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.

Stem growth of Amazonian species is driven by intra-annual variability in rainfall, vapor pressure and evapotranspiration

“…Thus, for this study, tree species were selected based on the availability of at least three trees of the same species, each of them with stem diameter (at 1.3 m above the ground -diameter at breast height, DBH) of at least 10 cm. In the experimental site, the annual rainfall is about 2,540 mm with a mild dry season from June through October (Antezana-Vera & Marenco 2021; Dias et al 2022), being July-September the driest months (INMET 2021 -climate data for the nearby city of Manaus). During 2013-2017, reference evapotranspiration (ET o ) was 120.8 mm month -1 , mean temperature 26.5 °C, and mean relative humidity (RH) 78.9% (Antezana-Vera & Marenco 2021).…”

“…S1-A). In these trees we measured the breast-height stem growth in diameter (S G ) at monthly intervals during 60 months (January 2008 -December 2012), as previously described (Dias et al 2022). The S G was measured using stainless steel dendrometer bands, which were installed at least two years before the beginning of data collection.…”

“…Studies that aim to assess the effect of the dry season on stem growth in the Amazon have led to contradictory conclusions. For instance, Silva et al (2003) and Dias et al (2022) found no effect of precipitation on stem growth in the central Amazon, while Yang et al (2018) found that photosynthesis, over the entire Amazon region, can decline in the dry season. Likewise, Méndez (2018) and Souza & Marenco (2022) reported a decline in stem growth during the dry season in a terra-firme rainforest of the central Amazon.…”