Land use/land cover and scale influences on in‐stream nitrogen uptake kinetics
Land use/land cover and scale influences on in‐stream nitrogen uptake kinetics
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土地利用/土地覆盖和规模对河流内氮吸收动力学的影响
DOI：
10.1029/2011jg001874
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发表时间：
2012
影响因子：
--
通讯作者：
R. McNamara
中科院分区：
文献类型：
--
作者：
T. Covino;B. McGlynn;R. McNamara
[1]土地利用/土地覆盖变化往往导致河流养分负荷增加；然而，其对河流生态系统养分运输的影响仍然知之甚少。鉴于营养负荷增加可能对水生生态系统产生有害影响，必须加强对跨河流尺度和流域发展梯度的养分保持能力的了解。我们在美国蒙大拿州西福克盖拉丁流域的6条溪流上进行了17个养分添加试验，以量化不同溪流大小(一到四级)和沿流域发展梯度的氮素吸收动力学和滞留动力学。我们观察到不同发育强度和规模的溪流对氮的吸收动力学和螺旋上升参数是不同的。在更发达的流域，我们观察到了施肥的影响。与未开发的溪流相比，这种施肥的影响是明显的，与未开发的溪流相比，发达的溪流无灰干质量、叶绿素以及环境和最大吸收速率都增加了。无灰干质量、叶绿素和次流域结构数与养分螺旋和动力学参数显著相关，而环境和年均N浓度与其相关性不显著。此外，发达河流最大吸收能力的增加有助于在生长季节期间河流中营养物质浓度较低，并有助于在基流期间将流域出口维持在较低水平。我们的结果表明，土地利用/土地复盖的变化可以增加河流对限制性养分的吸收，并突出了需要更好地了解控制不同尺度上的养分输出的流域动态以及缓解和保护水生生态系统的开发强度。
[1] Land use/land cover change often leads to increased nutrient loading to streams; however, its influence on stream ecosystem nutrient transport remains poorly understood. Given the deleterious impacts elevated nutrient loading can have on aquatic ecosystems, it is imperative to improve understanding of nutrient retention capacities across stream scales and watershed development gradients. We performed 17 nutrient addition experiments on six streams across the West Fork Gallatin Watershed, Montana, USA, to quantify nitrogen uptake kinetics and retention dynamics across stream sizes (first to fourth order) and along a watershed development gradient. We observed that stream nitrogen (N) uptake kinetics and spiraling parameters varied across streams of different development intensity and scale. In more developed watersheds we observed a fertilization affect. This fertilization affect was evident as increased ash-free dry mass, chlorophylla, and ambient and maximum uptake rates in developed as compared to undeveloped streams. Ash-free dry mass, chlorophylla, and the number of structures in a subwatershed were significantly correlated to nutrient spiraling and kinetic parameters, while ambient and average annual N concentrations were not. Additionally, increased maximum uptake capacities in developed streams contributed to low in-stream nutrient concentrations during the growing season, and helped maintain watershed export at low levels during base flow. Our results indicate that land use/land cover change can enhance in-stream uptake of limiting nutrients and highlight the need for improved understanding of the watershed dynamics that control nutrient export across scales and development intensities for mitigation and protection of aquatic ecosystems.