Idade, densidade da madeira e padrões de crescimento de espécies arbóreas amazônicas com até 10 cm de diâmetro

Abstract

The age and growth dynamics of trees with a diameter at breast height (DBH, 1.3 m above the ground) <10 cm is poorly understood. We investigated the age of trees with a DBH ≤10 cm and quantified their diametric and height growth for different species of Dense Ombrophilous forest and Campinarana located in central Amazonia. At the ATTO (Amazon Tall Tower Observatory) site, 72 trees were collected, 50 of which were sampled in 2 plots (2.25 x 2.25 m2) installed in each forest typology. In these plots, all tree species ≥1.3 m in height and DBH ≤10 cm were sampled. The base diameter (5 cm above the ground), DBH, diameter at commercial height and total height were measured for each individual. A total of 22 individuals were sampled at the edge of roads/trails. Three radial cuts (discs) were made for each individual: one at the base of the stem, one at the DBH and one at the top of the stem, totaling 216 discs. 22 species from different functional groups were selected for 14C radiocarbon dating. 0.005 g of structural plant tissue was extracted from the base and top of the selected species (44 samples). These were analyzed together with samples of 16 species collected in 2004 in the Dense Ombrophilous forest located at the Tropical Silviculture Experimental Station (EEST), for a total of 38 trees. The Modern Fraction (FM) of radiocarbon was quantified by Mass Acceleration Spectrometry. The age of the trees was estimated from FM measurements using the OxCal program, with the Southern Hemisphere 2021 calibration curve (SHCal21). Age varied between forest types. The range of ages of natural regeneration was Campinarana (3.5 to 66 years), Campinarana Trails (16 to 67 years), Dense Ombrophilous (4 to 66.5 years), Dense Ombrophilous Trails (6.5 to 67 years). The age and growth of the trees did not differ between the functional groups studied. Diametric increment did not vary between the forest types. The opposite was observed for height growth. Growth was positively related to the diameter and total height of the trees. This result corroborates the idea that individuals in the forest understory, and therefore with less light availability, grow relatively more slowly.