Table 2: The baseline SOC stocks of major land use classes and their change rates.

Land use type Number of pixela Change in pixel SOC in 1972 1972–1998b SOC in 1998 1998–2007 1972 1998 2007 1998–2007 Mg C/ha Mg C/ha/yr Mg C/ha Mg C/ha/yr Forest 275 237 297 60 74.0 −0.22 75.0 −0.02 Grassland 7344 6618 4865 −1753 81.9 −0.11 76.1 0.04 Agriculture 26327 24342 22705 −1637 86.6 −0.45 75.9 0.05 Wetland 1836 1684 3309 1625 95.9 −0.38 75.6 0.04 Mean         85.8 −0.38 75.9 0.04 Stdev 22.9 0.27 19.7 0.40

aPixel size =  m2. bBaseline SOC stocks in 1998 for each land use type are not necessarily associated with the calculation of annual SOC change rate for 1972–1998 because of land use change.