A Global Comparison of Direct and Legacy Effects of Drought on Ecosystem Productivity

Terrestrial ecosystems serve as a major carbon (C) sink, but the increasing frequency and intensity of drought threaten the C sink and ecological communities. A comprehensive understanding of the change in ecosystem productivity due to the direct effect versus the legacy effect of drought is still lacking. We quantify the magnitude change in terrestrial gross primary production (GPP) globally due to both direct and long-term legacy effects. We find that the direct effect causes significant GPP decreases in magnitude of -5.94% [-13.40%, -3.21%] per year, while the legacy effect-induced GPP change is weaker and non-significant at a global scale. Drought legacy effects, however, are detectable in dry sub-humid regions. The direct effect-induced change is highly correlated with that of the legacy effect, and rooting depth is a key driver for both. These findings demonstrate the current resilience of global ecosystems to drought but underscore the long-term vulnerability of dryland ecosystems.