Estimating soil carbon stocks in an upland area of Tokachi District, Hokkaido, Japan, by satellite remote sensing

Abstract

Soil carbon stocks (SCSs) in an upland area of Tokachi District, Hokkaido, Japan, were estimated by satellite remote sensing and a soil survey. The soil parent materials in the studied area were alluvial deposits, volcanic ash plus alluvial deposits, and volcanic ash. Surface soil carbon concentrations (SSCCs) were negatively correlated with satellite image data (green, red, and near-infrared reflectance) for each parent material. The highest correlations between reflectance and SSCCs were obtained from red wavelength reflectance for alluvial deposits (r = –0.82, p < 0.01) and volcanic ash plus alluvial deposits (r = –0.91, p < 0.01), and from near-infrared reflectance for volcanic ash (r = –0.90, p < 0.01). We generated an SSCC map of the study area using the regression equations and satellite reflectance data. The soil survey results showed that SSCCs were positively correlated with SCSs in the 0–30 cm depth interval for each parent material (best-fit regressions: alluvial deposits, r = 0.97; volcanic ash plus alluvial deposits, r = 0.97; volcanic ash, r = 0.97), and they were also positively correlated with SCSs in the 30–95 cm depth interval for volcanic ash (r = 0.94). We were therefore able to generate a map of estimated SCSs from the SSCC map and the regression equations developed between SSCCs and SCSs. The estimated and measured SCSs in both depth intervals showed an almost 1:1 relationship, with root-mean-square errors of 19.5 (0–30 cm) and 28.6 Mg carbon (C) ha–1 (30–95 cm). According to the SCS maps, SCSs at 0–30 cm depth in areas of alluvial deposits, volcanic ash plus alluvial deposits, and volcanic ash were mostly 50–150, 100–200, and 50–250 Mg C ha–1, respectively, whereas at 30–95 cm depth in the volcanic ash area they were mostly less than 250 Mg C ha–1.