Abstract
Knowledge about carbon dynamics on the organic matter pooled in the forest soil was important as basic data to discuss the effect of the progress of global warming. In this study, one treatment area (0.23 ha) and one control area (0.24 ha) were set in a 35-year-old Cryptomeria japonica plantation of Tokyo University of Agriculture Okutama Forest in Okutama-machi, Nishitama-gun, Tokyo, in December 2012, and clear-cutting and ground clearance were done in the treatment area in March 2013. Fixed-point measurements of soil respiration rate (RS) were conducted regularly from January 2013 to December 2018 at 19 and 21 points in the treatment and the control areas, respectively. Volcanic ash soil distributes in the study site. From the comparison of RS estimated at 20℃ （RS20), the ratios of RS20 in the treatment area to the control area were increasing from 0.60 in 2013 to 0.74 (highest) in 2016, but decreased to 0.49 in 2018. The carbon stocks in the surface soil (0-5 cm deep) measured in 2018 were 24.6 t ha-1 at the treatment area and 23.2 t ha-1 at the control area. The total carbon emission for six years was estimated to be 50.3 tC ha-1 in the treatment area, which could not be explained by the decomposition of the organic matter pooled in the surface soil before harvesting. These results support the importance of the carbon pool of subsurface soil for consideration of soil carbon dynamics.
