Variation in the water use and gas exchange of two Brazilian tropical dry forest phytophysiognomies in response to successional stage

Water availability is the main limiting factor to plants growth in tropical dry forests, influencing vegetation ecophysiological responses throughout ecological succession. In this study, we analyzed the water potential and gas exchange in two phytophysiognomies of a Brazilian tropical dry forest, along a chronosequence and in moments of low and high VPD. We selected an area of Crystalline Caatinga (CC) and Arboreal Caatinga (AC), and in both sites delimited three plots at different successional stages (initial, intermediate, and late). At each collection site within areas at each successional stage, we sampled the four most abundant species. For CC plants, water potential and gas exchange were similar at all successional stages, regarding VPD, and higher than in AC site. Trees growing in the AC site showed more plastic responses than those in the CC area, mainly in gas ex-change, whereas CC plants (mainly herbs) showed a higher variation in water potential. We established that this differential response occurred due to the structure of the plant community and soil water availability. Trees' leaf traits tend to present long-term responses, and we observed that vegetation in the AC site showed most markedly differences among successional stages than plants in CC site.