Herbivoria e características foliares de espécies florestais sob condições contrastantes de irradiância

Abstract

The herbivory is one of the biotic stress factors that affect the initial establishment of plants. The main factors that direct herbivory in tree species are still not well understood. In the present study, we investigated whether contrasting conditions of irradiance influence the herbivore and whether functional traits are related to interspecific variation in herbivory under different irradiance conditions. We measured the herbivory (leaf area loss by insect attack) in five forest species in an experiment of enrichment plantation on secondary forest from two indicators, accumulated herbivory (punctual) and herbivory rate (measured over the time). The measurements were made in three irradiance conditions (low irradiance, PPFD = 2.6 mol m2 dia-1; moderate irradiance, PPFD = 19.2 mol m2 dia-1 and high irradiance, 33.1 mol m2 dia-1). In addition, we analyzed seven morphophysiological leaf traits: specific leaf area, leaf water content, sclerophyll, phenolic compounds, tannin, condensed tannin and non-structural carbohydrate concentration (starch, sucrose, glucose, fructose and raffinose). The effect of the irradiance condition on herbivory differed between the indicators used. This, because the punctual measurement (accumulated herbivory) does not capture the effect of the leaf dynamics of the species. The species with more intense leaf dynamics (Tabebuia rosea) had the highest rates of herbivory. Among the leaf morphophysiological traits, chemical defense characteristics (phenolic compounds and tannin) were more related to the interspecific variation in herbivory rates in the most contrasting irradiance conditions (low and high irradiance). The interspecific variation in herbivory rates suggests that the selective pressure of herbivores is mainly determined by the degree of leaf digestibility.