This session will focus on the origin and significance of spatial variations in nutrient cycling and plant productivity within and across tropical ecosystems. The tropics contain as much if not more variation in ecosystem types as the extra-tropics, but are often described as if the biome were biogeochemically homogenous. This is clearly an oversimplification, given broad differences in geology, biota, and climate, but it’s an open question whether and how a clearer picture of spatial variation would change our understanding and management of tropical ecosystems. This session will identify biogeochemical patterns within the tropics, discuss how these patterns may affect the function and services of tropical ecosystems, and consider how to incorporate this variation into models for predicting the response of the tropics to anthropogenic changes. Speakers will include terrestrial and aquatic biogeochemists, modelers, community and ecosystem ecologists, soil scientists, and geomorphologists. Questions include: 1) how widely do tropical ecosystems vary in basic biogeochemical properties? How does such variation differ from that in temperate ecosystems? What structures this variation? What scales are the most important for understanding the differences among tropical ecosystems? 2) Are there feedbacks between community composition and biogeochemical processes in the tropics, and how do they differ from site to site? 3) What factors influence how tropical ecosystems will respond to land use and climate change? 4) How can we refine climate models to include different responses to climate change for different tropical ecosystems? By addressing these questions, we hope to elucidate what is known, and illuminate the questions that need to be addressed as we move forward in our efforts to understand and manage tropical ecosystems.