Soil respiration is correlated with rainfall and soil moisture at multiple temporal scales in a seasonal wet tropical forest

Soil respiration is the second largest natural flux of carbon (C) between terrestrial ecosystems and the atmosphere, with tropical forests amongst the largest contributors of such soil-derived carbon efflux. With climate change expected to drive changes in both temperature and rainfall, our ability to predict responses of the carbon cycle in the future hinges upon an understanding of how these factors influence soil respiration (Rs). However, these relationships remain poorly characterised across the seasonal tropics, especially south Asia. Here, for two seasonal tropical sites in the Western Ghats of India, we characterised annual, seasonal and temporal variation in Rs and assessed its temperature and moisture sensitivity over 6 years. At both sites, Rs was positively correlated with temperature at the instantaneous scale, but showed no relationship with temperature at seasonal or annual scales. In contrast, Rs showed significant relationships with rainfall and soil moisture at all temporal scales. At the annual scale, respiration was negatively correlated with total annual rainfall. At the seasonal scale, wet season Rs was significantly lower than in the dry season. At the instantaneous scale, Rs showed a parabolic relationship with soil moisture, where soil respiration increased with soil moisture up to ∼21% and decreased beyond that point. Our results suggest that future responses of soil respiration in this seasonal tropical forest will largely be driven by changes in the Indian Summer Monsoon, not only mean annual precipitation, but also the frequency and intensity of extreme rainfall events.