From tree to forest: Multiple carbon sink constraints

Schematic representation of carbon sink constraints under global change

Forests are the largest carbon sinks among terrestrial ecosystems. They sequestrate carbon primarily through tree growth but are currently under severe threat from global change. Recently, Tavares et al.1 identified a crucial trait, the xylem hydraulic safety margin (HSM), for predicting the risk of drought-induced tree mortality and biomass in Amazon forests. They also found that old-growth forests with wide HSMs build more biomass, while fast-growing forests are exposed to greater hydraulic risks and have a higher mortality rate. Therefore, they speculated that climate change could lead to further reductions in plant HSMs in the Amazon, resulting in a potential loss of biomass, which, in turn, would have major impacts on the carbon sink. However, a global perspective is urgently needed to evaluate the effects of global change on tree mortality and carbon sinks that encompass different physiological mechanisms and environmental factors across temporal and spatial scales. Therefore, we created a framework to examine forest response and adaptation in the context of future global change and discussed each issue.