Salinity Affected Gross Nitrogen Transformation in Reclaimed Boreal Forest Soils in the Oil Sands.

Peat-mineral mix is commonly used over tailings sand or overburden for oil sands reclamation in Alberta, Canada. Some of the tailings sand and overburden materials have high salinity and the salts may move into the peat-mineral mix layer. The peat-mineral mix layer may also have low nitrogen availability despite its high total nitrogen content. Salinity and nitrogen availability acting alone or in combination can influence plant growth in reclaimed boreal forest soils. The objective of this study was to investigate the effect of soil salinity on gross N transformation using the ¹⁵N tracing technique (Markov chain Monte Carlo method) in peat-mineral mix, tailings sand and overburden soils. A sodium chloride solution was added to the soils to form soil solutions with electrical conductivity 2, 4, 6 and 8 dS m^-1. After pre-incubating at 25 ¢ªC at 65% water holding capacity for one week, the soils were applied 2 mL ¹⁵NH₄NO₃ (10 atom %) or NH₄¹⁵NO₃ (10 atom %) solution, increasing 20 mg N kg^-1 soil. The soils were extracted after being incubated for 0.5 hour, 1, 2, 3 and 4 days. The extracts were distillated to obtain ammonium and nitrate distillates. After being oven-dried at 60 ¢ªC, the distillates were analyzed for ¹⁵N abundance of ammonium and nitrate. The gross N mineralization, nitrification and immobilization rates were calculated using the ¹⁵N tracing model developed by Christoph Müller. The study will help us understand the influence of soil salinity on gross rates of nitrogen transformation and the availability of nitrogen in salinity affected reclaimed boreal forest soils in the oil sands region.