Coordination of economics and hydraulic traits shapes the adaptive strategies of tree species in two forest communities with distinct water regimes.

Species distribution is strongly driven by local resource availability, while the coordination and trade-offs among plant functional traits can reveal their adaptive strategies and community assembly in environments of different resource availability. Plant economics and hydraulic traits play fundamental roles in plant environmental adaptation; however, how these key functional traits contribute to the formation of different adaptive strategies to shape community assembly in different environments remains largely unknown. Here, we assess the role of coordinated carbon economics and hydraulic strategies in shaping tree adaptation in environments with two distinct water regimes. We analyzed 20 leaf, stem and root functional traits related to plant economics and hydraulics for 10 tree species from a dry sandy land community and 10 tree species from a neighboring wet valley community. We found the economics spectrum that is coordinated with hydraulic traits, conveying a trade-off between stress tolerance associated with high tissue construction cost and resource acquisition efficiency. Trees in the dry sandy land community adopted a more conservative strategy, characterized by denser tissues, greater dry matter contents, lower carbon assimilation rates, higher leaf drought tolerance, narrower conduits and larger Huber values than trees from the valley. The functional coordination across organs was not detected in the sandy land forest, while the coupling of leaf economics and stem hydraulics occurred in the valley forest. Moreover, the trait network was looser in the sandy land forest compared with that in the valley forest. From sandy land to valley forests, the hub traits shifted from root diameter to stem vulnerability index and vessel diameter. Our results demonstrate that the coupled carbon and water-related functional traits have played important roles in shaping the adaptive strategies of forest communities with distinct water regimes.