LAUSR

Biogeographic patterns of soil fungal diversity have been well documented in forest ecosystems, but the underlying mechanisms and processes that shape these patterns remain relatively unknown. This study took soil samples from 300 forest plots spanning six forest types along a latitudinal gradient in eastern China, which ranges from tropical rainforest to boreal forest ecosystems. A null-model analysis was used to compare the observed soil fungal beta diversity (β-diversity) with the β-diversity expected from random sampling of each local species pool. We also compared the relative importance of environmental and spatial variables on soil fungal β-diversity among forest types along the latitudinal gradient. Our results found that observed β-diversity was greater than expected β-diversity in all six forest types, which means that species tend to be more aggregated than expected. We determined that this species aggregation resulted from both environmental filtering and species dispersal limitations. Further, environmental variables had stronger influences on β-diversity than spatial dispersions. Additionally, the co-occurrence network showed that more species interactions occurred in the mid-latitude forests which lead to decreased soil fungal β-diversity and low interpretations of environmental and spatial variables. Study of these processes in different forest types along latitudinal gradients will provide important insights that local differences in the relative importance of different community assembly processes creates different gradients in global biodiversity.