Intra-annual tree growth responds to micrometeorological variability in the central Amazon

Abstract

Intra-annual distribution of precipitation in central Amazonia leads to a short mild dry season, which is associated with an increase in irradiance and temperature and a decline in relative humidity; however, the independent effect of each individual climatic variable on tree growth is still under investigation. The objective of this study was to determine how tree growth (inferred from radial stem increment) responds to monthly variations of micrometeorological variables in the central Amazon. During five years (2013-2017) we measured tree growth in 51 trees from nine species and, above the forest canopy, collected environmental data, such as photosynthetically active radiation (PAR), air temperature (T), precipitation, air relative humidity (RH), air vapor pressure deficit (VPD), reference evapotranspiration (ETo), and soil water content (SWC). We used principal component regression to evaluate the effect of micrometeorological variability on tree growth. Mean tree growth across species was responsive to variations in almost all the micrometeorological variables examined, with the exception of mean and minimum temperature, maximum RH, and minimum VPD. Mean tree growth across species increased with increasing precipitation, RHmean, RHmin and SWC, while it decreased with increasing PAR, Tmax, and ETo. It was also shown that an increase in VPDmean and VPDmax has a negative effect on tree growth. These results contribute to improve our understanding of effect of climate variability on tree growth, and shed light on the potential effect of severe droughts in the central Amazon.

Wood and bark water content and monthly stem growth in Amazonian tree species

“…1). (Méndez 2018;Yang et al 2018;Antezana-Vera and Marenco 2021), so the effect of the environmental conditions on tree growth depends on the climatic conditions during the growing period, in particular the frequency and intensity of precipitation, which can change substantially over time (Ciemer et al 2019).…”

“…The climate in the region is tropical humid, with mean annual rainfall of 2,420 mm and a mild dry season from June through October, and, within this period, July, August and September are the driest months (< 100 mm per month, INMET 2021). The mean annual temperature is about 26 o C (Dias and Marenco 2016;Antezana-Vera and Marenco 2021). The vegetation is classified as dense terrafirme rainforest, and the soil is an Oxisol with low fertility, clay texture, and pH of 4.2 to 4.5 (Magalhães et al 2014).…”

“…Throughout the eastern and central Amazon, the Enhanced Vegetation Index (a surrogate of potential photosynthetic capacity) increased by 25% with increasing sunlight during the dry season (Huete et al 2006), and in the central Amazon, tree growth increased during dry periods (Laurance et al 2009). Likewise, Green et al (2020) reported that, in the rainiest part of the Amazon, photosynthesis increases in the dry season, when solar radiation, temperature, and vapor pressure deficit (a direct function of temperature) are higher (Costa et al 2010;Antezana-Vera and Marenco 2021). On the other hand, ecosystem photosynthesis over the entire Amazon can decline during prolonged droughts (Yang et al 2018), and stem growth can decline during rather prolonged dry seasons (Antezana-Vera and Marenco 2021).…”

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

“…Mean annual temperature is about 26 o C Marenco, 2016;Marenco, 2021b). The vegetation is classified as dense terra-firme forest, and the soil is an Oxisol with low fertility, clay texture, and pH (in water) of 3.9-4.0 (Magalhães et al, 2014).…”

“…It seems that the effect of climatic variability on tree growth in the central Amazon depends on the length of the dry season, as during prolonged droughts (such as that of 2015-2016) climatic parameters that increase in the dry season (e.g. irradiance, vapor pressure deficit) seem to have a negative effect on tree growth and ecosystem photosynthesis (YANG et al, 2018, ANTEZANA-VERA;MARENCO, 2021b). Other factors also affect tree growth, including site quality (e.g., soil fertility and topography), ontogeny -tree size (BOWMAN et al, 2013) andcompetition (VATRAZ et al, 2018).…”