REGULATION OF LEAF WATER POTENTIAL IN TREE SPECIES OF THE
CERRADO-AMAZONIA TRANSITION IN RESPONSE TO CLIMATE SEASONALITY
Abstract
Leaf water potential is a good indicator of tree species responses to
rainfall seasonality, allowing to better understand water stress effects
on vegetation. We investigated daily and seasonal patterns on leaf water
potentials of 21 dominant species in three distinct vegetation types
from the Cerrado-Amazonia transition to assess how they respond to
seasonal changes in water availability. We found that the variation on
leaf water potential (Ψl) across species was higher in the dry compared
to the rainy season, for all vegetation types. Typical cerrado and
cerradão species showed similar patterns, with higher Ψl regulation
under higher VPD and lower variation in predawn Ψl (ΔΨpd), indicating
root access to soil water even during intense drought. In contrast,
seasonal forest species showed lower regulation under lower VPD effects
in both seasons, and higher ΔΨpd, indicating lower access to deep water
in the soil. These differences revealed two main groups of species:
higher Ψl regulators with a strategy isohydric occurring in both typical
cerrado (savannah) and cerradão (woodland), and lower Ψl regulators with
anisohydric strategy, occurring in seasonal forest. Our results suggest
that seasonal tropical forest species will become very vulnerable to
predicted increases on drought severity in the region.