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

Abstract

Intra-annual distribution of precipitation in central Amazonia often leads to a short mild dry season and an increase in irradiance, temperature, and vapor pressure deficit; however, the accurate effect of intra-annual microclimatic variability on stem growth is still under investigation. The objective of this study was to determine how stem growth responds to monthly variations in microclimatic factors in the central Amazon. During five years (2008)(2009)(2010)(2011)(2012) we measured diameter stem growth of 109 trees (26 species) and used principal component regression to evaluate the effect of microclimatic variability on stem growth in diameter. We found that the mean stem growth in diameter across species increased in response to an increase in rainfall and reference evapotranspiration, but it decreased with a rise in mean and minimum vapor pressure deficit. A contribution of this study is to show that even when irradiance and temperature had no significant effect on stem growth, small changes in vapor pressure deficit significantly affect stem growth. If the dry season becomes longer, as predicted by models, trees currently more sensitive to microclimatic variability associated with droughts would be the most affected by climate changes.

Elevated CO2 induces down-regulation of photosynthesis and alleviates the effect of water deficit in Ceiba pentandra (Malvaceae)

“…Droughts cause a reduction in soil water content and an increase in vapor pressure defi cit, which can lead to a decline in photosynthesis and tree growth, and eventually to an increase in mortality of trees under severe drought (Duff y et al, 2015;Marenco and Antezana-Vera, 2021;Camargo and Marenco, 2023). Plant response to water defi cit varies with plant species, severity and duration of the drought stress (Kaur and Asthir, 2017;Fernando and Marenco, 2023).…”