Occurrence of annual growth rings in Rhizophora mangle in a region with low climate seasonality

ABSTRACT The formation of annual growth rings has been confirmed for several mangrove species in the last decade, among which is the Rhizophora mangle. However, the record of annual rings for this species was made in a region with high hydric seasonality, a widely recognized induction factor of annual rings in tropical species. In this sense, the present study aimed to verify the occurrence of annual growth rings in R. mangle in the mangroves of Guaratiba (Rio de Janeiro, Southeastern Brazil), a region with low hydric seasonality. For this purpose, the crossdating technique was applied in ten trees collected with known age (seven years). The growth rings are characterized by alternating layers of low vessel density (earlywood) and high vessel density (latewood). Multiple regression analysis indicated that growth rings width variation is driven by precipitation, water surplus, water deficit and water storage. Crossdating analysis confirmed the existence of annual growth rings in the R. mangle in Guaratiba. This discovery in a region with low hydric seasonality increases the dendrocronological potential of this species and suggests the importance of biological factors (eg. phenological behavior) as complementary inductors for the formation of growth rings in this species

Wood anatomy of Mollinedia glabra (Spreng.) Perkins (Monimiaceae) in two Restinga Vegetation Formations at Rio das Ostras, RJ, Brazil

This paper aimed to characterize the anatomical structure of the wood of specimens of Mollinedia glabra (Spreng.) Perkins growing in two contiguous formations of restinga vegetation at Praia Virgem, in the municipality of Rio das Ostras, RJ. Both the Open Palmae (OPS) and the Sandy Strip Closed Shrub (SSCS) formations are found in coastal regions that receive between 1,100 and 1,300 mm of rainfall per year. Sapwood samples were collected in both formations. Typical anatomical features for this species include: solitary vessels, radial multiples or clusters elements, that are circular to angular in outline, 5-15 barred scalarifor perforation plates, ood parenchya scanty, septate fiber-tracheids, and wide multiseriate rays with prismatic crystals. Statistical analyses indicated a significant increase in the frequency of vessel elements and an increase in fiber-tracheid diameters in OPS individuals. These characteristics are considered structural adaptations to increased water needs caused by a greater exposure to sunlight. Continuous pruning may be responsible for the tyloses observed in OPS plants. The greater lengths and higher frequencies of the rays in SSCS trees ay be due to the greater diaeters of their branches. ur results suggest that . glabra develops structural adaptations to the restinga micro-environmental variations during its development