Besides natural tree regeneration itself, the development of the forest understory community is highly indicative of the ecological recovery of forest stands postharvesting, and therefore of the sustainability of forest management. High mountain forests might show particularly slow recovery of the understory plant community because of harsh environmental conditions. We compared understory community richness and composition among three age classes of forest stands in the subalpine Engelmann Spruce-Subalpine Fir zone in the interior of British Columbia, Canada. Species composition was found to diVer signiWcantly between mature stands (>110 years old and never harvested) and both recent clearcuts (5-8 years old) and the oldest clearcuts present in the study area (second growth: 24-28 years old). A non-metric multidimensional scaling (NMDS) ordination revealed no unidirectional return of species composition in harvested stands towards that of mature forest; indeed, plots in recent clearcuts and second growth stands were similar to one another and clearly separated from the mature stands. Indicator Species Analysis revealed that moss species were particularly indicative of mature forest, with four moss species being common in mature stands but absent from both younger stages. Compared to what has been reported for lower elevation coniferous forests, e.g. in the U.S. PaciWc Northwest, redevelopment of the understory appears to be slow after harvesting in these high elevation mountain forests. Rotation intervals that consider the natural temporal pattern of species turnover and the occurrence interval of major natural disturbances (here: Wre) should provide eVective approaches to sustainable forest management of these forests.

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Regeneration of interior mountain forests still is not adequately understood, although these forests are subject to intensified use over the last decades. We examined factors influencing the success of natural tree regeneration after harvesting in the Engelmann spruce–subalpine fir zone of the Monashee Mountains, British Columbia, Canada. Distance from the forest edge was an important factor for regeneration; at distances exceeding 70 m from the forest edge only 50% of plots showed sufficient natural regeneration to meet stocking targets compared with 90% of plots closer to forest edges. Seedling density and growth were superior in the more protected southern portions of clearcuts. Seedling growth was less in plots containing high cover of downed woody debris. There was no relationship between understory plant diversity or composition and tree seedling regeneration. However, cover of fireweed (Epilobium angustifolium) had a significant negative relationship with density but not growth of tree seedlings, particularly for lodgepole pine (Pinus contorta var. latifolia). Cover of fireweed decline substantially within the first 10 years after clearcutting. We conclude that natural regeneration of trees has potential to help achieve stocking targets and also to maintain natural diversity of tree species if spatial constraints, especially thresholds in clearcut size, are considered.

Promotion of species diversity has become a major goal in forestry. This requires an understanding of the impacts of management disturbance on species diversity relative to natural drivers such as climatic or edaphic conditions on the relevant temporal scales, i.e., centuries. We examined the effects of long-term management disturbance on understory plant diversity in coniferous forests by comparing structure types (ages since disturbance) between regions with comparable abiotic settings but contrasting management history, i.e., management for centuries in central Europe versus the first logging in primary forests in western Canada. We systematically sampled three age classes after disturbance and compared their alpha diversity and species composition. The structure types (age classes) showed similar differences in alpha diversity in both landscapes, while the response of species compositions differed between the two. Fewer late-successional specialists occurred in the European landscape. Within the setting of our study, the structure types, which reflect the time since major forest management disturbance, affected understory species richness and composition at least as strongly as environmental conditions such as climate, soil, and tree layer diversity across the broad altitudinal gradients that we sampled. Our results suggest that forest management affects the diversity of coniferous forests, with management for centuries disadvantaging late-successional specialists. Furthermore, it appears that human action is becoming the major determinant of diversity of coniferous forests, emphasizing the need for sustainable management schemes.Résumé : La promotion de la diversité des espèces est devenue un enjeu forestier important. Pour ce faire, il est important de comprendre les impacts des perturbations causées par l'aménagement sur la diversité des espèces en relation avec des facteurs naturels comme les conditions climatiques ou édaphiques sur une échelle temporelle pertinente, c'est-à-dire des siè-cles. Nous avons étudié les effets à long terme des perturbations causées par l'aménagement sur la diversité des plantes de sous-bois dans des forêts de conifères en comparant le type de structure (temps écoulé depuis la perturbation) entre des ré-gions ayant des caractéristiques abiotiques semblables, mais un historique d'aménagement très différent, c'est-à-dire un amé-nagement séculaire en Europe centrale et une première coupe dans une forêt vierge de l'ouest du Canada. Nous avons systématiquement échantillonné trois intervalles de temps après la perturbation et comparé leur diversité alpha et leur composition en espèces. Les différences de diversité alpha entre les types de structure (classes d'âge) des deux milieux étaient semblables alors que la réaction de ces milieux en termes de composition en espèces était différente. Il y avait moins de spé-cialistes de fin de succession dans le milieu européen. Dans le cadre de notre étude, le type de structure, qui reflète le temps écoulé depuis la dernière perturbation forest...

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