Plant Community and Nitrogen Deposition as Drivers of Alpha and Beta Diversities of Prokaryotes in Reconstructed Oil Sand Soils and Natural Boreal Forest Soils

The Athabasca Oil Sands deposit is one of the largest single oil deposits in the world. Following surface mining, companies are required to restore soil-like profiles that can support the previous land capabilities. The objective of this study was to assess if soil prokaryotic α- and β-diversity in oil-sands soils reconstructed 20-30 years previously, and planted to one of three vegetation types (coniferous or deciduous trees and grassland) were similar to those found in natural boreal-forest soils subject to wildfire disturbance. Prokaryotic α- and β-diversity were assessed using massively parallel sequencing of 16S rRNA genes. β-diversity, but not α-diversity, differed between reconstructed and natural soils. Bacteria associated with an oligotrophic lifestyle were more abundant in natural forest soils, whereas bacteria associated with a copiotrophic lifestyle were more abundant in reconstructed soils. Ammonia-oxidizing archaea were most abundant in reconstructed soils planted with grasses. Plant species were the main factor influencing α-diversity in natural and in reconstructed soils. Nitrogen deposition, pH and plant species were the main factors influencing β-diversity of the prokaryotic communities in natural and reconstructed soils. The results highlight the importance of nitrogen deposition and aboveground - belowground relationships in shaping soil microbial communities in natural and reconstructed soils. Importance Covering over 800 km 2 , land disturbed by the exploitation of the oil-sands in Canada has to be restored. Here, we take advantage of the proximity between these reconstructed ecosystems and the boreal forest surrounding the oil-sands mining area to study soil microbial community structure and processes in both natural and man-made environments. By identifying key characteristics shaping the structure of soil microbial communities, this study improved our understanding of how vegetation, soil characteristics and microbial communities interact and drive soil functions.