Hydrological control points of biogeochemical cycling in suburbanizing stream corridors

加拿大的人口越来越多地居住在城市，这就要求更多地将土地利用转换为城市和郊区环境。在安大略省南部，目前的1300万居民人口预计到2040年将增长50%，这需要扩大现有的城镇。随着新的郊区发展，目前的土地规划者的目标是创建以现有和扩展的河流走廊为中心的绿色空间的综合自然遗产系统。这些郊区走廊的设计是为了模仿自然系统，增加了溪流的弯曲和广阔的河岸地带，与溪流相邻的土地通常比高地环境更湿润。在自然系统中，这些廊道特征增强了河流与陆地环境之间的连通性，从而提高了生物地球化学处理、物种生产和多样性的速度。这些改良后的郊区河流廊道是否具有天然类似物的功能还有待检验。本研究将探讨城郊和城郊河流廊道水文和生物地球化学功能的四个主要问题。(1)城郊河流廊道沿高地-河岸带-河流连续体的水文相互作用是什么？这些相互作用如何影响河流和河岸带内的营养动态？(2)在地下水-地表水相互作用和营养物质周转方面，城郊溪流的创造形态特征（宽阔的曲流弯曲，构造的溪流-水池序列）是否模拟了自然系统？(3)在高度改变的郊区河流中，营养物质的利用速度有多快，特别是在冬季冻融循环和极端降水事件中？(4)不同的雨水管理池设计对下游养分动态的影响是否不同？本研究的总体目的是为这些受影响的河流走廊开发一个概念性的工作模型，以便该模型可以应用于未来的设计，以改善郊区健康水生系统的创建和恢复。

Canada's population is increasingly housed in cities, requiring increased land-use conversion to urban and suburban environments. In southern Ontario, the current population of 13 million residents is expected to grow by 50 % by 2040, requiring expansion of existing cities and towns. With new suburban development, current land planners aim to create integrated Natural Heritage Systems of green space centered on existing and expanded stream corridors. These suburban corridors are designed to mimic natural systems, with increased stream meander bends and extensive riparian zones, the land adjacent to the stream often wetter than the upland environment. In natural systems these corridor features enhance connectivity between the stream and the terrestrial environment, leading to greater rates of biogeochemical processing and species production and diversity. Whether these modified suburban stream corridors function as their natural analogues remains to be tested. This research will address four main questions on the hydrological and biogeochemical functioning of suburban and suburbanizing stream corridors. (1) What are the hydrological interactions along the upland-riparian zone-stream continuum in suburban stream corridors, and how do these affect nutrient dynamics within the streams and riparian zone? (2) Do the created morphologic features of suburban streams (wide meander bends, constructed riffle-pool sequences) mimic natural systems in terms of both groundwater-surface water interactions and nutrient turnover? (3) How quickly are nutrients utilized in highly modified suburban streams, particularly in response to winter freeze-thaw cycles and extreme precipitation events? (4) Do different stormwater management pond designs affect downstream nutrient dynamics differently? The overall purpose of this research is to develop a conceptual working model for these impacted stream corridors, such that the model can be applied to future designs for the improved creation and restoration of healthy suburban aquatic systems. The proposed research will provide opportunities for three PhD students, five MSc students, and 11 undergraduate thesis students (plus many more field and lab assistants) to develop their intellectual and technical skills in the environmental sciences to advanced levels. These HQP will make meaningful contributions to the environmental protection of Canada both during their tenure in my research program and throughout their careers as environmental scientists.