Tracking Global Patterns of Drought‐Induced Productivity Loss Along Severity Gradient

Abstract

Droughts significantly impact land carbon uptake by reducing the gross primary productivity (GPP). Projections suggest an increase in severe and extreme droughts in the twenty‐first century. Despite the importance of droughts on carbon uptakes, it remains unclear about the GPP responses under different drought severity and its changes under current climate changes. Using four state‐of‐the‐science GPP products, we showed that moderate (−1 ≤ SPEI < −1.5), severe (−1.5 ≤ SPEI < −2), and extreme (SPEI < −2) droughts caused on average 5%, 7%, and 9% GPP reductions, respectively, across the globe during the recent decades. Although the mean reductions varied among GPP products, we observed similar spatial patterns. The reductions increased significantly along the severity gradient, while the sharpest increases were observed in semi‐arid and grassland ecosystems. On a biome level, we found that the reductions increased nonlinearly with increasing drought severities for almost all vegetation types, but the trends and slopes varied significantly. In addition, we found that the mean drought‐induced GPP reductions had increased in dry ecosystems but decreased in humid ecosystems from 2001–2008 to 2009–2016. The result highlights the potential increase of drought‐induced land carbon sink loss responding to more extreme climates and offers new perspectives to improve the prediction of global carbon fluxes in a changing climate.

Nitrogen deposition differentially regulates the sensitivity of gross primary productivity to extreme drought versus wetness

“…Thus, the conservation and management of these ecosystems deserve further attention. Third, the proposed mechanisms can help reconcile the conflicting results reported in previous case studies on various GPP responses to precipitation extremes (Jung et al, 2019;Li et al, 2023;Wang, Fu, et al, 2022). However, the unexplained variation in GPP responses by our model reflects the complexity of this issue (Figure 6), with other factors (e.g., symbiotic fungi that enhance plant water uptake) possibly also playing a role (Cleland et al, 2019).…”