Vegetation monitoring in a 100-year-old calcareous grassland reserve in Germany

Abstract

Calcareous grasslands harbor specialized species and are cultural relics. Therefore, they are prime habitates for conservation and restoration, but negative effects of inappropriate management, eutrophication and fragmentation continue to exist. These effects also influence grasslands which serve as target for restoration. Unfortunately, monitoring of long-term vegetation dynamics in calcareous grassland is rare. Here, we studied such changes over 35 years in the nature reserve ‘Garchinger Heide’, which is well known for its high abundance of rare species. Furthermore, it has been managed for conservation for more than 100 years. Therefore, species composition, total species richness, numbers of habitat specialists, red-list species and the proportion of graminoids were examined in 42 plots with frequency recording (1984–2018), and in 40 plots based on vegetation relevés (2003–2018). Ellenberg indicator values, specific leaf area, seed mass, and canopy height were analysed to detect patterns in trait response to environmental change. Within 35 years there were considerable vegetation dynamics. Specialist plants of calcareous grassland and red list species decreased, and insect-pollinated species declined in contrast to wind-pollinated species. Ellenberg N as well as graminoid abundance, canopy height, seed mass, and multi-trait functional dispersion increased, while specific leaf area showed no such change. Our results suggest that environmental change like deposition of atmospheric nitrogen, management regime, pollinator decline or isolation could be correlated with vegetation dynamics, while these correlations would need experimental confirmation. The grassland management certainly helped achieving several conservation goals, although it was not able to stop a decrease of rare species. The results show that also in nature reserves with long-term conservation management monitoring is essential to detect vegetation dynamics and to adjust the management to these changes.