Natural Resources Management Doctoral Work

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Browsing Natural Resources Management Doctoral Work by browse.metadata.department "Natural Resource Sciences"

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    Corn Yield Frontier and Technical Efficiency Measures in the Northern United States Corn Belt: Application of Stochastic Frontier Analysis and Data Envelopment Analysis
    (North Dakota State University, 2020) Badarch, Bayarbat
    About 75% of human food in the 21st century consists of just 12 crops, though specific crops vary among nations. Modern technology has allowed development of innovative food and non-food uses for these commodities. For instance, corn (maize (Zea mays L.)) is produced for many purposes, including food, livestock feed, biofuels, fiber for clothing, etcetera. Scientists project the human population will reach 9.2 billion in next 20 years—an 18% increase from the 2020 population of 7.8 billion—resulting in increased demand for corn and other crops. Hence, farmers must increase total crop production to meet demand; however, local agricultural resource endowments such as climate, land and water availability, and soil attributes constrain production. Perhaps the quickest yield and efficiency improvements will result from farm management practices that tailor input applications to match accurate seasonal weather forecasts. Regional seasonal weather forecasts would enable farmers to optimize yields by reducing yield risk from extreme weather events, as well as from less extreme inter-annual weather variability. Improved productive efficiency is also critical to reducing environmental harms, e.g. contaminated runoff from excessive agricultural input use. The objective of this dissertation is to estimate the corn yield frontier and efficiency measures based on agricultural input management and weather. This research contributes to an enhanced understanding of how the corn yield frontier responds to inter-annual weather variations, and how it may shift with climate change. The first chapter summarizes three main topics—farm technology, climate change and weather variability, and methods for evaluating production efficiency. The second presents estimated corn yield frontiers and efficiency measures based on stochastic frontier and data envelopment analyses for nine North Dakota Agricultural Statistics Districts from 1994 to 2018. The third presents corn yield efficiency measures for five states: Minnesota, North Dakota, Nebraska, South Dakota, and Wisconsin from 1994 to 2018. The results reveal the major causes of inter-annual yield variation are variability of rainfall and temperature. Development of accurate growing-season weather forecasts is likely to result in high value-added for farmers and downstream agribusinesses. Federal, state, and private research funding in seasonal weather forecasting would probably be well invested.
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    The Impacts of Exotic Species on Native Bee Communities and Interactions in Novel Northern Great Plains Grasslands
    (North Dakota State University, 2022) Pei, C. K.
    Human alterations to landscapes impose novel conditions on native plant and animal species. Exotic plants are among these changes and are presently common and prevalent across Northern Great Plains (NGP) grasslands. Their introductions alter plant communities and influence the wildlife species that rely on the resources provided by plant communities. Exotic plants displace native plant species, but we do not understand how or if some exotic plants can provide resources to pollinating insects requiring floral resources. Considering the spread of exotic plants and the important ecological services bees provide, it is important to understand how native bees value and interact with exotic plants, and how exotic plants may shape bee communities in the NGP. To address this, we employ a unique dataset built from a statewide survey of bees and associated plant species across North Dakota grasslands to investigate the broad questions of how bees select between native and exotic floral resources, how exotic grasses may indirectly affect bee diversity through the plant community, and how exotic species dominance changes the interaction structure between bees and plants. From our selection analyses, we found native bumble bees selected for native plants and plant diversity over exotic plants whenever significant selection occurred, while European honey bees selected for exotic plants and floral resource density. However, both benefited from floral resource diversity, indicating that common management may exist for both groups. Invasive grasses did not affect bee richness at a broad scale but negatively influenced particular bees, such as ground-nesting species. We found litter accumulation to be influential over plant communities and particular types of bees based on their life history traits, indicating the need for grassland management practices that prevent homogenous plant structure. Finally, we found that exotic bees and plants influenced bee-plant interaction network properties through their dominance over contemporary pollination networks. This implicates that managing exotic species may be needed to reduce effects on the complex bee-plant interactions and consequent pollination services. Broadly, this work provides further evidence of exotic species effects on ecological communities and the first large-scale assessment of their impacts on bee communities in NGP grasslands.
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    Patch-Burn Grazing in Southwestern North Dakota: Assessing Above- and Belowground Rangeland Ecosystem Responses
    (North Dakota State University, 2021) Spiess, Jonathan Wesley
    Rangelands are heterogeneous working landscapes capable of supporting livestock production and biodiversity conservation, and heterogeneity-based rangeland management balances the potentially opposing production and conservation goals in these working landscapes. Within fire-dependent ecosystems, patch-burn grazing aims to create landscape patterns analogous to pre-European rangelands. Little work has tested the efficacy of patch-burn grazing in northern US Great Plains. We investigated patch contrast in above and belowground ecosystem properties and processes during the summer grazing seasons from 2017 – 2020 on three patch-burn pastures stocked with cow-calf pairs and three patch-burn pastures stocked with sheep. We focused on vegetation structure, plant community composition, forage nutritive value, grazer selection, livestock weight gain, soil nutrient pools, soil microbial community composition, and decomposition activity. We used mixed-effect models and ordinations to determine whether differences: along the time since fire intensity gradient, between ecological sites, and between grazer types existed. Despite no significant shifts in the plant community, structural heterogeneity increased over time as the number of time since fire patches increased and was higher than homogeneously managed grasslands. Grazing livestock preferred recently burned patches where the available forage had a higher nutritive value and lower available biomass than surrounding patches at a given point in time. With the exception of 2018, livestock weight gains were consistent. Soil nutrient pools and microbial abundances differed more by ecological site than by the time since fire intensity gradient, and ecological sites exhibited similar nutrient and microbial responses to the time since fire intensity gradient. That belowground response variables were mostly resistant to patch-burn grazing is supportive of further use of this management, especially given the desirable results with aboveground response variables.