Abstract: In this study, the long-term fenced sample plots located in the Bayanbulak Steppe in the central Tianshan Mountains were focused, classical statistics and geostatistics were used to study the effects of long-term enclosure on the spatial variation of soil organic carbon content in the subalpine steppe. The results were as follows: (1) Long-term enclosure can increase soil organic carbon content, the average organic carbon content was 40.76 g/kg in soil layer of 0-20 cm in depth inside the fenced steppe, and it was 38.50 g/kg outside the fenced steppe; the average organic carbon content was 20.98 g/kg in soil layer of 20-40 cm inside the fenced steppe, and it was 18.70 g/kg outside. Soil organic carbon content inside the fenced steppe was higher than that outside at horizontal direction; (2) Variation degree of soil organic carbon content inside the fenced steppe was significantly higher than that outside. There was a moderate spatial correlation between organic carbon contents in the upper and lower soil layers no matter inside or outside the fenced steppe, and the variation degree of organic carbon content in the upper soil layer was higher than that in the lower soil layer; (3) Spatially, the distribution of soil organic carbon was different from different places, the soil organic carbon content in spatial distribution inside the fenced steppe was higher than that outside. From the spatial interpolation map, it was found that, if the soil organic carbon content in soil layer of 0-20 cm was high both inside and outside the fenced steppe, the soil organic carbon content in soil layer of 20-40 cm was oppositely low.

Key words: fenced enclosure, soil organic carbon content, spatial change, subalpine steppe, Bayanbulak Steppe