Nematodes and microarthropods as environmental indicators for terrestrial and wetland soils

Soil nematode and microarthropod communities are effective biological indicators of soil health across ecosystem types and large geographic regions. As primary consumers in the soil food web, their community composition integrates primary producers and decomposer communities and the physio-chemical environment. Indices of ecological succession are more reliable in detecting statistical differences than relative abundance of trophic groups. Interpretation of biological indicators depends on their ability to reflect ecological processes. Quantitative field experiments suggest that variation in soil nitrogen availability and decomposition rate are best explained by nematodes and arthropods, respectively. There are two major impediments to implement nematode communities in large-scale environmental monitoring programs, i.e., ecological interpretation and accessibility to non-specialists capable of identifying a multitude of non-pathogenic taxa. Although molecular tools assist in identification, they do not substitute for ecological interpretation. Metadata analyses are useful to identify sentinel taxa that respond consistently and predictably to different types of land management practices. However, independent validation of their status needs to be confirmed empirically. A long-term goal is to simplify invertebrate indicators to reference a subset of taxa and/or molecular biomarkers to reduce the labor and learning curve necessary for precise and accurate implementation on a large scale. A microarray or multiwall plate assay style kit could provide an economic solution to implementation of these indices on regional and national scales.