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，这就要求将更多的土地使用转化为城市和郊区环境。在安大略省南部，目前1300万居民的人口预计到2040年将增长50%，这需要扩大现有的城镇。随着新的郊区开发，目前的土地规划者的目标是创建以现有和扩大的河流廊道为中心的绿色空间综合自然遗产系统。这些郊区走廊被设计成模仿自然系统，增加了溪流曲折和广泛的河岸地带，与溪流相邻的土地往往比高地环境更潮湿。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，导致更快的生物地球化学处理速度以及物种生产和多样性。这些经过改造的郊区河流走廊是否起到了它们天然类似物的作用，还有待测试。这项研究将解决有关郊区和郊区化河流走廊的水文和生物地球化学功能的四个主要问题。(1)郊区河流走廊中沿高地-河岸带-河流连续体的水文相互作用是什么，这些如何影响河流和河岸带内的营养物质动态？(2)郊区河流(宽阔的曲折、构造的冲沟-水池序列)在地下水-地表水相互作用和养分周转方面是否模拟自然系统？(3)在高度修改的郊区河流中，养分利用的速度有多快，特别是在应对冬季冻融循环和极端降水事件时？(4)不同的雨水管理池塘设计是否对下游营养物质动态产生不同的影响？这项研究的总体目的是为这些受影响的河流廊道开发一个概念性工作模型，以便该模型可以应用于未来的设计，以改进创建和恢复健康的郊区水生系统。 这项拟议的研究将为三名博士生、五名硕士学生和11名本科生论文学生(加上更多的现场和实验室助理)提供机会，将他们在环境科学方面的智力和技术技能发展到高级水平。这些HQP在我的研究项目期间和作为环境科学家的整个职业生涯中，都将为加拿大的环境保护做出有意义的贡献。

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.