Effects of climate warming and biofuel feedstock harvest on belowground process in a tallgrass prairie

Background/Question/Methods: Knowledge of how belowground processes respond to climate warming is crucial for assessing impacts of climate change on terrestrial ecosystems and is one of the major uncertainties in projecting future global warming.  In this study, we examined belowground process in a warming and clipping experiment in a tallgrass prairie of the Great Plains, USA.  Infrared heaters have been used to elevate soil temperature by approximately 2.0^oC continuously since November 1999. Clipping once a year was to mimic hay or biofuel feedstock harvest.  We measured soil respiration, deep-collar SOM decomposition, root C and N content, soil C and N content, soil labile and recalcitrant C and N, and soil microbial biomass C and N. 
Results/Conclusions: Warming significantly stimulated soil respiration and deep-collar SOM decomposition by 11.4 and 13.5%, respectively, over the 9 years, largely resulting from increases in aboveground and belowground biomass.  Experimental warming also significantly increased labile C and N fractions and soil microbial biomass C and N content in the unclipped plots but not in clipped ones.  Clipping significantly decreased soil respiration and deep-collar SOM decomposition but increased root C content.  However, both warming and clipping did not change soil C and N content.  Our results suggest that an increase in plant aboveground and belowground biomass is a key mechanism underlying warming stimulation of soil respiration, labile and microbial biomass C content.