Long-Term Vegetation Trends on Grazed and Ungrazed Chihuahuan Desert Rangelands |
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| Authors: | Francisco Molinar Joe Navarro Jerry Holechek Dee Galt Milt Thomas |
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| Institution: | 1. Rangeland Management Specialist, US Department of Agriculture–Natural Resources Conservation Service, El Paso, TX 79821, USA;2. Rangeland Management Specialist, US Department of the Interior–Bureau of Land Management, Roswell, NM 88201, USA;3. Professor, Department of Animal and Range Sciences, New Mexico State University, Las Cruces, NM 88003, USA;4. Private Range Consultant, 3000 Devondale Ave, Las Cruces, NM 88005, USA;5. Professor, Department of Animal and Range Sciences, New Mexico State University, Las Cruces, NM 88003, USA;1. Professor, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996, USA;2. Graduate Research Assistant, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996, USA;3. Professor and Director, Center for Native Grasslands Management, University of Tennessee, Knoxville, TN 37996, USA;4. Professor, Department of Animal Science, University of Tennessee, Knoxville, TN 37996, USA;5. Graduate Research Assistant, Department of Animal Science, University of Tennessee, Knoxville, TN 37996, USA;6. Professor, Department of Plant Science, University of Tennessee, Knoxville, TN 37996, USA;7. Research Scientist, Center for Native Grasslands Management, University of Tennessee, Knoxville, TN 37996, USA;1. Research Assistant, Center for Integrated Pest Management, North Carolina State University, Raleigh, NC 27606, USA;2. Agriculture Extension Agent, Montana State University Extension, Livingston, MT 59047, USA;3. Professor, Department of Animal and Range Sciences, Montana State University, Bozeman, MT 59717, USA;1. Research Assistant, Zoology Department, Wildlife Data Integration Network, University of Wisconsin-Madison, Madison, WI 53706, USA;5. Technical Manager, Wildlife Data Integration Network, University of Wisconsin-Madison, Madison, WI 53706, USA;2. Research Assistant, US Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA;3. Research Statistician, US Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA;4. Research Wildlife Biologist, US Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA;7. Veterinary Medical Officer, US Geological Survey, National Wildlife Health Center, Madison, WI 53711, USA;6. Biologist, Land Management Research Demonstration Program, US Fish and Wildlife Service, Burbank, WA 99323, USA;1. Research Hydraulic Engineer, US Department of Agriculture (USDA)?Agricultural Research Service (ARS), Southwest Watershed Research Center, Tucson, AZ 85719, USA;2. Professor, School of Natural Resources, University of Arizona, Tucson, AZ 85719, USA;3. Senior Research Programmer/Analyst, Robotics Institute, Carnegie Mellon University, Pittsburgh, PA 15213, USA |
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| Abstract: | Long-term information on the effects of managed grazing versus excluded grazing effects on vegetation composition of desert rangelands is limited. Our study objectives were to evaluate changes in frequency of vegetation components and ecological condition scores under managed livestock grazing and excluded livestock grazing over a 38-yr period at various locations in the Chihuahuan Desert of southwestern New Mexico. Sampling occurred in 1962, 1981, 1992, 1998, 1999, and 2000. Range sites of loamy (1), gravelly (2), sandy (2), and shallow sandy (2) soils were used as replications. Black grama (Bouteloua eriopoda Torr.) was the primary vegetation component at the seven locations. Dyksterhuis quantitative climax procedures were used to determine trends in plant frequency based on a 1.91-cm loop and rangeland ecological condition scores. Frequency measures of total perennial grass, black grama, tobosa (Hilaria mutica Buckley), total shrubs, honey mesquite (Prosopis glandulosa Torr.), and other vegetation components were similar on both grazed and ungrazed treatments (P > 0.1) at the beginning and end of the study. The amount of change in rangeland ecological condition scores was the same positive increase (14%) for both grazed and ungrazed treatments. Major changes (P < 0.1) occurred within this 38-yr study period in ecological condition scores and frequency of total perennial grasses and black grama in response to annual fluctuations in precipitation. Based on this research, managed livestock grazing and excluded livestock grazing had the same long-term effects on change in plant frequency and rangeland ecological condition; thus, it appears that managed livestock grazing is sustainable on Chihuahuan desert rangelands receiving over 25 cm annual precipitation. |
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