Theses and Dissertations at Montana State University (MSU)
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Item Resilience of sagebrush steppe plants nine years after fire and soil disturbance in southwest montana(Montana State University, 2021) Newell, Isaac TodhunterSagebrush steppe in the western United States faces an increasing risk of degradation and overall habitat loss from land use and climate change. One important result of these drivers is the spread of the nonnative annual grass, Bromus tectorum. In many of these grasslands, B. tectorum has altered fire regimes through a positive feedback loop in which increased B. tectorum leads to more severe and frequent fires, and consequently increased B. tectorum cover. This ultimately displaces native flora and fauna, moving grasslands away from historic structure and function. However, in the northern portion of the sagebrush steppe, native communities were recently found to be resilient to fire 3 years post-fire, but not to soil damage. I revisited the study site (Red Bluff, Montana, US) to evaluate how this plant community has responded to fire and soil damage 9 years after disturbance. I sampled the same three treatments: an area burned by the 2012 Red Bluff fire, an adjacent unburned area, and a bulldozed firebreak between the two. In each treatment, 28 x 1m2-plots were sampled along three transects running parallel to the fire break. Percentage cover of each species, litter, bare ground, rock, and manure were recorded and analyzed for differences in richness, ground cover, and Bromus tectorum cover, as well as alpha- and beta-diversities, using generalized linear models. Nearly a decade after disturbance, fire and soil damage still significantly affected species richness (p = 0.05) and species composition (p = 0.02). Both the unburned and burned treatments had a greater cover of native species than did the bulldozed plots (p < 0.01). Bromus tectorum was the most abundant species in the bulldozed treatment, with 186.7% greater relative abundance than unburned treatment, and 107.6% greater than the burned treatment (p < 0.01). This shows that while the plant community is resilient and resistant to nonnative invasion after fire, it is much less so after soil disturbance. This may have implications on future applications of fire breaks and the way they are managed after fire, as well as other mechanical disturbances to soil structure.Item Impacts of low-tech restoration methods on soil, vegetation, and livestock grazing in Montana's sagebrush steppe(Montana State University - Bozeman, College of Agriculture, 2024) Lowing, Nicholas Allen; Chairperson, Graduate Committee: Bok SowellIn the semi-arid rangelands of western North America, water is a limiting factor for plant growth. In Montana's high elevation rangelands, snowmelt is the primary source of water for ephemeral streams and mesic meadows. Wildlife and livestock rely on these areas especially when surrounding uplands have dried. Less snowpack and early melt times associated with climate change pose a threat to forage resources in this region. In 2018 and 2019, small rock restoration structures were constructed in seven drainages in southwest Montana with the intention of increasing resiliency in these systems. In this study we compare stream reaches with restoration structures to reaches without structures to assess the impacts of this technique on soil moisture, plant cover, diversity, evenness, and production. We observed cattle grazing within and adjacent to treated drainages to determine how they use the landscape. We used soil moisture probes to measure soil water content once per month in June-September of 2021 and 2022. We used 0.5m2 frames to estimate plant cover, diversity, and evenness June-September in both years. At the end of each growing season, vegetation frames were clipped and weighed to estimate production. Soil and vegetation sampling occurred in 54 reaches across 7 drainages. We observed cattle near four treated drainages in mornings and evenings to assess whether cattle prefer mesic or upland areas. Cattle observations occurred in July and August of 2021 and 2022. Using linear fixed effects models, we detected no differences (p > or = 0.05) in soil moisture between treated and untreated reaches during any sampling period. We detected no differences in vegetation cover, richness, diversity, or evenness in 92% of sampling periods. No differences in plant production were detected in 2021 or 2022. Cattle used mesic areas in greater proportion to their abundance on the landscape in both years (p < or = 0.0001). Our results indicate that these structures have not yet had major impacts on soil moisture or vegetation metrics. However, our results indicate that mesic meadows are an important resource for grazing cattle in southwest Montana's high- elevation rangelands, supporting the idea that these areas warrant restoration efforts.Item Ecological responses to meadow restoration in the sagebrush steppe of Montana(Montana State University - Bozeman, College of Agriculture, 2023) Robison, Laura Margery; Chairperson, Graduate Committee: Bok SowellIn the semi-arid landscapes of the Western United States, water is scarce. In the high-elevation sagebrush steppe of Southwest Montana, mesic meadows are primarily fed by melting snowpack. These meadows, often centered around an ephemeral stream, collect and store water in the soil. Between 60-80% of wildlife rely on meadows for resources when surrounding upland environments are dry. Warming temperatures and declining snowpack are threatening water resources in this region. Stream incision, often induced by historic land use, decreases water storage in surrounding meadows. In 2018 and 2019, rock restoration structures, typically less than 0.3 m tall, were installed in seven impaired catchments in Southwest Montana to mitigate climate change and incision by slowing and spreading water. Catchments spanned an ecological and abiotic gradient that accounts for over 1/3 of the variation within the sagebrush biome. We compared reaches with structures built to reaches without to assess the impact of restoration on average soil moisture, soil drying rate, water storage, water retention time after rainfall events, and sage-grouse chick food resources (plants and arthropods). We installed soil moisture probes at 24 reaches in 4 catchments, recording hourly measurements from June through September in 2020, 2021, and 2022. Using 0.5 m 2 frames, we estimated vegetation canopy cover at the species level once per month in June through September. We set 24 hr pitfall traps once per month from June through August. Vegetation and arthropod sampling occurred in 2021 and 2022 at 54 reaches in 7 catchments. We detected an increase in water residence time at treated reaches of 1.67 days (p=0.0069) after controlling for variation between catchments and reaches. We also found evidence for a 27% increase in total canopy cover (p=0.004) at treated reaches when compared to control reaches. We found no evidence of a difference in seasonal soil moisture, seasonal drying rate, seasonal water storage, arthropod activity density, or arthropod biomass. Our results indicate that rock restoration structures are effective in increasing soil moisture and vegetation components in mesic meadows in Southwest Montana, potentially providing a tool to restore meadows in semi-arid landscapes and build resilience against climate change.