Abstract: To understand the effects of land use types on soil physicochemical properties and aggregate stability, we measured soil physicochemical properties, soil enzyme, soil labile carbon content, and aggregate stability under four land use types (secondary forest, shrub meadow, Carex swamp and cropland). The results showed that soil physicochemical properties varied greatly under different land use types, with soil pH being neutral or alkaline. Compared with Carex swamp soil, the electrical conductivity, water content, total nitrogen and alkaline hydrolyzed nitrogen of soils in secondary forest, shrub-meadow and cropland were significantly decreased. In the vertical direction, the available phosphorus content of cropland soil was the highest at the 0-20 cm soil layer. The activities of protease, cellulase, urease and β-glucosidase in Carex swamp soil were significantly higher than those of other land use types. There was no significant difference in nitrate reductase activity between Carexswamp and shrub meadow soil. The total organic carbon, dissolved carbon and microbial biomass carbon of Carex swamps were significantly higher than those of other land use types. The content of readily oxidized carbon in Carex swamp and shrub meadow was significantly higher than that of secondary forest and cropland across different soil depths. Compared with Carex swamp, cropland soil had higher content of small aggregates (<0.25 mm). The MWD and GMD indices of cropland soil decreased slightly compared with those of secondary forest, shrub-meadow, and Carex swamp. In conclusion, land use patterns changed the distribution of soil physicochemical properties in different soil layers of cold region wetlands. The Carex swamp (natural wetland) soil has good aggregate stability. Our results provide theoretical reference for sustainable utilization and protection of wetland soil in cold region.

Key words: cold region wetland, soil physicochemical property, soil organic carbon, soil enzyme activity, soil aggregate.