Abstract:

Surface soil organic carbon plays an important role in soil carbon cycle in the Loess Plateau. A prelimi-nary study was conducted on the storage and distribution characteristics of soil surface organic carbon (SOC) in Gansu Province in the western part of the Loess Plateau,and the distribution regularity of SOC in different land utilization patterns and soil types was analyzed. Meanwhile,the difference of SOC in different landform was compared with the results of the second soil census in Gansu Province. The results showed that the average organic carbon density,from high to low,was forest land,construction land,cultivated land,orchard,grassland,unutilized land. The highest average organic carbon density,from high to low,in each soil type was as follows: cinnamon soil,alpine meadow soil,chernozem,chestnut soil,red clay,irrigated desert soils,anthropoge-nic-alluvial soil,black gunny soil,black loessial soil,yellow loamy soil,sierozem and sand. And the organic carbon density in different geomorphologic units,from high to low,was tablelands,terraces,hillside fields,gullies. The total organic carbon storage in the western part of the Loess Plateau is 78.56 Mt now,which is 10.54% higher than that in 1990,and the soil organic carbon density is 1.87 kg/m². The storage of topsoil's organic carbon in the western part of the Loess Plateau is on the rise.

Key words: Loess Plateau, soil organic carbon, carbon density, soil type, land utilization type