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Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Botany is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Old-growth forests have been identified as a potentially important stage of stand development for maintaining biodiversity in the landscape, yet they have also been targeted by the forest industry in their drive to regulate the forest. We will attempt to propose a definition of old growth, applicable throughout the North American boreal forest, that takes into account the dynamic nature of forest development and that could be useful for management and conservation purposes. We define the start of the old-growth stage as occurring when the initial post-disturbance cohort begins dying off, concurrent with understorey stem recruitment into the canopy. We propose that species longevity and the regional fire cycle can be used to assess the extent of this phase in different regions. Using published data on fire history, we show that the amount of old growth expected to occur in western and central Canada is less than in eastern Canada, where most stands (in area) escape fire for periods longer than that necessary to incur substantial mortality of the initial cohort. At the stand level, we show that the old-growth stage is characterized by small-scale disturbances that engender gap dynamics. Until recently, this process had not been studied in the boreal forest. The old-growth index we present suggests that the relationship between time since the last major disturbance and old-growth status varies most in areas that have not been disturbed for long periods. Both management and conservation strategies have to take into account that old-growth forests are dynamic. To be effective, reserves should contain all stages of development and should be sufficiently large to encompass rare but large disturbances. The abundance of old growth in many boreal regions of North America also suggests that forest management strategies other than even-aged, fully regulated systems have to be developed. Key words: old growth, old-growth index, boreal forest, conservation, forest management, stand development.Les vieilles forêts ont été identifiées comme un stade potentiellement important de développement des peuplements pour le maintien de la biodiversité dans le paysage; elles ont cependant également été ciblées par l'industrie forestière dans ses activités d'aménagement. Les auteurs tentent de proposer une définition des vieilles forêts qui serait applicable à l'ensemble de la forêt boréale de l'Amérique du Nord et qui prendrait en compte la nature dynamique du développement du peuplement forestier tout en étant utile aux fins de l'aménagement et de la conservation. Les auteurs définissent le début du stade de vieille forêt comme le moment où la cohorte initiale post-perturbation commence à mourir, concurremment avec le recrutement de tiges du sous-étage dans la canopée. Pour évaluer l'importance de cette phase dans différentes régions, ils proposent d'utiliser la longévité des espèces et le cycle régional du feu. Avec l'historique des feux, ils démontrent que la quantité de vieilles forêts espérée dans le Canada central et de l'ouest est plus faible que dans l'est du Canada, où la plupart des peuplements (en superficie) échappent au feu pendant des périodes plus longues que celles qui sont nécessaires pour apporter une mortalité substantielle à la cohorte initiale. Au niveau du peuplement, les auteurs montrent que le stade de vieille forêt se caractérise par des perturbations à petite échelle qui engendrent une dynamique d'ouverture. Jusqu'à récemment, ce processus n'a pas été étudié en forêt boréale. L'index de vieille forêt présenté par les auteurs suggère que la relation entre le temps depuis la dernière perturbation majeure et le statut de vieille forêt varie le plus dans les régions qui n'ont pas été perturbées pendant de longues périodes. Les stratégies d'aménagement aussi bien que de conservation doivent prendre en compte le statut dynamique des vieilles forêts. Pour être efficaces, les réserves devraient contenir tous les stades de développement et devraient être suffisamment grandes pour inclure de rares mais vastes perturbations. L'abondance des vieilles forêts dans plusieurs régions boréales de l'Amérique du Nord suggère que des stratégies d'aménagement autre que les systèmes èquiennes visant la normalisation de la forêt doivent être développées. Mots clés : index de vieille forêt, vieille forêt, forêt boréale, conservation, aménagement forestier, stade de développement.[Traduit par la rédaction] [ABSTRACT FROM AUTHOR]

Copyright of Journal of Environmental Engineering & Science is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)