• Dependence of standing crop on range condition rating in New Mexico

      Tiedeman, J. A.; Beck, R.; Ecret, R. V. (Society for Range Management, 1991-11-01)
      The Sandy Ridge Site of southern New Mexico was studied to determine the dependance of total standing crop and components of standing crop on range condition rating. Total standing crop which included mesquite (Prosopis glandulosa Torr.) decreased, but total standing crop minus mesquite increased as range condition rating increased. These relationships were found to be highly significant (P less than or equal to 0.01) by regression analysis. Very low R-square values for these models indicate that the often assumed positive linear relationship of standing crop to range condition rating is not reliable. Prediction of standing crop from range condition ratings using linear or quadratic models was found to be unreliable for the Sandy Range Site in southern New Mexico.
    • Instantaneous intake rates of 9 browse species by white-tailed deer

      Koerth, B. H.; Stuth, J. W. (Society for Range Management, 1991-11-01)
      Instantaneous intake rate (IIR) and instantaneous nutrient intake rate (INIR) by tame white-tailed deer (Odocoileus virginianus) of 9 common browse species in south Texas were studied to determine if morphological properties of the plants were associated with intake rate, and if IIR and INIR correlated to preference ratings derived from percent time spent foraging a particular species and with total foliage consumed. Mean leaf mass showed a significant (P < 0.05) positive correlation to IIR (r = 0.75), INIR of neutral detergent fiber (r = 0.73), acid detergent fiber (r = 0.73), and acid detergent fiber nitrogen (r = 0.68). Mean leaf length showed a significant (P < 0.05) positive correlation to INIR of crude protein (r = 0.67). Thorn density showed no significant (P > 0.05) correlations to IIR or INIR. Leaf weight/stem weight ratio showed a significant (P < 0.05) positive-correlation to IIR (r = 0.65) and INIR of acid detergent fiber nitrogen (r = 0.81). Rankings of IIR and INIR did not agree with preference indices based on weight of forage removed or amount of time spent browsing. Significant (P < 0.05) positive correlations for all trials between preference indices based on weight removal and time spent browsing (r = 0.73 for new leaf development, r = 0.87 for stem elongation, and r = 0.70 for full leaf development) indicated these 2 techniques closely agreed on species rank.