Nematode community responses to a moisture gradient and grazing along a restored riparian corridor

Nematode assemblages were assessed to infer soil functions along a stream channel restored with native vegetation in a California on-farm study. Samples were taken at three distances from the water at six sites along the stream channel. Sites represented differences in grazing management and vegetation type. Bacterivorous nematodes, dominated by r-strategists, c–p 1 and 2 (colonizer–persister) categories, were in greater abundance in the ungrazed than the grazed sites. Among the fungivores, c–p 2 were abundant in the ungrazed sites and at positions closest to the water’s edge, while only one genus, c–p 4 Tylencholaimus, was more abundant at the top of the stream bank and in grazed sites. The stream edge had greater abundance of bacterivores than the drier uppermost soil. Nematode faunal analysis suggests that bacterial decomposition channels predominated near the water while fungal channels predominated in drier locations. Higher aboveground herbaceous plant biomass in the ungrazed sites and closer to the water might have contributed to greater abundance of c–p 1 and 2 bacterivores. Overall, nematode communities were not strongly affected by the restoration, possibly due to dampened effects on soil properties after seven years, lack of colonization from other riparian areas, and/or insufficient time for the restored plant communities to shape nematode communities.

► Bacterivorous nematodes dominated in greater abundance in the ungrazed than the grazed sites. ► The stream edge had greater abundance of bacterivores than the drier uppermost soil. ► Nematode faunal analysis suggests bacterial decomposition near the water. ► Fungal channels predominated in drier locations. ► Nematode communities were not strongly affected by the restoration.