| R. K. Heitschmidt, M. R. Haferkamp, M. G. Karl, and A. L. Hild |
| Authors are supervisory rangeland scientist and rangeland scientist, USDA Agricultural Research Service, Fort Keogh Livestock and Range Research Laboratory, Miles City, Mont. 59301, rangeland management specialist-ecologist, USDA Forest Service, Walla Walla, Wash. 99362, and assistant professor, Department of Rangeland Ecology and Watershed Management, University of Wyoming, Laramie, Wyo. 82071. At the time of the research, M.G. Karl and A.L. Hild were postdoctoral rangeland scientists at Fort Keogh. |
Abstract |
| This research addresses the hypothesis that grazing intensity during and following drought can dramatically alter community level, post-drought recovery patterns. Research was conducted during the 1993 through 1996 growing seasons at the Fort Keogh Livestock and Range Research Laboratory located near Miles City, Mont. Study plots were twelve, 5 x 10-m non-weighing lysimeters constructed in 1992 on a gently sloping (4%) clayey range site. An automated rainout shelter was constructed to control the amount of precipitation received on 6 lysimeters during the 1992 growing season. We conclude from study results that the independent and combined effects of the imposed late spring to early fall drought and associated grazing treatments were minimal relative to soil water dynamics and aboveground net primary production although both grazing treatments reduced herbage standing crops. We attribute the absence of a strong response to the drought to its timing (i.e., late growing season) in that most herbage production in these cool-season dominated grasslands is completed by early summer. Thus, annual production processes in these grasslands avoided the major impacts of the drought. The results do not provide convincing evidence, however, that would lead us to completely reject our original hypothesis. Rather, they simply provide evidence that these grasslands are well adapted to surviving late growing season drought with or without intensive grazing by ungulates. |
| Key Words: Primary production, species composition, standing crop, soil water |