RUI: Microbial Assimilation of Nitrate in Disturbed and Undisturbed Forest Ecosystems

对硝酸盐库控制因素的深入认识 尺寸对于最小化这些不期望的过程是至关重要的， 氮素流失、地下水硝酸盐污染和微量氮气体 生产 使用最近开发的15 N同位素稀释法 允许测量总氮转化率的技术 在相对未受扰动的土壤中，这些研究人员提供了 有证据表明，微生物对硝酸盐的同化作用是一个重要的 三种森林生态系统无机氮循环的组成部分。 虽然微生物对硝酸盐的同化作用通常是 他们认为，在森林土壤中， 从这项研究和其他研究中有足够的证据表明， 表明微生物对硝酸盐同化作用可能是 硝酸盐池大小的调节器。 该项目将研究森林 沿着两个样带（在俄勒冈州和新墨西哥州），并确定 碳氮供应的不均匀性对 同化率;温度和湿度的影响 无机氮同化和生产的总速率 负责硝酸盐的特定微生物种群 同化作用;以及植物作为碳源与 氮的竞争者。 这项研究将提供信息 这是制定基于过程的模型所必需的 预测了干扰对氮素循环的影响 预测潜在的反馈回路，将发展为C和N 在全球气候变化期间，对生态系统的投入发生了变化。

A thorough understanding of the factors controlling nitrate pool sizes is critical to minimizing such undesirable processes as nitrogen loss, nitrate pollution of ground water, and trace N-gas production. Using recently developed 15N isotopic dilution techniques that allow measurement of gross N-transformation rates in relatively undisturbed soil, these investigators have provided evidence that microbial assimilation of nitrate is a significant component in the inorganic N cycle of three forest ecosystems. Although microbial assimilation of nitrate has generally been discounted as being insignificant in forest soils, they believe that there is sufficient evidence from this and other studies to indicate that microbial assimilation of nitrate may be a primary regulator of nitrate pool sizes. This project will examine forest sites along two transects (in Oregon and New Mexico) and determine the effect of heterogeneity in carbon and nitrogen supply on assimilation rates; the influence of temperature and moisture on gross rates of inorganic N assimilation and production; the specific microbial populations responsible for nitrate assimilation; and the role of plants as sources of carbon versus competitors for nitrogen. This study will provide information that is necessary for the formulation of process-based models predicting the impacts of disturbance on N cycling as well predicting potential feedback loops that will develop as C and N inputs to ecosystems shift during global climate change.