• Contrasts of esophageal-fistula versus bite-count techniques to determine cattle diets

      Ortega, I. M.; Bryant, F. C.; Drawe, D. L. (Society for Range Management, 1995-11-01)
      To understand how different techniques might affect diet estimates for cattle, the esophageal-fistula and bite-count techniques were compared using trained cattle. For the Texas Coastal Bend, bite-count was not as reliable a technique as the esophageal fistula. These techniques differed in estimation of forage classes and plant species in cattle diets. The esophageal-fistula technique was more accurate however, the bite-count technique may be acceptable if analyses are limited to only those plant species making up >2% of the diet.
    • Invasive potential of ashe juniper after mechanical disturbance

      Owens, M. K.; Schliesing, T. G. (Society for Range Management, 1995-11-01)
      Reinvasion of mechanically disturbed juniper communities is possible through contributions from the soil seedbank, seed rain, and the juvenile seedling bank. We compared spatial distribution of the seedbank and seed rain of undisturbed communities to sites where trees were deliberately left as single trees, small mottes of less than 5 trees per group, or large mottes of 5-10 trees per group. Seed density in the litter layer ranged from 1,197 to 1,436 seeds m-2 and in the soil layer from 318 to 617 seeds m-2. Seed rain ranged from 275 to 366 seeds m-2 over all tree arrangements. The treatment associated with single trees caused the litter layer to be removed resulting in the removal of that portion of the seedbank, consequently most seeds (>80%) were found under the canopy of mature, seed-producing trees. Soil disturbance was less severe in small and large motte arrangements, so only 65% of the soil seed bank was under mature trees. In undisturbed communities, the seed population was distributed evenly under tree canopies and in interspaces. Viability and germinability within the seedbank were low (4% and 0%, respectively). Viability of new seed was 47% and germinability was approximately 5%. The juvenile seedling bank contained a sufficient number of seedlings (408 seedlings ha-1) for ashe juniper to regain dominance on the site through growth. There was no advantage to any spatial pattern of tree distribution in terms of invasive potential when fewer than 10 trees ha-1 were left on a site. However, when 20-50 trees ha-1 are left on a site, tree spatial arrangement has a significant effect on reinvasion rates.
    • Technical Note: Root-plowing effects on nutritional value of browse and mast in south Texas

      Ruthven, D. C.; Hellgren, E. C. (Society for Range Management, 1995-11-01)
      Leaf and mast material was collected from mesquite (Prosopis glandulosa Torr.), huisache (Acacia smallii Isely), granjeno (Celtis pallida Torr.), and hog plum (Colubrina texana (T.& G.) Gray) on both root-plowed and untreated sites in south Texas. Forages were analyzed for nitrogen (N), neutral detergent fiber (NDF), and in vitro dry matter digestibility (IVDMD). Forages differed among species for N, NDF, and IVDMD. Leaf IVDMD of huisache and hog plum was higher on untreated sites. Huisache mast was higher in N and NDF concentrations, but not IVDMD, on untreated sites. Browsers on root-plowed sites may be forced to use forages of fewer digestible nutrients than on untreated sites. The cause of changes in browse quality following brush manipulation should be examined.
    • Water erosion prediction project (WEPP) rangeland hydrology component evaluation on a Texas range site

      Savabi, M. R.; Rawls, W. J.; Knight, R. W. (Society for Range Management, 1995-11-01)
      The USDA-Water Erosion Prediction Project (WEPP) is a new technology based on the fundamentals of hydrology, soil physics, plant science, hydraulics, and erosion mechanics. WEPP hydrology includes simulation of excess rainfall using the Green and Ampt infiltration equation, surface runoff routing, evapotranspiration, percolation, and surface drainage. Hydrometeorological, soil, topography, and vegetation data from a range in Texas were used to test the WEPP rangeland hydrology model. Measured surface runoff and root zone soil water content from the site were compared with the simulated results of the WEPP model. The results indicate that the WEPP model (version 93.0) is capable of simulating soil water content and storm runoff. The Nash and Sutcliffe coefficient, NSR, between measured and simulated root zone soil water content and storm runoff was .88 and .84, respectively, for the bare ground plots. However, for the plots with herbaceous vegetation the discrepancy between model simulated storm runoff and soil water content was more than expected (NSR = .46 and NSR = .53, respectively).