Tropical forests hold 30% of Earth's terrestrial carbon and at least 60% of its terrestrial biodiversity, but forest loss and degradation are jeopardizing these ecosystems. Although the regrowth of secondary forests has the potential to offset some of the losses of carbon and biodiversity, it remains unclear if secondary regeneration will be affected by climate changes such as higher temperatures and more frequent extreme droughts. We used a dataset of 10 repeated forest inventories spanning two decades (1999-2017) to investigate carbon and tree species recovery and how climate and landscape context influence carbon dynamics in an older secondary forest located in one of the oldest post-Columbian agricultural frontiers in the Brazilian Amazon. Carbon accumulation averaged 1.08 Mg ha-1 yr-1 , while species richness was effectively constant over the studied period. Moreover, we provide evidence that secondary forests are vulnerable to drought stress: carbon balance and growth rates were lower in drier periods. This contrasts with drought responses in primary forests, where changes in carbon dynamics are driven by increased stem mortality. These results highlight an important climate change-vegetation feedback, whereby the increasing dry-season lengths being observed across parts of Amazonia may reduce the effectiveness of secondary forests in sequestering carbon and mitigating climate change. In addition, the current rate of forest regrowth in this region was low compared with previous pan-tropical and Amazonian assessments - our secondary forests reached just 41.1% of the average carbon and 56% of the tree diversity in the nearest primary forests - suggesting that these areas are unlikely to return to their original levels on politically meaningful timescales.

中文翻译：

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评估亚马逊森林高度砍伐地区次生林的生长和气候敏感性

热带森林拥有地球 30% 的陆地碳和至少 60% 的陆地生物多样性，但森林的丧失和退化正在危及这些生态系统。尽管次生林的再生有可能抵消部分碳和生物多样性的损失，但尚不清楚次生再生是否会受到气候变化（如更高的温度和更频繁的极端干旱）的影响。我们使用了跨越 20 年（1999-2017 年）的 10 个重复森林清单的数据集来调查碳和树种恢复以及气候和景观背景如何影响位于哥伦比亚最古老的后哥伦比亚农业前沿之一的古老次生林中的碳动态。巴西亚马逊。碳积累平均 1.08 Mg ha-1 yr-1 , 而物种丰富度在研究期间实际上是恒定的。此外，我们提供的证据表明次生林容易受到干旱胁迫：干旱时期的碳平衡和增长率较低。这与原始森林的干旱反应形成对比，原始森林的碳动态变化是由茎死亡率增加驱动的。这些结果突出了一个重要的气候变化 - 植被反馈，亚马逊部分地区观察到的旱季长度增加可能会降低次生林在固碳和缓解气候变化方面的有效性。此外，与之前的泛热带和亚马逊地区评估相比，该地区目前的森林再生率较低——我们的次生林仅达到 41 片。