Response of soil enzymes to soil properties and seasonal characteristics of cyanobacteria-dominated crusts in a dryland ecosystem

Purpose Cyanobacteria-dominated crusts are solid basis for the maintenance and improvement of soils in dryland ecosystem. The present study is to investigate the seasonal variations of cyanobacteria-dominated crust characteristics in a dryland ecosystem, including crusts thickness, chlorophyll a , proteins, polysaccharides, and carbon (C), nitrogen (N), and phosphorus (P) contents and to clarify the effects of crust characteristics together with soil properties on soil enzymes beneath crusts. Methods Cyanobacteria-dominated crusts and soils beneath crusts were sampled in spring (March 14), summer (June 15), autumn (September 14), and winter (December 15) of 2020 in the southeast edge of Tengger Desert in northern China. Results Chlorophyll a , proteins, polysaccharides, and crusts C and N showed higher values in spring and autumn, while thickness, crusts P, C: N, C: P, and N: P have no significant changes throughout all seasons. Soil enzyme activities beneath crusts declined with increasing depth, whereas enzyme behavior differed among seasons. Redundancy analysis indicated that crust proteins and soil water content were the important factors accounting for differences in soil enzymes in 0–5 cm soil layer, while the determining factors for soil enzymes in 5–10 cm soil layer were proteins, soil organic carbon, soil available phosphorus, and thickness. Conclusion The seasonal variations in cyanobacteria-dominated crusts mainly come from changing proteins, polysaccharides, C, and N contents. The stable C: N, C: P, and N: P ratios did not change significantly over the seasons, thus keeping a stable state of crusts in the current dryland ecosystem. Moreover, proteins, soil organic carbon, and soil moisture make great contributions to the seasonal variations of soil enzymes. Overall, our findings demonstrate the depth-related response of soil enzymes to cyanobacteria-dominated crusts in seasons and highlight the ecological function of cyanobacteria-dominated crust characteristics in seasonal fluctuations.