Validation of grassland indicator species selected for result-oriented agri-environmental schemes

A list of plant species indicating species-rich grassland was validated for use in an agri-environmental programme in the Federal State of Brandenburg (Germany). It has become common practice that suggested lists of indicator species pass through a process of coordination involving several experts and stakeholders. Therefore, an ‘aptitude test’ for indicator species was needed that would be transparent as well as comprehensible. The starting list of potentially suitable indicator species was filtered using criteria that removed rare, toxic and ubiquitous species and retained representative species relevant for extensively managed grassland habitats of Brandenburg and species that are easy to detect and identify. Vegetation surveys conducted on 50-m transects in about 120 grassland fields in Brandenburg served as the database for the validation. The data were grouped by the mean moisture levels of the sites. We examined the influence of the presence or absence of potentially suitable indicator species on diversity quality criteria for each site group using a single species testing procedure. Besides floristic species diversity (overall species number), the number of species indicating extensive use and the number of Red List species are criteria that can be used. In addition, weighted indices were computed which pool together the three quality criteria to establish a ranking of the pre-selected species. The quality criteria can be differentially combined depending on the needs of the individual project.