Influence of Stand Type On Forest Floor Development in Reclaimed Oil Sands.

In Northern Alberta, Canada oil sands extraction has so far disturbed 150km² of land and the reclamation of this formerly forested landscape represents a major ongoing challenge. The reestablishment of biogeochemical cycles is one of the most important requirements for long-term sustainability in these reclaimed forest landscapes.  Initially, these reclaimed sites rely on a peat-mineral mix for microbial energy and plant nutrient requirements, as peat is available in large quantities as a soil conditioner. Over time, microbial energy and plant nutrient requirements should increasingly be met by vegetation inputs to the soil organic matter and through the development of a forest floor layer.  This study assessed the influence of forest stand type (Populus tremuloides and Populus balsamifera, Pinus banksiana, and Picea glauca) on forest floor development, nutrient status and soil organic matter composition in 32 sites that range from 16 years to 33 years since reclamation.

Forest floor development was characterized by thickness, density, and total carbon and nitrogen.  Phospholipid fatty acids were measured to fingerprint microbial community composition, and soil organic matter (SOM) composition was characterized using ramped-cross-polarization (RAMP-CP) ¹³C Nuclear Magnetic Resonance (NMR).  Over time, stands dominated by P. tremuloides and P. balsamifera had a significantly thicker forest floor, greater contributions of litter to the SOM, and greater microbial biomass and diversity than reclaimed stands dominated by P. banksiana and P. glauca.  Soil carbon on the P. tremuloides and P. balsamifera sites also had a greater alkyl to o-alkyl ratio indicating greater decomposability.