Long-Term Effects of Aeration and Fire on Invasion of Exotic Grasses in Mixed-Brush Plant Communities |
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| Authors: | Felix Ayala-A J.Alfonso Ortega-S Timothy E. Fulbright G.Allen Rasmussen D.Lynn Drawe David R. Synatzske Andrea R. Litt |
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| Affiliation: | 1. PhD Candidate, Caesar Kleberg Wildlife Research Institute, Texas A&M University–Kingsville, Kingsville, TX 78363, USA;2. Professor and Research Scientist, Caesar Kleberg Wildlife Research Institute, Texas A&M University–Kingsville, Kingsville, TX 78363, USA;3. Regents Professor and Endowed Meadows Professor, Caesar Kleberg Wildlife Research Institute, Texas A&M University–Kingsville, Kingsville, TX 78363, USA;4. Dean, Professor, and Research Scientist, Dick & Mary Lewis Kleberg College of Agriculture, Natural Resources, and Human Sciences, Texas A&M University?–Kingsville, Kingsville, TX 78363, USA;5. Former Director, Rob and Bessie Welder Wildlife Foundation, Sinton, TX 78387, USA;6. Manager, Chaparral Wildlife Management Area, Texas Parks and Wildlife Department, Artesia Wells, TX 78001, USA;7. Assistant Professor, Department of Ecology, Montana State University, Bozeman, MT 59717, USA;1. Research Technician, Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA;2. Professor, Department of Biological Sciences, Idaho State University, Pocatello, ID 83209, USA;3. Research Ecologist, USGS Forest and Rangeland Ecosystem Science Center, Snake River Field Station, Boise, ID 83706, USA;1. Environmental Studies Dept., University of California, Santa Cruz, Santa Cruz, CA;2. LD Ford Rangeland Conservation Science, 5984 Plateau Dr., Felton, CA 95018;3. The Nature Conservancy of California, San Francisco, CA;4. LD Ford Rangeland Conservation Science, Livermore, CA;5. ICF, Sacramento, CA;6. Dept. of Environmental Science, Policy, and Management, University of California, Berkely, Berkley, CA |
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| Abstract: | Invasion of exotic grasses into grasslands dominated by native plants changes fire cycles and reduces biodiversity. Brush management practices that create soil disturbance, such as aeration, may potentially result in invasion of exotic grasses and replacement of native vegetation. We tested the hypothesis that a long-term effect of aeration and prescribed burning is an increase in exotic grasses. The study was conducted at the Chaparral Wildlife Management Area in the western south Texas plains where four treatments were evaluated: aeration, warm-season burn, aeration followed by a warm-season burn, and no treatment (control). The experimental design was a randomized complete block with four replicates. We estimated percentage canopy cover of exotic grasses, native grasses, forbs, litter, bare ground, and woody and succulent plants in 2007. There was a multivariate main effect among treatments for the dependent variables absolute canopy cover of exotic grasses, native grasses, forbs, litter, and bare ground (Wilks's Lambda F15,179.84 = 2.78, P = 0.001). Variables that contributed to the significant overall effect included litter (F3,69 = 4.32, P = 0.008) and native grasses (F3,69 = 6.11, P = 0.001). The multivariate main effect of treatment was significant (Wilks's Lambda F9,180.25 = 2.04, P = 0.038) for the relative canopy cover of herbaceous species. Relative cover of exotic grasses was 31% higher (P = 0.024) in control than in the prescribed burn treatment. Native grasses relative cover was 30% higher (P = 0.003) in prescribed burn than in the control treatment. We did not detect differences among treatments in the percentage of total woody and succulent plants canopy cover (P = 0.083). Under the environmental conditions at the time of the study, aeration and/or prescribed burning do not increase exotic grasses. |
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