Indicatiewaarden voor voedselrijkdom van de bodem : Een vergelijking tussen drie indicatiesystemen

For the Environmental Data Compendium, including the Digital Environmental Balance, ecosystem quality and trends in availability of nutrients are assessed by using indices based on plant species. This report presents a study to determine the most suitable indicator system for assessing nitrogen availability to plants. Three existing indicator systems were compared: ITERATIO, Ellenberg indicator value and Wamelink-NO3. First, correlations between the different indices were examined, then indices were calculated for different plant communities and the outcomes were evaluated by vegetation experts. Subsequently, three datasets on species composition and biomass/fertilisation rates were analysed in order to relate biomass/fertilisation data to trophic indicator values. Lastly, trends in trophic level were calculated for eleven time series of permanent vegetation recordings of the Strabrechtse Heide heathland. Based on these analyses it was concluded that ITERATIO and Ellenberg produced the most reliable results. Neither Wamelink-NO3, nor other Wamelink indicator values are deemed suitable for assessing nutrient availability as they each focus on a single macronutrient. This is not sufficient to grasp the complexity of nutrient availability in ecosystems.