Reclamation efforts promoting the re-establishment of native plant and soil microbial communities following large-scale disturbances are crucial in restoring natural ecosystems. It is important that the reclamation procedures most capable of facilitating the establishment of native plant species and pre-disturbance microbial communities be identified and put into practice. The objective of this research is to determine plant community development and microbial community composition in response to different combinations of coversoils and plant establishment treatments on an oil sands overburden waste area.
Eighteen field plots, established in 2014, were monitored annually to compare plant community development and trembling aspen seedling density on 3 soil types (forest floor-mineral mix [FFMM], transitional, peat-mineral mix [PMM]) with 4 plant establishment treatments (seeding native species, weeding undesirable weeds, seeding & weeding, control). During the 2016 field season, composite coversoil samples were collected from reclamation plots and reference forest stands for analysis of soil microbial community composition.
Soil type was found to be a dominant plant community driver, with FFMM and transitional soils showing higher species richness, diversity, and total vegetation cover than PMM, while PMM supported greater aspen seedling densities. Minimal weed establishment on transitional and PMM soils resulted in weeding treatments having no significant effect on plant community development; however, weeding on FFMM did result in the increased presence of native forb species, Galium boreale and Vicia americana. Additionally, seeding treatments resulted in the increased presence of Achillea millefolium on all soil types, and of Solidago canadensis on FFMM.
Initial analysis of microbial biomass and community function suggests soil type is also a dominant driver of soil microbial communities, while seeding and weeding treatments had lesser effect. PMM was found to support minimal microbial biomass, while FFMM and transitional soil supported greater biomass than reference sites. Microbial community function between all soil types and references shared a similar pattern in response to different carbon substrate-based stimulation; however, in several instances FFMM and reference sites had higher levels of substrate utilization, suggesting greater community function.
Effective reclamation is necessary to return disturbed oil sands to functioning natural ecosystems. Studying the effects of seeding and weeding on different coversoils will help determine the impacts of invasive weed species on plant community development, as well as belowground soil microbial communities. Identifying potential impacts of weed species on reclamation sites would aid oil companies in refining reclamation procedures to attenuate any negative effects caused by invasive weeds.