Biogeochemical cycling in central Ontario sugar maple forests

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Hardwood forests in southern Ontario have been, and will continue to be, subjected to a multitude of environmental stressors including acid deposition, elevated nitrogen and trace metal deposition along with climate change. The stressors can act individually and in concert to disrupt the ecological integrity of these important natural ecosystems. A key measure of this ecological integrity is nutrient cycling; acidification of soils for example can alter base cation and trace metal cycling while chronic inputs of elevated nitrogen deposition can disrupt the nitrogen cycling of these systems. Ultimately, alterations in biogeochemical cycling may lead to the disruption of other ecological parameters such as alterations in species composition and lead to a deterioration of forest health. Most previous studies on forest biogeochemical cycling in Ontario have generally focused on regions overlying the Precambrian Shield, where acid soils dominate; little is known about biogeochemical cycling in the southern part of the region, which may ultimately be more sensitive to polutants such as nitrogen. The overall short-term objective of this work is to characterize the biogeochemical cycling of major nutrients and trace metals at five sugar maple dominated sites in southern Ontario that are part of the Ontario Ministry of Environment's forest health monitoring program. The sites vary in terms of soil chemistry, climate and pollution loadings and are expected to have contrasting biogeochemical cycling. A number of biogeochemical models have been developed to assess the dynamic response of forest ecosystems to a number of pollutants (acid deposition, nitrogen, trace metals) which require detailed site-specific input data. Several models (e.g. (MAGIC, VSD, FORSAFE etc.) will be evalauted at the study sites, which represent the range of soil, climate and atmospheric deposition observed in Ontario's sugar maple forests. The long-term objective is to undertake a regional assessment of the response of Ontario's hardwood forests to acid, nitrogen and metal deposition under a changing climate using dynamic biogeochemical models.