Leaf (15)N abundance of subarctic plants provides field evidence that ericoid, ectomycorrhizal and non- and arbuscular mycorrhizal species access different sources of soil nitrogen

arctic tundra betula nana champignon du sol enzimas enzyme enzymes fixation de l'azote hongos del suelo isotope isotopes lichen lichenes mycorrhizae nitrate reductase nitrato reductasa nitrogen content nitrogen fixation nitrogen metabolism north polar region plant vascular system salix sistema vascular de la planta soil fungi teneur en azote toundra arctique tundra artica