Long-term vegetation changes in species-rich Nardus grasslands of Central Germany indicate eutrophication, recovery from acidification and management change as main drivers

Abstract

QuestionsThe impact of environmental changes on species-rich Nardus grasslands has been documented from the Atlantic biogeographic region but not from Central Europe. Which patterns and trends of community change in species-rich Nardus grassland of the Continental biogeographic region occurred in past decades? Are patterns and trends similar across areas within the Continental biographic region of Germany? Do they correspond to identified changes in the Atlantic biogeographic region of Europe? LocationEast Hesse Highlands, Germany MethodsIn 2012/15, we re-surveyed vegetation releves on quasi-permanent plots originally surveyed between 1971 and 1986/87 and re-measured soil parameters. We tested for differences in species frequency and abundance, mean Ellenberg indicator values, diversity measures and soil variables. Nitrogen and sulphur deposition data were analysed to evaluate effects of atmospheric pollutants. We used regression analyses to identify the contribution of environmental drivers to changes in species composition. ResultsWe found significant increases in soil pH, Ellenberg R and N values, species of agricultural grasslands and grassland fallows. C:N ratio, Nardus grassland specialists and low-nutrient indicators declined, while changes in species composition relate to changes in pH and management. There was a strong decrease in sulphur and a moderate increase in nitrogen deposition. Local patterns in atmospheric depositions did not correlate with local changes in species composition and soil parameters. ConclusionThe findings indicate significant overall eutrophication, a trend towards less acidic conditions, and insufficient management and abandonment. This is widely consistent across study areas and correspond to recent reports on vegetation changes and recovery from acidification in the Atlantic biogeographic region. We strongly assume reduction in sulphur deposition during recent decades to be a major driver of these changes combined with increased nitrogen deposition and reduced management intensity. This suggests a large-scale validity of processes triggering changes in Nardus grasslands across Western and Central Europe. NomenclatureThe nomenclature follows the German taxonomic reference list (GermanSL version 1.3) of Jansen & Dengler (2008).