Critical errors exist in some methodologies applied to evaluate the effects of using forest biomass for bioenergy on atmospheric greenhouse gas emissions. The most common error is failing to consider the fate of forest carbon stocks in the absence of demand for bioenergy. Without this demand, forests will either continue to grow or will be harvested for other wood products. Our goal is to illustrate why correct accounting requires that the difference in stored forest carbon between harvest and no-harvest scenarios be accounted for when forest biomass is used for bioenergy. Among the flawed methodologies evaluated in this review, we address the rationale for accounting for the fate of forest carbon in the absence of demand for bioenergy for forests harvested on a sustained yield basis. We also discuss why the same accounting principles apply to individual stands and forest landscapes.
Climate change may profoundly influence Ontario's forest ecosystems and their management. Elevated atmospheric C 0 2 concentrations, increased temperature and altered precipitation regimes will affect forest vegetation through their influence on physiological (e.g., photosynthesis, respiration) and ecological processes (e.g., net primary production, decomposition), and may result in dramatic northward shifts in the natural range of forest types and species. More importantly, climate change is expected to increase the frequency of natural disturbances. Silvicultural intervention will increasingly be relied on to maintain forest health, manage declining stands, regenerate disturbed areas and cutovers with desired species and genotypes, maintain genetic diversity, and assist in species migration. Given the increasingly important role of Ontario's forests in national and provincial efforts to meet greenhouse gas emission reduction targets of the Kyoto Protocol, afforestation, conservation of existing forests, and increased forest management activities to accelerate the storage of carbon in Ontario's forests will be key aspects of forestry at the start of the third millennium.Key words: adaptation, afforestation, bioenergy, carbon dioxide, climate change, disturbance, intensive forest management, migration, mitigation, sequestration, succession Le changement climatique pourrait modifier en profondeur les Ccosyst5mes forestiers de I'Ontario et la f a~o n de les amtnager. Les concentrations ClevCes de C02 atmosphCrique, la temptrature plus ClevCe et les regimes de precipitations modifiks affecteront la vCg& tation forestibre suite B leurs influences sur les processus physiologiques (p. ex. la photosynthbe, la respiration) et 6cologiques (p. ex. la production nette primaire, la dCcomposition), et pourraient entrainer des diplacements dramatiques vers le nord de la distribution naturelle des types de for& et des espbces. De f a~o n encore plus importante, on s'attend 2 ce que le changement climatique accroisse la frCquence des perturbations naturelles. Les interventions sylvicoles dCpendront de plus en plus du maintien de la santC des for&, de I'amCnagement des peuplements en dkclin, de la rkgtntration des superficies perturbhs et toupees au moyen d'espkes et de gCne types dCsirts, du maintien de la diversitt gCnCtique, et de l'aide clans la migration des espbces. fitant donne le r6le de plus en plus importants que jouent les for& de I'Ontario au niveau des efforts nationaux et provinciaux de correspondance aux objectifs de rtduction des gaz B effets de serre selon le protocole de Kyoto, le boisement, la conservation des forets actuelles, et l'accroissement des activitCs d'amknagement forestier pour accCl6rer la skquestration dur carbone dans les for& ontariennes seront des aspects dominants en foresterie au dtbut de troisibme millCnaire.
