Soil microbial communities in northern Alberta's boreal forest floors following resource extraction

Abstract

Land disturbance linked to resource extraction in Alberta ranges in severity from full ecosystem removal during surface mining to more surficial disturbance during clearcut timber harvesting. Changes to these ecosystems affect the soil microbial community, and the health of boreal forests is largely dependent on the soils in which they grow. Microbial communities are responsible for the decomposition and mineralization of forest litter, which converts major nutrients to useable forms for vegetation, thereby cycling the nutrients through the ecosystem. Phospholipid fatty acid (PLFA) and multiple substrate induced respiration (MSIR) analyses were used to assess the structural and functional diversity of forest floor soil microbial communities in two disturbed boreal forest ecosystems: (1) in a clearcut harvested stand 17.5 years post-harvest, and (2) in a 31 year chronosequence of reclaimed soils following surface mining. Disturbed stands were compared to their undisturbed counterparts in both forest ecosystems. In the harvested area, trembling aspen (Populus tremuloides) was the dominant tree species regenerating in both aspen and spruce (Picea glauca) clearcuts. PLFA and MSIR analyses demonstrated the importance of aspen stand regeneration on spruce clearcuts and its influence on soil properties. In both clearcuts, microbial communities exhibited comparable functional diversity, and a structure more similar to the communities in undisturbed aspen forest floors than undisturbed spruce. In the surface mined area, the novel forest floor that developed atop the peat-mineral coversoil was key to the reestablishment of a microbial community with different structure, yet similar biomass and function to that present in undisturbed soils.