Demographic and growth patterns of Pentaclethra macroloba (Willd.) Kuntze, a hyperdominant tree in the Amazon River estuary

Little is known about the life history and environmental factors that regulate the growth rate of hyperdominant trees in flooded Amazonian forests. Pentaclethra macroloba is a hyperdominant tree, and it is widely explored in the Amazon, because its seed oil is a powerful herbal medicine. We evaluated the demographic structure and growth patterns of P. macroloba and tested the effect of the Amazon River flood pulse on its growth. We modeled the growth and determined the age of P. macroloba by analyzing the growth rings of 30 monitored trees in relation to hydroclimatic variables. We also inventoried 240 juvenile and 2072 adult trees arranged in a clustered pattern. The diametric distribution pattern of the juvenile and adult trees was exponential and log-normal, respectively. The trees were found to be up to 102 years old, and 47% of them grew freely toward the canopy. Peak growth in height and diameter occurred at 24 (61.7 cm year(-1)) and 46 (9.38 mm year(-1)) years, respectively. Pentaclethra macroloba showed cambial dormancy during the seasonal peak of rainfall (R-2 = 0.41; t = -2.62; p < 0.01) and flooding of the Amazon River (R-2 = 0.47; t = -3.01; p < 0.01). Increases in rainfall and flood level of the river in the rainy season control the growth rate of P. macroloba, making it a seasonal process. The demographic and growth patterns of P. macroloba respond to the environmental heterogeneity of the estuarine floodplain forest and also reflect its life history over time.