Declining resistance of vegetation productivity to droughts across global biomes

Terrestrial vegetation productivity or gross primary productivity (GPP) is the main driver of the land carbon sink, and frequent and severe droughts largely affect the interannual variability of vegetation productivity and therefore land carbon sink. However, a comprehensive evaluation of spatiotemporal variation in drought response of global vegetation productivity is still lacking. Here, we used five long-term satellite-derived time series to quantify the global pattern and temporal changes of drought resistance (the ability to maintain its original levels during drought) and resilience (the ability to recover to pre-drought levels after droughts) during 1982-2015. Temporally, observed drought resistance showed a significantly declining trend across different biomes (P < 0.001), with evergreen broadleaf forests decreasing most (P < 0.001). Moreover, drought resilience showed a slight decreasing trend (P < 0.05) and has not decreased significantly among biomes. We attributed this declined resistance predominantly to temperature and soil moisture. Earth system models underestimate the drought resistance and resilience for the historical period, and project declining drought resistance and resilience to the end of 21st century. Our finding of the significant declining resistance but no increase in resilience implies the vulnerability of terrestrial carbon sinks to withstand future droughts.

Automated summary

This study evaluates the drought resistance and resilience of global vegetation productivity using long-term satellite observations, and finds a significant decline in drought resistance but no significant change in resilience. Temperature and soil moisture are identified as the main factors affecting drought resistance. Earth system models underestimate the historical drought resistance and resilience, and project further decline in the future.