Collaborative Research: Influence of the Riparian Zone on Nitrogen Cycling in Streams of Puerto Rico: Role of Nitrification and Denitrification

这个项目将调查的基本过程， 可能会影响热带雨中氮的行为 森林溪流 人们对水文学知之甚少 河流水和土壤水之间的相互作用或潜在的 影响这种相互作用可能对氮循环， 热带生态系统 在山区雨水中收集的初步数据 土壤水携带的波多黎各的森林流域 大量溶解态氮以铵态氮的形式进入河岸 区 在溪流中发现很少的铵或硝酸盐， 然而，这表明氮是从溶液中除去之前， 它进入整体物流。 重要的是要确定 从溶液中去除的氮从生态系统中输出 通过硝化或反硝化以气态形式存在，或者 它通过植物吸收在内部再循环。 据推测，在这些热带流：1）可用 河侧无机氮支持活性硝化作用， 反硝化偶联和2）该偶联具有主要 对气流中氮化学影响。 再者是 假设通过流侧区域的流动路径将 对氮的动态有可预测的影响。 到 调查这些假设工作将进行：1）， 在河流河段建立观测威尔斯样带， 不同河边水力特性及措施 无机氮和有机氮的初始浓度 2）测试氮素富集对氮素的影响 化学在这些网站;和3）估计的潜力， 实验室土壤和沉积物中的硝化和反硝化作用 系统，然后量化氮损失的具体机制， 氮-15示踪技术。 这种场的组合 测量、现场操作和实验室实验 将使我们能够检查相对重要性和空间 硝化、反硝化和植物特性 典型热带河流生态系统的吸收。

This project will investigate fundamental processes that are likely to influence the behavior of nitrogen in tropical rain forest streams. Very little is known about hydrologic interactions between stream water and soil water or the potential influences such interactions could have on the nitrogen cycle in tropical ecosystems. Preliminary data collected in montane rain forest watersheds in Puerto Rico indicae that soil water carries large amounts of dissolved nitrogen as ammonium into the riparian zone. Very little ammonium or nitrate is found in stream water, however, suggesting that nitrogen is removed from solution before it enters bulk stream flow. It is important to determine whether the nitrogen removed from solution is exported from the ecosystem in a gaseous form by nitrification or denitrification or whether it is recycled internally by plant uptake. It is hypothesized that in these tropical streams: 1) available stream-side inorganic nitrogen supports an active nitrification- denitrification couple and that 2) this couple has a major influence on in-stream nitrogen chemistry. Furthermore, it is hypothesized that flow paths through the stream-side zone will have a predictable influence on nitrogen dynamics. To investigate these hypotheses work will be performed: 1) to established transect of observation wells on stream reaches with differing stream-side hydraulic characteristics and measure initial concentrations of inorganic and organic nitrogen at these sites; 2) test the effects of nitrogen enrichments on nitrogen chemistry at these sites; and 3) estimate the potential for nitrification and denitrification in laboratory soil and sediment systems, then quantify specific mechanisms of nitrogen loss with nitrogen-15 tracer techniques. This combination of field measurements, field manipulations, and laboratory experiments will enable us to examine the relative importance and spatial characteristics of nitrification, denitrification, and plant uptake in typical tropical stream ecosystems.