ANALYSIS OF NEMATODES AND SOIL-BORNE FUNGI FROM AMMOPHILA-ARENARIA (MARRAM GRASS) IN DUTCH COASTAL FOREDUNES BY MULTIVARIATE TECHNIQUES

A survey was carried out at nine locations in the Dutch coastal foredu nes to identify the species of soil borne fungi and nematodes associat ed with Ammophila arenaria (Marram grass). Ammophila arenaria is a san d binding grass that is very important for the stabilization of coasta l foredunes. Degeneration of the plants occurs at stabilized sites and is supposed to be caused by a combination of soil-borne fungi and nem atodes. Canonical correspondence analysis (CCA) and two-way indicator species analysis (TWINSPAN) were used to examine which fungal and nema tode species usually coexist in the rhizosphere of vigorous and early declining stands of A. arenaria. In total, 47 species of fungi and 10 genera of plant-parasitic nematodes were found. According to CCA, the community of soil organisms of stands that were more than 10 years old was significantly different from recently established stands of 3 yea rs old. Also, the community of soil organisms isolated from calcareous locations differed significantly from that of lime-poor locations. No relationship between the vigour of the plants (vigorous vs. early dec lining) and the soil borne species composition was found, although in roots of vigorous stands, the number of nematodes was higher than that of early declining stands. A relatively large group of soil organisms occurred generally. This group possibly contains an ubiquitous pathoc omplex that cause the growth reducing effects of biotic origin which g enerally occur in A. arenaria. Analysis of this group of nematodes and fungi by TWINSPAN resulted in 9 different combinations of concurring soil organisms of which 5 combinations were present at all investigate d locations. Two of the latter combinations contained both nematodes a nd fungi. The first contained three endoparasitic nematodes (Meloidogy ne maritima, Heterodera spp. and Pratylenchus sp.) that concurred with the fungus Mucor hiemalis. The second group contained Heterodera spp. , Telotylenchus ventralis, Filenchus sp. together with the potentially plant-pathogenic fungi Microdochium bolleyi and Fusarium culmorum, as well as the fungi Mortierella sp. and Trichoderma harzianum, all in r elatively high numbers. It is concluded that both CCA and TWINSPAN are valuable exploratory techniques, especially when used in combination, to detect possible combinations of soil organisms which may be involv ed in the degeneration of A. arenaria. Further identifications of harm ful organisms should be obtained from experiments.