Mapping ecosystem types by means of ecological species groups

A method is presented to deduce nation-wide maps of ecosystem types from FLORBASE. This national database contains data, per km2, on the presence of indigenous plant species that grow in the wild. The ecosystem types on the maps are defined on the basis of abiotic factors that determine the plant species composition of the vegetation in the Netherlands: salinity, moisture regime, nutrient availability, acidity. Water management measures may cause changes in these four factors and, as a result, change the species composition of the vegetation. For the construction of the maps, species of the Dutch flora are first allotted to the ecosystem types. Then, on the basis of both the number and the indicative value of species, a botanical quality class of each km2 is assessed for each ecosystem map. The boundaries of the quality classes are obtained by expert judgement. It is possible, however, to compute class boundaries with a mathematical procedure, also for grid cells larger than 1 km2. The maps are corrected for regional differences in the detail of the plant inventorie