Nutritional environment of soil and roots in and around mycelial blocks of an ectomycorrhizal fungus Tricholoma bakamatsutake in an evergreen Fagaceae forest

Abstract

In the evergreen Fagaceae forests of Japan, an ectomycorrhizal fungusTricholoma bakamatsutake forms “shiros” or developing mycelial blocks. To determine the physiological characteristics of the mycelial blocks, organic acids of the soil and major nutrient elements of the soil and roots were compared at three types of sites: presently colonized mycelial blocks, previously colonized sites behind the blocks, and uncolonized sites in front of the blocks. The upper part of the mycelial blocks showed the following features compared with the uncolonized site: lower pH (5.1), higher concentrations of oxalic and gluconic acids, lower content of total nitrogen, a similar amount of total carbon, reduced total and available phosphorus, higher content of total calcium and lower content of exchangeable calcium. These findings suggested that the activity of the fungus led to soil acidification by the organic acids, an increase in C/N ratio, depletion of phosphorus and accumulation of calcium.