Synergistic effects of clays and cyanobacteria on the accumulation dynamics of soil organic carbon in artificial biocrusts.

Biocrusts are the primary organic carbon reservoirs in desert areas, in which inorganic clays potentially playing significant roles; however, the specific details of these roles remain largely unclear. In this study, typical 1:1 type (kaolin) and 2:1 type (montmorillonite, MMT) clay minerals were added to artificial biocrusts to investigate their effect on the acquisition performance of soil organic carbon (SOC). After 84 days of cultivation, the enhancement effects of kaolin and MMT were significant, resulting in SOC increments that were 5.03 times and 4.08 times higher than those of the Algae group (without clay). Notably, the two types of clay exhibited different advantages in SOC accumulation. Due to its larger external specific surface area and higher cation exchange capacity, MMT contributes more effectively to SOC stability. Specifically, the mineralization quotient (qM), hot-water extractable organic carbon (HWEOC), and molecular structural stability of SOC in the MMT group were 0.3, 0.34, and 1.31 times those of the Algae group, respectively. In contrast, kaolin was more favorable for microbial growth and SOC formation due to its higher dissolved organic carbon (DOC) content. Microbial biomass carbon (MBC), chlorophyll-a (Chl-a), photosynthetic performance index (PI), and Shannon index in the kaolin group were 5.67, 2.44, 11.95, and 1.82 times those of the Algae group, respectively. These findings highlighted the synergistic effect for SOC accumulation of clay and cyanobacteria in artificial biocrust systems, clarified the specific roles of two typical clay minerals, and offered new insights for accelerating the restoration of nutrient-limited areas such as deserts.