Nitrogen addition stimulates different components of soil respiration in a subtropical bamboo ecosystem

Soil respiration is an important carbon (C) flux of global C cycle, and greatly affected by nitrogen (N) addition in the form of deposition or fertilization. However, the effects of N addition on the different components of soil respiration are poorly understood. The aim of this study is to investigate how the components of soil respiration response to N addition and the potential mechanisms in a subtropical bamboo ecosystem. Four N treatment levels (0, 50, 150, 300 kg N ha−1 year−1) were applied monthly in a Pleioblastus amarus bamboo plantation since November 2007. Total soil respiration (RST) and soil respiration derived from litter layer (RSL), root-free soil (RSS), and plant roots (RSR) were measured for one year (February 2010 to January 2011). The results showed that the mean rate of RST was 428 ± 11 g C m−2 year−1, and RSL, RSS, RSR contributed (30.2 ± 0.7)%, (20.7 ± 0.9)%, and (49.1 ± 0.7)%, respectively. The temperature coefficients (Q10) of RST, RSL, RSS, and RSR were 2.87, 2.28, 3.09, and 3.19, respectively, in control plots. Nitrogen additions significantly increased RST and its three components. RSR was stimulated by N additions through increasing fine root biomass and root metabolic rate. The positive effects of N additions on soil fertility, microbial activity, and the quality and amount of aboveground litterfall also stimulated other CO2 production processes. In the background of increased N input, response of RST and components of RST are primarily due to the positive response of plant growth in this bamboo ecosystem.