Forest soil biodiversity is critical for maintaining forest health, ecosystem stability, nutrient cycling, and carbon sequestration. However, the intricate life in forest floors that drives these essential forest functions remains one of the least understood aspects of forest ecosystems. This study investigates the composition and drivers of soil biodiversity along an altitudinal gradient in beech to spruce-fir-beech forests of the Northern Limestone Alps in Austria. It examines how soil microbial communities are shaped by environmental gradients and forest structure. By linking soil biodiversity metrics to soil properties and forest biodiversity indicators, this research aims to identify the key drivers of mountain forest soil biodiversity and the interactions between above- and below-ground biodiversity. Thirty forest plots in and around the Gesäuse and Kalkalpen National Parks were surveyed for forest biodiversity indicators, including tree species, physical structure, deadwood, and tree related microhabitats. The topsoil and organic layers of these plots, all situated on limestone, were described and sampled for physicochemical, PLFA, and eDNA analysis targeting bacteria, fungi, and arthropods. Statistical analysis is ongoing; however, preliminary results indicate that microbial community structure correlates with soil pH, organic matter content, plot deadwood volumes, and altitude, among other factors. This research highlights the interconnectedness of soil and forest biodiversity and its role in maintaining ecosystem connectivity in Austrian mountain forests. By identifying the key drivers of soil biota diversity, this study contributes to forest conservation and restoration strategies, providing forest managers with tools to mitigate biodiversity loss. Future work should include forest soils from siliceous parent material to better understand soil biodiversity across more Austrian mountain forest types and integrate longterm monitoring to better understand the temporal dynamics of forest soil biodiversity under changing environmental conditions.
