Effect of antecedent hydrologic conditions and agricultural activity on riparian zone biogeochemistry

河岸湿地已被确定为有效减少农业用地化学物质负荷的重要地貌，但地下水和地表水中的硝酸盐负荷仍然是一个问题。这在大湖区尤其明显，那里的湖泊继续受到农业做法的影响。需要更好地了解河岸湿地何时以及为什么不能减少硝酸盐，特别是在存在气候变化增加威胁的五大湖地区。在评价河岸带功能时，人们对河岸湿地和旱地的物理特征关注较多，但对氮的命运和运输的时间格局关注较少。事件前先决条件可能通过影响土壤氮转化、径流途径以及这两个变量的相互作用，在控制氮动力学的时间模式中发挥重要作用。采用野外观测和室内实验相结合的方法，本研究的目的是：(1)确定和量化河岸土壤中氮的命运和运输的水文和生物地球化学控制；2)在双源水化学输入（高地和上游）条件下，对安大略省南部农业河岸湿地氮素命运和转移的水文控制特征；(3)量化前期水文条件（AHC）对基于事件的氮转移的影响。未来农业流域土地利用和气候变化对地表水质量的综合影响不容小觑；必须了解河岸缓冲湿地提供的自然服务的潜在减少，以便制定有效的未来管理战略。这项工作将有助于环境模型，也将有助于管理人员有效管理加拿大水资源。

Riparian wetlands have been identified as important landforms that effectively reduce the loading of chemicals from agricultural lands, yet nitrate loading in ground water and surface water remains a problem. This is particularly evident in the Great Lakes Region, where the lakes continue to be impacted by agricultural practices. An improved understanding of when and why riparian wetlands do not attenuate nitrate is needed, particularly in the Great Lakes region, where the threat of increased climatic variability exists.   Much attention has been given to the physical characteristics of riparian wetlands and upland fields in assessing riparian zone function, but little attention has been given to temporal patterns in the fate and transport of nitrogen. Pre-event antecedent conditions may play an important role in governing temporal patterns in nitrogen dynamics through their effect on soil nitrogen transformations, runoff pathways, and the interaction of these two variables.   Using a mixture of field observations and laboratory experimentation, the objectives of this research are to: (1) identify and quantify the hydrologic and biogeochemical controls on nitrogen fate and transport in riparian soils; 2) characterize hydrologic controls on the fate and transfer of nitrogen in an agricultural riparian wetland in Southern Ontario when hydrochemical inputs to the wetland originate from dual sources (upland, upstream); and (3) quantify the effects of antecedent hydrologic conditions (AHC) on event-based nitrogen transfer.   The future combined impacts of land-use and climate change in agricultural watersheds on surface water quality cannot be overstated; the potential reduction in the natural services provided by riparian buffer wetlands must be understood in order to develop effective future management strategies. This work will be useful in environmental models and will also be of use to managers in their effective management of Canadian water resources.