Herbivoria e defesas foliares ao longo de um gradiente sucessional em uma floresta tropical seca

Abstract

Herbivory and foliar defenses along a successional gradient in a tropical dry forest The aim of this study was compare the leaf damage caused by herbivores over a successional gradient in a tropical dry forest, relating this with sclerophyly, chemical defensive compounds, nutritional content and habitat structural complexity. Data of leaf damage, nitrogen content, phenolic compounds, tanins, sclerophylly and ambient complexity were take over three successional stages (early, intermediate and late). The samples were conducted in April-May of 2011 in 15 plots of 50 x 20 m each, located in three conservation units in north of Minas Gerais, Brazil. In each plot, the five most abundant plant species were selected and marked up to five individuals per specie. In each one, 20 leaves were collected randomly to make physicochemical analyses. Plots of early successional stages showed lowest values for height, density and holdridge complexity indices (HCI), compared with intermediate and late areas. In general way, the percentage of leaf area damage (2.5 - 4.2%), was lower than the observed in other studies in FTS areas, probably due the high concentration of defensive compounds or lower herbivores pressure in this ambient. Regarding defensive characteristics, specific leaf mass (SLM) varied along succession, decreasing gradually along stages, probably due the higher radiation observed in early areas. Levels of phenolic compounds were higher in late areas, and did not vary between early and intermediate stages. Tanins did not vary along successional stages, but showed negative relationship with herbivore. In another hand, HCI was positively related with herbivore and negatively with phenolic compounds concentration and SLM, probably due the high abundance of herbivores insects in late areas. Studies that investigate the relationship between habitat complexity and leaf features are needed to better understand ecological patterns in tropical dry forests.