Ectomycorrhizal fungi on established shrubs facilitate subsequent seedling establishment of successional plant species

Ectomycorrhizal (ECM) fungi are symbiotic microorganisms that can significantly improve the water and nutrient uptake of host plants. With reference to ECM fungi, we studied the effects of established shrubs on the subsequent seedling establishment of three woody plant species in a volcanic desert on Mt. Fuji, Japan, during early primary succession. Salix reinii, an alpine dwarf willow, is the pioneer ECM plant at this research site, and many ECM fungi have colonized established willow shrubs. ECM formation was found to be high on S. reinii seedlings that had been transplanted near established willow shrubs. The growth and nitrogen content of the seedlings increased significantly with the numbers of associated ECM fungal species and ECM root tips. ECM formation on transplanted seedlings of Betula ermanii and Larix kaempferi, two subsequent successional tree species, was also higher near the established willow shrubs. Molecular identification showed that almost all of the ECM fungi on transplanted seedlings of the three plant species were of the same species as those observed on the established willow shrubs. These results indicate that ECM fungi associated with established willow shrubs are essential in facilitating seedling establishment of successional plant species in the early successional volcanic desert.