Temperature and substrate availability regulate soil respiration in the tropical mountain rainforests, Hainan Island, China

Abstract

AimsTropical forest plays a key role in global C cycle; however, there are few studies on the C budget in the tropical rainforests in Asia. This study aims to (i) reveal the seasonal patterns of total soil respiration (RT), litter respiration (RL) and soil respiration without surface organic litter (RNL) in the primary and secondary Asian tropical mountain rainforests and (ii) quantify the effects of soil temperature, soil moisture and substrate availability on soil respiration.MethodsThe seasonal dynamics of soil CO2 efflux was measured by an automatic chamber system (Li-8100), within the primary and secondary tropical mountain rainforests located at the Jianfengling National Reserve in Hainan Island, China. The litter removal treatment was used to assess the contribution of litter to belowground CO 2 production.Important FindingsThe annual RT was higher in the primary forest (16.73±0.87 Mg C ha-1) than in the secondary forest (15.10±0.26 Mg C ha-1). The rates of R T, RNL and RL were all significantly higher in the hot and wet season (May-October) than those in the cool and dry season (November-April). Soil temperature at 5cm depth could explain 55-61% of the seasonal variation in RT, and the temperature sensitivity index (Q10) ranked by RL (Q10 = 3.39) > R T (2.17) > RNL (1.76) in the primary forest and by RL (4.31) > RNL (1.58) in the secondary forest. The contribution of RL to RT was 22-23%, while litter input and RT had 1 month time lag. In addition, the seasonal variation of RT was mainly determined by soil temperature and substrate availability. Our findings suggested that global warming and increased substrate availability are likely to cause considerable losses of soil C in the tropical forests. © 2013 © The Author 2013.