Our objective was to assess the potential of carabid beetles (Coleoptera: Carabidae) as effective bioindicators of the effects of forest management at a Canadian national scale. We present a comparison of carabid beetle assemblages reported from large-scale studies across Canada. Based on the initial response following disturbance treatment, we found that carabid assemblages consistently responded to disturbance, but responses of individual species and changes in species composition were nested within the context of regional geography and finer scale differences among forest ecosystems. We also explored the relationship between rare and dominant taxa and species characteristics as they relate to dispersal capacity and use of within-stand habitat features such as coarse woody debris. We found no relationship between life-history characteristics (such as body size, wing morphology, or reported associations with downed wood) and the relative abundance or frequency of occurrence of species. Our results suggest that carabids are better suited to finer scale evaluations of the effects of forest management than to regional or national monitoring programs. We also discuss several knowledge gaps that currently limit the full potential of using carabids as bioindicators.

Rove beetles are useful subjects for Nearctic forest biodiversity work because they are abundant, diverse, and easily collected, and have strong habitat affinities. Excellent identification keys exist for most groups, although there is a dearth of ecological and life-history information. There is considerable variation in species composition and abundance within the active summer season and in abundance from year to year. Community composition varies among larger geographical regions and to a lesser extent among forest types in more localized areas. Within the Nearctic boreal forest there are significant differences between beetle communities from the eastern and western portions. For the most part, the same species tend to dominate rove beetle communities in the western boreal forest. At the landscape level there are differences in rove beetle communities along successional gradients. In the boreal forest the communities of younger aspen-dominated and older conifer-dominated stands are somewhat distinct, with intermediate-aged stands containing a mix of the two communities. At the ecosite and microsite level there is significant variation, which remains poorly understood. Fire is the dominant mode of disturbance in the Nearctic boreal forest. It has a profound effect on rove beetles by destroying the forest communities and resetting the successional trajectory to the earliest stages. The burn pattern results in a patchwork of different communities at various stages in the successional cycle. In contrast to fire, forest harvesting does not directly destroy the rove beetle community, but to a large extent it destroys the forest habitat. This results in a unique rove beetle community characterized by a mix of forest species and open-ground specialists, and overall high diversity in this period of flux. In the years after harvesting, the rove beetle community goes through successional changes and becomes more similar to the forest community, but it skips the early postfire stage and proceeds along the successional trajectory more rapidly than after fire. In at least one forest type in western Canada, the post-fire and post-harvest communities, though similar, have not converged after 29 years. Other less direct effects of harvesting on rove beetles are a decrease in the proportion of the land base suitable for communities associated with older successional stages; alteration of forests by post-harvest site preparations and planting of exotic tree species; edge and fragmentation effects that are detrimental to the remaining forest surrounding harvested areas; and an influx of exotic arthropod species with affinities for disturbed sites. More information is needed on the habitat affinities of individual species. It is recommended that future work explore the effects of post-harvest forestry activities, fragmentation, and edges on rove beetles in forested habitats. As well, such studies should consider the effects on beetles of riparian zones and wetlands.

Two large-scale forestry experiments, in Quebec (Sylviculture et aménagement forestiers écosystémique (SAFE)) and Alberta (Ecosystem Management by Emulating Natural Disturbance (EMEND)), were established in the late 1990s to test the effects of alternative silvicultural strategies (e.g., partial cutting) on biodiversity in northern boreal forests. We collected spiders in pitfall traps 2 years after the application of partial-cutting treatments in deciduous stands at EMEND and 6 years after similar treatments in deciduous stands at SAFE. Although we are aware of the challenges imposed by disparate locations and whole-scale experimental methods, our objective was to compare the effects of partial cutting on spider assemblages (diversity and community composition), and in doing so, to formulate a few general statements. Overall, 98 species (6107 individuals) were collected from Alberta and 86 species (3414 individuals) from Quebec. Of these, 44 species were common to both regions. Ordination and indicator-species analyses revealed a distinct effect of geographic separation: the spider assemblages in deciduous stands within the boreal plains ecoregion of Alberta and the boreal shield in Quebec were distinct. However, the effects of partial cutting on spider assemblages within each project were similar: removal of 25%–33% of trees shifted a characteristic old-growth fauna toward one more typical of clearcuts. Indicator-species analysis also revealed the dominance of wolf spider (Lycosidae) species in clearcuts within both experiments and we present evidence that clear-cutting homogenizes spider assemblages. Old-growth forests contain spider faunas that are easily disrupted by moderate partial cutting. In the face of intense harvesting practices, managing for the maintenance of biodiversity and conservation of spider faunas in northern forests will require retention of old-growth forests.

