Dissertation Research: Nitrogen Transformation and Transportation Along a Gradient in Soil Texture

被称为活性氮的化学活性氮化合物对生物圈的投入正在增加。这些投入有有益的影响，包括增加作物产量，也有有害的影响，如养分污染。森林土壤可作为活性氮的汇和源。确定允许森林土壤保留这种氮的机制是一个重要的研究目标。这项研究将土壤碳和土壤质地纳入到森林土壤氮素保持的分析中，从而提高了我们对反应氮保持的理解。土壤碳能促进活性氮向非活性氮的转化。相反，较粗的土壤质地可以促进活性氮向地表水和地下水的迁移。这些过程的相对重要性将根据切萨皮克湾流域的土壤碳和土壤质地的梯度进行评估。这些结果将被综合起来，以确定氮素转化和运输如何相互作用，以控制活性氮的生态系统损失。更好地理解促进氮保留的机制有助于确定活性氮何时、何地和为什么被输送到地表水和地下水中。土壤质地为解释这些关系提供了一个广泛适用的框架。由于全球各地的土壤质地都被绘制得很好，这项研究的结果将使管理者能够使用现有的土壤质地图来预测公开水域特别容易受到非点源营养物质污染的地点和时间，并相应地管理景观。本科生将参与这一项目，高中生将从这项研究开发的教材中受益。

Inputs to the biosphere of chemically active compounds of nitrogen, known as reactive nitrogen, are increasing. These inputs have beneficial effects including increased crop production, and deleterious effects such as nutrient pollution. Forest soils can serve as sinks and sources for reactive nitrogen. The identification of mechanisms that allow forest soils to retain this nitrogen is an important research goal. This research will improve our understanding of reactive nitrogen retention by incorporating soil carbon and soil texture into an analysis of forest soil nitrogen retention. Soil carbon can promote the transformation of reactive nitrogen into non-reactive forms. In contrast, coarse soil texture can promote the transportation of reactive nitrogen to surface and ground waters. The relative importance of these processes will be evaluated along gradients of soil carbon and soil texture in a Chesapeake Bay watershed. The results will be integrated to determine how nitrogen transformation and transportation interact to control ecosystem losses of reactive nitrogen. An improved understanding of the mechanisms promoting nitrogen retention can help to determine when, where and why reactive nitrogen is transported to surface and ground waters. Soil texture offers a broadly applicable framework for interpreting these relationships. Because soil texture is well-mapped across the globe, results from this research will enable managers to use existing soil texture maps to predict places and times where open waters are particularly susceptible to non-point nutrient pollution and to manage landscapes accordingly. An undergraduate student will participate in this project, and high school students will benefit from educational materials developed from this research.