Implications of Precipitation, Warming, and Clipping for Grazing Resources in Canadian Prairies

Climate change, in terms of both warming and altered precipitation, has the potential to affect grassland systems, with subsequent ramifications for grazing resources. Although grazing is the dominant land use in grasslands, little research has assessed how changes in climate might affect herbage quantity and quality, and how grazing intensity might influence these responses. We performed a fully controlled and factorial 3-yr, multisite experiment simulating climate change and grazing (via clipping). This experiment was conducted at three northern temperate grassland sites across the Canadian prairies. We increased air temperature by 2 to 4 degrees C, reduced precipitation by 60%, and clipped plants at low and high intensities. At one site, we also applied added (+60%) precipitation. We monitored changes in herbage quantity (regrowth and accumulated herbage) and one aspect of herbage quality (protein content) for both graminoid and forb components. Both climatic factors (i.e., warming and reduced precipitation) and clipping decreased season-long accumulated herbage, with similar magnitudes of response to precipitation and clipping and smaller responses to warming. Regrowth biomass following clipping declined with reduced precipitation but had a limited decline with warming. Reduced precipitation and warming both decreased herbage quality, and clipping increased quality. These results indicate that the potential for losses in herbage production under drought and warming may be exacerbated by decreased herbage quality. We also saw evidence that graminoids, rather than forbs, will be more sensitive to climate changes. Our results further support the idea that planning for altered grazing resources under future climate conditions will be necessary.