Abstract: Understanding the effects of biocrusts on soil ecological stoichiometry in black soil regions can provide a theoretical foundation for the assessment and scientific management of soil nutrients. Using a treatment with biocrust removal as the control, we analyzed the effects of no tillage, minimum tillage, and conventional tillage on the stoichiometric characteristics of soil C, N, P and microbial biomass C, N, P (MBC, MBN, MBP) in biocrusts from the black soil region of Northeast China. The results showed that the coverage of biocrusts under no tillage, minimum tillage, and conventional tillage was 31.8%, 40.5%, and 21.8%, respectively. In the 0-2 cm soil layer, total nitrogen content in biocrusts soils under no tillage and minimum tillage was three and two times of that in the control, respectively. MBC was significantly increased by 63.3% and 31.1%, and MBN was 6.1 and 6.9 times of that in the control, respectively. MBN under conventional tillage was twice of that in the control. Compared with conventional tillage, soil organic carbon content under minimum tillage was significantly increased by 26.6%, while under no tillage, soil total nitrogen content was 2.3 times of that under conventional tillage, and MBC was significantly increased by 48.7%. Additionally, MBN under no tillage and minimum tillage were 2.8 and 3.2 times of that under conventional tillage, respectively. Soil C/N ratios under conventional tillage, no tillage, and minimum tillage were decreased by 31.5%, 65.0%, and 43.7% compared with the control, respectively, while the MBC/MBN ratios were significantly decreased by 53.2%, 75.2%, and 82.6%, respectively. The N/P ratios under no tillage and minimum tillage were significantly increased by 197.3% and 86.6%, and the MBN/MBP ratios were 4 and 4.3 times of that in the control, respectively. Compared with conventional tillage, soil C/N ratio under no tillage was significantly decreased by 48.8%, while the C/P ratio under minimum tillage was significantly increased by 22.9%. Furthermore, the N/P ratios under no tillage and minimum tillage were significantly increased by 134.0% and 46.9%, and the MBN/MBP ratios were 2.3 and 2.5 times of that under conventional tillage, respectively. There were no significant differences in other indicators among the tillage treatments. Stoichiometric variations in the 2-5 cm soil layer were similar to those in the 0-2 cm layer. Total nitrogen, total phosphorus, available potassium, mean weight diameter, and geometric mean diameter were key factors influencing the ecological stoichiometric of biocrusts soils. In conclusion, the development of biocrusts improved soil nutrient status. Compared with conventional tillage, the development of biocrusts was promoted and nutrients were further increased by the implementation of no tillage and minimum tillage. The results suggested that the contribution of biocrusts to nutrient cycles from the perspective of soil ecological stoichiometric characteristics, which would provide a theoretical basis for the management of soil fertility in the Northeast black soil region.

Key words: conservation tillage, biocrusts, black soil regions of Northeast China, ecological stoichiometric characteristic