Nutrient Availability in Tropical Rain Forests: The Paradigm of Phosphorus Limitation

A long-standing paradigm in tropical ecology is that phosphorus (P) availability limits the productivity of most lowland forests, with the largest pool of plant-available P resident in biomass. Evidence that P limits components of productivity is particularly strong for sites in Panama and the Amazon basin. Analyses of forest communities in Panama also show that tree species distributions are strongly affected by P availability at the regional scale, but that their local distributions in a single site on Barro Colorado Island (BCI) are as frequently correlated with base cations as with P. Traits associated with species sensitivity to P availability require more detailed exploration, but appear to show little similarity with those associated with N limitation in temperate forests. Recent research indicates that a large fraction of P in tropical forests exists as organic and microbial J.W. Dalling (&) Department of Plant Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Avenue, Urbana, IL 61801, USA e-mail: [email protected] J.W. Dalling O.R. Lopez Smithsonian Tropical Research Institute, Apartado Postal, 0843-03092 Panama, Republic of Panama e-mail: [email protected] K. Heineman Program in Ecology, Evolution and Conservation Biology, University of Illinois at Urbana-Champaign, 505 S. Goodwin Avenue, Urbana, IL 61801 USA e-mail: [email protected] O.R. Lopez Instituto de Investigaciones Científicas y Servicios de Alta Tecnología, Apartado Postal, 0843-01103 Ciudad de Saber, Panama, Republic of Panama S.J. Wright B.L. Turner Smithsonian Tropical Research Institute, Apartado Postal, 0843-03092 Balboa, Panama, Republic of Panama e-mail: [email protected] B.L. Turner e-mail: [email protected] © Springer International Publishing Switzerland 2016 G. Goldstein and L.S. Santiago (eds.), Tropical Tree Physiology, Tree Physiology 6, DOI 10.1007/978-3-319-27422-5_12 261 P in the soil; plant adaptations to access organic P, including the synthesis of phosphatase enzymes, likely represent critical adaptations to low P environments. Plants also cope with low P availability through increases in P use-efficiency resulting from increased retention time of P in biomass and decreased tissue P concentration. Although foliar P responds strongly to P addition, we show here that foliar P and N:P are highly variable within communities, and at BCI correlate with regional species distributional affinity for P. An improved understanding of P limitation, and in particular the plasticity of responses to P availability, will be critical to predicting community and ecosystem responses of tropical forests to climate change.