In order to reveal the effect of desertification on soil active organic carbon fractions in Zoige alpine-cold grassland

the soil total organic carbon (TOC)

dissolved organic carbon (DOC)

easily oxidized organic carbon (EOC) and microbial biomass carbon (MBC) contents during the process of desertification were analyzed by space-for-time substitution. The results showed that the contents of SOC and its active fractions in 0—60 cm depth in alpine-cold grassland significantly decreased during desertification

from potential desertification stage to severe desertification stage

the TOC

DOC

EOC and MBC decreased by 74.76%

80.24%

76.02% and 83.24%

respectively. Compared with TOC

the loss of soil active organic carbon fractions were more obvious with the biggest decline observed in MBC

soil organic carbon contents in different degrees of desertification grassland and this variation showed a trend of decrease with the increase of soil depth

TOC

DOC

EOC and MBC decreased most significantly in the 0—20 cm soil layer among all layers within 0—60 cm. In the process of grassland desertification

TOC

DOC

EOC and MBC were highly significant correlation with each other (P＜0.01).