Theses and Dissertations at Montana State University (MSU)
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Item Non-target effects of a novel invasive species management strategy: benthic invertebrate responses to lake trout embryo suppression in Yellowstone Lake, Wyoming(Montana State University - Bozeman, College of Letters & Science, 2020) Briggs, Michelle Anne; Chairperson, Graduate Committee: Lindsey Albertson; Lindsey K. Albertson, Dominique R. Lujan, Lusha M. Tronstad, Hayley C. Glassic, Christopher S. Guy and Todd M. Koel were co-authors of the article, 'Carcassd deposition to suppress invasive lake trout causes differential mortality of two common benthic invertebrates in Yellowstone Lake, Wyoming' in the journal 'Fundamental and applied limnology' which is contained within this thesis.; Lindsey K. Albertson, Dominique R. Lujan, Lusha M. Tronstad, Hayley C. Glassic, Christopher S. Guy and Todd M. Koel were co-authors of the article, 'Non-target effects of a novel suppression technique for invasive fishes: responses of benthic invertebrate communities' submitted to the journal 'Ecological applications' which is contained within this thesis.Invasive species threaten native biodiversity and ecosystem function, and suppression is often required to reduce these effects. However, invasive species management actions can cause harmful, unintended consequences for non-target taxa. In Yellowstone Lake, Wyoming, invasive lake trout (Salvelinus namaycush) have reduced abundance of the native Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri), decreasing availability of an important food source for aquatic and terrestrial predators. Gillnets are used to suppress adult lake trout, and the lake trout carcasses are then deposited onto spawning sites in the littoral zone to cause embryo mortality by reducing dissolved oxygen concentrations as they decay. However, this management action may have non-target effects on organisms in the lake, including benthic invertebrates, which comprise a large portion of native trout diets. Some taxa of invertebrates may benefit from the addition of nutrients to the littoral zone, while other taxa may experience mortality in response to low dissolved oxygen conditions caused by carcass decay. We conducted two field experiments to understand how carcass treatment affects benthic invertebrates in Yellowstone Lake. First, we conducted an in situ experiment with individual invertebrates housed in small chambers covered by carcasses to determine if carcass treatment causes mortality of hypoxia-tolerant amphipods and hypoxia-sensitive caddisflies. We found that carcass treatment caused increased mortality in caddisflies but not amphipods. Second, we conducted a field experiment to investigate how carcass treatment affects invertebrate communities when applied at entire spawning sites. We also compared invertebrate communities at cobble-dominated lake trout spawning sites to macrophyte-dominated sites to determine if carcass treatment could alter food web dynamics at a lake-wide scale. We found that carcass treatment causes non-target effects on benthic invertebrates, specifically reducing immobile taxa, hypoxia-sensitive taxa, and Chironomidae, and altering community structure. Areas dominated by macrophytes had more abundant and larger invertebrates than spawning sites. Due to the small spatial extent of spawning sites and the higher abundance of invertebrates at other habitats in the lake, we conclude carcass treatment can have localized non-target effects at a local scale but is unlikely to alter food-web dynamics at a lake-wide scale.Item Can targeted cattle grazing increase abundance of forbs or arthropods in sage-grouse brood-rearing habitat?(Montana State University - Bozeman, College of Agriculture, 2018) Payne, Jarrett MacKenzie; Chairperson, Graduate Committee: Jeffrey C. MosleySuboptimal brood-rearing habitat often limits greater sage-grouse (Centrocercus urophasianus) populations in western North America. In mountain big sagebrush (Artemisia tridentata Nutt. ssp. vaseyana [Rydb.] Beetle) brood-rearing habitat, dense sagebrush canopy cover (> 25% cover) may limit the understory forbs and arthropods that sage-grouse prefer to eat during summer. Targeted cattle grazing is a potential habitat management tool to reduce dense sagebrush. This study evaluated targeted cattle grazing on a landscape scale to increase forbs and arthropods within core sage-grouse brood-rearing habitat. Objectives of this study were to evaluate how well targeted cattle grazing reduced mountain big sagebrush canopy cover, increased forb abundance and diversity, and increased arthropod abundance. Targeted cattle grazing was applied within two large, contiguous pastures (625 ha each) in the Beaverhead Mountains of southwestern Montana. The two pastures were grazed simultaneously at a light stocking rate (6.25 ha/AUM) for two weeks each year in mid-October 2015 and 2016. Vegetation and arthropod responses were measured during the following June-early July (2016 and 2017, respectively) within 32 microsites where mountain big sagebrush canopy cover exceeded 30% pre-treatment. Microsites were 0.008 ha to match the spatial scale at which sage-grouse broods select fine-scale habitat. One of two treatments was randomly assigned