| Abstract: | Abstract. Grassland in the semiarid shortgrass steppe, subjected to 50 years of heavy, light, and no grazing intensity, was clipped to simulate the natural pattern and intensities of defoliation by cattle or not clipped. A level of water resource treatment was superimposed upon the grazing and clipping treatments. Half of the plots were supplemented with additional water to simulate a wet year and half were not supplemented in a year of average precipitation. All three treatments interactively determined above-ground production. Water treatment had the largest overall effect on above-ground production. Current-year defoliation had no direct significant effect on production, but mediated differences between both longterm grazing and watering treatments. Long-term ungrazed compared to grazed grassland was capable of responding to high amounts of precipitation, but was also most affected by low amounts of precipitation and, therefore, displayed greater variability in above-ground production and rain use efficiency. Only in the year of average precipitation, defoliation increased rain use efficiency in long-term lightly, but not heavily, grazed treatment. This suggests a water conservation mechanism of defoliation that is reduced with heavy grazing. |
