Melissa Bridges

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Ecology & Environmental Sciences PhD
Montana State University
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It has long been recognized that understanding the spatial distribution and abundance of species is fundamental to linking pattern to ecological processes. Species distribution models (SDM) are typically correlative and statistically relate locations of measured species occupancy or density to geo-referenced environmental variables usually for the purpose of creating maps of environmental suitability. The central theme of my dissertation research is modeling invasive plant species distributions and integrating these models and environmental suitability maps into a management prioritization framework. <!--break--> Although SDMs for invasive species have been touted in the literature for their potential ability to inform land managers, no published studies directly test their applicability for management decisions. Further, the vast majority of SDM studies were focused on model development and validation over large spatial extents (e.g., continental or global) with coarse prediction resolutions (e.g., ≥1 km2). Coarse resolution, large extent distribution models may inform policy makers at national and international levels but are almost irrelevant at local spatial scales where actual management in response to policy takes place. The public agencies and private landowners often mandated by law to eradicate or control noxious or invasive weed species are typically faced with a lack of quality data at fine scales (e.g., ≤ 30 m2) and limited human and financial capital. Thus, it is crucial for applied scientists to develop efficient and cost effective frameworks within which management efforts are prioritized. Assessing the potential utility of fine scale SDMs as part of a weed management prioritization framework may be one of the most immediate, practical, and fruitful applications of such models. <!--break--> The primary objectives of my research are to 1) address methods of overcoming limited data by testing the transferability of SDMs “trained” in one watershed and extrapolated to neighboring watersheds with similar environmental characteristics but differing land use histories and 2) experimentally testing invasive plant populations’ responses to chemical management along their respective predicted gradients of environmental suitability. My study sites included the Northern Range of Yellowstone National Park, parts of the Gallatin National Forest, and Paradise Valley, MT. The results of my research suggest that current and historical land use play a critical role in determining the environmental suitability of various invasive plant species. Likewise, environmental suitability has the potential of predicting population characteristics and their responses to management (tested species were Linaria dalmatica (Dalmatian toadflax) and Bromus tectorum (cheatgrass)).


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