ECOLOGY OF THE PLANT-FEEDING NEMATODE FAUNA ASSOCIATED WITH SEA BUCKTHORN (HIPPOPHAE-RHAMNOIDES L-SSP RHAMNOIDES) IN DIFFERENT STAGES OF DUNE SUCCESSION

A field survey was carried out to investigate the development of the p lant parasitic nematode fauna under Hippophae rhamnoides ssp. rhamnoid es from the colonization to the degeneration stage. Samples from diffe rent sand dune locations along the Dutch coast were analysed and the o ccurrence and densities of different nematode taxa were studied in rel ation to soil parameters and plant productivity, using ordination and regression techniques. There appeared to be a succession of nematode t axa along with the development of soil and vegetation. The maturity in dex of the obligate plant-feeding nematode fauna and the mean number o f species increased significantly. The characteristics of sites, with respect to soil parameters and nematode fauna, diverged as it reached the degeneration stage. Tylenchorhynchus microphasmis Loof and Mesocri conema xenoplax (Raski) were common in all stages. The abundance of pl ant feeding nematodes in the rhizosphere of Hippophae increased toward s later stages in a succession gradient, whereas population densities in the bulk soil remained practically constant. The status of H. rhamn oides as a host of several free-living plant-feeding nematodes is disc ussed.