Seasonal variations in the response of soil CO2 efflux to precipitation pulse under mild drought in a temperate oak (Quercus variabilis) forest

Abstract

Extreme precipitation events are predicted to increase in intensity and duration, with uncertain implications for terrestrial carbon (C) cycling. However, knowledge on the responses of soil CO2 efflux to precipitation pulses in different seasons remains limited. Here we assessed the impacts of episodic precipitation pulses on soil respiration (SR) and its components [heterotrophic respiration (HR) and autotrophic respiration (AR)] under mild drought in different seasons in a temperate oak forest, Central China. Results showed that SR (24 h) increased with elevated precipitation levels, and the estimated precipitation-induced increases in the total amount of SR (3 months) in summer (17.86 g C m−2) and autumn (13.57 g C m−2) were greater than that in spring (9.73 g C m−2) and winter (3.71 g C m−2). Effects of precipitation pulse on HR and AR (24 h) varied with seasons, showing significant positive effects on HR in winter and AR in summer. Precipitation events significantly reduced the proportion of HR in SR in summer and autumn, but not in winter. Across all treatments, post-precipitation soil temperature, pre-precipitation soil moisture, and soil inorganic nitrogen are primarily responsible for the precipitation-induced increases in SR, whereas the stimulated HR after precipitation is largely depended on soil total porosity, pre-precipitation soil moisture, and microbial biomass C. Our study suggests that sporadic precipitation events have differential influences on SR and its components in different seasons. Our findings also emphasize that the importance of incorporating episodic extreme precipitation events and its influence on soil CO2 efflux into the future predictions of forest C cycling under climate change.