Dendroclimatologia da espécie arbórea Macrolobium acaciifolium (Fabaceae) em florestas de igapó na Amazônia central

Abstract

Forest dynamics in the Amazonian floodplains is strongly triggered by the flood-pulse. Trees respond to the unfavorable growth conditions during the flooded period by a cambial dormancy resulting in the formation of annual growth rings. In this study by indexed tree-ring chronologies of the tree species Macrolobium acaciifolium were established and compared with hydrological and climatic factors from three different black-water floodplain forests (igapó) in Central Amazonia growing under nutrient-poor conditions (Amanã and Uatumã Sustainable Development Reserves – RDSA e RDSU, respectively, National Park Anavilhanas - PNA). For data sampling in the field 20 emergent trees with diameter at breast height (DBH) above 60 cm were chosen at each site. Diameter and inundation height of each tree was measured and a wood sample of the trunk was obtained by an increment borer. Wood samples were sanded and tree rings were identified by marginal parenchyma bands to determine tree age and mean diameter increment rates. By cross-dating techniques indexed tree-ring chronologies were constructed for the PNA (1752-2006) and RDSU (1758-2004) using ten trees at each site. For the RDSA it was not possible to develop a tree-ring chronology due to a low number of samples with congruent ring-width patterns. Maximum tree age at the three sites varied between 341 years at RDSA, 418 years at PNA and 443 years at the RDSU. Diameter increment rates did not significantly differ between the three studied sites. Ring-width indices were significantly correlated with the duration of the terrestrial phase calculated from nearby hydrological stations for the period 1973-2008. Signals from sea surface temperature (SST) anomalies were more evident in the tree-ring series at the RDSU compared to the PNA. El Niño signals were not detected in the tree-ring chronologies.