Spatial and temporal variability of nitrogen cycling in forests

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The water quality of streams and lakes located in Canada's boreal forests depend in large part on the cycling of water and nutrients [e.g. nitrogen (N)] on the landscape. These water and N cycling processes are extremely variable in both space and time, which makes it hard to predict how these cycles will respond to environmental changes, such as changes in the frequency or intensity of precipitation events. These events change the way water flows through forests and alter soil properties such as temperature and moisture. These environmental conditions determine the rates of N transformation processes in forests which ultimately determine the chemistry of lakes and streams that drain these forests. There are gaps in our scientific understanding of the controls on N processes in forests, and this limits our ability to make predictions about forest water quality into the future.The major objective of this proposal is to investigate hydrological and landscape controls on spatial and temporal variability in N cycling processes in forests, with a particular focus on the impact of increasing frequency and intensity of hydroclimatic events. We will investigate controls on N cycling in soils near the edge of streams which are particularly vulnerable to droughts and freezing. We will assess how flowpaths of water and N vary during events of different magnitudes and frequencies. We will examine where and when N2O, a potent but elusive greenhouse gas, in produced in forest soils. Ultimately, this work will provide critical insights into N cycling in forests, and help refine models of water quality responses to climate change.