Ectomycorrhizal communities on tree roots and in soil propagule banks along a secondary successional vegetation gradient

Abstract

Changes in the composition of underground ectomycorrhizal communities along a secondary successional vegetation gradient were investigated in Kashiwa City, Kanto District, eastern Japan. Soil cores were sampled from the surface soils of six plots in a successional series of vegetation, and ectomycorrhizal root tips were classified into morphotypes by macroscopic observation and measurement of the internal transcribed spacer 3-4 length of rDNA. The inoculum potential of ectomycorrhizal fungi in the soils was also investigated by germinating and growing Japanese red pine seedlings in pots. The species richness of ectomycorrhizal fungi on tree roots increased along the successional gradient from the pioneer tree stage (Pinus densiflora Sieb. et Zucc. stands) to the middle stage (deciduous Quercus serrata Thunb. and Castanea crenata Sieb. stands) and then slightly decreased in the climax stage (evergreen Quercus myrsinaefolia Bl. stands). The increase in the number of ectomycorrhizal morphotypes was strongly correlated with the increase in the biomass of ectomycorrhizal trees along the succession. Ectomycorrhizal propagule banks were found in the soil of pioneer grass- and shrublands where ectomycorrhizal trees were not present. Unlike the diversity of ectomycorrhizal morphotypes on tree roots, the morphotype richness and diversity of ectomycorrhizal inocula in the soil infective to pine seedlings increased only from the grassland to the pine successional stage and not in the deciduous and evergreen-oak stages. The composition of ectomycorrhizal communities on mature trees and ectomycorrhizal propagule banks in soils showed a successional gradient along the secondary vegetation gradient, but many common morphotypes were present among the different vegetation stages. Copyright © 2007 by the Society of American Foresters.