Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Pollinator conservation and restoration in semi-natural ecosystems(Montana State University - Bozeman, College of Letters & Science, 2022) Glenny, William Robb; Chairperson, Graduate Committee: Laura Burkle; This is a manuscript style paper that includes co-authored chapters.Semi-natural ecosystems are areas with biological and physical characteristics that resemble natural ecosystems but are also affected by anthropogenic disturbances. Semi-natural ecosystems are also areas with high insect pollinator diversity. Land management actions within semi-natural ecosystems may therefore be important to counteract future declines of insect pollinators. However, current restoration strategies for insect pollinator communities are based on evidence from agricultural ecosystems, which have frequent human interventions to ensure plant success, neglect the importance of nesting materials, and primarily benefit generalist species. To inform management actions for the conservation and restoration of insect pollinators in semi- natural ecosystems, I (1) synthesized the current understanding of the effects of common land management actions on insect pollinators on public lands in the US, (2) identified habitat characteristics which structure the taxonomic and functional diversity of bee communities, (3) evaluated the strength of influence of mechanisms associated with diet breadth across groups of bee species and (4) designed a conceptual model which can be used to select flowering plant species to provide food resources for bee communities in semi-natural ecosystems. Management actions that increase the abundance of floral and nesting resources to support bee species from different functional groups are required to conserve and restore insect pollinator communities in semi-natural ecosystems. I found that (1) management actions have positive, neutral, and negative effects on insect pollinators, but research trends vary depending on the taxon and habitat type, (2) the taxonomic and functional diversity of bee communities are structured by the abundance of both floral and nesting resources, (3) patterns of abundance across space and time have a more positive effect on the diet breadth of bumble bee species compared to non- bumble bee species, and (4) wildflower species that receive a high visitation rate and richness, occupy functionally important positions within bee-flower interaction networks, and are spatially and temporally widespread are important to provide bee communities with food resources in semi-natural ecosystems. These wildflower species may be particularly important to include within seed mixes to revegetate semi-natural ecosystems and provide food resources for insect pollinators.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 The effects of timing of grazing on plant and arthropod communities in grasslands of southwest Montana(Montana State University - Bozeman, College of Letters & Science, 2013) Davis, Stacy Christine; Co-chairpersons, Graduate Committee: Laura Burkle and Wyatt F. CrossGrassland plants have co-evolved with native ungulate grazers for millions of years, but over the last 100 years there has been a shift towards grazing by domestic livestock in North America. Many of the grazing-induced changes in plant and arthropod communities depend on how the grazing regime is implemented. Timing of grazing is one component of the grazing regime that is less well understood than grazing intensity and type of grazer, but is predicted to have important implications for plant and higher trophic level responses. The purpose of this study was to experimentally assess how timing of grazing affected plant and arthropod communities in high-elevation grasslands of southwest Montana. We designed a 2-year field experiment that manipulated cattle grazing by implementing two grazing initiation dates, one beginning in mid-June and the other in mid-July. We compared plant (biomass and height) and arthropod characteristics (density and biomass of orders) across two years that differed in cumulative precipitation. Grazing reduced total plant biomass, forb biomass, and plant height with little to no recovery regardless of timing of grazing. The density of the most dominant arthropod order, Hemiptera, was reduced in both grazing treatments. By comparing end of season plant responses to grazing, we found that total plant biomass was unaffected in the drier year while forb biomass was unaffected in the wetter year. Many end of season arthropod responses were reduced by grazing in both study years. Although both grazing treatments reduced many plant and arthropod characteristics, grazing earlier in the growing season may impact higher trophic levels that are reliant on the presence of forbs and Hemiptera earlier in the growing season. These results have important implications for meeting conservation grazing objectives and for how timing of grazing may influence food availability for grassland-associated avian species of concern, in particular, smaller passerines.