Afforestation is an important strategy to enhance terrestrial carbon sink. It alters regional landscapes and affects microbial processes in soil ecosystems. In particular, soil fungi, which play an important role in carbon and nitrogen cycling, could be greatly affected. However, at a watershed scale, the changes of soil fungal communities under afforestation could not only be influenced by host plant and soil environment, but also by spatial distance. How to distinguish the sources of the influences is particularly important.