Comparing Plant and Microbial Community Recovery Between Land Reclamation and Wildfire in the Athabasca Oil Sands Region.

For reclamation to be considered successful, an ecosystem must be self-sustaining and have a recovery trajectory that falls within the range of natural variability in ecosystem function of locally common communities. This study examined soil nitrogen availability, soil microbial community, and plant community recovery following natural (wildfire) and anthropogenic (reclamation) disturbance, in the Athabasca Oil Sands Region. Eleven natural (aged 2-131 years) upland mixedwood boreal stands were compared with five reclaimed sites (aged 4-27 years). Soil nitrogen availability was assessed with an anaerobic incubation in the lab. Microbial respiration was measured as an indicator of activity, and microbial community fingerprint and biomass were determined using phospholipid fatty acid analysis. The vegetation was characterized by canopy cover, plant functional group, and composition survey at the genus level. The potentially mineralizable nitrogen trend with time was much higher on the natural sites than the reclaimed sites. Non-metric multi-dimensional scaling ordinations of the soil microbial community and understory vegetation composition revealed that reclaimed and unburned sites had significantly different communities with a low degree of similarity. The burned sites (aged 2-39 years) were more variable and bridged the difference between the reclaimed and mature sites. The microbial community of the oldest reclaimed sites were most similar to naturally disturbed sites. This work indicates that young naturally disturbed sites may be a more relevant comparison when evaluating reclamation trajectory than mature stands.