Hydrological niche segregation defines forest structure and drought tolerance strategies in a seasonal Amazon forest

1) Understanding if and how trees coordinate rooting depth and aboveground hydraulic traits to define drought-resistance strategies in seasonal Amazon forests is a major gap to model parametrization aimed at predicting the effects of climate change in these ecosystems.
2) We assessed the rooting depth of 12 dominant tree species (representing ~ 42% of the forest basal area) in a seasonal Amazon forest, using the stable isotope ratios (δ18O and δ²H) of water collected from tree xylem and soils from a range of depths. We took advantage of a major ENSO-related drought in 2015/2016 that caused substantial evaporative isotope enrichment on soil. We measured the minimum dry-season leaf water potential both in a normal year (2014; Ψnon-ENSO) and in an extreme drought year (2015; ΨENSO). Furthermore, we measured xylem hydraulic traits that indicate the range of water potentials that trees tolerate without risking hydraulic failure (P50 and P88).
3) We demonstrate that coexisting trees are lar...