Evaluation of bioindicator systems derived from soil arthropod communities

Abstract

Communities of microarthropods, especially those in forest soils with a well-developed litter and humus layer, are characterized by a great diversity of species. The intricate relationships of soil invertebrates with their ecological niches in the soil, the fact that many of them live a rather sedentary life, and the stability of community composition at a specific site provide good starting points for bioindication of changes in soil properties and impact of human activities. There are various ways in which the composition of a soil microarthropod community can be characterized. Nine different approaches towards the development of community bioindicators may be recognized in the soil zoology literature. Each of these approaches exploits a different aspect of community structure. For example, community composition may be summarized by its dominance structure, its diversity of feeding types, its diversity of life history patterns, etc. The different approaches are evaluated according to two criteria: specificity (how specifically does the indicator react to a certain soil factor or impact?) and resolution (how sensitively does it react to changes?). A conclusion from the review may be that a combination of physiotype classification and multivariate statistical analysis holds the greatest promise at the moment. Two examples of recent bioindicator approaches are discussed in more detail: the `bioindicator index for toxicant residues', which measures the extent to which internal concentrations of toxicants pose a risk to a soil community, and the `arthropod acidity index', which measures the average pH preference of a microarthropod community based on substrate choice experiments.