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

9630278迪根这个项目将研究亚马逊盆地将潮湿的热带森林转变为牧场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在一起。亚马逊是世界上自然生态系统向人类主导用途转化比率最高的地区之一。牛牧场是砍伐土地的主要用途。将原生森林转化为牧场会导致养分循环的模式和速度发生很大变化，并有可能造成土壤养分流失。小溪在旱地土壤和下游水生生态系统之间起着关键的水文和生化联系作用。该项目将研究巴西亚马孙西南部快速发展的隆多尼亚小流域的土壤和溪流。将对四对流域进行比较。每对中的一个盆地将排干完好无损的森林，另一个将排干已清理完毕并种植成牲畜牧场的土地。将检查流域土壤中氮、磷和主要离子的有效性。对成对集水区的溪水浓度和氮、磷、主要阳离子和阴离子、微量元素和悬浮物形态的测量将把土壤化学的变化与溪流生物地球化学联系起来。为了确定一种土地利用的影响在河流通过一种土地利用转移到另一种土地利用时维持多长时间，将通过测量土地利用边界上游和下游的溶质浓度以及在森林和牧场溪流中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吸收速度，以确定来自流域土壤的生物地球化学输入如何影响河流有机质生产。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有关土地利用变化如何影响维持水质和支持对人类福祉重要的渔业的生物功能的新信息。在更长的时间范围内，该项目将为今后的建模工作奠定基础，以便利用水路模型和溪流内生物地球化学处理模型，将小流域的土地利用变化与亚马逊河大河的生物地球化学变化联系起来。这项建议已提交给环境地球化学和生物地球化学征集，该项目得到了地球科学部(地球科学)、环境生物学(生物科学部)、数学科学部(数学和物理科学部)和巴西国际计划(社会、行为和经济学)的联合支持。

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).