Abstract:

By exploring the spatial distribution characteristics and influencing factors of soil organic carbon in the typical vegetation of the Qilian Mountains,we aimed to provide a scientific basis for evaluating the carbon sequestration effects of forest soil in the region.Using converted cultivated land as a control,five typical vegetation types were studied:grassland,natural trees(Picea crassifolia,Sabina przewalskii),artificial trees(Larix gmelinii)and shrub.Soil organic carbon content,organic carbon density,soil grades,pH,electrical conductivity,total nitrogen,total potassium,and total phosphorus were measured at depths of 0-100 cm compare and analyze the distribution differences and main influencing factors of organic carbon components in different vegetation soils.Results showed:1)The average soil organic carbon content and organic carbon density under different vegetation types were as follows:P.crassifolia(5.99 g/kg,3.43 kg/m²,respectively)>S.przewalskii(5.59 g/kg,2.76 kg/m²,respectively)>L.gmelinii(2.91 g/kg,2.16 kg/m²,respectively)>shrub(1.83 g/kg,2.08 kg/m²,respectively)>grassland(1.66 g/kg,2.00 kg/m²,respectively)>abandoned lands(1.16 g/kg,1.33 kg/m²,respectively).2)With soil layer deepening,the overall organic carbon content of different vegetation soils tended to decrease,while the density of soil organic carbon showed a trend of first increasing and then decreasing.3)In the 0-100 cm soil layer,the soil C/N content of different vegetation types ranged from 9.30 to 15.73,with mean values as follows:P.crassifolia(14.96)>grassland(11.66)>abandoned land(11.54)>shrub(10.83)>L.gmelinii(10.69)>S.przewalskii(10.63).4)Organic carbon and total nitrogen content in different vegetation types showed a highly significant positive correlation(P<0.01),and a highly significant or significant positive correlation with total phosphorus,clay,and silt(P<0.01,P<0.05),a highly significant or significant negative correlation with sand content(P<0.01,P<0.05),and a significant negative correlation with pH(P<0.05).Thus the soil organic carbon retention capacity of natural trees in the Qilian Mountains is superior.Future carbon sequestration forestry construction should consider factors affecting soil organic carbon and prioritize dominant vegetation.

Key words: Qilian Mountain, typical vegetation, organic carbon content, organic carbon density, influence factor