Between and within-site comparisons of structural and physiological characteristics and foliar nutrient content of 14 tree species at a wet, fertile site and a dry, infertile site in Panama

Structural and physiological characteristics and foliar nutrient content of 14 tree species were evaluated at two sites, one being seasonally wet with relatively fertile soils and the other being seasonally dry with relatively infertile soils. Differences in environmental stress between these sites drove the resulting differences in structural and physiological characteristics and leaf nutrient content of the investigated tree species. At the wet site, trees were more productive as site conditions allowed for greater photosynthetic activity to occur. The growth of pioneer tree species such as Spondias mombin, Guazuma ulmifolia, and Luehea seemanni, correlated strongly with high water-use efficiency and large, low-density leaves. Tree species, especially N-fixing species such as Albizia adinocephala, Albizia guachapele, Enterolobium cyclocarpum, and Gliricidia sepium, adapted to the greater levels of environmental stress at the dry site with infertile soils by increasing their water-use efficiency. Species differences were also significant, indicating that certain species adapted physiologically and structurally to environmental stress. Tree productivity operated under different structural and physiological constraints at each site. Leaf mass area (LMA), foliar N, and leaf area index (LAI) best predicted mass-based net photosynthetic capacity at the more fertile, wet site while foliar N was the best predictor of mass-based net photosynthetic capacity at the less fertile, dry site. Results from this study suggest the use of pioneer species at wet, fertile sites and N-fixing species at dry, infertile sites for restoration projects.