Theses and Dissertations at Montana State University (MSU)
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Item Bee and butterfly communities in roadside habitats: identifying patterns, protecting monarchs, and informing management(Montana State University - Bozeman, College of Letters & Science, 2023) Meinzen, Thomas Claasen; Chairperson, Graduate Committee: Diane M. DebinskiInsect pollinators play a critical role in our natural and agricultural ecosystems. With global pollinator declines and habitat loss, attention has turned to roadside right-of-way lands (ROWs) as potential areas for supporting pollinator populations. Although many roadsides host flowering plants, understanding whether--and under what circumstances--roadsides actually benefit pollinator populations is critical for good conservation decision-making. Through a literature review, we found that pollinator population data (e.g., birth and death rates) are lacking to assess whether roadsides are a source or sink for pollinator populations. However, conscientious management practices, including reduced, well-timed mowing, selective, targeted spraying, and well-placed native plantings can improve roadsides' potential to support robust pollinator populations. Identifying roadside habitat for diverse pollinator communities and imperiled species is essential to prioritize pollinator-focused management practices across ROW systems. To support efforts to conserve monarch butterflies (Danaus plexippus), we surveyed 1,465 km (910 miles) of southern Idaho highways, mapping 1,363 patches of showy milkweed (Asclepias speciosa), the monarch's host plant. Roadside milkweed often bordered irrigated fields and crops; water availability may best explain its distribution. Existing statewide milkweed models (Svancara et al., 2019) did not effectively predict milkweed distribution in ROWs, suggesting the importance of roadside-specific factors, such as ROW management and disturbance history. To identify patterns of pollinator richness and abundance in Idaho ROWs, we surveyed butterflies and sampled bees at a randomized set of 63 100-meter (328-foot) roadside transects in southeastern Idaho, stratified by highway class and NDVI (greenness) category. Lower NDVI (less green) sites, those with more flowering plant species, and sites along smaller, less-trafficked highways supported significantly more species of bees, while ROWs with more abundant flowers were associated with more species of butterflies. Low NDVI sites were often characterized by native sagebrush plant communities, while sites of high NDVI were associated with high proportions of non-native plants, suggesting that NDVI might be useful both in predicting bee richness and abundance (low values) and locating developing noxious weed patches (high values). These results, together with our management recommendations, can help prioritize ROWs for pollinator protection and increase their capacity to support diverse pollinator communities.Item Determining the suitability of native grasses for highway revegetation sod(Montana State University - Bozeman, College of Agriculture, 2007) Stott, Lance Vear; Chairperson, Graduate Committee: Tracy A.O. Dougher.In past years, the California Department of Transportation (Caltrans) has used hydroseeding, imprinting and drill seeding methods to revegetate highway construction sites with varying degrees of success. Ecological concerns have led researchers to consider using native species for revegetation as they are better suited to local environments, require less maintenance and do not pose a threat to adjacent ecosystems. In addition, the urgency for stabilizing areas of high erosion potential and that of establishing native plant cover quickly in order to prevent non-native plant and weed establishment, have led researchers to consider using native grass sod for highway revegetation. Twenty-one species of native grasses were selected in order to determine their suitability for sod production. Grasses were grown in six growth chambers; each mimicking one of the climates of the six selected California ecoregions. Mixtures of varying species included either one rhizomatous species with three bunch grasses, one rhizomatous species and five bunch grasses, two rhizomatous species with three bunch grasses, or two rhizomatous species with five bunch grasses.