Variation in bark water content in three Amazonian species in response to rainfall seasonality

Abstract

Stem water content is an important component of daily water balance, as water reserves in tree tissues can provide water to leaves when transpiration is intense, but how it varies over rainfall seasons is still unknown. The purpose of this study was to determine the variation of wood and bark water content and stem growth in response to microclimatic variability in three Amazonian species. Trees of Protium apiculatum, Lecythis prancei, and Rinorea paniculata (DBH ≥ 10 cm) were selected in a central Amazon forest. Wood water content (WWC) and bark water content (BWC) data were obtained in the dry and rainy season. Stem growth was measured at monthly intervals using dendrometric tapes during 24 months. Rainfall, air temperature and irradiance data were also recorded, and the effect of microclimatic variability on stem growth evaluated. WWC did not vary between seasons (p = 0.28), but BWC increased in the wet season (p = 0.07), particularly in R. paniculata. Although stem growth varied intra-annually (p < 0.01), none of the climatic variables investigated had a significant effect on stem growth (p = 0.97). This work shows that in a typical rainfall year, climatic variability is not large enough to cause significant variation in stem growth, even when rainfall seasonality may cause variation in bark water content.