Experimental throughfall reduction barely affects soil carbon dynamics in a warm-temperate oak forest, central China

Changing precipitation patterns could affect soil carbon (C) cycling in China’s forests. A throughfall reduction (TFR) experiment was conducted in a warm-temperate oak forest in central China to examine effects of reduced precipitation on total soil respiration (SR), heterotrophic soil respiration (HR), autotrophic soil respiration (AR), soil microbial biomass, and fine root biomass from 2013 to 2016. Rain-out shelters, excluding ~50% of throughfall, were applied between May and September, thereby simulating a ~30% reduction in annual precipitation. Although soil moisture was significantly reduced during TFR, microbial biomass and HR remained unaffected. SR, AR, as well as fine root biomass increased during TFR in a comparable dry year, but remained unaffected during all other years. Annual rates of SR, HR, and AR were all unaffected by TFR. Our results indicate that a mild, steady, reduction in growing season precipitation does not affect soil organic matter decomposition in the oak forest ecosystem studied. Low SR rates during a natural dry-spell indicate that SR can be significantly decreased under more severe drought than imposed by the TFR treatment. Our data suggest a low soil moisture threshold of about 10 vol% for SR in the studied soil.