Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Disturbance and site characteristics relate to cheatgrass (Bromus tectorum) abundance on ranches in Montana foothills ecosystems(Montana State University - Bozeman, College of Agriculture, 2016) Ozeran, Rebecca Kathleen; Chairperson, Graduate Committee: Craig CarrCheatgrass (Bromus tectorum L.), also known as downy brome, is an invasive, exotic annual grass found throughout North America. Cheatgrass has been extensively studied in the Great Basin region of North America, where the majority of precipitation comes in winter and early spring, and the vegetation consists primarily of cool-season species. However, little research has been done in northern foothills grasslands in and near Montana, where most precipitation comes in spring and summer, supporting a mixture of cool- and warm-season plant species. Climate and vegetation differ between the northern foothills grasslands and the Great Basin, so the ecological impacts of cheatgrass in the northern foothills grasslands are unknown. In order to better understand cheatgrass ecology in this region, we assessed cheatgrass abundance in foothills ecosystems in Montana. Fifteen study plots were established at each of two ranches in Montana, both of which are owned and operated by the Montana Agricultural Experiment Station: Thackeray Ranch, southeast of Havre, Montana, and Red Bluff Ranch, east of Norris, Montana. At these plots we examined relationships among cheatgrass abundance, biotic and abiotic site characteristics (e.g. species diversity, soil depth), and disturbance indicators (e.g. livestock fecal counts) in 2014 and 2015. Large generalized linear mixed-effects regression models for each ranch were reduced to simpler models by comparing the Aikake's Information Criterion (AIC) for each fitted model, and selecting for lower AIC to best describe cheatgrass abundance. Multimodel inference based on the best models for each ranch identified important variables to predict cheatgrass abundance. Disturbance and site characteristics such as aspect and soil texture are important predictors that land managers in the northern foothills grasslands could monitor to estimate the risk of cheatgrass invasion or dominance on the landscapes they manage.Item Effects of sugar beet pulp on cheatgrass and bluebunch wheatgrass growth under controlled conditions(Montana State University - Bozeman, College of Agriculture, 2011) Sloane, Charles Emanuel; Chairperson, Graduate Committee: Clayton B. Marlow.Cheatgrass (Bromus tectorum L.,) an invasive, annual grass species, degrades range and pasture lands by out competing and replacing preferred native grass species resulting in economic and ecological losses. Current control strategies are costly and ecological risky. Soil nitrogen depletion by promoting microbial nitrogen utilization by application of a carbohydrate energy source such as sucrose may decrease cheatgrass's competiveness and permit seedling establishment of preferred native species. Review of the literature reveals attempts at restoration of native grasses and elimination of cheatgrass by nitrogen depletion with sucrose applications have failed or at best achieved limited success. We believe one reason for failure is that soil microbes utilize applied simple carbohydrates such as sucrose too rapidly resulting in only short periods of nitrogen depletion, and that application of sugar beet pulp may promote a longer state of nitrogen depletion. We hypothesize the growth of nitrogen dependent invasive grasses will be inhibited by nitrogen deprivation produced by mulch application of coarse granulated sugar beet pulp, and that the inhibition of growth is not related to a passive mulch effect. In a four armed green house study, we compared cheatgrass and bluebunch wheatgrass growth after application of ground sugar beet pulp at rates of 0.0, 0.5, 1.0 2.0 and 4.0 tons per acre. As a control, granite chicken grit was similarly applied in equal volumes to rule out a passive mulch effect. At 35 days, there was a negative linear relationship between rate of sugar beet pulp application and cheatgrass growth (p <0.001) and BBW growth (p<0.002). The negative effect of sugar beet pulp on cheatgrass growth was twice the negative effect on blue bunch growth. Granite grit application did not decrease growth of either species. We conclude that sugar beet pulp application depresses cheatgrass growth and that the cause is not a passive mulch effect. Our data indicates that longer duration nitrogen deprivation may aid in promoting restoration of cheatgrass dominated acreages, and treatments such as sugar beet pulp application may permit native grass seedling emergence and establishment.