| Summary: | Soil microbial resource limitation is an important indicator of the ecosystem function and process, especially the response mechanism of the ecosystem under global change. Known as an oasis in the degraded karst landscape, the microbial resource limitations of the karst tiankeng ecosystem are still unclear. In this study, the soil extracellular enzyme activities (EEAs) and stoichiometry (EES) related to carbon (C), nitrogen (N), and phosphorus (P) acquisition were assayed in karst tiankeng. Soil samples were collected from the sunny slope of tiankeng (TSU), the shady slope of tiankeng (TSH), the base of tiankeng (TB), and outside tiankeng (OT). The results showed that the soil enzymatic acquisition of C: N: P in karst tiankeng was deviated by 1: 1: 1, indicating that the stoichiometry of soil enzymes in karst tiankeng was in an unstable state. Soil microbial communities in karst tiankeng were limited by soil C and P, which were mainly achieved by altering soil nutrient stoichiometry. At the TSH site, soil microbes were minimally limited by C and P. The P-limitation was more evident outside karst tiankeng than inside karst tiankeng. These results showed that the unique habitat of karst tiankeng can alleviate microbial community P-limitation in karst land. This study highlights the characteristics of karst tiankeng ecosystems and their role in maintaining microbial survival and ecological function in karst fragile ecosystems.
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