A decadal study reveals that restoration guided by an umbrella species does not reach target levels

Maintaining structural and functional elements of ecosystems are essential in order to preserve biodiversity and ecosystem function. As a means of guiding conservation work, the umbrella species concept was developed. In Sweden, one putative umbrella species, the white-backed woodpecker, has guided conservation and restoration of deciduous forests for two decades. Here, we evaluate the decadal effects of restoration aimed at the white-backed woodpecker on biodiversity of saproxylic beetles. We compare stands that were restored twelve to twenty-one years ago to non-restored stands and historical white-backed woodpecker habitats acting as restoration target stands. Restored stands contained higher deciduous deadwood volumes than non-restored stands but lower volumes than restoration target stands. The deadwood in restored stands was concentrated in later decay stages whereas target stand deadwood was more evenly distributed across decay stages. Restored stands had similar species richness and abundance of most groups of saproxylic beetles compared with non-restored stands while not reaching the levels of restoration target stands. Species assemblages differed among all stand types with restored stands supporting late decay stage and generalist species while target stands supported more deciduous associated and threatened species. 5. Synthesis and applications: We conclude that after one to two decades, restoration improve stand structure and benefit beetle diversity but that target levels are not yet reached. Thus, only partial restoration is achieved. Our results stress that for restoration to be successful both continuous and repeated restoration efforts are needed and that it is important to identify target levels of important habitat characteristics when assessing restoration outcome.