Climate-driven disturbances amplify forest drought sensitivity

Abstract

Forests are a major terrestrial carbon sink, but the increasing frequency and intensity of climate-driven disturbances such as droughts, fires and biotic agent outbreaks is threatening carbon uptake and sequestration. Determining how climate-driven disturbances may alter the capacity of forest carbon sinks in a changing climate is crucial. Here we show that the sensitivity of gross primary productivity to subsequent water stress increased significantly after initial drought and fire disturbances in the conterminous United States. Insect outbreak events, however, did not have significant impacts. Hot and dry environments generally exhibited increased sensitivity. Estimated ecosystem productivity and terrestrial carbon uptake decreased markedly with future warming scenarios due to the increased sensitivity to water stress. Our results highlight that intensifying disturbance regimes are likely to further impact forest sustainability and carbon sequestration, increasing potential risks to future terrestrial carbon sinks and climate change mitigation. The authors quantify how climate change-related disturbances—drought, fires and insect outbreaks—impact the sensitivity of primary productivity to subsequent water stress. They show significant increases in sensitivity following drought and fire, leading to decreased terrestrial carbon uptake.