Size dependence of parameters for ecological factors and for nature conservation evaluation of grassland relevés

In the interpretation of vegetation data originating from relevés (e.g. quadrats sensu Braun-Blanquet) which differ in size, it is important to know how substantial the size effect may be. This effect may be influenced by the score of parameters based on the composition of the vegetation, e.g. those indicating ecological factors (trophic state, type of land use) and the score of evaluation parameters (nature conservation value). Susceptibility to the size of the relevé may provide a criterion for parameter choice. In order to investigate the size dependence of some parameters for grassland vegetation, relevés were made on grassland (100–500 m 2 and the adjacent ditch banks (25–75 m 2). The study was performed in the peat polder district of the province of South Holland. Parameters for ecological factors scarcely showed any size dependene while parameters for nature conservation evaluation did. However, in order to lessen the size dependence of the latter, an evaluation parameter was designed which seemed to exclude size-dependence. The precision of ecological factor parameters and evaluation parameters did not differ substantially. The results of the field and ditch bank vegetation were fairly similar.