Long-Term Plant Community Removal Alters Soil Nematode Communities Mainly Through the Trophic Cascading Effects of Fungal Channel

Soil nematodes are ideal indicators for soil food webs, ecosystem conditions, and soil health. However, current research focuses on how plant removal affects soil nematodes while ignoring the importance of the trophic cascading effects. The study aims to elucidate the direct and indirect effects of long-term plant community removal on soil nematode communities, especially through soil physicochemical properties and trophic cascading effects. A 6-year field all-aboveground plant community removal experiment was conducted to evaluate the effects of plant removal on soil nematode communities and use piecewise structural equation modeling to better understand the direct and indirect effects of plant removal on different trophic group nematodes. The removal of plants did not significantly influence the total abundance, richness, or trophic group richness of soil nematodes, but it did considerably reduce the number of herbivorous and fungivorous nematodes. Our results revealed that the removal of plants significantly altered the nematode community composition mainly by changing the relative abundance of the genera Helicotylenchus , Tylenchus , Tylopharynx , and Aphelenchoides . The abundance of predatory-omnivorous nematodes was dramatically and directly enhanced by the removal of plants, but it was also indirectly changed by a decrease in the abundance of fungivorous and herbivorous nematodes. The most significant mechanism for plant removal to impact predatory-omnivorous nematodes might be through the fungal channels, which are mainly mediated by fungivorous nematodes. These results indicated that plant removal affects predatory-omnivorous nematodes primarily through fungal channels and elucidated the importance of trophic cascading in mediating the effects of plant communities on soil nematode communities.