Monitoring soil bacteria with community-level physiological profiles using Biolog™ ECO-plates in the Netherlands and Europe

• CLPP analysis with Biolog™ ECO plates was optimized for soil monitoring.
• The slope of the dilution curve was hypothesized to reflect functional diversity.
• Grasslands had higher functional diversity than arable systems in datasets from the Netherlands and Europe.
• Significant CLPP pattern in the Netherlands: current management is more important than soil texture.
• Significant CLPP pattern in Europe: soil pH was most important environmental variable.

Soil samples were analyzed with community-level physiological profiles (CLPP) using Biolog™ ECO-plates in the Netherlands Soil Monitoring Network (NSMN; 704 samples) and in a European-wide transect (73 samples). The selection of sites was based on a representative sample of major soil texture types, land uses and climate zones. This method for determination of CLPP was specifically designed to be applied in large and long-term monitoring activities. It encompassed a solution for the inoculum-density dependence of colour formation patterns in ECO-plates, through stepwise dilution to extinction of the bacterial inoculum. The CLPP in Dutch and European soil samples appeared to be reproducible and sensitive to land use and/or soil texture. Although the method is selective, CLPP based parameters correlated well with other microbial parameters and soil characteristics. Consistent patterns in CLPP and soil habitat characteristics are emerging, as brought about by environmental disturbances, land management and soil texture. The applicability of CLPP analysis in monitoring systems is discussed.