Quantitative aspects of heterogeneity in soil organic matter dynamics in a cool-temperate Japanese beech forest; A Radiocarbon-based approach

Koarashi, Jun   ; Atarashi-Andoh, Mariko  ; Ishizuka, Shigehiro*; Miura, Satoru*; Saito, Takeshi*; Hirai, Keizo*

Although it is well documented the possibility that global warming can lead to an acceleration of microbial decomposition of soil organic carbon (SOC), the magnitude and timing of this effect remains highly uncertain. The main reason is a lack of quantitative aspect of the heterogeneity in SOC biodegradability. To quantify the heterogeneity, we collected the soil and litter samples within a cool-temperate deciduous forest in Japan, separated chemically the samples into SOC fractions, determined their mean residence times (MRTs) based on the radiocarbon (C) measurements, and finally represented the soil as a complex of six SOC pools with different range of MRTs. Predicted response of the SOC pools to warming demonstrates that the rate of SOC loss from the fast-cycling SOC pool diminishes quickly because of the substrate availability; in contrast, the warming continues to accelerate SOC loss from slow-cycling pools with MRTs of 20-200 year over the next century.