Long-Term Effects of Fire,Livestock Herbivory Removal,and Weather Variability in Texas Semiarid Savanna |
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| Authors: | Charles A. Taylor D.r.c. Twidwell Nick E. Garza C.l.n. Rosser James K. Hoffman Terry D. Brooks |
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| Affiliation: | 1. Regent Fellow and Professor, Texas A&M University, Texas A&M Agrilife Research Center, Sonora, TX 76950, USA;2. Instructor and Tom Slick Graduate Fellow, Texas A&M University, Department of Ecosystem Science and Management, College Station, TX 77843, USA;3. Research Associate, Texas A&M University, Texas A&M Agrilife Research Center, Sonora, TX 76950, USA;4. Research Assistant, Texas A&M University, Texas A&M Agrilife Research Center, Sonora, TX 76950, USA;5. Undergraduate Research Assistant, Texas A&M University, Department of Ecosystem Science and Management, College Station, TX 77843, USA;1. Postdoctoral Fellow, Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Scottsville 3209, South Africa;2. Professor Grassland Science, Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Scottsville 3209, South Africa;3. Professor and Director, Research Centre for Plant Growth and Development, School of Life Sciences, University of KwaZulu-Natal Pietermaritzburg, Scottsville 3209, South Africa;1. Research geneticists, US Department of Agriculture–Agricultural Research Service, Forage and Range Research Laboratory, Utah State University, Logan, UT 84322, USA;2. Beaver County Extension Agent, Utah State University, Beaver, UT 84713, USA;1. Soil Scientist, US Department of Agriculture–Agricultural Research Service, Great Basin Rangelands Research Unit, Reno, NV 89512, USA;2. Research Technician, US Department of Agriculture–Agricultural Research Service, Great Basin Rangelands Research Unit, Reno, NV 89512, USA;1. Assistant Professor, Department of Environmental Studies, California State University, Sacramento, CA 95819, USA;2. Undergraduate Student, Department of Environmental Studies, California State University, Sacramento, CA 95819, USA |
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| Abstract: | We examined how the occurrence and structure of grasses and woody plants changed after 12 yr of a fire season manipulation and removal of livestock herbivores. Applying high intensity fires in the summer preserved the structural integrity of this semiarid live oak (Quercus virginiana Mill.) savanna while decreasing or eliminating numerous problematic plants in the understory and overstory, such as prickly pear cactus (Opuntia spp.), sacahuista (Nolina texana S. Watson), Ashe juniper (Juniperus ashei J. Buchholz), Pinchot's juniper (J. pinchotii Sudw.), and honey mesquite (Prosopis glandulosa Torr.). In the less intense repeat winter burning treatments, undesirable woody plants were generally maintained at pretreatment levels in the overstory but all woody plants except Ashe juniper increased in the understory. Alternatively, areas excluded from fire in the control treatment rapidly transitioned from a grass-tree codominated savanna environment to one that is heavily dominated by woody plants. In the grass community, the most frequently occurring grass species in the winter burn treatment differed from summer burn and control treatments, whereas the summer burn treatment was not different from the control. Of the herbaceous plants, only little bluestem (Schizachyrium scoparium [Michx.] Nash) responded to fire treatments. Little bluestem increased in the winter burn treatment, remained fairly constant in the summer burn treatment, and decreased in the control. Other grasses varied largely as a function of annual weather variability, the removal of livestock, and legacy effects resulting from pre-existing variability. These findings suggest that fire can reduce or eliminate woody plant species that threaten the stability of live oak savannas while having little long-term effect on grasses desired by rangeland managers. |
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