Will nitrogen deposition mitigate warming-increased soil respiration in a young subtropical plantation?

Global change such as climate warming and nitrogen (N) deposition is likely to alter terrestrial carbon (C) cycling, including soil respiration (Rs), the largest CO2 source from soils to the atmosphere. To examine the effects of warming, N addition and their interactions on Rs, we conducted a two-way factorial soil warming (control, 5 degrees C warming) and N addition (control, 40 and 80 kg N ha(-1) yr(-1)) mesocosm experiment in subtropical China. We measured Rs and nutrient availability. We found warming alone increased Rs by 15%, but warming plus high N addition treatment appeared to have offsetting effects as these plots were not significantly different from unheated and unfertilized controls. Warming alone increased soil available phosphorus (P) but availability declined in response to warming plus N additions. N additions alone had no effect on Rs in this study. Our results suggest that future increases in N deposition could mitigate warming-increased Rs in P-limited and relatively N-saturated subtropical forest ecosystems.