Widespread but divergent drought legacy effects on gross primary productivity

Abstract Droughts can impact terrestrial ecosystems concurrently but also lagged in time as legacy effects. Although drought legacy effects on plants have been thoroughly shown using tree radial growth and greenness, understanding of legacy effects on gross primary productivity (GPP) remains limited. Here, we quantify for the first time drought legacy effects on GPP at 73 long-term eddy covariance sites across biomes and climate regions. We find sizeable and widespread drought legacy effects at 57 out of 59 sites experiencing strong droughts. We find drought legacy effects diverge globally, with about as many sites experiencing positive (30 sites) and negative (27 sites) legacy effects. Grasslands tend to exhibit positive legacy effects, with GPP being stimulated after drought, whereas other ecosystems such as forests show a mixture of positive, negative, or no legacy effects. We find climatological aridity and drought duration to be the most relevant factors explaining spatial variability of drought legacy effects among forest sites. Our results demonstrate that drought legacy effects on GPP are widespread but divergent and should be considered more explicitly for understanding and projecting the impacts of drought on terrestrial carbon cycling.