Abstract: We investigated the communities of woody plants, ground-dwelling insects, soil bacteria, and soil fungi in both karst and non-karst forests within the Yachang Orchids Natural Reserve, Guangxi, to explore the role of plant communities, stand structure, soil and litter properties in driving the differences in biological community composition. The results revealed that species richness, Shannon index, and Simpson index of plants were significantly higher in karst forest than non-karst forest. There were no significant differences in the species richness or Shannon index of ground-dwelling insects, bacteria, and fungi between the two forest types. However, the Simpson index for ground-dwelling insects and bacteria was significantly lower in karst forest, while the Simpson index for fungi was significantly higher. Community composition of the four biological groups differed significantly between karst and non-karst forests. The difference in plant community composition was primarily driven by soil pH (explaining 24.0% of the variation) and total soil carbon content (19.8%), with most plant species contributing to the dissimilarity. The difference in community composition of ground-dwelling insects was mainly driven by plant community composition (30.3%), understory tree density (13.8%), litter total phosphorus content (29.9%), and soil temperature (7.1%). The dissimilarity in ground-dwelling insect community was largely attributed to the differences in the abundances of Nitidulidae, Blattellidae, Gryllidae, Scarabaeidae, and Pycnoscelidae. The difference in bacteria community composition was primarily driven by soil temperature (39.5%) and pH (10.3%), with an unclassified family 1 of Acidobacteria and Pyrinomonadaceae being the key family contributing to the dissimilarity. The difference in fungal community composition was mainly influenced by plant community composition (21.2%), soil temperature (7.6%), and litter total phosphorus content (7.2%), with Russulaceae being the key family contributing to the dissimilarity. Our results suggested that the alkaline soils in karst forests support higher plant diversity, which offsets the negative effects of exposed rock and low soil temperature, thereby maintaining the diversity of other biological groups.

Key words: karst forests, non-karst forests, plants, ground-dwelling insects, bacteria, fungi, diversity