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

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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.