Effects of multiple rotations of uneven-age forest management on mammal, insect, and fungus biodiversity in central Ontario

在20世纪70年代之前的几十年里，安大略省中南部的森林开发导致森林组成向落叶、耐阴物种的强烈转变。现代森林管理做法虽然旨在实现可持续发展，但也可能长期改变这些森林，对生物多样性产生重要影响。几项长期研究表明，该地区主要的森林经营活动——单树选择正在对森林组成和结构产生长期影响。重要的是，尽管维持了树木直径分布，让人想起未经管理的林分，但在采伐期间产生的均匀分布的小间隙导致了组成转变，有利于不耐阴的物种，失去了中等耐阴的物种和针叶林物种。此外，对林分改善和木材价值的重视意味着大树、患病和死亡的树木、倒下的原木和站立的死树的数量减少。不幸的是，尚未进行对生物多样性影响的多轮研究。对第一次轮作影响的研究表明，一些成熟的森林类群即使在轮作结束时仍处于低丰度，在多次轮作后种群可能会进一步减少。此外，结构变化预计只有在几次轮换之后才能达到平衡，这对关键的动物群具有重要影响。我的总体目标是测试安大略省中南部的单树选择是否能在多次轮作中维持生物多样性。具体目标是：1)比较已采伐1-2次、3-4次或未管理的林分的生境结构和关键指标分类群（小型哺乳动物、昆虫和真菌）的丰度；2)通过检查邻近林分组成和结构对响应的影响，包括林分间视角。小型哺乳动物研究将利用活体诱捕；昆虫研究将集中在飞行拦截和陷阱的群落上；真菌采样将包括子实体的区域搜索和羽绒木材的dna采样；景观水平评估将利用森林资源清查信息和遥感ADS40和激光雷达图像。早期演替物种在收获后的年轻林分中最为常见和多样，而晚几个、木质碎屑和针叶树相关物种的丰度将随着轮作次数而下降，特别是在附近针叶树覆盖和未管理林分稀少和孤立的情况下。昆虫和真菌群落之间的功能转变预计将导致腐殖酸和弱分散物种多样性的减少。这将是第一个研究在多次轮作后单一树种选择对生物多样性影响的研究。

In the decades prior to the 1970s, forest exploitation in south-central Ontario resulted in strong shifts in forest composition towards deciduous, shade-tolerant species. Although intended to be sustainable, modern forest management practices also may be altering these forests over the long term, with important implications for biodiversity. Several long-term studies indicate that single tree selection, the predominant forest management activity in the region, is having long-term effects on forest composition and structure. Importantly, despite the maintenance of tree diameter distributions reminiscent of unmanaged stands, the evenly distributed, small gaps created during harvesting have led to a compositional shift favouring shade-intolerant species, with a loss of mid-tolerant species and coniferous species. In addition, the emphasis on stand improvement and timber values has meant reductions in the abundances of large trees, diseased and dying trees, downed logs, and standing dead trees. Unfortunately, multi-rotation studies of effects on biodiversity have not been undertaken. Studies of first-rotation impacts indicate that some mature forest taxa remain at low abundances even at the end of the rotation, with the possibility that populations will be further reduced after multiple rotations. In addition, structural changes are expected to equilibrate only after several rotations, with important implications for key faunal groups. My overall objective is to test whether single-tree selection in south-central Ontario sustains biodiversity over multiple rotations. Specific objectives are to: 1) compare habitat structure and abundances of key indicator taxa (small mammals, insects, and fungi) among forest stands that have been harvested 1-2 times, 3-4 times, or are unmanaged and 2) include an among-stand perspective by examining the effects of neighbouring stand composition and structure on responses. Small mammal research will make use of live trapping; insect research will focus on communities from flight interception and pitfall traps; fungal sampling will include both area searches of fruiting bodies and DNA-based sampling of downed wood; and landscape level assessments will make use of forest resource inventory information and remotely-sensed ADS40 and LiDAR imagery. Early-successional species are expected to be most common and diverse in young post-harvest stands, whereas abundances of late seral, woody debris, and conifer associated species will decline with the number of rotations, especially where nearby conifer cover and unmanaged stands are rare and isolated. Functional shifts among insect and fungal communities are expected to result in reductions in the diversity of saproxylic and weakly-dispersing species. This will be the first study to examine biodiversity implications of single tree selection after multiple rotations.