CALIBRATING ELLENBERG INDICATOR VALUES FOR MOISTURE, ACIDITY, NUTRIENT AVAILABILITY AND SALINITY IN THE NETHERLANDS

A general calibration of Ellenberg indicator values for moisture, acid ity, nutrient availability and salinity was carried out on a large dat abase of relevees and environmental variables from a variety of ecosys tems in the Netherlands.Satisfying relationships with Ellenberg indica tor values for moisture, acidity and salinity were found for mean grou ndwater level in spring time, soil pH and chloride concentration in gr oundwater. For mean groundwater level in spring and chloride concentra tion in groundwater subdivision of the database led to clearer relatio nships with indicator values. For the Ellenberg indicator value for nu trient availability satisfying calibration results were only achieved with data on standing crops and N stock in standing crop. The relation ship with soil chemical variables was less clear. Although the correla tion between indicator and measured values is obvious, the variation a round the regression lines is considerable. However, because of the si ze and composition of the database, it is unlikely that our calibratio n results can be much improved by adding more (Dutch) data. The calibr ation results will be applied in the multi-stress model SMART-MOVE, de veloped to predict changes in species composition due to acidification , eutrophication and the effects of lowering groundwater.