Data and Code for: Admixed tree species in beech forests increase landscape-scale biodiversity but not fully preserve natural communities.

This repository contains data and code for the following publication in Ecological Applications: Heinrichs S., Leidinger J., Weisser W.W., Schall P. (2026) Admixed tree species in beech forests increase landscape-scale biodiversity but not fully preserve natural communities. Abstract: A diversification of tree species composition in managed forests is seen as beneficial for forest productivity, stability, and biodiversity. In Central Europe, mixed forests of European beech, the naturally predominant tree species, with other tree species are currently promoted to increase forest stability e.g. against the effects of climate change. However, the impact of such tree species mixtures on biodiversity can vary between taxonomic and functional groups, and with the identity of the admixed tree species. They can also cause distinct shifts in species composition. By combining 41 mature forest stands of a forest region in south Germany, comprising pure beech, beech/oak, beech/spruce and beech/pine stands, we investigated the effect of distinct combinations of these forest types on alpha, beta and gamma diversity of 12 species groups including vertebrates, arthropods, fungi and plants at the landscape level. We wanted to identify landscapes able to integrate multidiversity and the diversity of beech-associated species.The highest gamma multidiversity was reached in landscapes exclusively composed of the three mixed forest types, while landscapes of pure beech stands were least diverse, contrasting results at the alpha diversity level. The response of the different species groups depended on the admixed tree species. Thus, biodiversity benefits from additional tree species at the landscape scale. A marked decline in multidiversity occurred when the share of pure beech stands in a landscape exceeded 60%. The diversity of rare species followed the same pattern. Pure beech stands were, however, needed to conserve beech-associated species that were most sensitive to admixtures with other tree species.Our results emphasize the need to consider the landscape scale in conservation and show that focusing on maximizing overall diversity and rare species alone may not preserve the natural species composition of beech forests to the same degree. They also call for the establishment of clear conservation goals based on what biodiversity is targeted. Analyses including both gamma diversity as an important landscape-level biodiversity indicator and community composition can provide the basis for conservation-oriented landscape planning in the future.Zip-File Contents: EA_code: Provides R codes for reproducing figures and tables as well as calculating diversity of sampled landscapesEA_figs_and_tabs: Provides figures and tablesEA_output: Provides R code outputsEA_rawdata: Provides raw data