Scholarship & Research
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Item Quantifying tansy ragwort (Senecio jacobaea) population dynamics and recruitment in northwestern Montana(Montana State University - Bozeman, College of Agriculture, 2003) Trainor, Meghan AnnItem The population dynamics of tansy ragwort (Senecio jacobaea) in Northwestern Montana(Montana State University - Bozeman, College of Agriculture, 2006) Bauer, Brad David; Chairperson, Graduate Committee: Bruce D. Maxwell.Following the Little Wolf wildfire of 1994 in northwestern Montana, tansy ragwort (Senecio jacobaea) was classified as a state noxious weed. This project aimed to help prioritize the management of populations of tansy ragwort through an understanding of the biotic and abiotic factors influencing the species. Using field collected data and by constructing a prediction model, we found that the most important variables to predict the presence of tansy ragwort were distance from the main road, slope, cosine of aspect, and several remotely sensed LANDSAT ETM+ bands. Most of the predicted occurrences of tansy ragwort were within the boundary of the wildfire. The life stage and density of tansy ragwort plants in 94 plots in several environments created by the wildfire were used to project the population growth rate after seven to eleven years following the wildfire. Using the relative invasiveness (probability ë > 1.0) of populations to prioritize environments for management, the burned and salvaged logged population had the highest probability of being invasive with probability ë > 1.0 between 0.31 and 0.24. The burned but not logged had a probability ë > 1.0 between 0.20 to 0.10 and the non-burned meadow had a probability ë > 1.0 between 0.01 and 0.00. Additionally, as the native plant populations recovered, the population growth rate and rosette survival declined. Following a field study of the role of slashpiles in the establishment of tansy ragwort we found the highest maximum percent emergence of tansy ragwort seedlings in the low severity burn and non-burned disturbed environment of the slashpiles. The low survival of emerged seedlings and the low projected growth rates for the surviving plants indicated that the dynamics responsible for a large increase in tansy ragwort density did not occur within our slashpiles after two years. With the addition of biological control agents to populations of tansy ragwort, the seed predator fly did not negatively affect the relative invasiveness of tansy ragwort. However, the addition of a foliage herbivore to a limited number of populations reduced the relative invasiveness of these populations.Item The invasion potential and competitive ability of Camelina sativa (L.) Crantz (camelina) in rangeland ecosystems(Montana State University - Bozeman, College of Agriculture, 2010) Davis, Philip Browning; Chairperson, Graduate Committee: Fabian D. Menalled.Camelina sativa (L.) Crantz (large-seeded false-flax) is a recently introduced oilseed crop in Montana and has potential for large scale production for the biofuel market. However, due to weedy characteristics, the invasive potential of this species is of concern. A need exists to create a pre-entry protocol to accurately assess risk to minimize uncertainty inherent in qualitative weed risk assessment approaches. We assessed the probability of C. sativa to invade rangeland ecosystems of southwest Montana to address this concern. The objectives of this study were to 1) quantitatively assess the invasion potential of C. sativa by collecting demographic data over two years and developing a population dynamics model, 2) compare experimental results and modeling outcomes to predictions suggested by a qualitative weed risk assessment system, and 3) assess the impact of growing conditions on the relative competitiveness of C. sativa and Brassica napus (L.) (canola). Objective 1 was carried out in two contrasting rangeland ecosystems to assess the effects of disturbance and seeding season on emergence, survival, and fecundity rates of C. sativa. Population growth (lambda) was forecasted by developing a population dynamics model. Resulting lambda values from simulations using observed data never exceeded 0.03 and the maximum time to extinction was six years. The low lambda values indicate that the threat of invasion by this species in the studied ecosystems is low. Objective 2 compared quantitative results to predictions from the Australian weed risk assessment (WRA) model. In contrast to experimental results, outcomes from the WRA suggested that this species should not be allowed entry into the region. These opposing results highlight the need for a more comprehensive approach to weed risk assessment. Objective 3 was conducted over three trials in two greenhouses. A replacement series design was used to estimate the effects of soil conditions and the presence of an invasive weed, Bromus tectorum (L.) (cheatgrass, downy brome), on the competitive outcomes between C. sativa and canola. Replacement series diagrams determined that competition occurred and that canola was the superior competitor in all treatments, thus providing further evidence that the invasion potential of C. sativa is low.Item Detection of leafy spurge (Euphorbia esula) using affordable high spatial, spectral, and temporal resolution imagery(Montana State University - Bozeman, College of Agriculture, 2010) Jay, Steven Charles; Chairperson, Graduate Committee: Rick L. Lawrence; Kevin S. Repasky (co-chair)Leafy spurge is a designated noxious weed. Accurate mapping and monitoring of this species are needed to understand leafy spurge's extent and spread. Current methods are based on ground crews who survey patches. Development of an affordable technique to map and monitor leafy spurge would contribute to the control of this species. High spatial, temporal, and spectral resolution imagery was used to classify the amount of leafy spurge present with ground and aerial-based imagery. A proof of concept study was performed in 2008 using ground-based images of an area infested with leafy spurge. This proof of concept project guided the development of the methods to be used for the 2009 aerial portion of the study. Thirty-five randomly selected reference points were selected in a range area in southwest Montana. These reference points were ground surveyed to record the density of leafy spurge in a 0.5-m radius area around the reference point. Images were captured approximately 108-m from the study area and classified using random forest classification. Multiple images were collected throughout the summer in order to determine at which time period leafy spurge is most easily detected. A classification using multiple image dates was also performed to determine if a time series of images improves classification. Single date accuracies were highest late in the summer with the highest single date classification achieving 83% accuracy. The multiple date classification significantly increased overall accuracy. Several aerial images were acquired in southwest Montana over the 2009 summer. Fifty randomly selected 2-m x 2-m reference areas were surveyed for percent cover of leafy spurge as well as several other variables. Aerial images were collected at flight elevations between 300-m to 460-m. Classifications were performed using random forest classifier, and both single date and multiple date classifications were performed. Leafy spurge was most accurately detected early and late in the growing season, and significant classification accuracy increases were observed with the multiple date classification. Single date accuracies achieved 90% accuracy in early June, while multiple date classifications achieved over 96% accuracy.