Plant community composition regulates prairie soil respiration in response to decadal experimental warming

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.