Abstract

An experiment was initiated in 1997 in northeast Alberta at Syncrude Canada Ltd. Mildred Lake site to field test an innovative technique for reclamation of oil sands mine tailings. This technique was used to create an aggregated surface soil material from oil sand tailings. Plant community was successfully established on soil material created by this technique. However, whether the site would be capable of supporting a self-sustainable ecosystem for the long-term remained unknown. We evaluated the capability of these aggregated oil sands tailings by using biological indicators because the abundance and diversity of soil microbial biomass is a good measure of the health of soil-plant ecosystem. Soil respiration rates and soil microbial biomass were used to assess the abundance and activities of soil microbial communities. In addition, the ability of soil microbial biomass to utilize a diverse range of carbon substrates was used to assess the diversity of soil microbial communities. Soil biological activity increased with increasing growth of plant biomass and with time. Increasing amount of peat moss incorporated into the soil during reclamation resulted in higher organic carbon and nitrogen content and caused an increase in abundance and diversity of soil microbial biomass. These results indicate that measurements of soil respiration and substrate utilization by soil microbial communities may be used as biological indicators for assessing the capability of reclaimed soils.

Introduction

One active area of land reclamation research is to compare and synthesize patterns and processes in reclaimed soils and to assess their capability for supporting a self-sustaining ecosystem. Such comparisons and synthesis work best only when the measurements made are comparable and repeatable (Robertson et al., 1999). Using a standard methodology is a key to addressing many questions regarding longterm sustainability of reclaimed land.

A critical component in the reclamation of oil sands tailings is to create soil materials conducive to the growth of soil microorganisms and as a result, to stimulate soil microbial biomass mediated nutrient cycling process following initial reclamation. Soil organic carbon dynamics is at the center of these processes. Soil microbial biomass is largely responsible for the decomposition of soil organic matter and litters that contribute to soil nutrient pools through mineralization. Additionally, certain soil microorganisms form symbiotic associations (mycorrhizae, nodules) with plants and contribute to the overall success of plant growth. Thus the success of planting for reclamation purposes is affected by, and may be contingent upon, the quality and quantity of soil microbial communities and their activities.

This paper presents the use of a few simple measurements of soil microbial activities as biological indicators for evaluating the capability of reclaimed soil.

MATERIALS AND METHODS
Field Site

The site, located at the Syncrude Canada Ltd. Mildred Lake in northeastern Alberta, was established in 1997. Composite tailings (CT) weres used as a sub-material.

Five treatments were used for the top 20 cm layer. The composite tailings, amended with various amount of peat moss, were aggregated using an aggregation technology (Li and Fung, 1998).

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