Responses of forest soil respiration in the East Asian monsoon region to ENSO events

EL Nino-Southern Oscillation (ENSO) events exert significant effects on ecosystem carbon (C) cycle. However, how forest Rs in the East Asian monsoon region can respond to ENSO events remains unclear.

Based on multi-source databases, we conducted a synthesis to analyze the differential responses of forest Rs in different climatic zones of East Asia to ENSO events. The response differences between Rs components and the time lag effects were then further investigated.

We found that Rs in tropical-subtropical zones (TSZ) was positively correlated with ENSO, while in warm temperate zones (WTZ) it was negatively correlated, and there was no significant relationship in cold-middle temperate zones (CMTZ). Heterotrophic respiration and soil moisture also had significant linear correlation with ENSO. In TSZ, Rs lagged behind ENSO events by 9 months, while in WTZ, it led ENSO events by 4 months, and in CMTZ, Rs lagged behind ENSO events by 5 months.

The response of Rs to ENSO events was strongest in WTZ while weakest in CMTZ. Meanwhile, the response patterns in TSZ and WTZ were opposite. These abovementioned different responses were controlled by the precipitation anomaly arising from the variation of summer monsoon. Heterotrophic respiration was more sensitive to ENSO events than autotrophic respiration. The times lags of response of Rs to ENSO events in different climate zones were different. Our results have important implications for better understanding forest soil C emission processes under ENSO events and developing corresponding ecosystem C accumulation strategies.