Distinct leaf water potential regulation of tree species and vegetation types across the Cerrado-Amazonia transition

The Cerrado-Amazonia transition harbors forest and savanna formations under the influence of pronounced climate seasonality; however, the water use strategies of this key region is not yet well understood. This study aimed at deciphering in intra- and interspecific variability in leaf water potential regulation among species across three distinct vegetation types (typical cerrado, cerradao, and semideciduous seasonal forest) of the Cerrado-Amazonia transition region. We expected a variation across iso/anisohydric strategies driven by plant-environment interactions and by species attributes (phenology and wood density). We selected 21 dominant species (seven per vegetation type), recorded their phenological strategy and wood density, and measured leaf water potential (psi(l)) during the dry and rainy seasons to analyze variations associated with minimum psi(l), predawn psi(l) (Delta psi(pd)), and midday psi(l) (Delta psi(md)) under the effect of variable vapor pressure deficit (VPD). The variation in psi(l) across species was higher in the dry season than in the rainy season for all vegetation types. Most species from typical cerrado and cerradao showed similar behavior patterns, with higher psi(l) regulation under high VPD and lower Delta psi(pd). In contrast, most forest species showed lower regulation under high VPD, and higher Delta psi(pd). Total or partial deciduousness together with strong stomatal regulation seems to be common water regulation strategies in the dry season for cerrado species but not for forest species. Our results suggest that, if drought events become more intense and frequent as predicted, seasonal forest species may be more vulnerable due to their lower psi(l) regulation. Abstract in Portuguese is available with online material.