Local-scale soil nematode diversity in a subtropical forest depends on the phylogenetic and functional diversity of neighbor trees

Purpose Understanding the impact of neighbor tree diversity on soil biodiversity at the individual tree scale and clarifying which facets of neighbor tree diversity have a decisive impact on soil biodiversity. Methods We collected and identified soil nematodes underneath 256 individual trees of 16 species at four species-richness levels (1, 2, 4, 8 species) in a large tree diversity experiment in southeast China. We analyzed how the taxonomic, phylogenetic, and functional diversity of the nematode community were influenced by neighbor tree diversity. Results Our analyses showed that nematode alpha diversity at the individual tree scale decreased with increasing neighbor tree richness while beta diversity increased at taxonomic, phylogenetic, and functional levels. Nematode alpha diversity at the plot scale increased with increasing neighbor tree richness. Secondly, we found that reducing redundant species and increasing distinct species led to the differentiation of nematode communities under different individual trees in high-richness plots. Finally, our data revealed that the functional diversity of the neighbor tree community had the largest effects on the diversity of the local nematode community. Conclusion Our study emphasizes that there is a significant influence from neighboring trees, mainly the functional traits of the trees, even though they are spaced at distances multitudes greater than the distance over which soil nematodes can move. Hence it is important to consider these broader spatial aspects when examining the plant and soil biotic interactions.