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.
Keywords:
Stem water content; Tree growth; Bark thickness; Redundancy analysis (RDA)
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Source: Authors (2021). In where: Y represents tree growth; X represents the climatic variables.
Source: Authors (2021). In where: A: Mean air temperature (Tmean, in °C, diamond) and photosynthetically active radiation (PAR in mol m-2 day-1, circle); B: the relationship between mean stem growth over species (TG-mean) and Tmean and PAR; C: monthly rainfall (months of 2006 and 2007 indicated by numerals, being January of 2006: month 1, and December of 2007: month 24); D: the relationship between TG-mean and rainfall. Mean values (± SE) of climatic variables and p values of simple correlations (r) are also shown.
Source: Authors (2021). In where: A: Wood water content and B: bark water content during three months of the rainy season (March, April and May) and three months of the dry season (July, August and September) in the studied species (sp). Each box represents the mean of 30 observations (five trees, tree samples per tree and two years, 2006 and 2007). The boundaries of the box indicate the 25th and 75th percentile, while the solid line within the box shows the median, while the outliers are indicated by circles; Acronyms: 1: rainy season; 2: dry season; Pap: Protium apiculatum; Lpr: Lecythis prancei; Rpa: Rinorea paniculate.
Source: Authors (2021). In where: Each box represents the mean of 15 trees in the indicated month. Month 1 corresponds to January and month 12 to December. Data were log-transformed prior to analysis of variance.