Long-term decomposition of Betula glandulosa and Carex aquatilis under the framework of climate-induced shifts in vegetation (shrubification) in tundra ecosystems

In the wake of climatic warming, widespread shrub encroachment has been reported in tundra ecosystems of the circumpolar north. This project examines the impacts of increased shrubiness on decomposition rates, soil microbial community, and nutrient cycling in the continuous permafrost zone of the Hudson Bay Lowlands. Specifically, this investigation will (1) assess patterns of shrub encroachment near Churchill, Manitoba, using sequential analysis of Landsat imagery; and (2) compare long-term decomposition and nutrient release rates (over 10 years) for Betula glandulosa (shrubs) and Carex aquatilis (sedges) in a fen affected by shrub encroachment using litter bags, elemental analysis, and soil microbial community characterization. Preliminary results indicate significantly slower rates of decomposition for shrub litter, with k values of 0.137 (R² = 0.86) and 0.265 (R² = 0.92) for B. glandulosa and C. aquatilis respectively. These first results suggest that climate-induced shifts in vegetation structure may be associated with a negative feedback to climatic warming, as more carbon is stored in plant litter in areas with shrubby vegetation.