PARENT SESSION
Poster Session 7: Grasslands
Tuesday, August 9, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Warming and clipping effect on soil carbon and isotope carbon dynamics in a tallgrass prairie ecosystem.

Subedar, Afzal^*,1, Luo, Yiqi¹, ¹ The University of Oklahoma, Norman, OK, USA

ABSTRACT- Whether soils will continue to act as carbon (C) sinks under the present as well as predicted future global warming conditions is a matter of serious debate. This study, conducted in a tall grass prairie ecosystem in the US Great Plains, looked at whether approximately four years of experimental warming of about 2°C would cause any changes in soil organic matter (SOM) dynamics. The soil was segregated into chemical and physical fractions, resulting in different size classes of heavy, light, and mineral associated SOM fractions. Stable isotope C and organic C content of the different soil fractions were analyzed. No significant changes in organic C content were observed between the treatments, although the different fractions responded very differently from each other, with the mineral associated SOM (mSOM) showing an overall decrease in C content under warming. The stable isotope data also showed no significant isotopic signal shifts, except that the mSOM fraction shows a shift closer to C4 plants under warming. Root isotope values did indicate more C4 inputs under warming, but these were not significant. This study showed that the mSOM fraction may be more dynamic than proposed earlier and sheds light on the importance of delineating the different SOM pools in order to understand the soil system. Also, a longer time frame may be required to assess plant functional shifts and their role in soil C cycling and the implications, before we have high confidence in assessing whether soil systems will act as a C sink or source.°

Key words: carbon, clipping, soil fractions, warming