Response of grassland biomass production to simulated climate change and clipping along an elevation gradient
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Changes in rainfall and temperature regimes are altering plant productivity in grasslands worldwide, and these climate change factors are likely to interact with grassland disturbances, particularly grazing. Understanding how plant production responds to both climate change and defoliation, and how this response varies among grassland types, is important for the long-term sustainability of grasslands. For 4 years, we manipulated temperature [ambient and increased using open-top chambers (OTC)], water (ambient, reduced using rainout shelters and increased using hand watering) and defoliation (clipped, and unclipped) in three grassland types along an elevation gradient. We monitored plant cover and biomass and found that OTC reduced biomass by 15 %, but clipping and water treatments interacted with each other and their effects varied in different grassland types. For example, total biomass did not decline in the higher elevation grasslands due to clipping, and water addition mitigated the effects of clipping on subordinate grasses in the lower grasslands. The response of total biomass was driven by dominant plant species while subordinate grasses and forbs showed more variable responses. Overall, our results demonstrate that biomass in the highest elevation grassland was least effected by the treatments and the response of biomass tended to be dependent on interactions between climate change treatments and defoliation. Together, the results suggest that ecosystem function of these grasslands under altered climate patterns will be dependent on site-specific management.
KeywordsBunchgrass grasslands Drought Grazing Open-top chambers Rainout shelters
This study was supported with an NSERC IPS (in partnership with the BC Grassland Conservation Council), a BC Pacific Century Scholarship and a University of British Columbia Graduate Fellowship to C. N. C., and an NSERC discovery grant, a Canadian Foundation for Innovation grant, a BC Knowledge Development Fund grant and BC Forest Science Program Grant to L. H. F. Laura Gough and two anonymous reviewers greatly improved this manuscript. We thank Don Thompson, at Agriculture and Agri-Food Canada, and BC Parks for allowing access to the field sites. Brandy Ludwig, Amber Greenall, Montana Burgess, Eleanor Bassett, Lisa DeSandoli, Amy Bitz, Jessica Gosling and Anna-Marie Pellet assisted with the experiment. The experiment complies with the current laws of the country (Canada) in which the experiment was performed.
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