Urban nitrogen biogeochemistry

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Urbanization is one of the most conspicuous components of global change. In Canada, the urban population exceeds 80%, whereas the proportion is even higher in Ontario (85%) and virtually all future population growth is expected to occur in urban areas primarily through the process of 'suburbanization', or expansion at their outer margins. While the biogeochemical impacts of changes from native to agricultural land-use have been well studied, the effect of conversion to urban land use has received relatively little research attention. Of particular concern, is the effect of urban land use change on N biogeochemistry. Nitrogen inputs and outputs are greatly modified in urban systems compared with natural land use types and N retention is often reduced in urban streams due to their 'flashier' hydrology, reduced hydraulic residence times and altered riparian zone connections. Conversely, a number of unique hotspots for N storage and denitrification may exist in urban areas, including lawns, storm water detention ponds and roadside ditches. The long-term goal of this research program is to evaluate the impacts of land use change on biogeochemical cycling within urbanizing watersheds in southern Ontario - the most populated region in Canada. This 5-year research program will focus on the impacts of landuse change on nitrogen (N) cycling in a southern Ontario metropolitan area. Specifically, the short-term objectives of this proposal are to (a) investigate N cycling along an urban-suburban-rural edge gradient; (b) characterize the hot spots (i.e. storm water ponds, lawns and roadside ditches) of N cycling and, (c) quantify N release during hot moments (storms and spring melt) along the gradient. These short-term objectives will be met through 1 PhD, 3 MSc. and 4 undergraduate Honours thesis projects that combine the urban gradient, patch dynamic and small catchment (mass balance) approaches.