Interspecific variation of functional traits in a CAM-tree dominated sandy coastal plain

Question: Although the restinga vegetation lies adjacent to the species-rich Atlantic Rainforest, fewer species thrive due to low available resources of the sandy substrate. We asked whether there is a specific set of functional traits related to the ability to attain high dominance in a restinga dominated by a CAM photosynthesis tree. Location: Restinga of Jurubatiba National Park, north of the state of Rio de Janeiro, Brazil. Methods: We chose traits that are commonly used in large screenings, leaf mass per area (LMA), leaf longevity (LL) and leaf nitrogen concentration (LNC). We also measured the functional traits, midday leaf water potential (Psi(min)), pressure-volume curves, nitrogen isotope discrimination (delta N-15) and chlorophyll fluorescence. We compared species using ANOVA and ordination analysis. Results: The two most dominant species differed from subordinate species in terms of leaf succulence (SUC) and Psi(min). However, they were also significantly different from each other in LMA, SUC, leaf thickness and LNC. Psi(min) and delta N-15 had the strongest loadings on the third ordination axis, which, despite explaining only 18.2% of total variance, was the only axis reflecting variation in species dominance. Conclusions: Despite high interspecific variation, the most common traits of the leaf economic spectrum were not directly associated with variation in species dominance. In contrast, the bulk modulus of elasticity, Psi(min) and delta N-15 were important not only to track the connection between plant traits and environmental factors, but also between plant traits and community structure.