to each microsite: a low moisture block protein supplement or no supplement (unsupplemented). In the first summer after treatment, supplemented microsites averaged 78% less sagebrush canopy cover (8% vs. 36%; P < 0.001) and 25% more forb canopy cover (15% vs 12%; P = 0.122). Sage-grouse forb canopy cover was 50% greater in supplemented microsites (3% vs. 2%; P = 0.003). Forbs also comprised a greater proportion of the herbaceous understory in the supplemented vs. unsupplemented sites (48% vs. 36%; P = 0.002). Arthropod abundances were greater in supplemented than unsupplemented microsites only during the wet year of 2017 when arthropods were 1.7-1.8x more abundant in supplemented microsites. Sagebrush canopy cover was reduced by cattle trampling, not browsing. My results demonstrate that targeted cattle grazing can increase abundance of forbs and arthropods in mesic, dense stands of mountain big sagebrush in sage-grouse brood-rearing habitat.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 Effects of alternative management practices on the abundance of arthropods in a mixed-crop agroecosystem(Montana State University - Bozeman, College of Agriculture, 2013) Gill, Paramjit Singh; Chairperson, Graduate Committee: Kevin O'NeillWe evaluated the effects of alternative management practices on the abundance and diversity of arthropods in a mixed-crop agroecosystem in studies conducted in 2010 and 2011 at the Fort Ellis Experimental Station near Bozeman, MT. In one study, we quantified arthropod relative abundance in plots across three summer fallow weed management practices (sheep grazing, mechanical/tillage, and chemical herbicide) incorporated into a three-year rotation in two different sets of crops. Arthropod abundance was compared among 1) the spring wheat plots under the three management schemes with the rotational treatments (continuous spring wheat and rotational spring wheat), 2) the pea/hay barley plots under the different weed management schemes, and 3) fallow plots under the three weed management schemes. In a second study, we examined arthropod relative abundance in plots with alternative alfalfa cultivars (Cimarron SR, HayGrazer, and Shaw). Sweep net samples were taken to compare the abundances of the most common insect orders and families (as well as a few abundant species and genera). In addition, baited traps were used to compare the abundance of click beetle larvae or wireworms (Coleoptera: Elateridae) within the different management schemes and treatments. This study demonstrated that the number of arthropods in the continuous spring wheat was lower compared to the rotational spring wheat. Arthropod abundance in the pea/hay barley plots under the three different managements was inconsistent from one year to the other. In the summer fallow plots, abundance of most arthropod taxa was the lowest in the mechanically-treated plots, whereas there was no difference in the number of most arthropods present between the chemical and grazed plots which shows that sheep grazing was equally effective as the application of herbicides in reducing arthropod numbers on summer fallow plots. The abundance of most arthropod taxa did not differ among the Cimarron SR, HayGrazer, and Shaw alfalfa cultivars except for Aphididae, Formicidae, and Ichneumonidae in 2010. Nine species of wireworms were collected from the study site with Aeolus mellilus Say being the most common. In both years, A. mellilus was most abundant in the continuous spring wheat plots compared to the other plots.Item Creating a model curriculum for a certification program to train people to work in the field of exhibiting living arthropods(Montana State University - Bozeman, College of Agriculture, 2004) Whitman, Celia Stuart, 1965-; Chairperson, Graduate Committee: Martin J. Frick.The purpose of this project was to create a model curriculum for a certification program for the live arthropod exhibit industry. An overview of live arthropod exhibits and the current educational and training programs for the field were examined as well as reasons why a program of this type would be of value to the industry. The data for this project was collected using a web based survey instrument. The population consisted of 52 professionals from the live arthropod exhibitry field. These entomologists, USDA representatives, insect suppliers and educators were all members of a professional list serve which was a clearinghouse for the live arthropod display industry. The survey instrument consisted of four sections: demographic information about respondents; the respondentsα level of agreement or disagreement regarding areas of training to be included in a proposed certification program; preferences on prerequisites for the program; written comments and input. A demographic profile of the respondents was compiled showing that the majority were experienced in the live arthropod exhibitry field and possessed a variety of educational backgrounds. Overall, respondents supported the proposed certification program and felt it would benefit the live arthropod exhibit industry. Only four respondents were pessimistic about the proposed program. A model curriculum for a certification program for the live arthropod exhibit industry was created from the data gathered by the survey instrument.