Department of Plant Sciences, University of California Davis, Shields Avenue, Davis, California, 95616, USA.
Graduate Group in Ecology, University of California Davis, Shields Avenue, Davis, California, 95616, USA.
Ecol Appl. 2018 Jun;28(4):1055-1067. doi: 10.1002/eap.1709. Epub 2018 May 7.
Denitrification, the microbial conversion of NO to N gases, is an important process contributing to whether lotic and riparian ecosystems act as sinks for excess NO from agricultural activities. Though agricultural waterways and riparian zones have been a focus of denitrification research for decades, almost none of this research has occurred in the irrigated agricultural settings of arid and semiarid climates. In this study, we conducted a broad survey of denitrification potential in riparian soils and channel sediments from 79 waterway reaches in the irrigated agricultural landscape of California's Central Valley. With this approach, we sought to capture the wide range of variation that arose from diverse waterway management and fluctuating flow conditions, and use this variation to identify promising management interventions. We explored associations of denitrification potentials with surface water NO -N, organic matter, flow conditions, vegetation cover, near-channel riparian bank slope, and channel geomorphic features using generalized linear mixed models. We found strong associations of sediment denitrification potentials with reach flow conditions, which we hypothesize was the result of variation in microbial communities' tolerance to dry-wet cycles. Denitrification potentials in riparian soils, in contrast, did not appear affected by flow conditions, but instead were associated with organic matter, vegetation cover, and bank slope in the riparian zone. These results suggest a strong need for further work on how denitrification responds to varying flow conditions and dry-wet cycles in non-perennial lotic ecosystems. Our findings also demonstrate that denitrifier communities respond to key features of waterway management, which can therefore be leveraged to control denitrification through a variety of management actions.
反硝化作用，即微生物将 NO 转化为 N 气体的过程，是影响流水和河岸生态系统是否成为农业活动中过量 NO 汇的一个重要过程。尽管农业水道和河岸带几十年来一直是反硝化研究的重点，但几乎没有研究发生在干旱和半干旱气候的灌溉农业环境中。在这项研究中，我们对加利福尼亚中央谷灌溉农业景观的 79 个水道段的河岸土壤和河道沉积物中的反硝化潜力进行了广泛调查。通过这种方法，我们试图捕捉到由不同的水道管理和波动的水流条件引起的广泛变化，并利用这种变化来确定有希望的管理干预措施。我们使用广义线性混合模型探索了反硝化潜力与地表水 NO-N、有机质、水流条件、植被覆盖、近岸河岸坡度和河道地貌特征之间的关系。我们发现沉积物反硝化潜力与河段水流条件之间存在很强的关联，我们假设这是微生物群落对干湿循环的耐受性变化的结果。相比之下，河岸土壤中的反硝化潜力似乎不受水流条件的影响，而是与河岸带的有机质、植被覆盖和岸坡有关。这些结果表明，需要进一步研究非永久性流水生态系统中反硝化作用对不同水流条件和干湿循环的响应。我们的研究结果还表明，反硝化菌群落对水道管理的关键特征有反应，因此可以通过各种管理措施来控制反硝化作用。
