Mechanisms of artificial biological soil crusts development for anti-desertification engineering on the Qinghai-Tibetan Plateau

Qinghai-Tibetan Plateau, the worldwide “third pole”, is plagued by desertification with extreme environments. The strategy of artificial biological soil crust (ABSC) is a bottom-up ecological restoration approach by cyanobacterial inoculation and is applied to restore soil quality and fertility in some low-altitude deserts. Nevertheless, its feasibility on anti-desertification on the Qinghai-Tibetan Plateau has not been proven. Here, Phormidium was inoculated in an aeolian sandy land (Lhasa City) and we explored the effects of film mulching and irrigation on ABSCs development. During the 50-day-cultivation, ABSCs were successfully formed and topsoil TOC (from 0.51 to 0.88 %) and TN (from 300.0 to 779.2 mg/kg) significantly increased with cultivation time. Film mulching remarkably promoted nutrient accumulation (p < 0.05) and 20 mm H2O/d watering was the best irrigation condition. Redundancy analysis results suggested that topsoil nutrients were regulated by bacteria (64.3 %), while Cyanobacteria and Proteobacteria were further identified as having significant positive correlations with carbon and nitrogen based on Pearson correlations (p < 0.05), and especially Cyanobacteria also exhibited an increasing abundance along ABSCs development. Additionally, the topsoil ecological network structure changed significantly with cyanobacterial colonization compared to bare soil, especially new modules dominated by Cyanobacteria and Proteobacteria also remarkably correlated with TOC and TN, suggesting the accelerated C/N cycles and topsoil ecosystem reconstruction. Our findings explored the optimal engineering measures for ABSCs formation and unraveled the underlying mechanisms of ABSCs development, offering engineering clues for anti-desertification practices on the Qinghai-Tibetan Plateau.