Nematode community and trophic structure along a sand dune succession

Changes in below-ground nematode communities, in terms of abundance, diversity and trophic structure and the composition of the community in terms of sex bias and adult-juvenile ratio were related to edaphic factors from sites that represented a known sand dune succession. Nematode abundance increased along a 1-km transect from sandy beach (no vegetation cover, early successional stage) through active dune systems [Ammophila arenaria (L.) and Leymus arenarius (L.) dominated] to mature dunes (heath covered, mature successional stage). Furthermore, as the succession progressed, the adult nematode sex ratio changed from male biased to highly female biased. Consequently, the adult:juvenile ratio decreased as the nematode community became more female dominated. An assessment of nematode diversity using both univariate and multivariate analysis produced contradictory results. The univariate indices, Shannon-Weaver and evenness, were significantly lower (P<0.05) at the dune heath than the other sites whereas the maturity index was significantly lower (P<0.05) at the beach site. Multivariate analysis clearly separated the beach and dune heath samples from the other samples and each other, and to a lesser extent separated the fore dune samples from the grey and yellow dune. Omnivorous nematodes represented the largest trophic component of the nematode community in all successional stages of the terrestrial sites. Epistrate/epigrowth feeders represented ca. 80% of the nematode community at the beach site. A trend was apparent of increasing numbers of omnivorous nematodes along the succession in relation to increasing organic matter and/or litter accumulation.