Date of Award
Master of Science (MS) in Biology
"Prevention and management of exotic plant species invasion can diminish their negative ecological and economic impacts and maintain ecological functions provided by native species. This is particularly important in rare landscapes that provide essential habitat. The most successful management plans integrate techniques to reduce invasive species abundance, increase native species abundance and reduce invasibility. Eastern Washington's Channeled Scablands bioregion has highly fragmented remnant patches of grassland underlain by glacial alluvium and basalt bedrock that are dotted with Mima mounds (naturally occurring aggregations of fine particle soil). The mounds provide valuable habitat for native plants and animals and many have been heavily invaded by exotic plant species, particularly winter annual grasses such as Bromus tectorum and Ventenata dubia. This study was designed to characterize Mima mound plant communities in the Channeled Scablands and to test the effects of restoration techniques on those communities. I conducted a vegetation survey to characterize community composition and developed three experiments to: 1) test effectiveness of lmazapic, sucrose soil amendment and native seed addition (Pseudoroegnia spicata and Festuca idahoensis), for exotic plant reduction on two geologic substrates (basalt and alluvium), 2) test effectiveness of a biocontrol insect (Mecinus janthiniformis) to reduce Linaria dalmatica, and 3) test effectiveness of an experimental strain of rhizobacteria, Pseudomonas fluorescens D7, for invasive annual grass reduction. I surveyed plant species composition and cover in 235 1 m² vegetation plots in June-July 2009, measured environmental variables for 203 of the plots, applied treatments in summer and fall 2009, and resurveyed plots in June-July 2010. Species assembly was analyzed using NMS ordination, indicator species and cluster analyses. Preliminary abundance comparisons between substrates were conducted using Dunnett's T3 pair-wise comparisons for unequal variance. Mean change in abundance over time was compared among treatments using general linear models (GLM). Community analysis revealed ten community types and a distinct difference in species composition between substrate types. The experimental application of control techniques did not yield the expected results; treatments containing herbicide reduced all species, neither biocontrol agent reduced the abundance of target species, native seed addition had no effect and sucrose addition reduced native species cover but did not affect exotic cover. In control plots, invasive species cover increased significantly over the course of one year, suggesting that management is needed to prevent further invasion. Insight gleaned from both the community analyses and experimental results will be used to direct future study and guide adaptive management practices"--Document.
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Reynecke, Brandy K., "Plant community restoration on mima mounds at Turnbull National Wildlife Refuge, WA" (2012). EWU Masters Thesis Collection. 62.