Trajetórias de crescimento de Cedrela spp. em florestas neotropicais úmida e sazonalmente seca

Abstract

The Neotropical region harbours one among the world's most threatened megadiverse forests. Therefore, the development of studies that produce reliable data and arguments to favour its conservation is urgent. Dendrochronology, the science of tree-rings, is a tool that allows the reconstruction of the tree's life history and thus, a better understanding of tree growth. In view of its widespread distribution in the Neotropics and the formation of very distinct annual growth rings, the genus Cedrela is the target for this study. We reconstructed the growth trajectories of Cedrelaspp.trees in two contrasting regions: Cedrelaodorata from the Tropical Moist Forest of the Amazon and Cedrelafissilis from the Tropical Dry Forest of the Cerrado-Caatingaecotone. We used cross sections and cores obtained by increment borer. We prepared the samples following standard dendrochronological procedures, including the skeleton-plot method for crossdating tree-ring time series. We calculated relative changes in growth per individual, detected annual disturbance events (releases and suppressions) and tested the climatic correlation using the Palmer Drought Severity Index (PDSI) at both sites. When we synchronized the frequency of the disturbance events per calendar year, we observed that the population of Cedrelaodorata from the moist forest had a lower frequency compared to the C. fissilis population from the dry forest, where suppression events are more related to climatic influence. When related to tree age, the moist forest presented low frequency of suppression events, while the dry forest presented low frequency of suppression and release events. The radial growth pattern of Tropical Dry Forest correlated positively with the index derived from PDSI, whereas no correlation was found for the moist forest, showing that tree growth variation may be influenced by complex forest dynamics, including light competition and other non-climatic factors. These results provide information on the growth of Neotropical native species that can serve as a basis for future research and monitoring for conservation.