Rainfall pulse primarily drives litterfall respiration and its contribution to soil respiration in a young exotic pine plantation in subtropical China

Although litterfall respiration (R-L) is a key process of soil carbon dynamics in forests, factors that drive R-L and its contribution to soil respiration (R-S) have not been sufficiently studied. Using a litter removal method, we researched R-L and the ratio of R-L:R-S in a 20-year-old exotic slash pine (Pinus elliottii Englem.) plantation in subtropical China. Soil temperature explained 67%, 78%, and 25% of variation in R-S, mineral soil respiration (RS-L), and RL, respectively, but had little impact on R-L:R-S. To study influences besides temperature, measured R-S and RS-L were normalized using the Arrhenius equation. Even though this subtropical plantation was characterized by a humid climate with abundant precipitation, a rainfall pulse induced increase in soil moisture primarily drove R-L and its contribution to R-S but depressed RS-L. The response of R-L to rainfall and soil moisture was significantly more sensitive than that of RS-L. Furthermore, the effects of rainfall and soil moisture on R-S, R-L, and R-L:R-S were higher during the dry season (July-December) than during the wet season (January-June). In the context of climate change, R-L and its contribution to R-S are expected to decrease because of the predicted decrease in rainfall amount and frequency in subtropical regions.