Drought and grazing: I. Effects on quantity of forage produced

This research addresses the hypothesis that grazing intensity during and fo llowing drought can dramatically alter community level, post-drought recove ry patterns, Research was conducted during the 1993 through 1996 growing se asons at the Fort Keogh Livestock and Range Research Laboratory located nea r Miles City, Mont. Study plots were twelve, 5 x 10-m non-weighing lysimete rs constructed in 1992 on a gently sloping (4%) clayey range site. An autom ated 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 minima l relative to soil water dynamics and aboveground net primary production al though 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 domina ted grasslands is completed by early summer. Thus, annual production proces ses in these grasslands avoided the major impacts of the drought. The resul ts do not provide convincing evidence, however, that would lead us to compl etely reject our original hypothesis. Rather, they simply provide evidence that these grasslands are well adapted to surviving late growing season dro ught with or without intensive grazing by ungulates.