Links Between Soil Nutrient Dynamics and Surface Water Biogeochemistry Following Deforestation for Pasture Agriculture in Amazonia

这个项目将研究亚马逊流域潮湿的热带森林向牧场的转变如何改变土壤中元素循环的模式和速率，以及这些变化如何与小溪的化学和生态变化联系起来。亚马逊是世界上自然生态系统向人类主导利用转化速度最快的地区之一。放牧是毁林土地的主要用途。原生森林向牧场的转变使养分循环的模式和速率以及土壤养分流失的可能性发生了巨大变化。溪流是陆地土壤和下游水生生态系统之间的关键水文和生化环节。该项目将检查朗多尼亚小流域的土壤和溪流，朗多尼亚是巴西亚马逊西南部快速发展的州。对四对流域进行比较。每对盆地中的一个将排出完整的森林，另一个将排出已被清理并种植为牧场的土地。研究了流域土壤中氮、磷和主要离子的有效性。在成对的集水区测量水流的浓度和氮、磷、主要阳离子和阴离子、微量元素和悬浮沉积物的形式，将把土壤化学变化与河流生物地球化学联系起来。为了确定河流从一种土地利用流向另一种土地利用时，一种土地利用的影响能维持多久，将通过测量土地利用边界上游和下游的溶质浓度，以及通过在森林和牧场河流中实验性地注入硝酸盐和磷酸盐以及一种非反应性示踪剂来确定养分被吸收的速率，以确定流域土壤的生物地球化学输入如何影响河流有机质的产生。这项工作将提供重要的新信息，有助于预测农业发展和森林砍伐的影响。对河流生产力的研究将提供新的信息，说明土地利用变化如何影响维持水质和支持对人类福祉至关重要的渔业的生物功能。在更长的时间框架内，该项目将为未来的建模工作提供基础，通过水路线模型和溪流内生物地球化学处理，将小流域的土地利用变化与亚马逊大河的生物地球化学变化联系起来。该提案已提交给环境地球化学和生物地球化学招标，该项目由地球科学部（地球科学）、环境生物学部（生物科学）、数学科学部（数学和物理科学）和国际项目-巴西（社会、行为和经济科学）共同支持。

9630278 Deegan This project will examine how the conversion of moist tropical forest to cattle pasture in the Amazon Basin alters the patterns and rates of element cycles in soils and how these changes are linked to changes in the chemistry and ecology of small streams. The Amazon is a region with one of the world's highest rates of conversion of natural ecosystems to human dominated use. Cattle pasture is the dominant use of deforested lands. Conversion of native forest to pasture causes large changes in the patterns and rates of nutrient cycling and the potential for nutrient losses from soils. Small streams function as key hydrologic and biochemical links between upland soils and downstream aquatic ecosystems. This project will examine soils and streams in small drainage basins in Rondonia, rapidly developing state in the southwest Brazilian Amazon. Four pairs of drainage basins will be compared. One basin in each pair will drain intact forest, the other will drain land that has been cleared and planted to cattle pasture. The availability of nitrogen, phosphorus and major ions will be examined in drainage basin soils. Measurements of streamwater concentrations and forms of nitrogen, phosphorus, major cations and anions, trace elements and suspended sediments in the paired catchments will link changes in soil chemistry with stream biogeochemistry. To determine how long the influence of one land use is maintained as streams pass through one land use to another, the rates at which nutrients are taken up will be determined by measuring solute concentrations upstream and downstream of land use boundaries and by experimental injections of nitrate and phosphate and a non-reactive tracer in forest and pasture streams to determine how biogeochemical inputs from soils in the drainage basin affect stream organic matter production. This work will provide important new information that will help to predict the effect of agricultural development and deforestation. Examination of stream pro ductivity will provide new information on how land use change affects biological functions that maintain water quality and support fisheries that are important to human well-being. On a longer time frame, this project will provide a foundation for future modeling efforts to link land use changes in small watersheds with biogeochemical changes in the larger rivers of the Amazon using models of water routing and within stream biogeochemical processing. This proposal was submitted to the Environmental Geochemistry and Biogeochemistry solicitation, and the project is being jointly supported by the Divisions of Earth Sciences (Geosciences), Environmental Biology (Biological Sciences), Mathematical Sciences (Mathematical and Physical Sciences) and International Programs -Brazil (Social, Behavioral & Economic Sciences).