Résumé
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.