Litter properties influence decomposition more than local soil environment in a boreal tree species common garden experiment

Boreal forests store significant quantities of carbon (C), particularly in their soils. Thus, selecting tree species that promote slow decomposition, due to either their inherent litter properties or soil microbial communities, may be a suitable tool to enhance C uptake in boreal forests. In this study we used two common garden experiments and employed a reciprocal litter transplant decomposition experiment using four common Swedish tree species ( Betula pendula, Larix sp., Picea abies and Pinus sylvestris ), with varying plant economics strategies. We aimed to partition the relative effects of litter quality and soil environment on litter and humus decomposition rates. Our results showed that litter mass loss was much more dependent on tree species than soil environment, a result further reinforced by the lack of tree species differences in the soil microbial community. The rates of decomposition did however appear to converge over time, as humus mass loss was not responsive to either tree species or soil environment. Our result therefore suggests that tree species selection, as a forest management tool, should be based on each species site-specific growth potential, instead of initial differences in decomposition rate, which could serve to maximize the ecosystem C stock and in turn increase the climate benefits of boreal forest.