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