Soil-stream Interfaces as Control-Points for Speciation and Transformations of Nitrogen in a Heterogeneous Landscape

这个项目的重点是土壤-河流界面作为物种形成控制点的作用(NO3-vs.第二名--与NH4+、DON、N2O)和异质地貌中的N通量。N在土壤-河流界面的生物地球化学转化可能对流向下游生态系统的N的数量和质量(形态)产生重要影响，并可能改变流域河流化学受流域过程影响的程度。因此，为了预测流域干扰(短期和长期)将如何影响地表水化学，从机理上理解这种沿土壤-溪流流动路径的氮转化可能是至关重要的。来自Augusta Creek流域的初步研究表明，土壤-河流界面是N的下游形态和通量的潜在控制点。本项目概述的工作旨在提供对流域中明确的土壤-河流水文路径N转化的速率和机制的理解。首席调查员将使用描述性方法和实验方法，包括使用水文径流示踪剂(溴化锂)和特定生物地球化学反应的示踪剂(稳定氮同位素)。主要目的是了解土壤-河流界面的N转化模式如何在空间、时间和作为水文函数变化。

This project focuses on the role of soil-stream interfaces as control-points for the speciation (NO3-vs. NO2-vs. NH4+vs. DON vs. N2O) and flux of N in a heterogeneous landscape. Biogeochemical transformations of N at the soil-stream interface may have important effects on both the quantity and quality (speciation) of N lost to downstream ecosystems, and may modify the extent to which h the chemistry of watershed streams are affected by watershed processes. A mechanistic understanding of such N transformations along soil-stream flowpaths may therefore be critical in order to predict how watershed disturbances (both short-term and chronic) will affect surface-water chemistry. Preliminary studies from the Augusta Creek Watershed have pointed to soil-stream interfaces as potential control-points for downstream speciation and flux of N. The work outlined in this project seeks to provide an understanding of rates and mechanisms of N transformations along explicit soil-stream hydrologic flowpaths in the watershed. The principal investigators will use both descriptive and experimental approaches, including the use of tracers of hydrologic flowpaths (LiBr) and tracers for specific biogeochemical reactions (stable N isotopes). The main goal is to understand how patterns of N transformations at soil-stream interfaces vary in space, time,and as a function of hydrology.