Abstract
Both earthworms and plants may affect the soil nematode community. However, the effects of earthworms and plant species interactions on soil nematode community are poorly understood. We explored how an epigeic earthworm Eisenia fetida affects the soil nematode community in systems with three representative plants (wheat, cotton and cabbage) which were grown in pots with or without added earthworms under greenhouse conditions. Earthworm presence decreased the abundance of total nematode and all four nematode trophic groups, except for the fungivore and predator/omnivore nematodes in wheat systems, but increased the genus richness of nematode in all treatments. Due to plant identity and different root exudates, plants had significant effects on soil nematode abundance. Compared with the no plant and without earthworm treatment, wheat and cabbage had the higher stimulation of the abundance of total nematode, bacterivores and fungivores, and cotton had the higher stimulation of the abundance of fungivores and predators-omnivores; whereas earthworm presence mostly weakened the stimulation effects of plant species on soil nematode abundance which indicated earthworms had the enhanced effects in the presence of plants. The interaction affected soil nematode abundance (total nematodes, bacterivore, fungivore and omnivore-predators) and community diversity indices (diversity index H′, evenness index J′, community maturity index ∑MI, Simpson dominance index λ and nematode channel ratio NCR). Principal component analysis showed that plant species affected soil nematode community composition. Redundancy analysis indicated plant species and biomass accounted for 41.60% and 34.13% of the variation in soil nematode community structure, respectively; while earthworms explained only 6.13%. Overall, current study suggest that earthworm could inhibit nematode abundance; whereas, plants have exerted greater influences on nematode community structure than earthworm presence due to their species-specific effects on different trophic groups of nematodes.
Highlights
Www.nature.com/scientificreports compared to the control, the introduction of epigeic earthworms (Lumbricus rubellus) decreased the total number of nematodes after 30 days, while 120 days after earthworm addition, the total nematode numbers showed no significant difference[17]
In the absence of earthworms, the dominant genera Cephalobus and Rhabditis were identified in no plant and wheat; Cephalobus and Tylenchus which has been classified as “plant associated”[41] were identified in cotton; and Cephalobus, Acrobeles and Rhabditis were identified in cabbage
This study demonstrated epigeic earthworm addition suppressed the soil nematode abundance, which is consistent with previous reports[9,10,14,17,42] and demonstrated partly our first hypothesis “earthworm presence may decrease nematode abundance under planting crops”
Summary
Www.nature.com/scientificreports compared to the control (without earthworms), the introduction of epigeic earthworms (Lumbricus rubellus) decreased the total number of nematodes after 30 days, while 120 days after earthworm addition, the total nematode numbers showed no significant difference[17]. These results indicated that the effects of epigeic earthworms depended on the soil or substrate systems, nematode trophic groups or even the duration of earthworm presence. The combined effects of earthworms and plant species can be expected to affect soil nematode communities in different ways. We hypothesized: (1) that earthworm presence may decrease nematode abundance under planting crops, and such effect may be enhanced in a system where earthworms stimulated plant growth; (2) that either plant species or earthworms may have a more significant effect on the soil nematode community composition; (3) that the interactive effects of earthworms and plant species would influence soil nematode abundance and community structure
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