Contribution of wetlands to nitrate removal at the watershed scale
Contribution of wetlands to nitrate removal at the watershed scale
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DOI：
10.1038/s41561-017-0056-6
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发表时间：
2018-02-01
影响因子：
18.3
通讯作者：
Finlay, Jacques C.
中科院分区：
文献类型：
--
作者：
Hansen, Amy T.;Dolph, Christine L.;Finlay, Jacques C.
集约管理的行作物农业通过大规模改变土地覆盖、水文和活性氮有效性，从根本上改变了密西西比河流域的地表过程。这些变化造成了泄漏的地貌，过量的农业衍生硝酸盐在地方、区域和大陆范围内退化了河流水质。就个别而言，湿地可以去除硝酸盐，但多个湿地有效降低河流硝酸盐浓度的条件尚未建立。只有密西西比河流域的一个地区--44,000公里(2)的明尼苏达河流域--在其集约化农业管理的流域内仍然有足够的湿地覆盖，从经验上解决了这个问题。在这里，我们结合了明尼苏达州河流域的高分辨率土地覆盖数据和空间上广泛的重复水样数据。通过清楚地将湿地与作物覆盖的影响隔离开来，我们表明，在中高径流下，湿地在降低河流硝酸盐浓度方面的单位面积效率是最有效的陆基氮素缓解策略的五倍，这些策略包括覆盖作物和土地退耕。我们的结果表明，考虑到河流网络中空间位置的影响的湿地恢复可以提供比先前假设的更大的水质效益。
Intensively managed row crop agriculture has fundamentally changed Earth surface processes within the Mississippi River basin through large-scale alterations of land cover, hydrology and reactive nitrogen availability. These changes have created leaky landscapes where excess agriculturally derived nitrate degrades riverine water quality at local, regional and continental scales. Individually, wetlands are known to remove nitrate but the conditions under which multiple wetlands meaningfully reduce riverine nitrate concentration have not been established. Only one region of the Mississippi River basin-the 44,000 km(2) Minnesota River basin-still contains enough wetland cover within its intensively agriculturally managed watersheds to empirically address this question. Here we combine high-resolution land cover data for the Minnesota River basin with spatially extensive repeat water sampling data. By clearly isolating the effect of wetlands from crop cover, we show that, under moderate-high streamflow, wetlands are five times more efficient per unit area at reducing riverine nitrate concentration than the most effective land-based nitrogen mitigation strategies, which include cover crops and land retirement. Our results suggest that wetland restorations that account for the effects of spatial position in stream networks could provide a much greater benefit to water quality then previously assumed.