Soil nematode community structure as affected by temperature and moisture in a temperate semiarid shrubland

Nematodes are key agents in important soil processes, such as decomposition, mineralization and nutrient cycling. Therefore, alterations of the nematode community structure induced by global change may have a considerable influence on ecosystem functioning. However, it is not clear whether minor changes in soil temperature and/or moisture have any significant effect on nematode community structure. A field experiment was performed in a mosaic of open sand grassland and Juniper-Poplar woodland (VULCAN Project). Soil temperature and moisture were modified to the extent expected for the near future due to global changes. Community diversity and multivariate structure of the nematode community proved to be more sensitive to minute changes in soil temperature and moisture than different indices, such as specific richness (SR), maturity index (MI), plant parasite index (PPI), enrichment index (EI), channel index (CI), fungal feeder to bacterial feeder ratio (F/B) and nematode channel ratio (NCR). Nematode genera with high densities (>0.1 individual g−1 soil) were better indicators of the temperature and moisture changes than those of low density (<0.1 individual g−1 soil) in this sandy soil. Both drying and warming had significant influence on low density (Wilk's lambda: 0.02) and high density (Wilk's lambda: 0.002) genera according to canonical variate analysis. Cephalobus and Plectus were associated with the dried plots, while Cervidellus, Ditylenchus, Eudorylaimus, Seinura and Thonus were favoured by warming. Drying induced the development of a more structured nematode community in the bare soil compared to the control. Drying and warming effects on the soil nematode community were most pronounced in bare soil, less so in soil under poplar, while no significant effect was found in the fescue grass soil.