Canopy asymmetry in solitary Diphysa americana trees: wind and landscape on the Mexican coast

Abstract

On the coast of the Gulf of Mexico, Diphysa americana is one of the first species to colonize coastal dunes and it is very common to find this species as isolated trees in abandoned sites that were deforested for agricultural purposes. Different species of frugivorous birds perch in these trees, dropping fruit and seeds in their shade. This species, constantly exposed to intense winds from the north, favors and has a selective effect on the establishment of species from the seasonal dry forest beneath its canopy. In this study we evaluated the direction of prevailing wind and its relationship to canopy shape (thigmotropism). We also evaluated differences in the abundance and richness of the plants that establish in the shade of D. americana by comparing trees exposed and not exposed (control) to the prevailing winds. The results indicate that the prevailing winds come from the north and that D. americana is sensitive to both wind strength and direction (F(3) = 13.43, P < 0.001). Its canopy stretches towards the south, where we find greater plant cover (F(3) = 29.61 P < 0.001) and a different species composition compared with the cover to the north. Canopy asymmetry results in differences in the abundance and composition of the species below, and this may have consequences to the process of succession. D. americana trees contribute to the regeneration and conservation of seasonal forest on the coast of central Veracruz, Mexico.