• Effect of grazing and abandoned cultivation on a stipa-bouteloua community

      Dormaar, J. F.; Adams, B. W.; Willms, W. D. (Society for Range Management, 1994-01-01)
      A Stipa-bouteloua community, cultivated in the autumn of 1928 and abandoned in the spring of 1932, reverted to a community dominated by needle-and-thread (Stipa comata Trin. and Rupr.). An exclosure to prevent grazing was constructed in 1978 to include equal portions of previously cultivated and adjacent native range, while the remainder of the area continued to be subjected to moderate to heavy grazing pressure. This permitted a study to determine the effects of the brief period of cultivation on forage production, species recovery, and soil physical and chemical characteristics compared to those of native prairie. After 14 years of protection from grazing, needle-and-thread accounted for 79% of foliar cover of the abandoned cultivation and 18% of the untreated range while blue grama [Bouteloua gracilis (HBK.) Lag. ex Steud] occupied 1 and 51% on the same treatments, respectively. After 60 years, the soil on the abandoned cultivated area showed reduced carbon, total nitrogen, available phosphorus, and hydraulic conductivity but increased N03-N. Grazing reduced hydraulic conductivity, NH4-N, available mineralizable nitrogen (chemical index), available phosphorus, and total carbohydrates but increased carbon, total nitrogen, and N03-N. Cultivation and grazing resulted in reduced root mass. To facilitate a rapid transition from blue gramb to needle-and-thread stable communities, input of energy, such as cultivation, may well be required.
    • Impacts of rotational grazing on mixed prairie soils and vegetation

      Dormaar, J. F.; Adams, B. W.; Willms, W. D. (Society for Range Management, 1997-11-01)
      In this study the impact of a rotation grazing system on the soil and vegetation of a Stipa-Bouteloua-Agropyron community in the mixed prairie ecoregion was compared with the ungrazed treatment in exclosures. At a low stocking rate, grazing had no effect on the vegetation but did alter soil quality. Grazing pressure was so light in the rotational grazing treatment that recovery of productivity, as measured by standing crop and litter, was not significantly different from the ungrazed treatment. Conversely, the species distribution was unchanged but was indicative of a lower seral state for this mixed prairie. The effect of grazing on this community was indirect, possibly by altering the microenvironment. The relationships observed among forage production, soil chemistry, and species composition raise questions on the importance of any one variable expressing range condition on the mixed prairie.
    • Response of the mixed prairie to protection from grazing

      Willms, W. D.; Dormaar, J. F.; Adams, B. W.; Douwes, H. E. (Society for Range Management, 2002-05-01)
      The Mixed Prairie plant communities developed with the influences of fire and grazing. Available evidence suggests that removal of these disturbances could cause succession toward a more mesic type with the accumulation or litter or loss in productivity as nutrient turnover is delayed. Exclosures constructed in 1927 in a semiarid Mixed Prairie community provided an opportunity to examine the effects that protection had on vegetation and soils. Fifteen exclosures were selected for detailed examination; of these, 11 were located on Chernozemic soil and 4 on Solonetzic soil. We measured plant and soil variables both inside and outside the exclosures in a test of the hypothesis that protection from grazing will lead to a loss of production potential of the semi-arid. Mixed Prairie communities in the Northern Great Plains of southeastern Alberta. We found little evidence that 70 years of protection from large animal disturbance reduced the production potential of the plant communities. Conversely, most evidence suggested a neutral effect or an improvement as reflected in an increased cover of Pascopyrum smithii Rydb. (Löve) (P = 0.049) and increased annual net primary production (P = 0.047). The effect of protection appeared largely driven by the accumulation of litter mass that primarily benefits soil and plant indices of quality on the Chernozemic soil type. Although protection tended to reduce species diversity (P = 0.097) among native plants on the Chernozemic soil type, evenness and richness were not affected (P > 0.10). The potential effect that reduced diversity might have on reducing production stability appears more than compensated for by increased litter mass.
    • Seasonal changes of herbage biomass on the fescue prairie

      Willms, W. D.; Adams, B. W.; Dormaar, J. F. (Society for Range Management, 1996-03-01)
      Knowing the amount of herbage on rangeland is basic to management decisions related to livestock grazing. However, the amount of herbage available for grazing changes seasonally. Therefore, changes in herbage biomass were examined in different communities of the fescue prairie. The study was conducted at 2 sites in southwestern Alberta. In the Porcupine Hills near Stavely, changes in herbage biomass components were examined in 3 communities: rough fescue (Festuca campestris Rydb.), Parry oat grass (Danthonia parryi Scribn.)-Kentucky bluegrass (Poa pratensis L.), and Kentucky bluegrass-sedge (Carex spp.) by sampling at monthly intervals from April or May to late September. Observed trends among the rough fescue, Parry oatgrass-Kentucky bluegrass, and Kentucky bluegrass-sedge communities were, for peak current year's standing production, 398, 305, and 226 g m-2, respectively; for spring current year's standing production as a percent of its peak, 73, 50, and 35%, respectively; and for percent losses of total herbage biomass, from fall to spring, 24, 43, and 56%, respectively. In the foothills near Pincher Creek, the standing crop of grasses and fortes was sampled using paired subplots. One subplot was harvested in October and the other in April. Dry matter losses over winter averaged 27 and 58% for grasses and fortes, respectively. Of the 3 communities examined, production on the rough fescue community was the greatest, least dependent on precipitation during the growing season, and least susceptible to weathering losses and, therefore, had the greatest forage values. The Kentucky bluegrass-sedge community had the lowest forage values.