Saproxylic insect assemblages inhabiting dead wood in Canadian forests are highly diverse and variable but quite poorly understood. Adequate assessment of these assemblages poses significant challenges with respect to sampling, taxonomy, and analysis. Their assessment is nonetheless critical to attaining the broad goals of sustainable forest management because such species are disproportionately threatened elsewhere by the reductions in dead wood generally associated with commercial exploitation of northern forests. The composition of the saproxylic fauna is influenced by many factors, including tree species, degree of decay, stand age, and cause of tree death. Wildfire and forest harvesting have differential impacts on saproxylic insect assemblages and on their recovery in postdisturbance stands. Exploration of saproxylic insect responses to variable retention harvesting and experimental burns is contributing to the development of prescriptions for conserving saproxylic insects in boreal forests. Understanding of processes that determine diversity patterns and responses of saproxylic insects would benefit from increased attention to natural history. Such work should aim to provide a habitat-classification system for dead wood to better identify habitats (and associated species) at risk as a result of forest management. This tool could also be used to improve strategies to better maintain saproxylic organisms and their central nutrient-cycling functions in managed forests.

We review the existing literature on patterns of moth (Lepidoptera) species richness and community composition in northeastern Nearctic forest ecosystems across hierarchical scales ranging from individual trees to entire managed ecoregions. Moths are species-rich in northeastern forests of North America, with the most diverse families being Noctuidae and Geometridae. Individual trees and forest stands, however, are often dominated by few species. Climate, stand age, disturbance regime, and landscape heterogeneity are significant predictors of abundance of dominant species. Most other moth species in the regional pool are patchily distributed and appear to occur regularly at very low abundance. Moth communities respond predictably to forest-management practices, and the outcomes of postmanagement response are largely driven by changes in the plant community. Significant reductions in moth species richness and changes in community composition are correlated with clear-cut harvesting, whereas selective logging appears to cause more moderate changes in moth community structure. Broad-scale effects of forest fragmentation on moth communities in unglaciated regions are best described by species replacement rather than species loss; moth species richness decreases slightly across a gradient of fragment sizes, but shifts in moth community composition are more important, especially in the relative importance of herbaceous-plant-feeding species in large and small fragments. Species that appear to be most sensitive to timber management or habitat loss are dietary specialists as larvae, dispersal-limited as adults, or dependent on commercially valuable tree species such as oaks, Quercus L. (Fagaceae). Restored forest stands tend to converge in terms of lepidopteran species dominance and diversity among stands, suggesting that the long-term consequences of timber management or habitat loss include a significant reduction of regional β-diversity. Finally, future research on forest Lepidoptera should include an emphasis on understanding the role of urban woodland habitat in retaining viable and diverse moth communities and how the spatial pattern of timber harvest affects the relative magnitude of α- and β-diversity components within a given ecoregion.

Aquatic arthropods can be affected by forest management through increased amounts of light, discharge, and sediment runoff, alteration of the supply of basal resources, changes in the supply of large wood, temperature modifications, and food-web effects. This syndrome of alterations varies geographically in magnitude, and the specific details depend on initial biotic and abiotic conditions, local topography, climate, and the particular management practices used. Impacts on standing water appear to be subtle, and most attention has focussed on streams, where changes are often more obvious. The intensity of any changes in processes affecting aquatic arthropods depends, in part, on the proximity of logging to the shoreline and the proportion of watershed harvested, and also on the condition and frequency of forest access roads crossing or near water bodies. Some groups of species are particularly vulnerable, but others, particularly generalist species such as some Baetis Leach (Ephemeroptera: Baetidae) and some Chironomidae (Diptera), appear to benefit from harvesting. In general, outcomes of harvesting near streams are temporary increases in production and abundance but reductions in diversity. Impacts on all trophic levels, especially in streams, can occur from forest harvesting. The primary tool for mitigating these impacts is the use of riparian buffers, but there are still major uncertainties about the effectiveness of specific widths and configurations of buffers and their use for additional types of disturbance.

The Canadian insect fauna is too inadequately understood to support well-informed assessments about its conservation status; however, the foregoing collection of synthetic papers illustrates potential threats from industrial forestry. Loss of forest species and dramatic changes in forest insect assemblages driven by forestry activities are well illustrated by studies from places where industrial forest management has been more intensive or of longer duration. Improved understanding of how arthropod species are coupled to habitats, especially microhabitats, appears to be central to progress toward their conservation. Studies of arthropods conducted at the species level are most relevant for applied conservation purposes, because only species-level work that is well documented with voucher specimens provides adequate comparative data to document faunal change. Although taxonomic infrastructure required to support such work is seriously under-resourced in Canada, entomologists can help themselves by producing useful modern resources for species identification, by undertaking collaborative biodiversity work that minimizes the split between taxonomists and ecologists, and by supporting incentives for work at the species level. Securing the future of arthropod diversity in Canadian forests through effective policy will require sound regionally defined bases for whole-fauna conservation that mesh with broader land-use planning. Building these will require a practical understanding of how “ecosite”-classification systems relate to arthropod diversity, accurate inventories of the predisturbance forest fauna in all regions, and development of sound monitoring plans designed to both detect faunal change efficiently and identify its drivers. Such monitoring plans should include both baseline inventories and monitoring of designated control areas. In addition, effective biomonitoring efforts will facilitate the development of suites of arthropod indicators, accommodate both seasonal (especially phenological) and annual variation, clarify the relationship between cost-effective samples and reality, and ensure adequate consideration of “rare” species. Return on investment in monitoring will depend on effective preplanned linkage to policy development that can respond to drivers of faunal change in a way that effectively addresses undesired changes.