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Title: Empirical evidence for resilience of tropical forest photosynthesis in a warmer world
Authors: Smith, Marielle N.
Taylor, Tyeen C.
van Haren, Joost L.M.
Rosolem, Rafael
Restrepo-Coupé, Natalia
Adams, John
Wu, Jin
Oliveira, Raimundo Cosme de
Silva, Rodrigo da
Araüjo, Alessandro Carioca de
Camargo, Plínio Barbosa
Huxman, Travis E.
Saleska, Scott Reid
Issue Date: 2020
metadata.dc.publisher.journal: Nature Plants
metadata.dc.relation.ispartof: Volume 6, Número 10, Pags 1225-1230
Abstract: Tropical forests may be vulnerable to climate change1–3 if photosynthetic carbon uptake currently operates near a high temperature limit4–6. Predicting tropical forest function requires understanding the relative contributions of two mechanisms of high-temperature photosynthetic declines: stomatal limitation (H1), an indirect response due to temperature-associated changes in atmospheric vapour pressure deficit (VPD)7, and biochemical restrictions (H2), a direct temperature response8,9. Their relative control predicts different outcomes—H1 is expected to diminish with stomatal responses to future co-occurring elevated atmospheric [CO2], whereas H2 portends declining photosynthesis with increasing temperatures. Distinguishing the two mechanisms at high temperatures is therefore critical, but difficult because VPD is highly correlated with temperature in natural settings. We used a forest mesocosm to quantify the sensitivity of tropical gross ecosystem productivity (GEP) to future temperature regimes while constraining VPD by controlling humidity. We then analytically decoupled temperature and VPD effects under current climate with flux-tower-derived GEP trends in situ from four tropical forest sites. Both approaches showed consistent, negative sensitivity of GEP to VPD but little direct response to temperature. Importantly, in the mesocosm at low VPD, GEP persisted up to 38 °C, a temperature exceeding projections for tropical forests in 2100 (ref. 10). If elevated [CO2] mitigates VPD-induced stomatal limitation through enhanced water-use efficiency as hypothesized9,11, tropical forest photosynthesis may have a margin of resilience to future warming. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.
metadata.dc.identifier.doi: 10.1038/s41477-020-00780-2
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