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Employing the Unit Soil Carbon Amount(USCA) approach,soil carbon storage was calculated across the Northeast Plain of China based on the Multi-purpose Regional Geochemical Survey conducted in 2004—2006(MRGS).The results indicated that the soil organic carbon(SOC) storage in topsoil (0-0.2 m),subsoil(0-1 m) and deep soil(0-1.8 m) was 768.1 Mt,2978.4 Mt and 3729.2 Mt with densities of 3327.8 t/km~2,12.904.7 t/km~2 and 16.157.5 t/km~2.respectively.These values were consistent with national averages,whereas the soil carbon densities showed a clear increasing trend from the southern area of the Northeast Plain(Liaoning).to the middle(Jilin) and the northern Plain(Heilongjiang)—particularly in terms of topsoil carbon density,which increased from 2284.2.to 3436.7 and 3861.5 t/km~2.respectively.In comparison to carbon data obtained from the Second National Soil Survey in 1984—1986(SNSS),the topsoil SOC storage values from the MRGS were found to have decreased by 320.59 Mt(29.4%),with an average annual decline of 16.0 Mt(1.73%) over the 20 years.In the southern, middle and northern areas of the plain,soil carbon densities decreased by 1060.6 t/km~2,1646.4 t/km~2 and 1300.2 t/km~2,respectively,with an average value of 1389.0 t/km~2 for the whole plain.These findings
The soil carbon storage was calculated across the Northeast Plain of China based on the Multi-purpose Regional Geochemical Survey conducted in 2004-2006 (MRGS). The results indicated that the soil organic carbon (SOC (0-1.2 m) was 768.1 Mt, 2978.4 Mt and 3729.2 Mt with densities of 3327.8 t / km ~ 2, 12.904.7 t / km ~ 2 and 16.157.5 t / km ~ 2.respectively.These values were consistent with national averages, but the soil carbon densities showed a clear increasing trend from the southern area of the Northeast Plain (Liaoning) .to the middle ( Jilin) and the northern plain (Heilongjiang) -particularly in terms of topsoil carbon density, which increased from 2284.2.to 3436.7 and 3861.5 t / km ~ 2.pectively.In comparison to carbon data obtained from the Second National Soil Survey in 1984- 1986 (SNSS), the topsoil SOC storage values from the MRGS were found to have decreased by 320.59 Mt (29.4%), with an average annual decline of 16.0 Mt (1.73%) over the 20 years.In the southern, middle and northern areas of the plain, soil carbon densities decreased by 1060.6 t / km ~ 2,1646.4 t / km ~ 2 and 1300.2 t / km ~ 2, respectively, with an average value of 1389.0 t / km ~ 2 for the whole plain.These findings