Konstanz und Dynamik in einem artenreichen Kalkbuchenwald - Fortführung einer Zeitreihe von 1981 bis 2021.

In 2021, a large transect with 281 10 × 10 m grid cells was re-surveyed in a limestone European beech forest (Hordelymo-Fagetum lathyretosum) on the plateau of the Göttingen Forest after surveys in 1981, 1991, 2001, and 2011. The stand, which has not been managed by forestry since the beginning of the permanent plot study, initially showed an increasing cover of the tree layer and, as a consequence of game-proof fencing until 2005, also an increasing cover of the shrub layer. Since 2011, the tree layer cover has decreased due to small openings after drought years and winter storms. Also, the shrub layer cover declined significantly since 2011, mainly due to ash dieback and the growing impact of deer browsing. In both vegetation layers, Fagus sylvatica was able to expand its dominant role. In the herbaceous layer, the sharp decline and loss of numerous species is striking, among them typical forest species that have been classified as characteristic for species-rich European beech forests on limestone (e. g., Lathyrus vernus, Mercurialis perennis). The large number of losers (27 species) is matched by only a small number of winners (5 species) between 1981 and 2021. Especially Allium ursinum and Hedera helix, but also the two Orchidaceae Epipactis helleborine and Neottia nidus-avis have increased significantly since 1981. The increase of the highly competitive Allium ursinum, probably due to an earlier start and a longer lasting vegetation period, is accompanied by an increasing share of beech in the tree layer. At the same time, the species diversity decreased, and the herb layer composition became more homogeneous across the transect. Hedera helix seems to have benefited mainly from climate change (lack of severe winter frosts, CO2 increase), but also from the temporary exclusion of roe deer browsing. Based on the analysis of mean indicator values shade-tolerant, oceanic-distributed species, as well as nitrogen and moisture indicators have increased, while more light demanding species continuously decreased between survey years. Compared to intensively managed stands with massive thinning and/or soil disturbances, as in coppice-with-standards or large shelterwood systems, these species suffered from a closed canopy after management abandonment. The small-scale disturbances caused by drought and windthrow in the period 2012-2021 are obviously not sufficient to provide favourable conditions for these species, including a large number of species that have been classified as typical for European beech forests on limestone and that have been present in the beginning of the longterm study. Thus, the presented time series indicates that eutrophic beech forests without forest management are species poorer than previously reported. [ABSTRACT FROM AUTHOR]