Functional traits of leaves and forest structure of neotropical mangroves under different salinity and nitrogen regimes

To explore the species-specific relationships between anatomical and physiological traits related to salt tolerance and forest structure, we tested the hypothesis that mangrove trees living under different long-term salinity and nitrogen regimes have different leaf anatomical traits and intrinsic water use efficiency (WUE) patterns, leading to differences in forest structure. A comparative account has been made with respect to δ13C signature and stomatal frequency of three mangroves, Avicennia germinans, Laguncularia racemosa and Rhizophora mangle from two different habitats in terms of salinity and N concentration. The results show that soil salinity and N concentration have definite species-specific impact on photosynthetic carbon gain and stomatal conductance. In euhaline conditions, under relatively high salinity and low N concentrations, A. germinans may achieve lower photosynthetic rates than the other mangrove species, and dominate the assemblage. In oligohaline conditions, under permanently low salinity and relatively high N concentrations, R. mangle may achieve lower photosynthetic rates than the other mangrove species, and dominate the assemblage. This study shows an example in which the coexistence of the three Neotropical mangrove species may be facilitated by the divergence of intrinsic water use efficiency patterns and variations in both salinity and N availability.