美国亚利桑那大学Chen, Shuli和Saleska, Scott R.团队报道，生物地理学预测亚马逊森林抵御干旱的恢复力和脆弱性。相关论文于2024年6月19日发表在《自然》杂志上。

据介绍，亚马逊河流域拥有地球上最广阔的热带森林，但亚马逊河流域大气中CO₂的碳汇正在减少，因为森林砍伐和与气候变化相关的干旱威胁着这些森林，使其超过崩溃的临界点。森林的恢复力(光合变绿)和脆弱性(褐变和树木死亡)表现出复杂的干旱响应，这很难单独用气候变化来解释。

该团队将遥感光合指数与地面测量的树木人口统计相结合，以确定不同完整森林生态区(由地下水位深度、土壤肥沃度和质地以及植被特征决定)的干旱恢复/脆弱性的潜在机制。在肥力较高的亚马逊南部地区，干旱响应由地下水位深度决定的，浅地下水位森林具有弹性绿化(在那里，FC碰碰胡老虎机法典-提高赢钱机率的下注技巧的水可用性增强了对过量阳光的响应)，与较深地下水位森林的脆弱性(褐变和过量树木死亡)形成对比。

值得注意的是，浅水地下水位森林的恢复能力随着干旱的延长而减弱。相比之下，土壤肥力较低的亚马逊北部，树木生长缓慢，但更顽强(或者，有根深蒂固水通道的高大森林)，支持了更具抗旱能力的森林不受地下水位所影响。这种干旱响应的功能性生物地理学为保护决策提供了一个框架，并改进了对未来气候变化的异质性森林响应的预测。研究人员强调，亚马逊地区最多产的森林也面临最大的风险，更长/更频繁的干旱正在破坏亚马逊森林恢复力的多种生态水文战略和能力。

附：英文原文

Title: Amazon forest biogeography predicts resilience and vulnerability to drought

Author: Chen, Shuli, Stark, Scott C., Nobre, Antonio Donato, Cuartas, Luz Adriana, de Jesus Amore, Diogo, Restrepo-Coupe, Natalia, Smith, Marielle N., Chitra-Tarak, Rutuja, Ko, Hongseok, Nelson, Bruce W., Saleska, Scott R.

Issue&Volume: 2024-06-19

Abstract: Amazonia contains the most extensive tropical forests on Earth, but Amazon carbon sinks of atmospheric CO₂ are declining, as deforestation and climate-change-associated droughts threaten to push these forests past a tipping point towards collapse. Forests exhibit complex drought responses, indicating both resilience (photosynthetic greening) and vulnerability (browning and tree mortality), that are difficult to explain by climate variation alone. Here we combine remotely sensed photosynthetic indices with ground-measured tree demography to identify mechanisms underlying drought resilience/vulnerability in different intact forest ecotopes (defined by water-table depth, soil fertility and texture, and vegetation characteristics). In higher-fertility southern Amazonia, drought response was structured by water-table depth, with resilient greening in shallow-water-table forests (where greater water availability heightened response to excess sunlight), contrasting with vulnerability (browning and excess tree mortality) over deeper water tables. Notably, the resilience of shallow-water-table forest weakened as drought lengthened. By contrast, lower-fertility northern Amazonia, with slower-growing but hardier trees (or, alternatively, tall forests, with deep-rooted water access), supported more-drought-resilient forests independent of water-table depth. This functional biogeography of drought response provides a framework for conservation decisions and improved predictions of heterogeneous forest responses to future climate changes, warning that Amazonia’s most productive forests are also at greatest risk, and that longer/more frequent droughts are undermining multiple ecohydrological strategies and capacities for Amazon forest resilience.

DOI: 10.1038/s41586-024-07568-w

Source: https://www.nature.com/articles/s41586-024-07568-w