Soil nematode communities on Surtsey, 50 years after the formation of the volcanic island

Soil nematodes are a key group that can both influence and reflect changes in the soil ecosystem. We investigated the generic composition, abundance and community structure of soil nematodes in two contrasting vegetation successional seres now found on the 50 year old volcanic island of Surtsey, Iceland. One represented the primary succession without much external input of nutrients (S1), while the other was a grassland that has evolved under a strong influence of allochthonous nutrient inputs by gulls (S2). In 2012 in total 25 genera of nematodes were identified, of which 14 were reported on Surtsey for the first time. Across the whole island, the nematode abundance and distribution was most strongly related to soil C:N ratio, soil acidity, plant cover and biomass. The nematode abundance was higher at S2 and there the trophic structure was dominated by bacterialand plantfeeders, while hyphal-feeders were more dominant at S1. Nematode communities have continued to change at S1 since the last nematode survey, which took place 17 years ago, even where the vegetation cover and composition has remained stable. This may indicate a gradual change in the soil environment at S1. Within S2, the nematode community had become denser and more structured, but still it had lower generic diversity than found at S1. Resource availability was found to be an important driver for nematode colonization and primary succession on this isolated volcanic island. However, the study also found that soil nematode communities may show a different pattern of succession than plant communities.