Factors contributing to greater soil organic carbon accumulation after afforestation in a Japanese coniferous plantation as determined by stable and radioactive isotopes

Soil organic carbon accumulation following afforestation in a Japanese coniferous plantation based on particle-size fractionation and stable isotope analysis

“…All samples had similar particle-size distributions (29 ± 1.9% sand, 68 ± 1.9% silt, and 4.0 ± 0.45% clay in the natural forest, n = 24; about 29 ± 0.76% sand, 67 ± 0.68% silt, and 4.0 ± 0.30% clay in the plantation stand, n = 29 [mean ± S.E. ]; Arai and Tokuchi, 2010) and low pH (4.7 ± 0.02 in the natural forest and 4.8 ± 0.03 in the plantation stand; Arai and Tokuchi, 2010).…”

“…The soil samples used for particle-size fractionation were identical to those used in our previous study (Arai and Tokuchi, 2010). Three soil profiles (~100 cm wide) were made in both stands in October 2004, July 2005, and June 2006.…”

“…The data for B.D., D, and S were obtained in our previous study (Arai and Tokuchi, 2010). The profiles of the SOC content of both fractions with depth were regressed using the equation from Jobbágy and Jackson (2000):…”

“…plantation (16.5 ± 0.57 kg C m −2 m −1 ) that had been converted from Miscanthus sinensis Andress grassland than in an adjacent natural forest (9.1 ±4.5 kg C m −2 m −1 ; Arai and Tokuchi, 2010). The results suggested that the larger SOC stock in the plantation stand was caused by restriction of the initial SOC reduction with afforestation and a large net SOC accumulation after plantation establishment, which, in turn, was a result of the litter quality (high C/N ratio with C. japonica litter) and the relatively low level of disturbance at the site because of the absence of site preparation before afforestation (Arai and Tokuchi, 2010).…”

“…To test these hypotheses, we separated the identical soils used in Arai and Tokuchi (2010) into coarse (63-2000 μm) and fine (b63 μm) fractions, which have different sensitivity to land use change, determined the SOC stocks in the physically separated fractions in both natural forest and a C. japonica plantation, and clarified the distribution patterns in the physical fractions of newly input C and old SOC derived from the previous vegetation.…”