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Empirical evidence for resilience of tropical forest photosynthesis in a warmer world
Nature Plants ( IF 18.0 ) Pub Date : 2020-10-12 , DOI: 10.1038/s41477-020-00780-2
Marielle N. Smith , Tyeen C. Taylor , Joost van Haren , Rafael Rosolem , Natalia Restrepo-Coupe , John Adams , Jin Wu , Raimundo C. de Oliveira , Rodrigo da Silva , Alessandro C. de Araujo , Plinio B. de Camargo , Travis E. Huxman , Scott R. Saleska

Tropical forests may be vulnerable to climate change1,2,3 if photosynthetic carbon uptake currently operates near a high temperature limit4,5,6. 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.



中文翻译:

在温暖的世界中热带森林光合作用的复原力的经验证据

如果目前光合作用的碳吸收量接近高温极限4,5,6,则热带森林可能容易受到气候变化1,2,3的影响。预测热带森林功能需要了解高温光合下降的两种机制的相对贡献:气孔限制(H1),由于温度相关的大气蒸气压亏缺(VPD)7的间接变化和生物化学限制(H2) ,直接的温度响应8,9。他们的相对控制预测了不同的结果-预期H1随着对未来共同出现的大气升高[CO 2],而H2则表明随着温度的升高,光合作用下降。因此,区分高温下的两种机理至关重要,但是却很困难,因为VPD与自然环境中的温度高度相关。我们使用森林中观宇宙来量化热带总生态系统生产力(GEP)对未来温度状况的敏感性,同时通过控制湿度来限制VPD。然后,我们通过四个热带森林站点的原位通量塔得出的GEP趋势,将当前气候下的温度和VPD效应解析解耦。两种方法均显示出GEP对VPD具有一致的负敏感性,但对温度几乎没有直接反应。重要的是,在低VPD的中观环境中,GEP持续高达38°C,这一温度超过2100年热带森林的预测(参考文献10))。如果升高的[CO 2 ]通过提高水的利用效率(假设为9,11)减轻了VPD引起的气孔限制,那么热带森林的光合作用可能具有抵御未来变暖的余地。

更新日期:2020-10-12
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