Metabarcoding reveals landscape drivers of beetle community composition approximately 50 years after timber harvesting

Landscape conservation planning in managed forests requires information on the relative importance of different aspects of mature forests. Regeneration forest sites with greater access to source populations for re-establishment of biodiversity are expected to have greater similarity in species composition to unharvested mature areas, i.e., when sites are in close proximity to mature forest (forest influence), and/or have a high percentage of mature forest in the surrounding landscape (landscape context). We investigated how recovery of ground-active beetle biodiversity in the mid-late successional stage (40-58 years) of previously harvested regeneration forests is affected by forest influence, landscape context, and other characteristics of the surrounding landscape. We used DNA metabarcoding to characterise beetle communities in 12 mature forest sites and 64 regeneration forest sites. Generalized dissimilarity modelling (GDM), constrained redundancy analysis, and ordinations evaluated the contribution of predictors (i.e., bioclimate, landscape configuration, regeneration age, spatial position and topography) to beetle composition. Beetle composition was significantly different between different forest ages and landscape context classes. GDM of all predictors explained 34.1% of total variance in beetle community turnover. While the geographic locations of sites accounted for most (75.1%) of composite ecological gradients, the beetle community is subtly influenced by the effects of landscape context (1.8%), forest influence (1.2%) and other variables relating to landscape configuration (collectively 5.2%). Long-term conservation of local biodiversity in managed forests requires maintaining a certain amount of mature forest, but their importance as beetle source populations declines as the regeneration forests mature.