|Hopp, D; Dengler, J: Scale-dependent species diversity in a semi-dry basiphilous grassland (Bromion erecti) of Upper Franconia (Germany), Bulletin of the Eurasian Dry Grassland Group, 28, 10–15 (2015)|
|Key words: lpha diversity; Bavaria; beta diversity; biodiversity; Brachypodietalia pinnati; Festuco-Brometea; species-area relationship (SAR); species pool; species richness; syntaxonomy; world record|
We analysed a semi-dry basiphilous grassland near Bayreuth, Upper Franconia, Germany with nested-plot sampling on areas from 0.0001 to 100 m². The stand clearly belongs to the order Brachypodietalia pinnati of the class Festuco-Brometea. Within this order, the affinity to the subatlantic alliance Bromion erecti was higher than to the subcontinental Cirsio-Brachypodion pinnati, while the assignment to any of the current Bromion erecti associations remained unclear due to a lack of an up-to-date syntaxonomic revision of the dry grasslands in Germany. The species richness for the different grain sizes was always above those for Brachypodietalia pinnati communities in NE Germany, but below the extremely rich stands in the White Carpathians or Transylvania. Also the species-area relationships had a very low slope (e.g. z = 0.18 for all species combined), pointing to an unusually high homogeneity of the stand or rather a limited regional species pool. The richness values in Bayreuth at smallest grain sizes reached about ¾ of the known maxima in European grasslands, but only about ½ for the areas from 1 m² upwards. When comparing our richness data with data from the literature, we came across one previously overlooked world record, i.e. 7 vascular plant species on 1 cm² in two Ukrainian grasslands (old record was 5 species). In general, our small dataset is a valuable contribution to the envisaged synthesis of scale-dependent diversity patterns in grasslands across the Palaearctic.