used to compare the two sites. To determine the restoration potential of cottonwood gallery forests at Devils Tower, planting trials were conducted to provide a methodology for greater seedling survival, testing effects of residual herbicide, species planted, preliminary soil preparation including disking, herbaceous understory control, and irrigation. We observed higher groundwater and greater cottonwood age class diversity at the Powder River site, in contrast to the DT site. At DT, tree health was significantly higher (p=.0003) with shallower groundwater. Tree mortality was highest among boxelder and bur oak in sites with deepest groundwater levels. At the same time, irrigation at economically feasible levels had no significant effect on tree survival. This research suggests that site potential for cottonwood re-establishment is poor along the Belle Fourche riparian corridor due to deep groundwater tables (1.7-2.2m) and regulated flow patterns with limited sediment delivery to the floodplain environment. A successional shift resulting from regulated streamflow conditions now favors green ash over any other species.Item Riparian vegetation of the Montana Yellowstone and cattle grazing impacts thereon(Montana State University - Bozeman, College of Letters & Science, 2005) Eggers, Margaret Joy Slack; Chairperson, Graduate Committee: Theodore WeaverThe objects of my research were two. To describe ungrazed vegetation of thirty sites well dispersed along the 500 mile length of the Yellowstone River. And to measure the effects of gazing on this vegetation by describing/comparing vegetation of these ungrazed 'control' sites with the vegetation of nearby grazed sites. Vegetation of the Yellowstone consists of three lateral bands on open shore (gravel or sandbar), willow thicket, and cottonwood forest. Their appearance on successively older deposits suggests control both by decreasing water availability (greater depth to water on inland sites with 'over deposits') and increasing age (overtopping, first by willow and then by cottonwood, and accumulation of shrubs). The primary longitudinal (downstream) change between foothill and plains sites, probably driven by decreasing rainfall, was the change of forest dominant from P. angustifolia to P. deltoides. The apparent failure of P. deltoides reproduction could eventually eliminate the forest zone. Grazing affects all of the five communities identified. With grazing, overall cover decreased in every vegetation type, with the greatest losses in sandbars, willow thickets and P angustifolia forests. Cottonwood seedlings were grazed on bars and in willow thickets.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.