Qualitative And Quantitative Research Of Soil Organic Carbon Transfer To Soil Inorganic Carbon In Desert Grassland

Soil samples were collected from a Stipa breviflora dominated desert steppe in Inner Mongolia for analysis of content andδ13C of soil carbonates,δ13C of CO2 and parent rocks, hence to explore effect of formation and turnover of pedogenic carbonates on sequestration of CO2 and calculate the amount of CO2 sequestrated. We combined with theδ13C value of soil organic carbon (SOC), plant and atmospheric CO2 to caculate the transfer carbon content that from SOC to SIC. And study the effect of spatial distribution Characteristics of soil organic carbon and difference in stable carbon isotope composition with the increase of grazing. Results shown that, (1) theδ13C value of PIC was determined mainly by the composition of carbonate isotopes of soil CO2 and it can be figured out with the aid of theδ13C value of soil CO2. Fractionation of the SC in the study area revealed that PIC accounted for 83.6%,65.4%,41.7% and 17.4% in the soil layers of 40-50 cm,50-60 cm,60-80 and 80-100 cm, respectively. (2) By the help ofδ13C values and the principles in chemical balance, the amount of CO2 sequestrated during the process of PIC formation and turnover was worked out, is 38.3,39.2,25.1 and 9.2 g·kg-1soil in these layers, respectively. That is to say, every square meter soil area can fixed the volume of CO2 about 23.098 Kg in the depth of 1 m. (3) 40-50 cm,50-60 cm, 60-80 and 80-100 cm soil layer fixed the soil CO2 that come from the root and microbial respiration, SOC released by oxidation and decomposition were 22.5,23.3,13.2 and 4.6g respectively. (4) The influence of grazing on soil organic carbon mainly in 0-20 cm layer, and the greater the grazing intensity the lower the soil organic carbon contents, the greater the degree of organic matter decomposition, and the great theδ13C value. The spatial distribution characteristics ofδ13C also shows that the local climate and vegetation changed a lot when soil profile development processes, and experienced the changes of C4 to C3 in the dominant plant possibly.