Soil nematode populations in a grassland plant diversity experiment run for seven years

Abstract

Plant species identity and diversity may greatly influence the composition of the nematode fauna. The abundance of various nematode populations was investigated in a field experiment on plant diversity. 58 plots in an arable field planted with plant species growing alone or together up to a richness of 12 species were sampled after seven years for analysis of composition of the nematode fauna. Two additional control plots without vegetation were also sampled. Plant species identity was generally more important than plant diversity for the composition of the nematode fauna. Only the omnivorous Aporcelaimidae was positively related to plant species richness, and the fungal-feeding Aphelenchus and the bacterial-feeding Prismatolaimus were affected by functional diversity. Some nematode populations were strongly influenced by plant species composition, e.g. the plant-feeder Tylenchorhynchus maximus was clearly coupled to the grass Phleum pratense. Nematode species within a feeding group sometimes had a rather specific abundance patterns under various plant species and plant species combinations. This was especially the case with the plant-feeding nematodes some of which obviously were directly influenced by the host suitability of specific plant species. Other nematode species were probably more influenced by indirect effects of plants on edaphic and nutrient conditions including biotic interactions from other components in the soil organism community. Yet other nematode species were little influenced by the kind of vegetation in the different plots. Our results show that to fully understand plant community effects on the nematode fauna there is a need to go further than just a division into nematode feeding groups.