Effects of lateral nitrate flux and instream processes on dissolved inorganic nitrogen export in a forested catchment: A model sensitivity analysis
Effects of lateral nitrate flux and instream processes on dissolved inorganic nitrogen export in a forested catchment: A model sensitivity analysis
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DOI：
10.1002/2014wr015962
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发表时间：
2015-04
影响因子：
5.4
通讯作者：
Laurence Lin;J. Webster;T. Hwang;L. Band
中科院分区：
文献类型：
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作者：
Laurence Lin;J. Webster;T. Hwang;L. Band
陆地和水生生态系统在控制河流氮动力学中的重要性是生态学家研究流域溶解无机氮（DIN）输出的关键兴趣。在本研究中，我们将河流模型与陆地生态水文模型相结合，并进行了全球敏感性分析，以评估两种生态系统对氮输出的相对重要性。我们构建了两种情景（“正常”和高硝酸盐负荷）来探索陆地（横向硝酸盐通量）或水生生态系统（溪流营养过程）在控制DIN出口方面可能更重要的条件。在森林流域，虽然森林生态系统控制着流向河流的氮负荷，但敏感性结果表明，陆地生态系统的大部分氮输出被与底栖动物碎屑相关的河流微生物固定化吸收并保留在碎屑中。再将固定化氮再矿化为DIN。因此，该河中DIN浓度的年际格局为秋季低，春季高。在高氮负荷情景下，微生物固定化不仅达到饱和状态，而且固定化和矿化对DIN输出的净影响也被最小化，因为有机和无机形式之间的氮循环被加速。总体而言，我们的陆地-水生模型模拟表明，当陆地系统的氮输出较低时，溪流过程会显著影响流域氮输出的数量和时间。然而，当陆地系统的氮输出量高时，水流过程的影响最小。
The importance of terrestrial and aquatic ecosystems in controlling nitrogen dynamics in streams is a key interest of ecologists studying dissolved inorganic nitrogen (DIN) export from watersheds. In this study, we coupled a stream model with a terrestrial ecohydrological model and conducted a global sensitivity analysis to evaluate the relative importance of both ecosystems to nitrogen export. We constructed two scenarios (“normal” and high nitrate loads) to explore conditions under which terrestrial (lateral nitrate flux) or aquatic ecosystems (instream nutrient processes) may be more important in controlling DIN export. In a forest catchment, although the forest ecosystem controls the nitrogen load to streams, sensitivity results suggested that most nitrogen output from the terrestrial ecosystem was taken up by instream microbial immobilization associated with benthic detritus and retained in detritus. Later the immobilized nitrogen was remineralized as DIN. Therefore, the intra‐annual pattern of DIN concentration in the stream was low in fall and became high in spring. Not only was instream microbial immobilization saturated with the high nitrogen load scenario, but also the net effect of immobilization and mineralization on DIN export was minimized because nitrogen cycling between organic and inorganic forms was accelerated. Overall, our linked terrestrial‐aquatic model simulations demonstrated that stream process could significantly affect the amount and timing of watershed nitrogen export when nitrogen export from the terrestrial system is low. However, when nitrogen export from the terrestrial system is high, the effect of stream processes is minimal.