Long-term decomposition of above- and below-ground tissue of two Arctic shrub species

Arctic soils may become a major source of greenhouse gas emissions, as the climate changes. It is thus crucial to understand decomposition dynamics of permafrost soils, which are influenced by a myriad of abiotic and biotic factors including changing plant communities. Here, litterbags filled either with dried twigs, leaves, and roots of two shrubs ( Salix arctica Pall and encroaching Salix richardsonii Hook) were buried at two different soil depths (0–10 and 10–20 cm) at a site on Bylot Island, Nunavut, Eastern Canadian Arctic, to assess the decomposition (i.e., percent mass loss) of the plant material after a 4-year incubation period. Decomposition was greatest for leaf litter, followed by twigs, and then root tissue of S. richardsonii at shallow depths. Further, root tissue (and to a lesser degree leaf tissue) of S. arctica was more susceptible to decomposition than that of S. richardsonii. Also, mass loss of S. arctica leaf tissue was greater at shallow soil depths compared to deeper soil depths. Hence, shrubification can impact Arctic decomposition dynamics.