Objective We studied the effects of biological soil crusts (BSCs) on soil enzyme activities in Artemisia ordosica community of Mu Us Desert, northwestern China, aiming to explore the effects of different types of biological soil crusts on soil nutrient turnover in arid and semi-arid area, which could provide theoretical basis for understanding the effects of biological soil crusts on vegetation restoration.
Method We took soil between Artemisia ordosica community (bare land), lichen crust layer, moss crust layer and its underlying soil as objectives, and analyzed their physical and chemical properties and soil enzyme activities.
Result (1) Both the lichen crust layer and the moss crust layer significantly improved the soil physical and chemical properties, which were highest in moss crust layer compared with bare land and lichen crust layer. Compared with bare land, soil organic carbon content (SOC) in lichen crust layer and the moss crust layer increased by 3.30 times and 6.51 times, microbial biomass carbon content (MBC) increased by 2.79 times and 6.58 times, microbial biomass nitrogen content (MBN) increased by 3.49 times and 12.73 times, soil total nitrogen content (TN) increased by 2.67 times and 4.46 times, and total phosphorus content (TP) increased by 1.82 times and 2.06 times, respectively. There was no significant difference in microbial biomass nitrogen (MBN), TN and TP among the underlying soil in lichen crust layer, moss crust layer and bare land. The MBC content was significantly decreased in underlying soil of lichen crust layer and moss crust layer compered with bare land. (2) The invertase and urease activities in lichen crust layer and the moss crust layer were higher than bare land. Compared with bare land, the invertase and urease activities in lichen crust layer and moss crust layer were significantly increased by 3.58 times and 2.80 times, respectively, and the invertase activity was significantly increased by 4.23 times in moss crust layer. There were no significant differences among the underlying soil in lichen crust layer, moss crust layer and bare land on the three enzyme activities. There were no significant differences on alkaline phosphatase activity between the biological soil crusts and bare land. (3) Soil physicochemical properties significantly affected the three soil enzyme activities. SOC, MBC, MBN, TN and TP were significantly positively correlated with soil invertase activity, and pH was significantly negatively correlated with soil invertase activity. SOC, MBN and TP were significantly positively correlated with soil urease activity. pH was significantly negatively correlated with soil alkaline phosphatase activity.
Conclusion Both lichen crust and moss crust can improve the carbon transformation in Artemisia ordosica community; however, the nitrogen transformation in Artemisia ordosica community was mainly regulated by lichen crust. In addition, only the biological soil crust layer could improve the nutrient turnover in Artemisia ordosica community. The results show that biological soil crust can accelerate the turnover of soil nutrients and improve soil quality, which are conducive to the restoration of vegetation and desert ecosystems.