Effects of climate and forest development on habitat specialization and biodiversity in Central European mountain forests

Mountain forests are biodiversity hotspots with competing hypotheses proposed to explain elevational trends in species richness. The altitudinal-niche-breadth-hypothesis suggests decreasing specialization with elevation, which could lead to decreasing species richness and weaker differences in species richness and beta diversity among habitat types with increasing elevation. Testing these predictions for bacteria, fungi, plants, arthropods, and vertebrates, we found decreasing habitat specialization (represented by forest developmental stages) with elevation in mountain forests of the Northern Alps – supporting the altitudinal-niche-breadth-hypothesis. Species richness decreased with elevation only for arthropods, whereas changes in beta diversity varied among taxa. Along the forest developmental gradient, species richness mainly followed a U-shaped pattern which remained stable along elevation. This highlights the importance of early and late developmental stages for biodiversity and i..., We collected data from 14 taxonomic groups across 150 plots at Berchtesgaden National Park. For the selection of the study plots, we differentiated five forest development stages (gap, establishment, optimum, plenter, terminal) replicated ten times each across three elevation zones (submontane, montane, subalpine), ranging between 605 and 1725 m asl. Field sampling was conducted in 2021 and 2022. Bacterial and fungal communities in the soil were identified through metabarcoding of four soil samples from each plot, consisting of mineral and organic soil samples taken at approximately 3 m distance from the plot centre in each of the four cardinal directions. Percent cover of plants by species was recorded on a 200 m2 quadratic area, distinguishing the herb (<1 m height) and shrub layer (>1-5 m height). Arthropods from pitfall and light traps were identified by taxonomists, while those from Malaise traps were analysed by metabarcoding. Due to the different underlying species concepts..., , # Effects of climate and forest development on habitat specialization and biodiversity in Central European mountain forests

The repository contains 26 data and 5 software files (4 R scripts and 1 renv.lock file). The analysis and thus the R scripts are divided into the 3 steps: *data preparation and metric calculation* with an additional script for *simulating communities for null models*, *model fitting and checking*, and *model predictions and preparation of figures and tables*. Data files contain biodiversity data of 14 species groups (during data preparation pooled into 6 taxa), data characterizing the study plots (elevation, forest development stage), LiDAR data used to quantify canopy cover, temperature data describing microclimatic conditions, and additional files needed for data processing (plant trait data) or supplementary material.

The data was collected at 150 plots along gradients of forest development (5 stages: gap, establishment, optimum, plenter, terminal) and elevati...