Hydrologic control of nitrogen removal, storage, and export in a mountain stream
Hydrologic control of nitrogen removal, storage, and export in a mountain stream
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DOI：
10.4319/lo.2009.54.6.2128
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发表时间：
2009-11
影响因子：
4.5
通讯作者：
R. Hall;M. Baker;C. Arp;B. Koch
中科院分区：
文献类型：
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作者：
R. Hall;M. Baker;C. Arp;B. Koch
溪流和河流中的养分循环和输出应随流量变化而变化，但大多数关于溪流养分转化的研究并未包括水文变异性。我们使用了一种稳定的氮同位素示踪剂（15N）来测量美国爱达荷州泉溪一条山溪中硝酸盐（NO3−）的吸收、储存和输出。我们在融雪和基流期间进行了两次为期2周的示踪试验。在三个季节中监测了15N的溶解和颗粒形式，以验证河流N循环将以洪水期间的输出和低流量期间的储存为主的假设。洪水比基流条件下输出更多的氮；然而，由于潜流交换，融雪洪水对NO3−的需求高于预期。在两种示踪剂试验中，底栖藻类和木材生物膜等短暂池的底栖氮停留时间均大于100 d。细碎碎屑、昆虫和来自潜流带的颗粒态氮的停留时间要长得多，表明同化和水文储存可能是保留颗粒态氮的重要机制。在河流中储存的示踪氮的主要出口形式是在夏季暴雨或次年春季融雪产生的高流量期间通过季节出口。在高流量期间，春溪不一定是营养物质的管道；河流与河谷间的水文交换是一种重要的蓄水机制。
Nutrient cycling and export in streams and rivers should vary with flow regime, yet most studies of stream nutrient transformation do not include hydrologic variability. We used a stable isotope tracer of nitrogen (15N) to measure nitrate (NO3−) uptake, storage, and export in a mountain stream, Spring Creek, Idaho, U.S.A. We conducted two tracer tests of 2‐week duration during snowmelt and baseflow. Dissolved and particulate forms of 15N were monitored over three seasons to test the hypothesis that stream N cycling would be dominated by export during floods, and storage during low flow. Floods exported more N than during baseflow conditions; however, snowmelt floods had higher than expected demand for NO3− because of hyporheic exchange. residence times of benthic N during both tracer tests were longer than 100 d for ephemeral pools such as benthic algae and wood biofilms. Residence times were much longer in fine detritus, insects, and the particulate N from the hyporheic zone, showing that assimilation and hydrologic storage can be important mechanisms for retaining particulate N. Of the tracer N stored in the stream, the primary form of export was via seston during periods of high flows, produced by summer rainstorms or spring snowmelt the following year. Spring Creek is not necessarily a conduit for nutrients during high flow; hydrologic exchange between the stream and its valley represents an important storage mechanism.