Dendrocronologia e caracterização do crescimento radial de espécies da família Leguminosae em uma Floresta Estacional Semidecidual das Terras Baixas Mata Atlântica

Abstract

The understanding of tree growth dynamics is essential for the protection and the sustainable use of forest resources. In this way, the study of tree ringsrepresents an important knowledge, as it allows determining increment rates, life expectancy and tree responses to environmental variations. Thus, the present study aims to investigate radial growth dynamics of Leguminosae species native from Seasonal Semidecidual Lowland Forest. To this end, trees of Dalbergia nigra, Pterocarpus rohrii (Papilionoideae), Copaifera langsdorffii, Schizolobium parahyba e Senna multijuga (Caesalpinoideae) from a native area and from experimental plantations were selected at Reserva Natural Vale, in order: i) to evaluate the distinctiveness of tree rings in the study site; ii) to determine the periodicity of tree rings formation, through trees from experimental plantations with known age; iii) to characterize trees grow that plantation and natural area conditions; iv) to evaluate the influence of climatic factors on tree rings width, and v) to evaluate age structure of trees growing in the native area, along a topossequence at the margin of Pau Atravessado River, which is formed by swamp, river slope and plateau.For the investigation of tree rings in the experimental plantations, stem samples were obtained through the section of stem discs. In the trees from the native area, stem samples were obtained with increment borer. For microscopic analysis of tree rings, the samples were sectioned and processed following usual Plant Anatomy techniques. For macroscopic analysis, samples were polished and analyzed under a stereoscope microscope, for determining the number of growth rings. Rings width was measured with Image Pro Plus software.All the species showed distinct tree rings, and the number of rings corresponded to the age of the planted trees, or to values very close to the plantation age.This result led to the characterization of tree rings as annual rings for the five studied species. Values of increment rates; growth period needed for economical utilization; the growth trajectories and the relation among age and diameter of the studied species were determined for growth comparison among the plantation and the native area. The annual growth rates of the early secondary species (C. langsdorffii, D. nigra; and P. rohrii) were higher in the plantation area, while growth rates of the pioneer species (S. multijuga and S. parahyba) were higher in the native area.Dendroclimatogical analysis were made for S. parahyba growing in the native area. The results showed that rainfall has positive influence and temperature has negative influence on the species radial growth. The analysis of tree age structure along the topossequence indicated the presence of older trees at river slope and plateau regions, which indicates that areas located further from the river bank must also be included as priority sites in the conservation of riparian forests.