Short-term response of soil respiration to nitrogen fertilization in a subtropical evergreen forest

Little is known about the effects of nitrogen (N) additions on soil respiration (Rs) in tropical and subtropical forests. We therefore conducted an N-fertilization experiment in a subtropical evergreen forest in eastern China to better understand the short-term response of Rs to increased N availability. N additions stimulated Rs compared to control plots, yet the magnitude of the increase depended on the amount of N added, with Rs being greater in the low-N treatment (50 kg N ha−1 yr−1) than the high-N treatment (100 kg N ha−1 yr−1). Differences in Rs among treatments correlated with changes in fine root biomass, suggesting increases in Rs reflect those in autotrophic respiration. Our findings challenge the dogma that N fertilization often reduces soil respiration and highlights the need to better understand the effects of low N additions, so as to reliably predict how projected climate change scenarios may affect the cycling of soil carbon (C) in tropical and subtropical forests.