PS 30-160 - CANCELLED - Shedding light on natural disturbances as long-term drivers of European temperate primary forest communities: A multi-taxonomic analysis

Abstract: Primary forests are important biodiversity refuges and reference areas for understanding ecosystem functioning. Historical land-use change in Europe resulted in the near elimination of such forests, whilst insufficient protective legislation facilitates their ongoing loss. Therefore, there is an urgent need to quantify the natural processes and ecological value of Europe’s last primary forests, and their potential resilience to natural disturbance intensification. Using a dendrochronological approach, this research aims to: (i) characterize multi-taxonomic communities of Slovakian primary spruce-dominated forests, and; (ii) understand how historical natural disturbances help shape these present-day communities. Forest structural, wood-inhabiting macrofungi, saproxylic beetle, epixylic lichen, vascular plant and bird inventories were conducted across ten of Europe’s best-preserved temperate primary forest stands following standardised protocol. Increment cores were extracted from 1450 trees to reconstruct 250 years of disturbance history and their characteristics.

High species richness - including numerous red-listed and old-growth specialists - was recorded across all surveyed groups. Disturbance frequency, severity, timing and their interactions significantly shaped contemporary forest structure which drove distinct community responses. Fungal species richness significantly declined with increased disturbance severity and canopy openness, and increased with deadwood volume, whilst red-listed species increased with disturbance frequency. Disturbances benefitted early-successional bird species, whilst species richness, abundance and Shannon diversity was unaffected. Saproxylic beetle abundance and functional diversity increased after recent disturbances, whilst phylogenetic diversity increased with canopy openness. Lichen richness declined with disturbance severity and increased with time since disturbance, and red-listed richness significantly increased with standing dead tree presence. Severe disturbances occurring approximately 150 years ago homogenised vascular plant communities, whilst lower disturbance severity and extent promoted diversity.

The results highlight the complex processes driving community assemblage; whilst lichen and vascular plants generally required recent but low-severity disturbances for optimal habitat availability, saproxylic beetles and early-successional birds benefited more from recent high-severity events through their dependence on deadwood quantity and quality and canopy openness. Fungi required sufficiently frequent disturbances for deadwood provisioning however, at low severities, likely to maintain closed-canopy microclimates. The study highlights the importance of various diversity metrics, as different community components (e.g. red-listed species, functional groups) can require distinct structural parameters. Therefore, the results indicate the importance of landscape-level configuration for diverse community maintenance; large areas are likely required to allow a full range of disturbance types to maintain structural heterogeneity. These initial results thus provide novel insight into these vulnerable ecosystems, applicable to their conservation and ecological management strategies.