Impacts of rising atmospheric dryness on terrestrial ecosystem carbon cycle
摘要
Rising atmospheric dryness is affecting the terrestrial ecosystem carbon cycle through its influence on plant physiology. In this Review, we synthesize historical and projected trends in atmospheric vapour pressure deficit (VPD), a proxy for atmospheric dryness, and the mechanisms by which it affects the terrestrial carbon cycle. Since the late 1990s, global mean VPD has increased at a mean rate of 0.0155 ± 0.0041 hPa yr−1. VPD-driven reductions in leaf area index (0.11 ± 0.07 m2 m−2 hPa−1, 1982–2015), gross primary production (13.82 ± 3.12 PgC hPa−1, 1982–2015), light use efficiency (0.04 ± 0.02 gC MJ−1 hPa−1, 2001–2020) and net ecosystem production (5.59 ± 1.15 PgC hPa−1, 1982–2013) have been observed globally. However, attributing changes in the terrestrial carbon cycle to VPD is still challenging, owing to the confounding influence of other environmental factors, such as soil moisture, temperature and radiation. The mechanisms underlying plant responses to VPD — which include stomatal closure, hydraulic failure, abscisic acid biosynthesis, and cascading effects on fires and soil moisture deficits — are also poorly constrained, limiting the predictive capabilities of terrestrial carbon cycle models. Future research should prioritize establishing global VPD-manipulation experiments to enhance understanding of feedbacks between VPD, plants and the carbon cycle, and these mechanisms should then be integrated into terrestrial carbon cycle models.