Ecologische kwaliteit van de bodem

This report describes the meaning of ecological quality of soil and two ways to quantify such quality. A high number of processes takes place in the soil. These processes are important for mankind (ecosystem services) as they contribute to, e.g., food production, the quality and type of nature and the production of clean groundwater (for the drinking water production). The role of soil organisms is important in these processes. For a sustainable use of the soil it is important to use and manage the soil organisms in a way that these processes are secured for the future. Also a change in soil use must always be possible. To facilitate a sustainability policy for the soil a biological indicator for soil quality (BISQ) is being developed, which is designed for application on a national scale. Therefore ecological data are collected on species diversity, species abundance and activity of soil organisms. For environmental policy making a system must be developed to characterise the ecological quality of soil as 'good' or 'bad', or in a sense of 'desired' and 'undesired'. Two ways to derive quality criteria for soil based on interpretation of the collected data are described. The mechanistic or functional method: In this method the wanted combination of ecosystem services on a certain place is determined and subsequently the optimal biodiversity within such an ecosystem is deduced by statistic interpretation of soil ecological data that have been collected. The statistic method: In this method for a certain combination of land-use and soil type data are collected from a group of reference locations that have been classified on beforehand as 'good'. Based on these data, a statistically derived optimal composition of an ecosystem type is given, with the label 'good quality'. In the application of the indicator, in both approaches it is possible to formulate how far a present local quality satisfies the desired state. Because of the complexity of the subject it is proposed to use both approaches independently in further development according to the 'multiple lines of evidence' principle. Ideally both approaches will lead to corresponding results. Finally the further development of the indicator for application on both international and local scale is discussed