Abstract
Soil nematode densities and family-level faunal compositions were investigated for five months after chloropicrin fumigation in soybean fields in Japan. Our objective was to examine whether diversity measurements and ecological indices can describe appropriately structural changes in nematode communities after chemical disturbance. The total nematode density in the fumigated plots drastically decreased just after chloropicrin treatment, but gradually recovered. After the chemical treatment, the dominant nematode taxon changed from Rhabditidae to Cephalobidae; the fungivorous nematode guild and guilds with cp value 3-5 (CP35, K-strategists) were hardly detected. In the non-fumigated control plots Rhabditidae still predominated, and the fungivorous guild and CP35 guilds increased. Among the diversity indices and the ecological indices examined, Shannon- Wiener's H', Maturity Index (MI), Maturity Index without opportunistic bacterivorous guilds (MI (2-5)), Enrichment Index (EI) and Structure Index (SI) described these structural changes in the nematode communities. The Channel Index failed to detect significant effect of fumigation on decomposition pathways because both the fungivorous nematode guild and Rhabditidae were reduced in the fumigated plots. Replacement of Rhabditidae with Cephalobidae in the plots required careful interpretation of MI and EI behaviors. Even under such a replacement, MI (2-5) and SI were still useful in evaluating appropriately the ecological status of nematode communities after chemical disturbances. Jpn. J. Nematol. 34 (2), 89-98 (2004).
