Abstract:

To elucidate the effects of different land use types on soil chemical properties and enzyme activities in the Horqin sandy land, and assess the resulting disparities in ecosystem functions, providing a scientific basis for optimizing land resource management and facilitating ecological restoration in the region. The investigation was conducted within the Horqin sandy land located in Right Wing, Middle Banner of Horqin, Xing’an League, during the maize harvest period, and soil samples were systematically collected from 5 representative land use types: Caragana microphylla shrubland (S), natural grassland (M), Malus ‘Jinxiu’ forest land (D), ground cover flower land (G), and maize farmland (F). Sampling was stratified into depths of 0-10, 10-20, and 20-30 cm. A comprehensive set of analyses was performed to determine key soil chemical properties, including alkaline hydrolysis nitrogen, available phosphorus, available potassium, pH, electrical conductivity, and exchangeable sodium, as well as the activities of sucrase, urease, cellulase, alkaline phosphatase, and catalase enzymes. The results demonstrated that: land use types significantly altered soil characteristics. In terms of soil fertility, maize farmland (F), benefiting from anthropogenic fertilization, exhibited the highest concentrations of alkaline hydrolysis nitrogen and available potassium, exceeding those in natural grassland (M) by 143.4% and C. microphylla shrubland (S) by 230.5%, respectively. C. microphylla shrubland (S) displayed a pronounced nitrogen-fixing ecological function, with its alkaline hydrolysis nitrogen content surpassing that of natural grassland (M) and ground cover flower land (G) by 140.1% and 99.5%, respectively. Regarding soil enzyme activities, forest land (D) and ground cover flower land (G) showed notably higher activities of enzymes associated with carbon and phosphorus cycling. The average sucrase activity in D and G was 99.1% and 127.6% higher than in maize farmland (F) and C. microphylla shrubland (S), respectively; the alkaline phosphatase activity in ground cover flower land (G) was 138.2% higher than in maize farmland (F). In contrast, maize farmland (F) exhibited the highest nitrogen cycle enzyme activity, with its urease activity exceeding that in natural grassland (M) and C. microphylla shrubland (S) by 459.5% and 314.8%, respectively. In the nutrient-impoverished natural grassland (M), the cellulase activity in the deepest soil layer (M3) increased anomalously, reaching a level of 5.8 times that of the surface layer in maize farmland (F). In conclusion, different land use types in the Horqin sandy land lead to significant differentiation in soil ecological functions. While farmland management can rapidly enhance nitrogen and potassium levels, it remains dependent on external inputs. C. microphylla shrubland demonstrates a superior capacity for maintaining nitrogen under natural conditions, whereas forest land and ground cover flower land are more conducive to foster a healthy and active soil biochemical cycle. Therefore, ecological restoration efforts should prioritize models integrating leguminous shrubs with trees, shrubs, and grasses, while special attention is required for the restoration and management of degraded grasslands.

Key words: Horqin sandy land, land use type, soil chemical properties, soil enzyme activity