Context Tropical forests are great reservoirs of carbon but they still suffer high rates of deforestation despite their importance. Yet, large uncertainty remains about the effects of landscape-level forest loss on biomass of forest remnants, and how these effects vary with disturbance intensity at larger regional scales. Objectives We evaluated whether the effects of forest loss on aboveground biomass (AGB) and stem density depend on the regional disturbance context. We predicted stronger responses to forest loss in intermediately disturbed regions (e.g. moderately deforested and defaunated). Methods Using a large dataset (10.399 trees) from Brazil and Mexico, we tested the response of AGB and stem density to landscape-level forest loss. We used 136 old-growth forest sites encompassing a gradient of forest cover distributed in eight Neotropical regions with contrasting disturbance conditions. Regional disturbance was ranked according to a gradient of deforestation level and history, matrix harshness, and defaunation degree. Results We found that forest loss simplified forest structure within forest remnants by decreasing AGB, but mainly in moderately disturbed regions. Yet, stem density was weakly related to forest cover in most regions. Conclusions The regional context can mediate the effect of landscape structure on AGB. Preventing forest loss and increasing forest cover at landscape scales are needed to preserve AGB and carbon stocks in anthropogenic landscapes. Such management strategies can be more effective in moderately disturbed regions where relatively small increases in forest cover can significantly enhance AGB, thereby optimizing the delivery of carbon storage and other key ecosystem services.

中文翻译：

---

景观森林损失降低了中度干扰地区新热带森林斑块的地上生物量

背景热带森林是巨大的碳库，但尽管它们很重要，但它们仍然遭受高森林砍伐率。然而，景观水平森林损失对森林残余生物量的影响以及这些影响如何随更大区域尺度的干扰强度而变化，仍然存在很大的不确定性。目标 我们评估了森林损失对地上生物量 (AGB) 和茎密度的影响是否取决于区域干扰背景。我们预测中度受干扰地区（例如中度森林砍伐和动物区系丧失）对森林丧失的反应更强烈。方法使用来自巴西和墨西哥的大型数据集（10.399 棵树），我们测试了 AGB 和茎密度对景观级森林损失的响应。我们使用了 136 个原始森林遗址，包括分布在八个新热带地区的森林覆盖梯度，具有对比的干扰条件。根据毁林程度和历史、基质粗糙程度和动物区系丧失程度的梯度对区域干扰进行排序。结果 我们发现森林流失通过降低 AGB 简化了森林残余区内的森林结构，但主要是在中度干扰地区。然而，在大多数地区，茎密度与森林覆盖率的相关性较弱。结论 区域环境可以调节景观结构对 AGB 的影响。需要在景观尺度上防止森林流失和增加森林覆盖，以保护人为景观中的 AGB 和碳储量。