Detecting Vulnerability of Humid Tropical Forests to Multiple Stressors

Humid tropical forests are under increasing threats from changes in land-use and climate. Here, we develop a new tropical forest vulnerability index (TFVI) to detect and evaluate the vulnerability of global tropical forests to these threats across space and time. We show that the climate change as an emerging large-scale and persistent stress together with the land-use change have slowed the recovery rate of forest carbon cycling since the early 1980s. Temporal autocorrelation, as an indicator of this slow recovery, rises substantially for above ground biomass, gross primary production, and evapotranspiration when climate stress reaches a critical level. Forests in Americas exhibit extensive vulnerability to coupled land-use and climate change, while in Africa show relative resilience to climate, and in Asia reveal more vulnerability to land-use and fragmentation. TFVI is capable to systematically track the response of tropical forests to multiple stressors and provides spatially explicit early-warning signals of critical transitions.

湿润热带森林正面临着来自土地利用变化与气候变化的日益加剧的威胁。本研究构建了全新的热带森林脆弱性指数（Tropical Forest Vulnerability Index, TFVI），用于在全球时空尺度下检测并评估全球热带森林面对上述威胁时的脆弱性。研究结果显示，作为一种新兴的大规模持续性胁迫因子，气候变化与土地利用变化自20世纪80年代初以来，已减缓了森林碳循环的恢复速率。当气候胁迫达到临界水平时，作为该缓慢恢复过程的指示指标，时间自相关性在地上生物量、总初级生产力与蒸散发三项指标上均出现显著上升。美洲地区的热带森林对土地利用与气候变化的复合胁迫表现出广泛的脆弱性；非洲地区的热带森林对气候胁迫则呈现出相对的韧性；而亚洲地区的热带森林则更易受土地利用变化与森林破碎化的影响。该热带森林脆弱性指数（TFVI）能够系统性追踪热带森林对多重胁迫因子的响应，并为临界转变提供空间明晰的早期预警信号。