Data from: Globally consistent impact of tropical cyclones on the structure of tropical and subtropical forests

1. Tropical cyclones (TCs) are large-scale disturbances that regularly impact tropical forests. Although long-term impacts of TCs on forest structure have been proposed, a global test of the relationship between forest structure and TC frequency and intensity is lacking. We test on a pantropical scale whether TCs shape the structure of tropical and subtropical forests in the long-term. 2. We compiled forest structural features (stem density, basal area, mean canopy height and maximum tree size) for plants ≥ 10 cm in diameter at breast height from published forest inventory data (438 plots ≥ 0.1 ha, pooled into 250 1 x 1-degree grid cells) located in dry and humid forests. We computed maps of cyclone frequency and energy released by cyclones per unit area (power dissipation index, PDI) using a high- resolution historical databases of TCs trajectories and intensities. We then tested the relationship between PDI and forest structural features using multivariate linear models, controlling for climate (mean annual temperature and water availability) and human disturbance (human foot print). 3. Forests subject to frequent cyclones (at least one TCs per decade) and high PDI exhibited higher stem density and basal area, and lower canopy heights. However, the relationships between PDI and basal area or canopy height were partially masked by lower water availability and higher human foot print in tropical dry forests. 4. Synthesis. Our results provide the first evidence that TCs have a long-term impact on the structure of tropical and subtropical forests in a globally consistent way. The strong relationship between PDI and stem density suggests that frequent and intense TCs reduce canopy cover through defoliation and tree mortality, encouraging higher regeneration and turnover of biomass. The projected increase in intensity and poleward extension of TCs due to anthropogenic climate change may therefore have important and lasting impacts on the structure and dynamics of forests in the future.

1. 热带气旋（Tropical Cyclones, TCs）是一类大规模扰动事件，会持续对热带森林造成干扰。尽管已有研究提出热带气旋会对森林结构产生长期影响，但目前仍缺乏在全球尺度下检验森林结构与气旋发生频率、强度之间关系的研究。本研究在泛热带尺度上检验了热带气旋是否会长期塑造热带与亚热带森林的结构。
2. 我们从已发表的森林清查数据中收集了胸径≥10 cm的植物的森林结构特征，包括茎密度、胸高断面积、平均冠层高度以及最大树木尺寸；所涉及的样地共438个（单个样地面积≥0.1 ha，合并为250个1×1度的网格单元），分布于干旱与湿润森林中。我们利用高分辨率的热带气旋轨迹与强度历史数据库，计算了气旋发生频率与单位面积气旋释放能量（即功率耗散指数，Power Dissipation Index, PDI）的空间分布图。随后，我们在控制气候因子（年平均温度与水分可利用性）和人类干扰（人类足迹指数）的前提下，利用多元线性模型检验了功率耗散指数与森林结构特征之间的关系。
3. 经历高频气旋（至少每十年一次热带气旋）与高功率耗散指数的森林，呈现出更高的茎密度与胸高断面积，同时冠层高度更低。不过，在热带干旱森林中，功率耗散指数与胸高断面积或冠层高度之间的关系，部分被较低的水分可利用性与较高的人类足迹指数所掩盖。
4. 综合分析。本研究结果首次提供了全球一致的证据，表明热带气旋会以统一的长期方式影响热带与亚热带森林的结构。功率耗散指数与茎密度之间的强相关性表明，频繁且强烈的热带气旋会通过落叶与树木死亡降低冠层覆盖度，进而促进生物量的更新与周转。鉴于人为气候变化预计将导致热带气旋强度增加、影响范围向极地方向扩展，这一现象未来可能会对森林结构与动态产生重要且持久的影响。