Land ownership drives stand structure and carbon storage of deciduous temperate forests

• We sampled clusters of beech dominated forest stands of different land ownership.
• Forest ownership drives stand structure; biogeography determines tree diversity.
• Carbon storage is higher in small-scale private forests than in public forests.
• Small-scale private forests comprise higher habitat diversity and dead wood amounts.
• Consideration of ownership is central for forest conservation on a landscape-scale.

In European cultural landscapes, forest area is subdivided into a mosaic of stands of different ownership types and sizes. Differences in ownership and different goals of the owners have a potentially decisive influence on the provision of forest ecosystem services and the implementation of instruments for the conservation of biodiversity. This study hypothesizes that forest ownership is an indirect determinant of forest management approaches and is thereby relevant for biodiversity conservation and carbon sequestration. We compared structure and species composition of forest stands in clusters of different ownership types, namely state-owned, municipal and small-scale private forests, in southwestern Germany. Although close-to-nature management has been practiced in public forests for some time, our study demonstrates that tree species diversity does not vary significantly between ownership types but is correlated with biogeographical factors. However, small-scale private forests comprise significantly higher levels of structural diversity, more dead wood and greater carbon storage capacity than both categories of public forests. This is contrary to other studies, where publicly owned lands were found to host higher biodiversity, and differs from the global trend, where continued fragmentation of private lands threatens forest sustainability. The importance of small-scale private forests, e.g. for the conservation of old-growth and dead wood dependent species, seems due to less intensive and more diverse forest management. The role of such forests for biodiversity conservation and carbon regulation may be jeopardized through forest conversion and wood mobilization initiatives accompanying rising natural resource prices. To safeguard forest biodiversity and ecosystem services, ownership-specific incentive schemes should be coordinated and refined. In public forests, close-to-nature management approaches should be complemented with binding goals aimed at promoting old-growth forest attributes and allowing site-specific variation in management practices. To conserve diversity in small-scale private forests, financial incentives and remuneration schemes for the provisioning of forest biodiversity and ecosystem services should be developed. Moreover, consulting and the provision of information on sustainable forest and conservation management should be intensified.