Do Tropical Storm Regimes Influence the Structure of Tropical Lowland Rain Forests?

Abstract

It has been suggested that the average canopy height of Madagascar's lowland rain forests is shorter and the average tree density is greater than in other tropical lowland rain forests of the world. The cause was hypothesized to be frequent cyclone disturbances. We compared the structure of the lowland rain forests in Madagascar to the structure described in published accounts of other tropical lowland rain forests. We found that the eastern coastal lowland forests of Madagascar have short canopy heights relative to that of many other lowland tropical rain forests, and that these Malagasy forests also have relatively high tree densities. On a worldwide basis, there is a significant correlation between short forest canopies and occurrence of tropical cyclones. The association between high tree density and occurrence of tropical cyclones is valid for Africa, but the pattern does not hold up globally. RÉSUMÉ II a été conjecturé que la taille moyenne de la canopée des forȩts basses ombrophiles de Madagascar est moindre, et que la densité des arbres est plus grande, que pour d'autres forȩts tropicales ombrophiles du monde. L'hypothèse a été avancée que les perturbations fréquentes des cyclones en sont la cause. Nous avons compare la structure des forȩts ombrophiles de basse altitude de Madagascar avec la structure d'autres forȩts tropicales ombrophiles du monde. La hauteur de la canopée des foréts de I'est de Madagascar est relativement plus courte que celles de beaucoup d'autres forȩts tropicales humides de basse altitudes, et la densité des arbres est relativement élevée. A l'échelle globale, il y a une relation entre courte canopée et perturbations par les cyclones. La relation entre densité des arbres et perturbations par les cyclones est validée par cette étude seulement pour le continent Africain.

The value of forest fragments for maintaining amphibian diversity in Madagascar

“…The eastern rainforest belt of Madagascar was originally completely forested (Green and Sussman, 1990) and thus the majority of species in our study region should be typical forest species. Nevertheless, frequent cyclone disturbances influence forest structure (de Gouvenain and Silander, 2003;Birkinshaw and Randrianjanahary, 2007), microclimate (Turton and Siegenthaler, 2004), and tree biology (Ganzhorn, 1995), and thus may have also favored amphibian adaptations to disturbed habitats. Consequently, species adapted to natural disturbances may have a higher ability to cope with anthropogenic disturbances.…”

Cyclones influence native plant diversity on 22 remote high islands of French Polynesia and Pitcairn (eastern Polynesia)

“…Some tree species are more vulnerable to cyclonic winds (Burslem, Whitmore, & Brown, 2000;Curran et al, 2008;Elmqvist et al, 1994;Herbert, Fownes, & Vitousek, 1999) and this selective mortality influences structure and composition of the tropical rain forests in the long term (Keppel, Buckley, & Possingham, 2010). Indeed, lower canopies and higher tree densities on the windward coast of Madagascar (de Gouvenain & Silander, 2003) and in Southwest Pacific islands (Keppel et al, 2010) have been related to the high frequency of cyclones in these regions. In the long term, a high frequency of cyclones disturbance drives diversity not only in tree communities (de Gouvenain & Silander, 2003;Keppel et al, 2010), but also in non-arborescent understory communities where an increasing diversity of ferns and vines was observed in Puerto Rico (Royo, Scalley, Moya, & Scatena, 2011).…”

Tropical forest structure: a missing dimension to Pleistocene landscapes

“…Field research indicates that tree mortality in ENSO-induced drought events is much higher relative to other years (Williamson et al, 2000;. De Gouvenain and Silander (2003) demonstrate a statistical significance between the high frequency of cyclones hitting Madagascar and the short and dense canopy characteristics of lowland rainforest found on the island. More profound variations in Amazonian landscape LAI can occur in seasonal forest, where increased drought during the dry season causes substantial reductions in forest LAI.…”