Calibrating ecological indicator values and niche width for a Mediterranean flora

Abstract

International audienceBioindication of ecological variables such as humidity, temperature or pH by ecological indicatorvalues of plants is a powerful tool for research in plant ecology, e.g. to detect early vegetationchanges. Here, we provide a data set of ecological indicator values including niche width for anentire regional flora. We used an extensive data-base with floristic relevés from Southern Franceto recalibrate indicator values for light (L), temperature (T), continentality (K), air humidity (A),soil moisture (F), pH (R), productivity (N), soil texture (G), soil organic matter content (O) andsalinity (S). Values were recalibrated using average values from co-occurring plants, enabling todevelop indicator values for species not yet evaluated previously. Recalibrated values are on acontinuous scale and we add standard deviation, median, first and third quartile for each indicatorvalue. Linear regression of average indicator values against measured factors showed highercorrelation with recalibrated values compared to original indicator values for temperature, pH andnitrogen, and comparable R 2 for moisture. Individual indicator systems performed better than acombination and applying different weighting procedures demonstrated the usefulness of inversevariance. We further illustrate graphically how recalibrated values and niche width increaseecological knowledge on plants