Theses and Dissertations at Montana State University (MSU)
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/733
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Item Sierran mixed conifer forest wildfires: a biodiversity comparison between active and passive timber land management(Montana State University - Bozeman, College of Agriculture, 2019) Dalby, Caitlin M.; Chairperson, Graduate Committee: William KleindlThe mixed conifer forests of the Northern Sierras have great value in their biodiversity. Timber land management in this region varies by land owner and their objectives, including timber harvest and conservation. An increase in annual wildfires each year indicates a need to understand how different silvicultural strategies before and after fires affect the overall ecosystem biodiversity. Ecosystem functions and services can be affected by many factors involving anthropogenic activities in combination with fires. The aim of this study was to determine to what degree active (private timber company) and passive (United States Forest Service) management after a wildfire may affect plant biodiversity, and to compare those silvicultural approaches to active and passive pre-fire management. The study takes place within the vicinity of the 2012 Chips fire burn scar in Plumas County, California. Using tree canopy and plant species percent cover, in addition to presence and absence data, within frames and nested frames along 50 meter transects, statistical analyses revealed little significant difference between active and passive management. Analysis from data collected in this study concluded that tree canopy cover is significantly different under active post-fire management than under passive post-fire management and pre-fire conditions. There was not a significant difference in understory biodiversity (richness and evenness) among the four treatments. Dissimilarity in plant species composition was significant among the burned and unburned treatments, as well as between the two differently managed burned treatments. While the treatments were significantly dissimilar, there was not enough data collected to account for the high degree of variability seen in the data and so further data collection and analyses across multiple spatial and temporal scales would give better insight into the differences in biodiversity between treatments.Item Integrating cover crop mixtures in the northern Great Plains: an ecological assessment on crop productivity, biodiversity, and temperature and moisture conditions(Montana State University - Bozeman, College of Agriculture, 2020) DuPre, Mary Ellyn; Chairperson, Graduate Committee: Fabian D. Menalled and Tim F. SeipelCropping systems can impact crop productivity and functioning of biodiversity in the Northern Great Plains, a region heavily reliant on low diversity crop rotations and off-farm inputs, and a region predicted to experience warmer and drier climate scenarios by mid-century. In three complementary studies, I compared the impacts of cover crop mixtures and termination methods on crop productivity and three forms of the associated biodiversity (weeds, soil fungi, and ground beetles), under varying temperature and soil moisture conditions. First, I assessed the impacts of the presence (cover crops and fallow) and composition (cover crop mixtures) of cover crops, termination methods (herbicide, cattle-grazing, and haying), as a function of temperature and soil moisture conditions on crop yields, and weed communities. A 5-species, early-spring mixture generated cooler temperatures, produced more biomass, and suppressed weed biomass under warmer and drier conditions, compared to summer fallow and the 7-species, mid-spring mixture. However, lower soil moisture and subsequent reduced grain yields following the mixtures, especially under warmer and drier conditions, suggests that continuously rotating wheat with mixtures may not be the optimal method to diversify small-grain cropping systems. Second, I assessed the impacts of the presence and composition of cover crops, termination methods and temperature and soil moisture conditions on fungal communities. The early-season cover crop mixture reduced plant pathogen abundance and enhanced AM fungal richness in both the soil and subsequent wheat root crop. The enhancement of beneficial fungi and fewer plant pathogens may be a proxy to better support ecosystem services through the use of cover crop mixtures. Third, I compared ground beetle communities among cover crops treatments and termination methods. Ground beetle activity density was not impacted by termination methods and was greatest in the early-season mixture at the beginning of the growing season and in summer fallow at the end of the growing season, while the mid-season mixture peaked in the middle. Ground beetle diversity peaked in the middle and differed in community composition earlier in the growing season. These results indicate that cover crop mixtures can act as an ecological filter to ground beetle communities to better support pest regulation. Overall, these studies indicate that cover crop mixtures can support crop productivity and the associated biodiversity with changes to temperature and soil moisture, although, with agronomic and ecological trade-offs.Item Multi-species cover crops in the northern Great Plains : an ecological persepctive on biodiversity and soil health(Montana State University - Bozeman, College of Agriculture, 2016) Housman, Megan Leigh; Chairperson, Graduate Committee: Catherine A. Zabinski; Susan M. Tallman, Clain A. Jones, Perry R. Miller and Catherine Zabinski were co-authors of the article, 'Soil water, soil nitrate, and residue quanity associated with cover crop mixtures in the northern Great Plains' submitted to the journal 'Agriculture, ecosystems, and environment' which is contained within this thesis.; Susan M. Tallman, Clain A. Jones, Perry R. Miller and Catherine Zabinski were co-authors of the article, 'Multi-species cover crops: effects on soil biology after one and two rotations in the semi-arid northern Great Plains' submitted to the journal 'Soil biology and biochemistry' which is contained within this thesis.As summer fallow is replaced by cover crops, we aim to address how cover crops influence soil properties. Past studies conducted across the Northern Great Plains have investigated the short- and long- term effects of LGMs on water, nitrate, and carbon storage, soil parameters including potentially mineralizable nitrogen (PMN) and enzymatic activity, and wheat yield. Less knowledge exists regarding similar short- and especially long-term effects of CCMs in the NGP. This four-year study replicated at four sites in Montana allows us to investigate how site characteristics and annual weather patterns can influence the performance of cover crop growth and the subsequent effect on soil quality. Our research approach to building cover crop mixtures using functional group composition rather than species composition aims to make the work more broadly applicable to other regions. Other regions may utilize more adapted legume or brassica species and could still use our results to estimate their effects on soil and nitrate use throughout the soil profile or their effects on soil biological parameters.