Litter priming and trenching greatly affect soil respiration in a mature subtropical evergreen broadleaf forest in Southwestern China

Global warming will stimulate primary production, which is likely to drive shifts in litter production and lead to an increase in carbon (C) inputs to soil. However, the effects of such changes on soil C cycling in subtropical forests remain largely unknown. In a typical subtropical evergreen broadleaved forest in Southwestern China we conducted a controlled experiment that included addition and removal of litter, and trenching. Annual soil respiration in control, trenching, litter addition, and litter removal treatments were 1083.47, 521.50, 1363.30, and 896.15 g C m(-2) y(-1), respectively. Soil respiration was significantly related to temperature in all treatments, but was independent of soil moisture, except in control plots. Q(10) values in control, trenching, litter addition, and litter removal treatments were 3.46, 6.36, 2.72, and 4.85, respectively. Litter addition reduced Q(10), but litter removal and trenching increased it. Average heterotrophic soil respiration produced C in the amount equivalent to 48% of the efflux from the soil. Soil respiration in the litter addition treatment was 25% higher than in the control treatment; this increase is about 8% larger than the 17% decrease in soil respiration caused by litter removal. This implies a priming effect on soil respiration. Our results suggest that increases in litter production in response to human disturbances and global warming could have rapid and important consequences on soil respiration in subtropical evergreen broadleaved forests.