Landscape context modulates the effect of local canopy cover on forest multidiversity across elevations

Abstract Declining forest biodiversity has increased focus on forest conservation and restoration. Many efforts to conserve and restore tree cover focus on the local scale, but their outcomes are frequently modulated by landscape context. While the diversity and composition of communities is strongly driven by local‐scale canopy cover, landscape‐scale habitat characteristics affect dispersal pathways and determine the species pool available for colonization of local patches. Moreover, local and landscape‐scale habitat attributes vary with elevation, but how their effects on biodiversity change with elevation remains poorly understood. We examined how local canopy cover affects forest biodiversity, and how these effects are modulated by the amount of total and disturbed forest available in the surrounding landscape along an elevational gradient. We used remote sensing and multi‐taxa biodiversity data covering plants, aculeata, moths, beetles and birds (a total of 2319 species) across 150 plots in naturally developing forests in a forest‐rich region in the northern European Alps. We calculated multidiversity across all species and for three habitat affinity guilds (forest, mixed, open‐habitat) to test for differences based on varying habitat associations. Local canopy cover negatively affected multidiversity, with the weakest effect observed for forest species. An increasing amount of forest in the surrounding landscape amplified this negative effect, while an increasing amount of disturbed forest reduced it. The negative effect of local canopy cover on multidiversity weakened with elevation and became neutral across all guilds close to the tree line. Our findings highlight that disturbances promote forest biodiversity via two fundamental pathways: reducing local canopy cover and creating a more open and diverse landscape context. Moreover, the effects of canopy cover on forest biodiversity are modulated by environmental conditions that change with elevation. Synthesis and applications . Conservation and restoration efforts should consider landscape context more explicitly when planning specific management measures. Our results suggest that canopy openings benefit biodiversity especially in landscapes with high forest cover and in low elevation areas, while conserving and re‐establishing tree cover is important in landscapes with low forest cover and close to the upper tree line.