Collaborative Research: Coupled Biogeochemistry and Geomorphology in Three Tropical Forest Ecosystems

生物地球化学中占主导地位的范例之一是，由于岩石破裂提供的养分长期枯竭，古老的土壤变得贫瘠。养分枯竭，特别是磷的枯竭，被认为在热带低地普遍存在，那里没有历史上的冰川，这表明土壤比许多温带地区更古老。然而，这种假设几乎肯定是过于简单化了。热带地貌是动态系统，在不同的地质和气候环境中，基岩向土壤的转化和土壤侵蚀的清除以不同的速度发生。因此，绘制热带地区磷耗竭的程度需要解决一个基本且鲜为人知的问题，这是该项目的重点，即热带地区的磷停留时间是多少，它们是否足以使磷耗尽？这一问题将在一项多学科、多地点的研究中得到解决，这将是第一次将土壤肥力评估与有助于量化土壤停留时间的新技术相结合。该项目将把生物地球化学和地貌学结合起来，回答有关土壤肥力和养分循环的基本问题，并将促进对热带地区肥力差异进行量化的迫切需要的努力。它将支持几个机构的国际研究，并让每个地点的当地科学家和学生参与。除了培训研究生和博士后学者外，该项目还将为一门整合了热带生态学、生物地球化学和地貌学的野外课程确定地点。

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.