Data from: A cross-continental comparison of plant and beetle responses to retention of forest patches during timber harvest

Timber harvest can adversely affect forest biota. Recent research and application suggest that retention of mature forest elements (‘retention forestry’), including unharvested patches (or ‘aggregates’) within larger harvested units, can benefit biodiversity compared to clearcutting. However, it is unclear whether these benefits can be generalized among the diverse taxa and biomes in which retention forestry is practiced. Lack of comparability in methods for sampling and analysing responses to timber harvest and edge creation presents a challenge to synthesis. We used a consistent methodology (similarly spaced plots or traps along transects) to investigate responses of vascular plants and ground-active beetles to aggregated retention at replicate sites in each of four temperate and boreal forest types on three continents: Douglas-fir forests in Washington, USA; aspen forests in Minnesota, USA; spruce forests in Sweden; and wet eucalypt forests in Tasmania, Australia. We assessed (i) differences in local (plot-scale) species richness and composition between mature (intact) and regenerating (previously harvested) forest; (ii) the lifeboating function of aggregates (capacity to retain species of unharvested forest); and whether intact forests and aggregates (iii) are susceptible to edge effects and (iv) influence the adjacent regenerating forest. Intact and harvested forests differed in composition but not richness of plants and beetles. The magnitude of this difference was generally similar among regions, but there was considerable heterogeneity of composition within and among replicate sites. Aggregates within harvest units were effective at lifeboating for both plant and beetle communities. Edge effects were uncommon even within the aggregates. In contrast, effects of forest influence on adjacent harvested areas were common and as strong for aggregates as for larger blocks of intact forest. Our results provide strong support for the widespread application of aggregated retention in boreal and temperate forests. The consistency of pattern in four very different regions of the world suggests that, for forest plants and beetles, responses to aggregated retention are likely to apply more widely. Our results suggest that through strategic placement of aggregates, it is possible to maintain the natural heterogeneity and biodiversity of mature forests managed for multiple objectives.

木材采伐会对森林生物群落造成不利影响。近期研究与实践表明，与皆伐（clearcutting）相比，保留成熟森林要素的保留式营林（retention forestry）——包括在大型采伐单元内保留未采伐斑块（或称‘聚集团块（aggregates）’）——可提升生物多样性（biodiversity）。然而，目前尚不清楚这些益处能否推广至实施保留式营林的各类类群（taxa）与生物群区（biomes）中。林木采伐与边缘效应（edge effects）响应的采样及分析方法缺乏可比性，这给研究综合带来了挑战。

本研究采用统一的方法学方案（沿样带（transects）设置等间距样方或诱捕器），对三大洲四类温带与寒温带森林类型的重复样地中，维管植物（vascular plants）与地表活动甲虫（ground-active beetles）对聚集式保留采伐（aggregated retention）的响应展开调查：分别为美国华盛顿州的花旗松林、美国明尼苏达州的美洲山杨林、瑞典的云杉林，以及澳大利亚塔斯马尼亚州的湿润桉树林。我们评估了四项内容：(i) 成熟（未受干扰）林与更新（曾经采伐）林在局域（样方尺度）的物种丰富度与组成差异；(ii) 聚集团块的物种留存功能（即保留未采伐森林物种的能力）；以及未受干扰森林与聚集团块是否(iii) 易受边缘效应影响，以及(iv) 对邻近更新林产生影响。

未受干扰林与采伐林在物种组成上存在差异，但维管植物与甲虫的物种丰富度并无显著不同。这种组成差异的幅度在各区域间总体相似，但重复样地内部及样地之间的物种组成存在显著异质性。采伐单元内的聚集团块可有效实现植物与甲虫群落的物种留存。即便在聚集团块内部，边缘效应也较为罕见。与之相反，未受干扰森林对邻近采伐区域的影响效应十分普遍，且其强度在聚集团块与大型未受干扰林块中并无显著差异。

本研究结果为聚集式保留采伐在寒温带与温带森林中的广泛应用提供了有力支撑。全球四个差异显著的区域所呈现的模式一致性表明，针对森林植物与甲虫而言，对聚集式保留采伐的响应或可推广至更广泛的场景。本研究结果显示，通过对聚集团块进行战略性布局，可在多目标经营的成熟森林中维持其自然异质性与生物多样性。