• Mountain big sagebrush browse decreases dry matter intake, digestibility, and nutritive quality of sheep diets

      Ngugi, R. K.; Hinds, F. C.; Powell, J. (Society for Range Management, 1995-11-01)
      A metabolism study evaluated the influence of increasing quantities (0-30% dry matter basis) of mountain big sagebrush (Artemisia tridentata ssp. vaseyana Rydb. Beetle) on dry matter intake and in vivo digestibility of wether diets. Diets consisted of hand-harvested, coarse-ground and frozen current year's growth of mountain big sagebrush leaves and twig tips mixed with chopped native grass hay. Dry matter intake decreased from 93 to 23 g dry matter day-1 kg metabolic weight-1 and in vivo dry matter digestibility from 59 to 0% with increasing levels of sagebrush in the diet. With increasing levels of sagebrush in the diet, water, lignin, and nitrogen contents increased in the diet, but decreased in the dung, while fiber components decreased in both the diet and dung. Total nitrogen intake decreased from 1.58+/-0.041 to 0.406+/-0.070 g day-1 kg metabolic weight-1, and nitrogen retention decreased from 0.80 g day-1 kg metabolic weight-1 with no sagebrush to a slight loss of nitrogen with 30% sagebrush in the diet. Mountain big sagebrush was not readily consumed by wethers when fed together with grass; as low as 10% sagebrush in the diet seems to adversely influence intake and digestibility. Therefore, when other more favorable forages are not available, sheep and other ruminants with similar physiological responses to mountain big sagebrush may not meet their nutrient requirements through increased sagebrush consumption.
    • Observations on spread and fragmentation of blue grama clones in disturbed rangeland

      Samuel, M. J.; Hart, R. H. (Society for Range Management, 1995-11-01)
      Establishment of blue grama (Bouteloua gracilis [H.B.K.] Lag ex. Steud.) depends on adequate precipitation at critical times and on reduced competition from associated vegetation. These conditions rarely occur on Central Plains rangelands. Therefore, rapid vegetative spread of new seedlings is desirable for colonizing disturbed rangeland. Blue grama genotypes selected for rapid spread would also be desirable for rangeland seeding. For 6 years, we followed the rate of spread of 19 blue grama clones originating from seedlings which emerged in 1980 and grew under natural competition. We observed a 4.5-fold difference in basal area and a 16.3-fold difference in above-ground biomass of these clones, perhaps because of genetic differences among clones and varying levels of competition. Clones must be tested under uniform competition with clonal replication to obtain reliable estimates of their capacity to spread.
    • Response to comment: Ungulate herbivory on willows on Yellowstone's northern winter range

      Singer, F. S.; Cates, R. G. (Society for Range Management, 1995-11-01)