Fen Revegetation Research

Processing oil sands produces large volumes of wet tailings material including sand, silts and clays in suspension with soluble organic chemicals, ammonia, heavy metals and salts, collectively termed oil sand process‐affected water (OSPW). Materials containing OSPW may adversely affect the ecology of systems being reclaimed, including peatlands. Given the recent thrust to reclaim post‐mined landscape to fen peatlands and use of peat in artificial soil cover during reclamation, determining transport and fate of OSPW in peat soils and impact on peatland plant communities is essential. It is not known whether fen plants can survive long‐term exposure to OSPW, or how these contaminants move through peat and interact with plant roots. A research program was initiated to address these challenges. Laboratory and greenhouse experiments were run to determine how OSPW is transported through peat driven by evapotranspiration from a moss and/or vascular plant cover; and how plants and microbial communities react to OSPW contamination. Main objectives were to characterize: (1) the movement of process‐affected water in peat substrate; (2) survival and growth of common fen species native to the oil‐sands region in greenhouse trials; and (3) the changes in microbial functional diversity in the contaminated peat under two fen vegetation structures.

(1) Contaminant transport in peat: transport of Na and NAs is highly delayed due to adsorption onto peat and diffusion in the dual porosity medium, affecting concentration of potentially toxic compounds in the plant rooting zone. The complex structure of peat is an important factor on attenuating process in groundwater transport and can remove toxic compounds from the peatland; (2) OSPW and plants: Typical fen graminoid plants were able to tolerate a realistic contamination scenario; only 3 species showed a short decrease of transpiration, and vascular plants spontaneously recolonized peat in seed bank transfer experiments. Results for mosses were less positive – health was negatively affected by OSPW or salt, probably due to both contaminant and drought effects. Water control should be a crucial step in constructed fens. Campylium stellatum had highest OSPW contact survival potential. Vascular plants and mosses OSPW tolerance should be tested in the field and over a longer time period; (3) OSPW and microbes: Functional diversity of the microbial community in fen peat is strongly influenced by aboveground vegetation, with higher diversity under graminoids than mosses. It will be essential to document microbial communities in natural fens to establish appropriate references.