How does decreasing aboveground biodiversity influence belowground communities? Studies involving a broad range of aboveground ecosystems and taxonomic groups have shown that changes in diversity in one group within a community can affect the diversity and composition of other groups. Conversely, many soil ecologists have argued that belowground diversity is thought to be more strongly influenced by the presence and identity of the dominant aboveground species than by aboveground diversity itself. To explore the interaction between aboveground diversity and belowground communities, we examined soil nematode diversity and community composition directly under switchgrass in areas of high and low plant diversity.  

Results/Conclusions

We found that soil nematode diversity under switchgrass in native prairies (high plant diversity) is not significantly different from soil nematode diversity under switchgrass in monoculture (low-to-zero plant diversity). This result indicates that plant diversity itself does not influence nematode diversity in this system. An examination of nematode community composition, however, revealed that plant diversity is linked to compositional shifts in nematode communities under switchgrass. Nematode communities under switchgrass in monoculture were more compositionally similar to each other than they were to nematode communities under switchgrass in native prairies and vice versa. Interestingly, fewer herbivorous nematodes were seen under switchgrass in monoculture than under switchgrass in native prairies, suggesting that nematode herbivory may be reduced in monocultures of switchgrass. Our study shows that both diversity and dominance are important aboveground factors influencing the structure of belowground communities.