Soil Microbial Biomass and C Storage of an Andosol

Volcanic soils (Andosols) cover about half of the arable upland in Japan, and these soils generally have a high amount of soil carbon. Soil microbial biomass C (MBC) and soil organic C (SOC) was compared in an Andosol and non-Andosol (Sand-dune Regosol) from Japan. Significant linear correlations were observed for Japanese Andosols but the slope of the correlation (MBC/SOC) was significantly lower for Andosol compared to such published relationships for non-Andosols. MBC was relatively lower at the same SOC level in the Andosol than non-Andosol. Subsurface Andosol had higher MBC indicating that cumulated soil C may be substrate for microorganisms even after thousand years of eruption and surface horizon formation. These finding indicate unique features of microbial biomass and C turnover in Andosols.