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Colline/submontane acidic grasslands, elements of pre-industrial farming, are declining throughout Central Europe. As they correspond largely to the priority EU habitat type 6230 (Species-rich Nardus grasslands), a syntaxonomically sound delimitation is of importance. In the Rhenish Massif (Western Germany), acidic grasslands form diverse and syntaxonomically intricate vegetation patterns. We studied such grasslands in the Lahn-Dill district near Donsbach based on 292 original relevés from 1987. The dataset was classified into nine clusters. The clusters were aligned with syntaxa according to the proportions of diagnostic species. Four associations (with subunits) and one community specified to alliance were distinguished (in brackets corresponding alliances and classes): Polytricho piliferi-Scleranthetum perennis (Hyperico perforati-Scleranthion perennis, Sedo-Scleranthetea), Airo-Festucetum (Thero-Airion, Sedo-Scleranthetea), Campanulo rotundifoliae-Dianthetum deltoidis and Hypericum perforatum-Gnaphalium sylvaticum community (Violion caninae, Nardetea strictae), Arrhenatheretum elatioris ranunculetosum bulbosi (Arrhenatherion elatioris, Molinio-Arrhenatheretea). The Polytricho piliferi-Scleranthetum perennis and the Campanulo rotundifoliae-Dianthetum deltoidis, to our knowledge, are described for the first time for Germany. By NMDS ordination we detected soil fertility and soil acidity as the main drivers for vegetation differentiation followed by moisture-related variables. On average we found 37.7 vascular plant species, 4.3 bryophyte species, and 0.6 lichen species per plot which was on average 15.6 m² in size. Thirty-five threatened vascular plant species, two bryophyte and eight lichen species of the German Red List indicate the area's eminent conservation value. By our study, we extended the national list of syntaxa by two associations and appreciate the diverse acidic grasslands at the eastern edge of the Rhenish Massif. [ABSTRACT FROM AUTHOR]

The priority habitat type "Species rich mountainous Nardus grassland" (6230*) still faces considerable threats due to habitat losses and unfavourable conservation status; many characteristic species are still declining. This study aims at identifying underlying drivers and optimizing management, based on a detailed analysis of vegetation changes and management history. We studied two Natura 2000 sites (Meißner, Hirschberg) in northern Hesse, Germany, where a continuing management of grassland areas took place since the 1990s. We analysed data from 35 permanent and quasi-permanent plots with a number of one to three re-surveys per plot. Per plot, we calculated annual change rates from successive surveys for several parameters (vegetation structure, phytosociological-ecological species groups, functional species groups, mean indicator values) and single species. Change rates were arranged along a timeline from 1987 to 2019. We calculated mean change rates for each year and tested for significant difference from zero with a Wilcoxon rank sum test. For two specific sites we compiled additional relevés, partly dating back to the 1930s. We analysed species' changes in frequency and used redundancy analysis to test for influences of time and vegetation type on species composition. Whereas only two plots were lost as Nardus grassland, there was still a significant tendency towards eutrophication and insufficient management. This was indicated by continuous positive mean change rates (i.e. increasing values) for mean nitrogen indicator values, species numbers and cover sums of species of cultural grassland and fallow indicators. In contrast, character species showed continuously negative mean change rates (i.e. decreasing values) most of the time. Mean indicator values for soil reaction and moss cover consistently increased. It was only since 2012 that some of these trends weakened to a certain extent. For the site "Hausener Hute" (Meißner), the changeful management and deposition history since the 1930s, was reflected well in vegetation changes. The detected eutrophication phenomena had multiple possible drivers like nitrogen deposition and enhanced mineralisation caused by increased soil pH or rising temperatures. The management during the last decades with late mowing dates, very extensive grazing and low disturbance levels was obviously insufficient to counteract increasing eutrophication threats. Moreover, high moss and litter cover impeded the regeneration of weak competitors. For the mown areas, we therefore suggest earlier mowing dates (usually in July), chain-harrowing (i.e. removal of mosses and grass litter) in spring and extended aftermath grazing in autumn. Higher stocking rates should be applied at grazed areas. Some plots already mowed earlier since 2018 have recently shown positive trends (i.e. increasing character species, less eutrophication). However, this could also have been a consequence of recent drought years. Regarding such extreme events we recommend more flexible contracts with managers based on annual agreements and further monitoring based on permanent plots. [ABSTRACT FROM AUTHOR]