Date of Award
Master of Science
Background: Lespedeza cuneata is a perennial invasive legume native to Asia that is common across grasslands in the eastern half of the United States and parts of Canada. The competitive nature and limited palatability of L. cuneata for grazers in the tallgrass prairie has made it an undesirable and invasive weed. Objectives: This study was conducted to investigate an invasive species management plan for restored grasslands and prairie areas. Methods: Study plots (n=144) for experiment 1 (summer treatment) were established at Crab Orchard Wildlife Refuge in Jackson County Illinois in August of 2012 and were situated to contain infestations of the target species. Two herbicides, in five concentrations were applied in August of 2012. A native seed mix was added to a portion of the summer plots later, in February of 2013. These treatments were assessed in June and August of 2013 to determine herbicide effects on stem count and percent cover of L. cuneata, along with the composition and percent cover of other species present. Spring herbicide applications (n=18) for experiment 2 were established, assessed for L. cuneata cover and density, and treated with two herbicide treatments in May of 2013. Spring treatments were identical to existing plots and were re-assessed in August 2013 to determine species composition and the abundance of L. cuneata. Seed was not added to these plots. Analysis: Mixed Model analysis by site was performed to test the effect of herbicide and seeding treatments on L. cuneata for both experiments 1 &2. The summer plots were also tested for effects on other plant groups. A repeated measures PERMANOVA along with ANOSIM and PERMADISP was performed to assess community composition response to seeding and herbicide treatments in the summer plots. Results: Abundance of L. cuneata was reduced 67 to <90% following herbicide treatment in Experiments 1 and 2. There were no differences in the effectiveness of herbicide treatments in in experiment 1, sites 1 &3, and in experiment 2. Supplemental seeding in the summer plots did not reduce the abundance of L. cuneata consistently across sites. Conclusion: Considerable short-term control of the target species was achieved in both the summer and spring plots, providing a window of opportunity for the imposition of additional methods of control. However, data from the summer plots suggest recovery of L. cuneata some sites, indicating further control would be necessary, with potentially the addition of other control methods or site alterations.
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