The inclusion of clay minerals accelerates biocrust formation and potentially boosts carbon storage capabilities

Biocrusts, prevalent in desert areas, play a pivotal role in mitigating soil degradation, shaping a common natural landscape. However, amidst climate change and human activities, biocrust coverage is encountering the risk of degradation. The restoration of degraded biocrusts and the construction of artificial ones are regarded as promising technologies for combating soil degradation. Although clay minerals are a crucial abiotic factor in biocrust formation and are directly influence their development and succession, they have not gained widespread attention. The aim of this study was to investigate the mechanism of action of clay minerals in biocrusts. Various quantities of sepiolite were amalgamated with cyanobacteria—Microcoleus vaginatus (ratios of 1:0, 1:10, 1:20, 1:50, 1:100; cyanobacteria dry weight to sepiolite weight), to construct artificial biocrusts and observe the formation and development of them. The results showed that the addition of small quantities of sepiolite (ratios of 1:10 and 1:20) not only facilitated the accumulation of cyanobacterial biomass (1.47–1.86 times) and exopolysacchrides (EPS) (1.73–2.58 times) compared to the control (ratio of 1:0), but also notably enhanced the accumulation of total carbon, total organic carbon, and microbial biomass carbon, highlighting its potential in enhancing the carbon sequestration capabilities of biocrusts. Scanning electron microscope (SEM) analysis revealed that sepiolite serves as a “receiver and bridge” within the biocrust structure, enhancing its compactness and stability, thereby fostering the growth of cyanobacteria and facilitating nutrient transport. Further, Fourier Transform Infrared (FTIR) and X-Ray Photoelectron Spectroscopy (XPS) analysis reviewed changes in some functional groups of EPS and sepiolite after mixing, validating that EPS can function as a “binder” to unify particles. Our findings demonstrate that the incorporation of clay minerals can facilitate biocrust formation, presenting a practical and economical approach, and providing a novel perspective for constructing artificial biocrusts and rehabilitating degraded desert soils.