Sphagnum Moss Enzymatic Activity Responses To Elevated Nitrogen Inputs in Ombrotrophic Peatlands

Emissions of NOx associated with Alberta oil sands development are leading to increased atmospheric nitrogen deposition in a pristine region (<1kg N/ha/yr). Nitrogen deposition has the potential to alter the ecosystem function, which can be manifested by changes in plant and microbial enzymatic activities. Since 2011, we experimentally added nitrogen in simulated precipitation to an Alberta bog and poor fen. In 2013, phosphorus and nitrogen mineralization enzymatic activities of three Sphagnum moss species were quantified using methylumbelliferone fluorescent detection. Phosphatase activities increased from the control to the 25 kg N ha-1yr-1 up to five-folds in all three species and in both peatlands. Chitinase activity also increased with nitrogen addition for Sphagnum magellanicum in the poor fen but not the bog. Increasing enzymatic activity suggests nitrogen and phosphorus co-limitation in these boreal peatlands and sensitivity to increasing nitrogen deposition from oil sands development, with potential consequences for peatland nutrient cycling.