Jürgen Dengler, Stefan Widmer, Eline Staubli, Manuel Babbi, Jamyra Gehler, Daniel Hepenstrick, Ariel Bergamini, Regula Billeter, Steffen Boch, Sven Rohrer and Iwona Dembicz
The upper Rhone valley in the Swiss canton of Valais is one of the driest and most continental of the inner-alpine valleys and harbours a rich xerothermic flora. We studied syntaxonomy and ecology of dry grasslands and their species richness patterns. In 2018 we recorded 28 vegetation plots (10 m2) and three nested-plot series of 0.0001 to 100 m2 on the south-facing slopes above the village of Ausserberg. Mean richness of all species ranged from 1.7 on 1 cm2 to 47.3 on 100 m2, with little contribution of bryophytes and lichens. The species-area relationship for total richness closely followed a power function. Modified TWINSPAN yielded a three-cluster solution, which could easily be matched with three orders of the class Festuco-Brometea: Stipo pulcherrimae-Festucetalia pallentis (xeric, rocky), Festucetalia valesiacae (xeric, non-rocky) and Brachypodietalia pinnati (meso-xeric). The subdivision of the xeric types into two orders is new for Swiss dry grasslands, where these types up to now had been joined in a single alliance Stipo-Poion within the Festucetalia valesiacae.