Primary colonisation of newly formed soils by actinedid mites
In the brown-coal open-cast mining district near Cottbus, Germany, an artificial, experimental water-catchment system was constructed in 2005. The purpose of the experiment is to observe the development of the soil ecosystem during simulated primary succession. Within these studies the development of the soil fauna has been monitored since late 2005, of which the results regarding actinedid mites are presented here. Actinedida represented the major microarthropod group colonising the newly developing soils, having been present within months after exposition of the substrates to the surface, albeit in very low densities and only in sporadic samples. Initially, species richness was also extremely low, with practically only Nanorchestes sp. und Speleorchestes sp. present. Three years after site initiation, the abundances and species richness increased significantly, although they were still low compared to mature soils. The microarthropod communities continued to be strongly dominated by actinedid mites and colonisation of the soils remained spatially heterogeneous. The sporadic individual-richness was mostly caused by strong population development of single species in a few samples, e.g., Siteroptes sp. and Bakerdania sp. The abundance and distribution of Nanorchestes sp. originally increased strongly in the first two years. However, as many more species were found thereafter, the density of this species decreased briefly; dramatically in samples containing high densities of Siteroptes sp., indicating successional species replacement. Remarkable is the occurrence of species such as Cheletomimus vescus, Hawaiieupodes thermophilus and Xerophiles ereynetoides, which are rare, most likely xero-thermophilous species adapted to nutrient-poor soils. The results described here represent only those of the first 2.5 years and sampling and evaluation will continue.
Actinedida, succession, sand, colonisation