engleski

Delimitation between semi-dry and mesic meadows in Central Europe

Phytosociological relevés representing the orders Brometalia erecti (semi-dry meadows) and Arrhenatheretalia (mesic meadows) were obtained from the national databases and private sources of the seven Central European countries using a selection criteria based on species composition. The selection criteria was that any of nine typical mesic-xeromesic grassland species (Agrostis capillaris, Anthoxanthum odoratum, Arrhenatherum elatius, Avenula pubescens, Brachypodium pinnatum, Briza media, Bromus erectus, Festuca rubra, Trisetum flavescens) should reach at least 10% cover. Only plots from 4 sqm to 25 sqm were included. The selection yielded 22807 relevés (Austria: 1324, Croatia: 329, Czech Republic: 7868, Germany: 7100, Hungary: 1204, Slovakia: 4478, Slovenia: 504). The data set was geographically stratified by 6’ latitude × 10’ longitude grid cells and from each grid cell 20 relevés were selected by heterogeneity-constrained random resampling. In the HCR between-plot dissimilarities were expressed by the Horn- Morisita index calculated after square root transformation of the cover values. Statistical noise of the resampled data set were eliminated by retaining the principal coordinates (obtained by using the same dissimilarity measure and data transformation) as variables that explain higher amounts of variation than the expectations based on the broken stick model. Retained coordinates of relevés were classified hierarchically by Ward’s agglomerative procedure. The optimal number of clusters was identified using the Optimclass method. Clusters were characterized by dominant, constant and faithful species (phi coefficient with correction for group sizes). The resulting clusters were compared to existing syntaxonomical units at the level of alliances and associations. The applied softwares are Turboveg, Juice and the R Environment with several packages. Results: The results were presented in a dendrogram, an ordination diagram, and the geographical distribution of the clusters were also plotted onto a map. We clarified the positions of several ’transitional’ associations and refined their geographical ranges. We also outlined a practical definition for the delimitation between Brometalia erecti and Arrhenatheretalia.

semi-dry; mesic; meadows; central Europe; classification; Brometalia erecti; Arrhenatheretalia

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