CARBON STORAGE IN LANDSCAPES AFFECTED BY OIL SANDS MINING IN ALBERTA'S NORTHERN BOREAL FOREST

摘要

The objective of reclamation of surface mined lands in the Athabasca Oil Sands Region in northern Alberta is to return the land to an equivalent land capability. The native soils disturbed by surface mining must be salvaged and replaced during reclamation in accordance with the current provincial legislation, consequently, the topsoil (LFH or Ah, Ahe, Ae, Oa, Oi, Oe horizons) and subsoil (B and C horizons) or upper two meters of organic soil are removed and stockpiled during overburden and resource extraction activities and are replaced over tailings sand or overburden during reclamation. The objective of this research was to assess the carbon (C) balance within the reclaimed landscape by monitoring the soil, biomass and dead organic matter carbon pools from the time of initial reclamation forward at the operations of Syncrude Canada Ltd. To achieve this objective C losses and gains were monitored through respiration and biometric assessments, respectively. These methods were then used to evaluate the C dynamics of various reclamation strategies and soil prescriptions compared to targeted natural undisturbed ecosites. Net C accumulation was determined using biometric measurement techniques for three years at several long-term-monitoring sites representing six soil cover prescriptions and three of the most common natural soil types. Measurements of the annual production of above and below ground C biomass and soil respiration were used to develop biometric estimates of net ecosystem productivity. The soil component comprised a substantially larger proportion of the total C pools in the reclaimed areas. The soil C pool was larger for all reconstructed sites with a peat-mix or LFH cap than for the natural sites, especially sites with mature tree stands 70 years of age or greater which had substantially more C stored in the above ground biomass than in the soil. Measurement of inputs to and output (losses) from the total C pool for reclaimed sites with different soil covers indicated that losses were nearly balanced by inputs in the early years following revegetation.