Similarity in Nutrient Profiles of Reclaimed and Natural Benchmark Soils in the Alberta Oil Sands.

Comparing functional similarity in reconstructed upland forest ecosystems with natural benchmarks can provide ecologically meaningful information to measure reclamation success. We examined nutrient supply rate as a measure of ecosystem function in two reclaimed soils in the mineable oil sands region of northern Alberta, Canada. The reconstructed soils are mixtures of organic and mineral matter salvaged during mine development from either upland (referred to as forest floor-mineral mix (FFMM)) or lowland (referred to as peat-mineral mix (PMM)) forests. We compared these reclaimed soils, half of which included an initial fertilization treatment, with young natural fire disturbed and mature aspen forests on alfisols, the common upland soil type in the region. Nutrient (macro and micro) supply rates were measured for three consecutive years using plant root simulator (PRS) probes during the peak growing season. Results indicated that nutrient supply profiles of reclaimed soils were more similar to each other than to the natural benchmarks with FFMM being more similar to natural soils than was PMM. Reclaimed soils had lower P and K supply rates and higher S, Ca, and Mg supply rates than benchmark soils with no significant differences in inorganic N supply rates. The expected nutrient flush post-fertilization was only apparent in N and P supply rates but the effect was transient and levelled off the year after fertilization in most cases. However, fertilization did align the temporal trajectory of the nutrient supply profile in PMM to be similar to benchmark conditions indicating potentially greater ecological benefit of fertilization than in FFMM. Fertilization prescriptions focusing on P and K rather than N are also likely more ecologically appropriate for establishing natural ecosystem function on peat based reclaimed soils.