Inconsistent diversity patterns of soil fungi and woody plants among habitat types in a karst broadleaf forest

The diversity patterns of macroorganisms (i.e., plants) among different habitats have been well documented, however, those of microorganisms (i.e., fungi) as well as the relationships between them are still unclear. Here, we tested whether and to what degree fungal diversity was related to habitat types and compared diversity patterns of woody plants and soil fungi. We carried out field investigations on soil fungi in different habitat types (i.e., valleys, foothills, hillsides, and hilltops) in a 25-ha karst broadleaf forest in Southwest China. The tree richness, Shannon index, and Simpson index significantly increased from valleys to hilltops. While the soil fungal N₁ diversity (the exponential Shannon index) marginally increased toward valleys, fungal N₀ (richness) and N₂ (the inverse Simpson index) diversity exhibited significantly reduced and increased patterns, respectively, from valleys to hilltops. The major fungal functional groups (i.e., EcM, AM, saprotrophic, and pathogenic fungi) showed similar increasing richness patterns in valleys. Moreover, woody plant alpha diversity was an important indicator of fungal functional groups except for EcM and AM fungi. In addition, woody plants increased in species turnover rate (β_SIM) from valleys to hilltops, while fungal species had a concave distribution. The patterns of nestedness (β_SNE) for tree species decreased from valleys to hilltops, while the opposite was true for soil fungal species. Our findings indicated that the diversity patterns of woody plants and fungi were inconsistent among habitat types, and the relationships between fungal and woody plant communities depended on habitat types in the karst forest.