Indicative Value of Soil Nematode Food Web Indicesand Trophic Group Abundance in DifferentiatingHabitats with a Gradient of Anthropogenic Impact

摘要

Indicative value of nematode food web indices and trophic group abundance wasassessed for differentiating habitats in two soil types. A total of 604 soil samples werecollected from croplands, grassy borders, turfgrass lawns, shrublands and forests inHuron County, Ohio characterized by muck soils. Also, a total of 242 soil sampleswere collected from two habitats, turfgrass lawns and croplands, in Wayne County,Ohio characterized by mineral soils. All nematodes extracted from soil samples wereidentified to genus level, categorized to trophic groups and various nematode commu-nity indices were calculated. Multivariate analysis of variance using composite ofnematode measures revealed that croplands were significantly different from forests,shrublands, turfgrass lawns and grassy borders in the muck soils. Turfgrass lawns inmuck soils were not different from forests but were different from shrublands. Nodifferences were observed between forests and shrublands. Turfgrass lawns in mineralsoils differed significantly from croplands in the mineral soil. No differences wereobserved between the soil types when nematode data from croplands and turfgrasslawns from each county were lumped together. All habitats showed moderatelyenriched food webs [enrichment index (El) 69-78%I in both soil types. Forests,shrublands and turfgrass lawns in muck soils had high maturity (MI) and structureindex (SI) whereas grassy borders and turfgrass lawns in mineral soils had intermedi-ate and croplands in both muck and mineral soils had the lowest MI and SI values.Principal component analysis ( PCA) indicated that MI and El contributed the most todifferences between habitats in the PC1 while SI and channel index significantlyinfluenced PC2 axis. Forests and shrublands had highly structured food webs asexpected but their high enrichment may be unique to the muck soils. Ordination ofhabitats using nematode indices revealed that grassy borders and turfgrass lawns holdan intermediary position between undisturbed habitats (forests and shrublands) andhighly disturbed habitats (croplands). Although overall contribution of plant-parasiticnematode index (PPI) was less compared to the other indices, PPI explained the variationamong the habitats in the PC3 axis. Ordination using trophic group abundance showedlower resolution compared to the food web indices.