Document: SHI-3-34-43

Warming and clipping effects on tallgrass prairie: A preliminary study and its implication for global change.

WAN, S.*, Y.LUO, L.L.WALLACE, L.FARBER, P.KORES, L.R.KRUMHOLZ and M.HOEFNAGELS

University of Oklahoma, Norman, OK 73019-0245 USA 1

Abstract:
Global warming and land use will have considerably impacts on terrestrial ecosystems. This study used infrared radiators and clipping to mimic global warming and grazing, respectively, with an attempt to examine their impacts on tallgrass prairie in Oklahoma. The experiment used a factorial design with warming as the main factor nested with clipping. There are totally ten 2 m by 2 m plots, five of which have been warmed continuously using infrared radiators since 21 November, 1999 and the other five are the control. Each plot was divided into four 1 m ' 1 m subplots. Two diagonal subplots were clipped on 15 November, 1999, the other two are the unclipped control. We have measured aboveground biomass, plant pheonology, species composition, air temperature (at the height of 25 cm), soil temperature (at the depth of 2.5 cm), soil moisture (0-5 cm), soil respiration, soil C and N content, soil ammonium and nitrate concentration, and N mineralization (0-15 cm). Warming treatment significantly increased daily mean and minimum air temperature (0.7C and 1.8C, respectively), daily maximum, mean, and minimum soil temperature each by approximately 2.2C, and decreased soil moisture by 24%. Clipping treatment had no significant effect on daily mean soil temperature, increased daily maximum soil temperature by 2.0C, decreased daily minimum soil temperature by 1.2C and decreased soil moisture by 21.4 %. Clipping and warming have interactive effects on soil temperature and moisture. Our 6-month data did not show a significant effect of warming or clipping on soil respiration. However, warming and clipping significantly altered phenology and species composition in the tallgrass prairie.

Keywords: Clipping, Global change, Soil moisture, Tallgrass Prairie, Temperature, Warming

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