Changes in nematode communities following cultivation of soils after fallow periods of different length

The composition of the nematofauna was studied in four soils that differed in the length of fallow restoration period since previous cultivation. The longest fallow period was 21 years. Plots were sampled for 2 years after st arting cultivation of the fallow soils. The treatments were ranked followin g a restoration-exploitation gradient depending on fallow duration and the number of years of millet cultivation after fallow clearing; components of the nematofauna were analysed for correlation with this ranking. The nematode community structures at the first date of sampling during cult ivation clearly reflected the length of the fallow period. Nematode communi ty structures in the fallow soils rapidly approached those in the continuou sly cultivated soil; they were hardly distinguishable during the second yea r of cultivation. One-third of the recorded nematode taxa exhibited pronounced responses to t he cultivation. Mononchidae. Anatonchidae, Tylencholaimoidea, Acrobeles, Ps eudacrobeles, Tylenchidae and Helicotylenchus preferred sites of more matur e successional status, while Dorylaimoidea, Tylenchorhynchus and Rhabdolaim idae dominated the cultivated sites. The maturity index (MI) did not distin guish the management regimes. The plant parasite index (PPI) tended to decr ease with higher restoration status linked to greater abundance of the Tyle nchidae in these situations. The decrease of fungal to bacterial feeders re flected a decreasing importance of the fungal decomposition pathway after r esuming cultivation. (C) 2001 Elsevier Science B.V. All rights reserved.