| Isaac M. Ortega, Sergio Soltero-Gardea, Fred C. Bryant, and D. Lynn Drawe |
| Authors are research associate, former graduate student, former professor, and assistant director, Department of Range, Wildlife, and Fisheries Management, Texas Tech University, Lubbock, Tex. 794092125 (IMO); Instituto Nacional de Investigaciones Forestales y Agropecuarias, Jalisco, Mexico (SSG), Welder Wildlife Foundation, P.O. Box 1400, Sinton, Tex. 78387 (DLD), and Caesar Kleberg Wildlife Research Institute, TAMU-Kingsville, Kingsville, Tex. 78363 (FCB). |
Abstract |
| We documented vegetation dynamics (April 1986July 1989) as part of a larger study to understand botanical composition and nutritional components of cattle and deer diets under 2 grazing systems (continuous and short-duration), and 2 stocking rates (heavy and moderate) at the Welder Wildlife Refuge, Sinton, Tex. Objectives of the study were to examine initial vegetation homogeneity and floral changes over time in the plant community, and to determine phytomass dynamics. Results indicated that grazing treatment had no impact on homogeneity of the plant community. Cattle grazing, regardless of treatment, increased diversity with time until drought conditions persisted and diversity declined. Shannon's diversity index (H) changed from a pre-treatment value of H = 2.41 in April 1986, to H = 3.08 in April 1988, to H = 2.61 in April 1989. There was no difference (P > 0.05) in diversity index between grazing treatments or replication within years. Stocking rates (heavy = 198 g/m2 differed (P < 0.05) from moderate = 258 g/m2) had a more significant impact on phytomass than grazing system (continuous = 225 g/m2; short-duration grazing = 231 g/m2; P > 0.05) by the end of the study period. Precipitation was a determinant factor in the seasonal dynamics of phytomass of the various forage classes. Phytomass of forbs was unaffected by grazing system or stocking rate. Phytomass of grasses and grass-like plants important to deer was lower (P < 0.05) under short-duration than continuous grazing. Phytomass of grasses and grass-like plants preferred by deer was greater under moderate than heavy stocking rates. We recommend continuous over short-duration grazing, and moderate over heavy stocking rates, when white-tailed deer habitat quality is a primary concern. Less intensive grazing systems should be acceptable as well. |
| Key Words: diversity, phytomass, white-tailed deer, Odocoileus virginianus, cattle, Coastal Bend of Texas, short-duration grazing, continuous grazing |