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.

维持生态系统的结构与功能要素，是保护生物多样性、维系生态系统功能的核心前提。为指导生物保护工作，伞护种（umbrella species）概念应运而生。在瑞典，白背啄木鸟作为一种候选伞护种，已主导当地落叶林的保护与修复工作长达二十余年。
本研究评估了以白背啄木鸟为修复目标的森林修复工作，对蛀木甲虫（saproxylic beetles）生物多样性产生的十年尺度影响。我们将12至21年前完成修复的林分、未修复林分，以及作为修复参照标准的历史白背啄木鸟栖息地林分进行对比分析。结果显示，修复后林分的落叶枯木蓄积量高于未修复林分，但低于作为修复参照的目标林分。修复林分的枯木多集中于后期腐朽阶段，而目标参照林分的枯木则在各腐朽等级间分布更为均匀。相较于未修复林分，修复林分的多数蛀木甲虫类群拥有相近的物种丰富度与个体多度，但仍未达到目标参照林分的水平。三类林分的物种群落组成存在显著差异：修复林分以后期腐朽阶段关联物种与广食性物种为主，而目标参照林分则承载了更多与落叶林共生的受威胁物种。
5. 综合与应用：本研究结论表明，历经一至二十年的修复后，此类森林修复可改善林分结构并提升甲虫多样性，但尚未达到预设的修复目标水平，仅实现了部分修复成效。研究结果强调，若要达成成功的生态修复，需开展持续性、重复性的修复工作；同时，在评估修复成效时，明确关键生境特征的目标阈值至关重要。