Como a desfolha causada por Atta spp. (Hymenoptera: Formicidae) afeta as variáveis dendrométricas de eucalipto em biomas e sítios de produtividade

Abstract

Eucalyptus plantations are distributed all over Brazil, and leaf-cutting ants are the main pests of these plantations. The eucalyptus plantations are inserted in different biomes and productivity sites, which present different climatic characteristics, such as availability of water, nutrients, and light. Defoliation associated with these variables may cause differences in tree growth. The objective of this work was to verify the influence of infestation of leafcutting ants, ant size, and defoliation, together with the effect of different biomes, productivity sites, spacing and age on the growth of Eucalyptus urograndis until the end of the production cycle; to verify the diameter growth, height and volume of wood of Eucalyptus urograndis defoliated by leaf-cutting ants at different intensities, in different productivity sites and in Mata Atlantica, Cerrado and Pampa biomes. Plots were laid in plantations that were between 2 and 3 years of age, inserted in each biomes. The defoliation caused by leaf-cutting ants was measured in each tree of the plot, being classified in relation to its intensity. The nests were measured, combated. The plots monitored until the end of the cycle. The diameter, height, and volume of each tree were measured every year until the end of the productive cycle, at 7 and 8 years. All plots were classified using the site index. The different biomes, productivity sites, spacing, age, loose soil and defoliation intensity were analysed in a single growth model, by adjusting for a multivariate multiple linear regression. The defoliation caused by leaf-cutting ants was one of the main causes of the reduction of the trees dendrometric variables. All the defoliation classes reduced the values of diameter, height and volume of wood in all sites of productivity and biomes. The 75-100% defoliation reduced the volume of wood in the Cerrado biome and the less productive site by 35% and 51.1%, respectively. It is concluded that the defoliation caused by leaf-cutting ants is one of the main factors that reduce the growth of eucalyptus at the end of the productive cycle. Different defoliation intensities cause distinct reductions in the Eucalyptus urograndis plants inserted in the Mata Atlântica, Pampa and Cerrado. The same happens with the plantations of different productivity sites. The joint action of defoliation and low productivity can compromise the increase of DAP, height, and volume of wood at the end of the productive cycle. The remnants of higher intensities cause higher reductions in DAP, height and higher volume of wood at the end of the productive cycle.