Soil nematode communities of Alpine summits–site differentiation and microclimatic influences

Nematode communities and the differences in microclimatic conditions were studied on three summits (altitude 1900–2250 m a.s.l.) in the calcareous Alps of Austria (Styria). Family composition and trophic structure (feeding types) were assessed and were analysed for (1) between-summit variation, and (2) differences between summit plots facing the four compass directions, i.e. microclimate variation. Soil temperatures were recorded at all plots.The summits differed significantly in family composition in that the lowest summit strongly deviated from the other two summits similar in altitude. Total nematode abundance and diversity were similar, however, among summits (342–444 individuals per 100 g dry soil, 18–23 families per summit). Maturity indices (3.0–3.3) and the plant parasite indices (2.4–2.6) were also within a narrow range. The most pronounced result was that nematode abundances on the south or east facing side were higher, by a factor of 4, than on the northern and western sides. This pattern applied to most families and feeding types, albeit to varying degrees. Across all summits nematode diversity and family composition were correlated with winter temperature minima. Total nematode abundance, however, covaried with annual mean temperature and growing season duration within summits.We conclude that nematode assemblages are potentially good bioindicators of climate change. They reacted sensitively and predictably to microclimatic conditions, sampling techniques are inexpensive and well standardized. Furthermore, feeding types can be determined with minimal taxonomic skills and largely reflect results based on classification by family.