Data from: Forest restoration as a double-edged sword: the conflict between biodiversity conservation and pest control

1. Forestry has markedly changed a large proportion of the world’s boreal forests, often with negative effects on biodiversity. As a result, forest restoration is increasingly implemented to counteract the negative effects. However, restoration measures aimed at mimicking natural disturbance regimes could simultaneously increase the risk of unwanted negative effects, such as damage by forest pest species. This study compares the effect of two restoration methods (prescribed burning and gap-cutting), on both biodiversity conservation and pest control, to provide a basis for solutions to this potential conflict. 2. Bark beetles are ideal for studying this conflict, as this group is both species-rich and contains notorious pest species. We conducted a unique, large-scale field experiment in which we compared the effect of two different restoration methods on the abundance, species richness and assemblage composition of bark beetles. In addition, we estimated uncontrolled tree mortality by the number of trees that died post-restoration. 3. Beetles were divided in two groups, primary and secondary, the former with an ability to kill growing trees. Bark beetle diversity did not differ between treatment groups prior to restoration. However, after restoration, assemblage composition and primary bark beetle abundance differed between the treatments. Furthermore, species richness was higher in burned and gap-cut stands compared to reference stands. 4. The number of trees that died post-restoration was highest on burned sites, whereas no difference was found between gap-cut and reference stands. The number of dead trees was correlated with the number of primary beetles. 5. Synthesis and applications. We demonstrate the potential for a conflict between forest restoration for biodiversity conservation and the potential risk for tree mortality caused by forest pests. This is likely to become a problem in many boreal forests; however, our results suggest that this conflict can be moderated by the choice of restoration method. The restoration method gap-cutting had a similar positive impact on bark beetle species richness as compared to the burning method, but did not as burning increase tree mortality. Thus, in areas where there is an apparent risk for pest outbreaks, our data suggest that gap-cutting should be the chosen method to avoid an unwanted increase in tree mortality at the stand level. 13-Mar-2017

1. 林业活动已显著改变了全球范围内大面积的寒温带针叶林（boreal forests），且常对生物多样性造成负面影响。为此，森林恢复（forest restoration）举措的应用愈发广泛，以抵消这些不利影响。然而，旨在模拟自然干扰格局的恢复措施，却可能同时增加额外的负面风险，例如森林有害生物引发的危害。本研究对比了两种恢复方法——计划火烧（prescribed burning）与林隙采伐（gap-cutting）——对生物多样性保护与害虫防控的影响，旨在为解决这一潜在冲突提供理论依据。
2. 小蠹虫（bark beetles）是研究该冲突的理想类群：其一，该类群物种丰富度极高；其二，其中包含诸多臭名昭著的林业害虫。本研究开展了一项独特的大规模野外试验，对比两种恢复措施对小蠹虫种群数量、物种丰富度及群落组成的影响；此外，通过恢复后死亡的树木数量，评估了非人为调控的树木死亡率。
3. 研究将小蠹虫划分为初生型与次生型两类：前者具备侵染健康活立木并致死的能力。恢复试验前，各处理组间的小蠹虫多样性并无显著差异；但在恢复措施实施后，不同处理组的小蠹虫群落组成与初生型小蠹虫种群数量均出现显著分化。此外，实施计划火烧与林隙采伐的样地，其小蠹虫物种丰富度均显著高于对照样地（reference stands）。
4. 恢复后，计划火烧样地的死亡树木数量最多；而林隙采伐样地与对照样地的死亡树木数量并无显著差异。死亡树木数量与初生型小蠹虫的种群数量呈显著正相关。
5. 综合与应用：本研究证实，以生物多样性保护为目标的森林恢复，与森林有害生物引发的树木死亡风险之间，确实存在潜在冲突。这一问题在全球诸多寒温带针叶林区均可能出现；但研究结果表明，通过选择合适的恢复措施，该冲突可得到缓解。相较于计划火烧，林隙采伐对小蠹虫物种丰富度的正向提升效果相当，但不会像计划火烧那样显著增加树木死亡率。因此，在存在明显害虫暴发风险的区域，本研究数据建议采用林隙采伐作为恢复方法，以避免样地尺度上出现非预期的树木死亡率上升。2017年3月13日