Contrasting latitudinal diversity and co-occurrence patterns of soil fungi and plants in forest ecosystems

The diversity patterns of plants at large scale are broadly documented, but that of soil fungi remains elusive. Limited reports on soil fungal biogeography mainly are based on species richness. We carried out a large-scale field investigation on soil fungi originating from 365 forest plots covering five climate zones in China. We tested whether and to what degree a range of different fungal diversity estimates are subject to latitudinal constraints and compared co-occurrence patterns of plants and soil fungi. We found that alpha diversity of plants increased towards lower latitude, while that of soil fungi only tended to increase. Abiotic but not biotic factors controlled fungal alpha diversity. Multiple-site and pairwise beta diversity of soil fungi were closely linked to plant communities. Null model revealed an increasing interaction strength between plant species, while there was a hump-shaped pattern of interaction strength between fungal species from high-latitude towards low-latitude. Our results allow a deeper insight into the multidimensional distribution of soil fungal diversity and reveal contrasting co-occurrence patterns between soil fungi and plants along a latitude gradient, highlighting the need for more inclusive theories to explain these disparities between micro- and macroorganism communities.