Precipitation frequency controls interannual variation of soil respiration by affecting soil moisture in a subtropical forest plantation

Despite the significance of interannual variation of soil respiration (R-S) for understanding long-term soil carbon dynamics, factors that control the interannual variation of R-S have not been sufficiently investigated. Interannual variation of R-S was studied using a 6-year data set collected in a subtropical plantation dominated by an exotic species, slash pine (Pinus elliottii Engelm.), in China. The results showed that seasonal variation of R-S was significantly affected by soil temperature and soil water content (SWC). R-S in the dry season (July October) was constrained by seasonal drought. Mean annual R-S was estimated to be 736 +/- 30 g C.m(-2).year(-1), with a range of 706-790 g C.m(-2).year(-1). Although this forest was characterized by a humid climate with high precipitation (1469 mm.year(-1)), the interannual variation of R-S was attributed to the changes of annual mean SWC (R-2 = 0.66, P = 0.03), which was affected by annual rainfall frequency (R-2 = 0.80, P < 0.01) and not rainfall amount (P = 0.84). Consequently, precipitation pattern indirectly controlled the interannual variation of R-S by affecting soil moisture in this subtropical forest. In the context of climate change, interannual variation of R-S in subtropical ecosystems is expected to increase because of the predicted changes of precipitation regime.