Extreme rainfall impacts on soil CO2 efflux in an urban forest ecosystem in Beijing, China

Extreme rainfall events are infrequent disturbances that affect urban environments and soil respiration (Rs). Using data measured in an urban forest ecosystem in Beijing, China, we examined the link between gross primary production (GPP) and soil respiration on a diurnal scale during an extreme rainfall event (i.e., the "21 July 2012 event"), and we examined diel and seasonal environmental controls on Rs. Over the seasonal cycle, Rs increased exponentially with soil temperature (Ts). In addition, Rs was hyperbolically related to soil volumetric water content (VWC), increasing with VWC below a threshold of 0.17 m(3) m(-3), and then decreasing with further increases in VWC. Following the extreme rainfall event (177 mm), Rs showed an abrupt decrease and then maintained a low value of similar to 0.3 mu mol m(-2) s(-1) for about 8 h as soil VWC reached the field capacity (0.34 m(3) m(-3)). Rs became decoupled from Ts and increased very slowly, while GPP showed a greater increase. A bivariate Q(10)-hyperbolical model, which incorporates both Ts and VWC effects, better fits Rs than the Q(10) model in summer but not for whole year.