Influences of forest decline on various properties of soils on Mt. Hirugatake, Tanzawa Mountains, Kanto District, Japan

To evaluate the influences of forest decline on microbial properties, the biomass carbon content and the activities of several enzymes in surface soils under different degrees of forest decline at Mt. Hirugatake, Tanzawa Mountains, Kanto district, Japan were investigated. The biomass carbon content as well as the activities of the dehydrogenase, β-glucosidase, and protease enzymes was significantly decreased with forest decline, and the correlation analysis suggested that these decreases were caused by the decrease in the soil organic matter content associated with forest decline. Moreover, the changes in the composition of soil organic matter might exert a significant influence on the microbial properties, since the proportions of the decrease in the biomass carbon content and enzyme activities were higher than those of the decrease in the total carbon content when a healthy forest site and other five sites with forest decline were compared. Furthermore, stepwise multiple regression analysis strongly indicated that the microbial properties were also affected by the changes in the water-holding capacity and porosity of the soils associated with forest decline in the study area.