Effect of Range Condition on Density and Biomass of Nematodes in a Mixed Prairie Ecosystem

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Abstract
Nematode density and biomass were determined by taxa from exclosures in excellent or fair range condition in western South Dakota [USA]. Density of plant feeding nematodes in both treatments varied from 2-6 million/m2 to a depth of 60 cm. Biomass of plant feeders was greater in the excellent condition range due principally to high numbers of dagger nematodes (primarily Xiphinema americanum). The main contributors to biomass estimates in fair range condition were Tylenchida, principally stunt and spiral nematodes. Biomass of predaceous forms was similar to that of plant feeders. Microbial feeders, although numerous, constituted a relatively small proportion of biomass in both treatments. Approximately 70% of nematodes in all trophic levels occurred above 20-cm sampling depth in both range conditions. Stunt nematodes were nearly limited to the upper 10 cm of soil, with spiral nematodes predominating with increasing depth, particularly in fair condition range. Nematodes constitute a major portion of the faunistic biomass in a mixed prairie ecosystem.