The Role of the Forest Soil Propagule Bank in Assisted Natural Recovery after Oil Sands Mining

Abstract

This study was undertaken to determine if use of stratified organic layers of intact litter, fragmented litter, and humus on the forest floor (LFH) improves establishment of upland native boreal plant species during oil sands reclamation in Alberta, Canada. The abundance and composition of vascular plant species in the soil propagule bank were determined for LFH and peat materials before salvage from donor sites and 18 months after application on the receiver site. Applications of 10 and 20 cm were evaluated. Various soil properties were assessed to determine impacts of donor materials. In the growth chamber, LFH donor material had significantly more plant species emerge (37) from the propagule bank than did peat donor material (19). In the field, LFH treatments had significantly higher species richness (49, 47, 24, and 25 species for LFH 10 cm, LFH 20 cm, peat 10 cm, and peat 20 cm treatments, respectively), plant abundance, and soil nutrients than peat treatments. Application thickness of peat had little effect, but 20 cm of LFH was more beneficial for plant community establishment than 10 cm. LFH treatments had narrower C:N ratios and higher soluble potassium and available phosphorus than peat. Applying 10 versus 20 cm of donor material increased admixing of finetextured subsoil, reducing organic carbon, nitrogen, and potassium; these effects were greater for LFH than peat treatments. Thus, addition of LFH aids in creating diverse ecosystems on reclaimed upland landscapes by providing a source of propagules for revegetating upland boreal forest communities and improving nutrient availability for plants.

Temporal Trends of Ecosystem Development on Different Site Types in Reclaimed Boreal Forests

“…The reclaimed areas in which the LTPN plots are established were generally constructed in this fashion using peat-mineral mix as the surface soil so the main differences among reclamation sites are in the lower soil layers. Newer reclamation techniques, including the use of upland forest floor material [9], application of coarse woody debris [10] or the creation of wetlands [11], are not included in this analysis of the LTPN.…”

Evaluation of soil reclamation techniques at the Key Lake uranium mine

“…The LFH treatment did not improve nutrient composition relative to the Control as expected in spite of the higher fertility and nutrient pools often associated with LFH material (Mackenzie and Naeth 2010). This may be due to admixing of the natural LFH with mineral soil in this study.…”

“…Forest floor (referred to as LFH) is a rich source of plant propagules, soil microbes and nutrients, and is widely applied in land reclamation in the Alberta oil sands region (Mackenzie and Naeth 2010). Most ecosites within the Key Lake mining footprint are designated as BS6 ecosite (McLaughlan et al 2010), typically with a shallow LFH over Ae, Bm and C horizons classified as Eluviated Dystric Brunisols.…”

“…In the past 30 yr, the soil capping prescriptions commonly used in the oil sands reclamation include a mixture of peat and mineral soil (peat-mix) or subsoil or both, placed over either tailings sand, overburden, Clearwater shale or lean oil sands (Rowland et al 2009). The utilization of litter-fibric-humic (LFH) and Ae horizons as topsoil material in the upland boreal forest areas is also a promising technique as was investigated by Mackenzie and Naeth (2010). The LFH material was shown to stimulate diverse ecosystems by providing a viable source of nutrients and propagules for revegetation (Mackenzie and Naeth 2010).…”

“…The utilization of litter-fibric-humic (LFH) and Ae horizons as topsoil material in the upland boreal forest areas is also a promising technique as was investigated by Mackenzie and Naeth (2010). The LFH material was shown to stimulate diverse ecosystems by providing a viable source of nutrients and propagules for revegetation (Mackenzie and Naeth 2010).…”