The effect of stand structure and landscape fragmentation on saproxylic polypores and epiphytic lichens in boreal Sweden

Habitat fragmentation, driven by forestry and land-use changes, threatens biodiversity in boreal Sweden. While most forests in this region are heavily managed, historical forestry intensity varies geographically, with more intact old-growth forests remaining in mountain regions. Saproxylic polypores and epiphytic lichens, reliant on deadwood and old trees, are particularly sensitive to these changes. We surveyed 26 woodland key habitats in boreal Sweden, analysing total and red-listed species of wood fungi and epiphytic lichens, including functional traits relevant to fragmentation sensitivity. Landscape structure was assessed at three spatial scales (0.5, 5, 15 km), capturing habitat amount, quality, and geographic gradients reflecting historical forestry. Local environmental conditions were also evaluated. Local-scale factors were the strongest drivers of species richness: deadwood volume was critical for fungi, while tree age and stand size were key drivers for lichens. Landscape level effects were less pronounced. Total polypore richness and several of the fungal functional groups responded to landscape structure at either immediate (0–5 km) or broader (5–15 km) scales, while lichen richness was not affected by the measured landscape parameters. Both polypore and lichen communities reflected influence from past forestry and current stand structure. These findings underscore that expanding forest area alone is insufficient unless structural complexity and deadwood availability improves. Conservation efforts should prioritize preserving and restoring mature forest patches to sustain fungal and lichen diversity in managed boreal landscapes. • 26 woodland key habitats were surveyed for lichens and polypores. • Polypores, but not lichens, responded strongly to landscape fragmentation. • Polypore functional groups differed in their responses to fragmentation. • Lichen richness was driven by stand age and stand size.