The contribution of ericoid plants to soil nitrogen chemistry and organic matter decomposition in boreal forest soil

Nitrogen (N) availability restricts plant carbon assimilation from the atmosphere in N-limited boreal ecosystems. Boreal forest floor is covered with ericoid plants and in soil, ectomycorrhizal and ericoid mycorrhizal plant roots and fungal hyphae are intermixed. How different mycorrhizal plants affect N mobilization from soil organic matter (SOM) has yet to be elucidated. Here we compared the effects of ericoid plants (Calluna vulgaris, Vaccinium myrtillus, Vaccinium vitis-idaea), forming ericoid mycorrhiza (ERM), on soil N chemistry, plant N uptake and SOM decomposition and compared them with ectomycorrhizal (ECM) Pinus sylvestris in a microcosm experiment. Pine and ericoid plants affected soil N similarly, accessing both degradable and recalcitrant N pools. Both ericoid plants and pine took up N from organic source. Ericoid plant roots contained more phenolic compounds and condensed tannins than pine roots which together with lower pH under ericoids suggests substantial changes in soil chemistry and biology. This study underlines the plant stimulation of SOM degradation with special emphasis on ericoid plants. We point out that both ericoid and ectomycorrhizal plants and their interactions should be of interest when N uptake and SOM decomposition in boreal forests are studied.