Spatial Pattern of Soil Respiration and Soil Microbial Biomass: Indicators for Reclamation Success.

Surface mining of oil sands in northern Alberta is a large scale disturbance with over 750 km² affected to date. Extraction companies are required by law to return the environment to ‘equivalent land capability’, but this has proved challenging to quantify meaningfully and only one site has been certified as reclaimed. Restoring ecosystem function might be more realistic and may be quantifiable by examining spatial patterns of microbial and nutrient indices. In an ongoing study, soil respiration and microbial biomass carbon data was collected from 6 different sites and evaluated using spatial statistics. The reclamation treatments considered were peat mineral mix (PMM) and forest floor mineral mix (FFM) and these were compared to natural benchmarks including a mature forest stand, and stands recovering from fire and clear cutting. We measured the CO₂ flux monthly during the growing season using a Li‑Cor 8100A Soil CO₂ Flux system. Microbial biomass data was sampled using a lab incubation of a subset of soil samples and FTIR was used to extrapolate to the whole spatial data set. The data indicated that there were differences in the pattern of soil respiration between different sites. Reclaimed sites seemed to show smaller scale spatial patterns than sites disturbed by clear cutting and forest fire. Higher rates of soil respiration were observed on PMM and correlate with higher microbial biomass. This might be an indication that heterotrophic respiration is a main driver of soil respiration on sites reclaimed with PMM. These interactions must be understood in order to understand if sites function as carbon sink or carbon source post disturbance.