Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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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.Item Classification of the grasslands, shrublands, woodlands, forests and alpine vegetation associations of the Custer National Forest portion of the Beartooth Mountains in Southcentral Montana(Montana State University - Bozeman, College of Letters & Science, 2012) Williams, Kristin Louise; Chairperson, Graduate Committee: David Roberts; Dave W. Roberts was a co-author of the article, 'Classification of shrubland associations of the Beartooth Mountains study area and comparison to existing grassland and shrubland habitat type classifications' in the journal 'Western North American naturalist' which is contained within this thesis.; Dave W. Roberts was a co-author of the article, 'Classification of woodland and forested vegetation associations of the Beartooth Mountains study area and comparison with existing woodland and forested habitat type classifications' in the journal 'Western North American naturalist' which is contained within this thesis.; Dave W. Roberts was a co-author of the article, 'Classification of the alpine vegetation associations of the Beartooth Mountains study area' in the journal 'Western North American naturalist' which is contained within this thesis.The purpose of this thesis was to classify and describe low-elevation grassland and shrubland vegetation, mid-elevation woodland and forested vegetation, and high elevation alpine vegetation associations of the Beartooth Mountains study area and to compare newly derived associations with existing habitat type and community type classifications of ecologically relevant environments in Montana, Wyoming and Idaho. Five grassland/shrubland associations, twelve woodland/forested associations and thirteen alpine associations were classified and described for the Beartooth Mountains study area. Prior to this thesis, no comprehensive vegetation association classification of the Beartooth Mountains, the highest, largest and easternmost alpine region in Montana, has been conducted.Item Remote sensing grassland phenology in the greater Yellowstone ecosystem : biophysical correlates, land use effects and patch dynamics(Montana State University - Bozeman, College of Letters & Science, 2012) Piekielek, Nathan Brian; Chairperson, Graduate Committee: Andrew J. HansenVegetation phenology refers to the seasonal timing of repeat biological events such as bud burst and primary-productivity and their relationship to climate. The spatial location and timing of phenology is relevant to a wide-variety of questions in ecology including the space use and population dynamics of migratory herbivores. Recent technological (remote sensing) and methodological (statistical smoothing algorithms and weighted-regression) advancement now allow for mapping spatial and temporal patterns of vegetation phenology across large spatial extents and at fine-temporal scales. It also allows for examination of vegetation response to climate. An understudied topic investigates how human activity (i.e. land use) modifies broad-scale patterns of phenology from their natural state. Land use effects on phenology is important in the context of parks and protected areas where human activity in surrounding areas can compromise biodiversity conservation goals. With this in mind, we posed the following research questions for a study-area within the Greater Yellowstone Ecosystem: 1) What are the biophysical correlates and likely drivers of landscape-scale grassland phenology under wildland conditions? 2) How do different types of land use modify grassland phenology from its wildland state? And, 3) Do spatial and temporal patterns of green forage patches produced with new tools and datasets display seasonal-dynamics that are consistent with current ecological understanding? To answer these questions we used the Normalized Difference Vegetation Index (NDVI) produced by the Moderate Resolution Imaging Spectroradiometer (MODIS) as input to the TIMESAT algorithm to produce estimates of grassland phenology. Our principle findings are that: 1) Seasonal variation in solar radiation, water availability, evaporative demand and temperature explained much of the variation in the timing of wildland grassland phenology; 2) All land use types extended the length of the growing season and agriculture increased two estimates of productivity; And, 3) New tools are capable of producing nearly-spatially and -temporally continuous maps of the pattern of green forage patches that are consistent with current ecological understanding. Results of the present study suggest that land use intensification in the Greater Yellowstone Ecosystem has the potential to alter landscape-scale ecosystem process with a variety of expected consequences for wildlife conservation and management.