Forest clear-cuts support diverse moth fauna but lack common grassland species

Forests ecosystems sustaining most of the terrestrial biodiversity are
under increasing anthropogenic pressure. Both the protection of the
remaining natural forests and the mitigation of the negative effects of
silviculture are of primary conservation concern. Clear-cut areas are the
main open habitats in production forests, potentially offering temporary
refuge for species from declining semi-natural grasslands. Although
several groups of flower-visiting insects, including butterflies, have
been reported to thrive in clear-cuts, a taxonomically comprehensive
understanding of the insect fauna utilising these habitats is lacking. In
this study, we examined the assemblages of nocturnal macromoths
(Lepidoptera: Marcoheterocera) in forest clear-cuts of varying age (2–6
years) and regeneration regimes (natural vs. artificial) in Northern
Europe. Using automatic sugar-bait traps, we sampled 50 clear-cuts and
three pairs of forest-grassland reference sites over two summers.
Nocturnal moths of the clear-cuts were highly diverse, harbouring 50% of
the regional species pool of noctuids. However, several common
grassland-associated species, as well as a few forest species, were nearly
absent. Although the similarity between clear-cut and forest assemblages
increased with clear-cut age, the recorded characteristics of the
clear-cuts had little overall influence on moth assemblages. Artificially
regenerated clear-cuts, characterised by a more open vegetation structure,
supported slightly higher moth species richness and diversity compared to
naturally regenerating sites. Policy implications: Our results highlight
the role of forest clear-cuts in supporting insect biodiversity. As such,
clear-cuts warrant special consideration as a distinct habitat type.
However, the effects of clear-cut regeneration and maintenance methods on
assemblages of moths appear weaker than in various other insect groups.
More importantly, the absence of several common grassland species
highlights that clear-cuts cannot fully replace traditional open habitats.
This underscores the importance of conserving semi-natural grasslands.

维持绝大多数陆地生物多样性的森林生态系统（forest ecosystems）正面临日益加剧的人为活动压力。保护现存天然林与缓解营林（silviculture）活动带来的负面影响，均是生物多样性保护的核心关切。皆伐迹地（clear-cut areas）是用材林主要的开阔生境，可为逐渐衰退的半自然草原（semi-natural grasslands）中的物种提供临时庇护所。尽管已有研究表明，包括蝴蝶在内的多个访花昆虫（flower-visiting insects）类群在皆伐迹地中长势良好，但目前学界对利用此类生境的昆虫区系仍缺乏分类学层面的全面认知。本研究以北欧不同林龄（2~6年）、不同更新方式（regeneration regimes）的森林皆伐迹地为研究对象，聚焦夜行性大蛾类（鳞翅目：大蛾亚目，Lepidoptera: Macroheterocera）的类群组成。研究依托两年夏季的野外调查，利用自动糖诱陷阱（automatic sugar-bait traps）对50处皆伐迹地与3对林草对照样地进行了采样。皆伐迹地的夜行性蛾类类群多样性极高，涵盖了该区域夜蛾科（noctuids）物种库的50%。但多种常见的草原伴生物种，以及少量森林物种，在此类生境中几乎绝迹。尽管皆伐迹地与原生林的蛾类类群相似性随迹地林龄增长而提升，但整体而言，皆伐迹地的自身特征对蛾类类群组成的影响较小。与天然更新迹地相比，以更为开阔的植被结构为特征的人工更新迹地，其蛾类物种丰富度与多样性略高。政策启示：本研究结果凸显了森林皆伐迹地在支撑昆虫生物多样性方面的重要作用。因此，皆伐迹地作为一类独特的生境类型，值得被纳入专项保护考量范畴。不过，相较于其他多种昆虫类群，皆伐迹地的更新与管护方式对蛾类类群的影响相对较弱。更关键的是，多种常见草原物种的缺失表明，皆伐迹地无法完全替代传统的开阔生境。这进一步强调了保护半自然草原的必要性。