• Predicting big sagebrush winter forage by subspecies and browse form class

      Wambolt, C. L.; Creamer, W. H.; Rossi, R. J. (Society for Range Management, 1994-05-01)
      Improved regression models were developed to predict winter forage production from big sagebrush (Artemisia tridentata Nutt.) through consideration of the subspecies variation among mountain big sagebrush (A.t. ssp. vaseyana [Rydb.] Beetle), Wyoming big sagebrush (A.t. ssp. wyomingensis Beetle and Young), and basin big sagebrush (A.t. ssp. tridentata). Changes in shrub morphology from browsing were also accommodated in our models. Colinearities among some variables used in previous studies were found and avoided in our models. Models used easily measured objective variables of which major axis and average cover of shrubs were most useful. Multivariable models without colinearities were evaluated on the basis of their R2a values which increased by an average of 10% to near 0.90, with taxa and browse form class included, compared to a model ignoring these differences.
    • Vegetation characteristics influencing site selection by male white-tailed deer in Texas

      Pollock, M. T.; Whittaker, D. G.; Demarais, S.; Zaiglin, R. E. (Society for Range Management, 1994-05-01)
      We studied the effects of vegetation characteristics in southern Texas on site selection by mature, male white-tailed deer (Odocoileus virginianus Raf.). Thirteen, radio-collared animals were monitored during winter, spring, summer, and fall of 1986-87 and 1987-88 to determine area-usage patterns within each animal's respective seasonal home range. After each season, structural vegetation attributes were measured with transect-oriented data collection techniques inside the most heavily used and unused areas of each animal's home range. Comparisons were made between these areas to determine whether site selection by deer was in response to differing vegetation characteristics. In general, the most heavily used areas possessed a greater amount of woody canopy cover (greater than or equal to 85%), woody species richness (18-20), and horizontal screening cover than areas with no use. In contrast, herbaceous densities did not differ between the most heavily used and unused areas. Consequently, habitat management manipulations conducted specifically for mature male white-tailed deer in southern Texas, should include provisions for creation or maintenance of sites possessing dense woody canopy cover, a high number of woody species and dense horizontal screening cover.