PS 55-93
Plant community composition regulates prairie soil respiration in response to decadal experimental warming

Thursday, August 14, 2014
Exhibit Hall, Sacramento Convention Center
Xia Xu, Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA
Background/Question/Methods: Ecosystem production as a principal driver of soil respiration has long been recognized. However, little is known about plant community regulation of soil respiration – climate interactions. Here we used a long-term field warming experiment to explore the mechanisms underlie plant community regulation of soil respiration feedback to climate change in a tallgrass prairie in Oklahoma, USA. Infrared heaters were used to elevated temperature about 2 oC since November 1999. Annual clipping was used to mimic hay harvest.

Results/Conclusions: Our results showed that experimental warming significantly increased soil respiration approximately from 10 % in the first 7 years (2000-2006) to 30 % in the next 6 years (2007-2012). The 2-stage “stimulatory” effect of warming on soil respiration was closely coupled with warming-induced changes in ecosystem production over the years. Moreover, we found that plants regulated warming-induced temporal changes in soil respiration through the mechanisms of plant community control on the quantity and quality of organic carbon (C) inputs to soils and the amount of photosynthetic C allocated belowground. Clipping, the interaction of clipping with warming, and warming-induced changes in soil temperature and moisture all had little effects on soil respiration over the years (all P>0.05). Our results suggest that increases in C stocks in ecosystem production are approximately offset by the increased soil respiration under warming. Additionally, warming may affect ecosystem C cycling through altering plant community composition.