One of the dominant paradigms in biogeochemistry is that old soils are infertile as a result of the long term depletion of nutrients supplied through the breakdown of rocks. Nutrient depletion, particularly of phosphorus, is postulated to be widespread in tropical lowlands where the lack of historic glaciation suggests that soils are older than in many temperate regions. This assumption, however, is almost certainly an oversimplification. Tropical landscapes are dynamic systems in which the conversion of bedrock to soil and the removal of soil through erosion occur at different rates in different geologic and climatic settings. Thus mapping the extent of phosphorus depletion in the tropics requires addressing a fundamental and little acknowledged question that is the focus of this project, what are phosphorus residence times in the tropics and are they sufficient for phosphorus depletion to occur? This question will be addressed in a multidisciplinary, multisite study that will be the first to integrate assessments of soil fertility with new technologies that can help quantify soil residence times. This project will integrate biogeochemistry and geomorphology to answer fundamental questions about soil fertility and nutrient cycling and will promote a much needed effort to quantify differences in fertility in the tropics. It will support international research at several institutions and involve local scientists and students at each location. In addition to training graduate students and postdoctoral scholars, this project will establish site locations for a field course that integrates tropical ecology, biogeochemistry, and geomorphology.
