Relationships among spatial distribution of soil microarthropods, earthworm species and soil properties

This paper examines the spatial distribution pattern of earthworm species and microarthropod groups, with the aim of detecting and explaining the relationships between them. Microarthropods and earthworms were sampled at 42 uniformly distributed points, with physical and chemical analyses performed at each site as well. Distribution patterns were described using geostatistical tools. Aggregation of populations, determined using a dispersion index, showed that all soil groups presented clumped distributions. Geostatistical analysis indicated that soil groups were spatially auto-correlated and facilitated a description of the spatial pattern of each group. Cross-semivariograms showed cross-correlation of different types (either negative or positive) between various groups of microarthropods and some earthworm species. Mantel tests were used to assess these correlations and to determine whether the relationships were true or spurious. Partial Mantel tests confirmed positive relationships between H. elisae – Isotomidae and A. trapezoides – Entomobryidae and negative relationships between H. elisae – Poduromorpha, H. elisae – other arthropods and A. rosea – Gamasida. No true relationships were found between fauna distribution and soil physical/chemical properties. Different earthworm species influenced each microarthropod group in diverse ways showing complex relationships between them. Additional manipulative experiments are necessary to unravel the processes affecting the specific patterns observed in the present study.