Water table depth modulates productivity and biomass across Amazonian forests

Abstract

Aim: Water availability is the major driver of tropical forest structure and dynamics. Most research has focused on the impacts of climatic water availability, whereas remarkably little is known about the influence of water table depth and excess soil water on forest processes. Nevertheless, given that plants take up water from the soil, the impacts of climatic water supply on plants are likely to be modulated by soil water conditions.Location: Lowland Amazonian forests.

Interspecific and intraspecific variation of tree branch, leaf and stomatal traits in relation to topography in an aseasonal Amazon forest

“…Despite valleys are significantly wetter than ridges and slopes in this forest plot (Figure S1), soil water contents do not necessarily correlate with plant water availability (Kupers et al, 2019), which may be influencing the relatively poor role of topography in determining most of the trait variation in this study. Increasing efforts to characterize soil water potential (Kupers et al, 2019), water table dynamics (Sousa et al, 2022) and species rooting depths (Chitra‐Tarak et al, 2021) in tropical forests will improve our understanding on the underlying processes determining small‐scale variation in tree performance.…”

Soil fertility and drought interact to determine large variations in wood production for a hyperdominant Amazonian tree species

“…Maués was the second lowest fertile site in our study (see PCA soils in Supplementary Figure 1), where two trees increased their growth during periods with a higher drought index (negative SPEI values). This pattern of increasing productivity in dry years was also observed in forests that have a shallow water table and excess water limits growth (Sousa et al, 2022). We do not have information about the depth of the water table at the Maués site, but our results suggest that more studies monitoring the influence of a shallow water table on tree growth across the Amazon basin are necessary in order to understand this tree growth pattern.…”

“…Growth rates and turnover of woody biomass are important components of carbon (C) cycling in the Amazon basin (Zhao and Running, 2010). At the broad scale of the basin, growth rates have been shown to vary according to water availability and soil fertility (Toledo et al, 2011;Quesada et al, 2012;Sousa et al, 2022). High water availability increases forest productivity in the tropics (Pereira da Silva et al, 2002;Zuidema et al, 2022), thus the extreme drought events suppress this productivity (Phillips et al, 2009;Doughty et al, 2015).…”

“…The environmental resources have diverse effects on forest productivity due to the heterogeneity of habitats in the tropics, where nutrients, water availability and radiance (light) vary over space and time (Muller-Landau et al, 2021;Sousa et al, 2022). However, the effect of these environmental factors on tree growth does not follow a certain pattern.…”

“…However, the effect of these environmental factors on tree growth does not follow a certain pattern. For example, the literature indicates that the increase in water availability increases production (Zuidema et al, 2022), but an inverse behavior is observed in forests with shallow groundwater (Sousa et al, 2022). Another example is photosynthetically active radiation (PAR), which would not be a limiting factor in the tropics, but the cloud cover limits PAR in tropical wet forests, and this limitation affects forest productivity (Clark and Clark, 1994;Schuur, 2003).…”