Sources, transformations, and hydrological processes that control stream nitrate and dissolved organic matter concentrations during snowmelt in an upland forest
Sources, transformations, and hydrological processes that control stream nitrate and dissolved organic matter concentrations during snowmelt in an upland forest
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DOI：
10.1029/2008wr006983
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发表时间：
2008-12
影响因子：
5.4
通讯作者：
S. Sebestyen;E. Boyer;J. Shanley;C. Kendall;D. Doctor;G. Aiken;N. Ohte
中科院分区：
文献类型：
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作者：
S. Sebestyen;E. Boyer;J. Shanley;C. Kendall;D. Doctor;G. Aiken;N. Ohte
我们探索了在美国佛蒙特州东北部的一片山地森林中控制溪流养分浓度的集水过程，那里通过大气沉积输入的氮是美国最高的之一，并影响到生态系统的功能。我们使用春季融雪期间高频采集的溪水样本来追踪水、硝酸盐和溶解有机物(DOM)的来源。水化学、同位素示踪和端元混合分析表明了水和营养物质进入溪流的时间、来源和来源区域。虽然水溶有机碳(DOC)和溶解有机氮(DON)都来源于可溶性有机质的淋溶，但由于提供DOC和DON最高浓度的水文径流和来源的动态变化，这两种DOM组分之间的冲刷响应不同。高浓度的溪水硝酸盐既来自大气来源，也来自集水区土壤的硝化来源。在积雪融化后期，我们检测到表层土壤中的硝化作用，这影响了可输送到溪流中的硝酸盐供应。然而，同位素示踪表明，融雪后上坡表层土壤水中的硝酸盐大部分来自大气来源。大气中的一小部分氮被直接输送到溪流中，这一发现突显了融雪事件期间快速流动路径的重要性。这些发现表明，必须破译来源、转化和水文传输过程之间的相互作用，以了解浓度为什么会随着时间和空间的变化而变化，并阐明人类活动对旱地森林溪流养分动态的直接影响。
We explored catchment processes that control stream nutrient concentrations at an upland forest in northeastern Vermont, USA, where inputs of nitrogen via atmospheric deposition are among the highest in the nation and affect ecosystem functioning. We traced sources of water, nitrate, and dissolved organic matter (DOM) using stream water samples collected at high frequency during spring snowmelt. Hydrochemistry, isotopic tracers, and end‐member mixing analyses suggested the timing, sources, and source areas from which water and nutrients entered the stream. Although stream‐dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) both originated from leaching of soluble organic matter, flushing responses between these two DOM components varied because of dynamic shifts of hydrological flow paths and sources that supply the highest concentrations of DOC and DON. High concentrations of stream water nitrate originated from atmospheric sources as well as nitrified sources from catchment soils. We detected nitrification in surficial soils during late snowmelt which affected the nitrate supply that was available to be transported to streams. However, isotopic tracers showed that the majority of nitrate in upslope surficial soil waters after the onset of snowmelt originated from atmospheric sources. A fraction of the atmospheric nitrogen was directly delivered to the stream, and this finding highlights the importance of quick flow pathways during snowmelt events. These findings indicate that interactions among sources, transformations, and hydrologic transport processes must be deciphered to understand why concentrations vary over time and over space as well as to elucidate the direct effects of human activities on nutrient dynamics in upland forest streams.