Soil basal respiration and nitrogen mineralization from C3 and C4 grass dominated plant communities respond differently to temperature and soil water variation

Key environmental influences on soil basal respiration (Rs) and nitrogen mineralization (Delta IN) are temperature and soil water content (SWC) and both are being altered by climate change. Yet we cannot expect that variation in temperature and SWC will equally affect all ecosystems. We examine the influences of temperature and SWC on Rs and Delta IN in two grassland plant communities dominated by C3 or C4 species. We collected soil samples from these communities and incubated them at temperatures (5 degrees C, 10 degrees C, 15 degrees C, and 25 degrees C) and four SWC (10%, 20%, 30% and 40% by weight). After four one-month incubation experiments, we found that (1) plant communities, temperature, and SWC significantly influenced Rs and Delta IN; (2) the highest Rs and Delta IN occurred at 25 degrees C and 30% SWC in the C4 plant community; (3) in the driest soils, N was immobilized in both communities regardless of temperature. We suggest that there is a greater limitation to C and N mineralization in the C3 plant community than in the C4 plant community making the C3 community less sensitive to variation in temperature and SWC.