Effects of mammal browsing on salicaceous fine root biomass, and mycorrhizal colonization

In an exclosure experiment in the willow stage of primary succession on the floodplain of the Tanana River, we tested the hypothesis that browsing can reduce mycorrhizal colonization. We measured the effects winter browsing by moose (Alces alces) and snowshoe hare (Lepus americanus) had on mycorrhizal colonization and fine root biomass of willow (Salix spp.) and balsam poplar (Populus balsamifera). We found that protection from winter browsing increased ectomycorrhizal colonization by 10% in the top 5 cm of the soil profile, by 23% between 5-10 cm, and by 42% at the 10-15 cm depth. Mammal browsing in taiga forests is now recognized as a major cause of the shift from palatable deciduous species such as willow and balsam poplar to less palatable species such as alder and spruce. We suggest that browsing-induced reduction in ectomycorrhizal colonization of salicaceous species plays a central role in this shift in plant community composition.