Rebuilding the boreal: analyzing the replicability of the bacterial community structure and soil functioning of forest floor mineral mix with peat subsoil admixtures

Abstract

Alberta law requires reclamation of lands disturbed by surface mining operations, such as those occurring at the Athabasca Oil Sands Region, however, reclamation rates lag far behind continued disturbance rates. Due to cost, mining companies must make use of the materials on site, of which the majority is mineral subsoil and peat. The far less abundant forest floor material is the most suitable base for a reclamation substrate, however its quantity is limited. The bacterial community of the soil is inherently linked to soil functioning, and can potentially be used as a proxy to investigate the likelihood of success of a reclamation regime. To investigate if peat and subsoil could be mixed to produce a FFM-like bacterial community, we supplemented FFM, as well as peat and subsoil mixed at different ratios, with/without biochar and/or a trembling aspen seedling and incubated for 12 weeks in a greenhouse. We measured bulk soil respiration throughout the incubation period, and performed end-point high throughput sequencing of the 16s rRNA gene and bacterial community analysis. The overall diversity of the peat containing admixtures was indistinguishable from that of FFM, while that of subsoil was lower than all other admixtures. However, this was not reflected in the soil respiration, as the respiration rate was indistinguishable for all peat containing admixtures, which was lower than for the FFM and higher than for the pure subsoil. The trends seen in the soil respiration rate correlated to the community composition, where there were three distinct groups; peat containing admixtures, FFM, and subsoil. Biochar and tree additions had minimal effects on any of the admixtures. These results show that peat cannot be used if the goal is to approach a FFM-like community and that subsoil can be used to “dilute” the peat microbial community without an effect on its composition.