Leaf habit differentiation explains trait tradeoffs across savanna woody plants

Abstract

Identifying how leaf habit subdivisions link to the fast–slow and avoidance–tolerance trait tradeoffs can provide new insight into divergence in ecophysiological strategies among plant functional groups. Here, we tested a hypothesis that the differentiation across deciduous, semi-deciduous and evergreen woody species contributes to physiological trait tradeoffs in a dry-hot valley savanna. We investigated 11 photosynthetic, morphological and hydraulic traits of 24 species including 8 deciduous, 10 semi-deciduous and 6 evergreen species. Deciduous species were grouped in the fast and avoidance side associated with high values of maximum photosynthetic rates, stomatal conductance and leaf size, while evergreen species were grouped in the slow and tolerance side associated with high photosynthetic water use efficiency, leaf mass per area, sapwood density, Huber value, leaf water potential at turgor loss point and water potential causing 50% loss of stem hydraulic conductance. Semi-deciduous species generally had intermediate trait values and represented different physiological characteristics when compared to deciduous and evergreen species. The physiological trait tradeoffs showed a close linkage to the differentiation of these three leaf habits. Our findings clearly reveal trait tradeoffs related to fast–slow and avoidance–tolerance strategies among diverse savanna plants, suggesting a syndrome in multiple ecophysiology strategies across different leaf habits.

Keywords

• Dry-hot habitat
• Gas exchange
• Hydraulics
• Phenology
• Tolerance
• Valley savanna