Short-term root and leaf decomposition of two dominant plant species in a Siberian tundra

In tundra ecosystems, global warming is expected to accelerate litter decomposition and to lead to shifts in vegetation composition. To understand these shifts, it is important to understand the interactions between global warming, vegetation composition, litter quality and decomposition in the tundra. In addition, it is important to consider root litter since roots are the major part of plant biomass in the tundra. In order to increase our understanding of decomposition, and root decomposition in particular, we performed a litter transplant experiment in northeastern Siberia, in which we measured mass loss for leaf and root litter (live and dead material) of the two dominant plant species, graminoid Eriophorum vaginatum and shrub Betula nana, in three vegetation types (E. vaginatum or B. nana dominated and mixed vegetation) during the growing season.Our results show that although leaf decomposition did not differ between the two species, root decomposition showed significant differences. Mass loss of live roots was higher for E. vaginatum than for B. nana, but mass loss of E. vaginatum dead roots was lowest. In addition, we found evidence for home-field advantage in litter decomposition: litter of a plant decomposed faster in vegetation where it was dominant. Mass loss rates of the litter types were significantly correlated with phosphorus content, rather than nitrogen content. This indicates that phosphorus limits decomposition in this tundra site.The low decomposition rate of B. nana live roots compared to E. vaginatum live roots suggests that the acceleration of decomposition in the Arctic may be partly counteracted by the expected expansion of shrubs. However, more information on litter input rates and direct effects of climate change on decomposition rates are needed to accurately predict the effects of climate change on carbon dynamics in tundra ecosystems.