Karst Tiankeng Is the Refuge of Microbial Diversity in the Degraded Karst Landscape

Known as the largest negative terrain on the earth's surface, the karst tiankeng is isolated by vertical cliffs and maintains a unique ecosystem within it. However, knowledge of the microbial ecology of karst tiankengs does not match their importance. To this end, we conducted extensive sampling across 16 karst tiankengs and 2 sites and used high-throughput sequencing methods to analyze soil bacteria and fungi. This study found abundant and diversified microbial communities in karst tiankengs, with Proteobacteria, Acidobacteriota (Bacteria), and Ascomycota, Basidiomycota (Fungi) being the main phyla. Compared to the degraded karst landscape, karst tiankengs maintained a higher richness of bacterial taxa. The common and exclusively microbial taxa in karst tiankengs follow copiotrophic and opportunistic strategies, and these taxa are associated with high soil nutrients (TN and SOM) and water content. Karst tiankeng maintained a stable microbial network structure through cooperation, and the dispersal limitation dominated the bacterial and fungal community assembly. Our results enhance the understanding of microbiomes in subterranean karst ecosystems, highlighting that karst tiankengs are important refuges for microbial diversity in degraded karst landscapes.