Vegetation change in dry grasslands in Northeast Germany over two decades: A resurvey

Semi-natural dry grasslands in Central Europe harbor many rare and specialized species and face threats due to altered management practices and environmental change. However, more studies on vegetation change and management effects in dry grasslands are needed, especially with consideration of non-vascular taxa. Here we used a resurvey approach to analyze vegetation change in dry grasslands on loamy and sandy soils (Festuco-Brometea, Trifolio-Geranietea sanguinei and Koelerio-Corynephoretea canescentis) in Brandenburg, Northeastern Germany. We surveyed 157 plots (10 m²) at each of two time points, 1993–1997, and 20–25 years later, 2017–2018. We recorded a total of 362 vascular plants and 84 non-vascular taxa. Species richness per plot remained stable across surveys. We detected, on average, 32.2 and 21.9 species per plot in dry grasslands on loamy and sandy soils, respectively, including 3.25 and 4.8 non-vascular taxa and 7.6 and 2.2 endangered species according to the regional Red List. We found evidence for vegetation homogenization and a reduction in Shannon diversity and Shannon evenness in the recent survey, suggesting early signs of biodiversity decline. Analyses of mean ecological indicator values and plant traits, as well as of winner and loser species, revealed that changes in vegetation composition were accompanied by an increase in competitive, mesophytic species and a decline in disturbance-tolerant specialists. We further show that the highest diversity in dry grasslands on loamy soils was associated with intermediate levels of grazing. Our findings highlight the conservation significance of dry grasslands and suggest intermediate grazing pressure as a suitable management strategy.