Assisted migration has been proposed as one tool to reduce some of the negative ecological consequences of climate change. The idea is to move species to locations that could better suit them climatically in the future. Although humanmediated movements are not a recent phenomenon, assisted migration has lately been the source of debate, in particular within conservation biology circles. In this paper, we outline the major perspectives that help define differing views on assisted migration and shed some light on the ethical roots of the debate in the context of Canadian forests. We emphasize that there are many different forms of assisted migration, each responding to different (often unstated) objectives and involving unique risks and benefits, thus making the debate more nuanced than often portrayed. We point out certain seeming contradictions whereby the same argument may be used to both support and oppose assisted migration. The current debate on assisted migration primarily focuses on ecological risks and benefits; however, numerous uncertainties reduce our capacity to quantitatively assess these outcomes. In fact, much of the debate can be traced back to fundamental perspectives on nature, particularly to the ethical question of whether to deliberately manage natural systems or allow them to adapt on their own. To facilitate discussion, we suggest that the focus should move towards a clearer identification of values and objectives for assisted migration.Keywords: assisted colonization, climate change, environmental ethics, species conservation, forest management RÉSUMÉ La migration assistée a récemment été suggérée comme outil permettant de réduire les conséquences écologiques néga-tives des changements climatiques. L'idée est de déplacer des espèces vers des sites qui leur conviendraient mieux dans le futur. Le déplacement d' espèces par l'homme n' est pas un phénomène nouveau. Cependant, la migration assistée a soulevé des débats récemment, particulièrement dans la sphère de la biologie de la conservation. Cet article a pour objectif de souligner les racines éthiques du débat en clarifiant les principales perspectives et visions sur la migration assistée au Canada. Le terme migration assistée s'applique à plusieurs types d'intervention, chacune correspondant à des objectifs différents (souvent non mentionnés) et impliquant des risques et bénéfices qui lui sont propres. Le débat serait en fait beaucoup plus nuancé que souvent décrit. Nous soulignons certaines contradictions où un même argument est utilisé pour supporter ou s' opposer à la migration assistée. Le débat actuel sur la migration assistée se concentre principalement sur la détermination scientifique des risques et bénéfices écologiques. Cependant, de nombreuses incertitudes réduisent notre capacité à évaluer de façon quantitative les résultats de ces interventions. Une grande partie du débat est en fait liée à notre perspective fondamentale sur la nature, particulièrement à la question éthique de la prise en charge des processus naturels...
The heat tolerance of actively growing 13-15-week-old black spruce (Picea mariana (Mill.) B.S.P.) was determined by exposing seedlings to temperatures of 40 to 60 degrees C for durations of 5 seconds to 3 hours by direct immersion in a hot water bath. Direct and indirect heat damage to needles were differentiated by assessing damage 5 minutes (direct) and 3 weeks (indirect) after exposure to high temperature. Both direct and indirect damage increased exponentially with the duration of exposure to high temperatures. However, indirect damage occurred at lower temperatures and with shorter periods of exposure than direct damage. Arrhenius plots of length of exposure versus exposure temperature revealed that the energy of activation for indirect damage was 384 kJ mol(-1), 36% higher than for direct damage. Both direct and indirect damage were less in seedlings preconditioned by a heat shock treatment (3 hours of exposure to an air temperature of 38 degrees C on each of 6 days prior to immersion in the water bath). Preconditioned seedlings withstood higher temperatures and longer durations of high temperature exposure than seedlings not preconditioned by heat shock.
-Picea mariana (Mill.) B.S.P. seedlings were hardened for overwintering under four regimes. In three regimes, seedlings were kept inside a heated greenhouse for 11 weeks during and after dormancy induction (August to mid-November), with either 1. Natural daylengths (46°31' N) and warm temperatures of 20 °C or more (NDW), 2. As 1, but fertilized (NDWF) or 3. As 1, but with shortened daylengths (SD). In the fourth regime (OD), seedlings were hardened outside at naturally declining temperatures and daylengths without fertilizer. Seedlings hardened in any warm temperature treatment had buds with more needle primordia and shoots more resistant to desiccation than OD seedlings. Initially, cold hardiness tended to be greatest in SD seedlings. As hardening progressed OD seedlings became equally cold hardy to SD. In late November when all trees were outside, NDW seedlings were usually least cold hardy. Spring root growth potential was least in OD seedlings.cold hardiness / desiccation / needle primordia / transpiration / water potential Résumé -Effets de la longueur du jour, de la température et de la fertilisation sur la résistance à la dessiccation et au froid, et au potentiel de croissance de plants de Picea mariana. On a soumis des semis de Picea mariana (Mill.) à quatre traitements pour les endurcir au froid en vue de la période hivernale. Pour trois traitements les plants ont été installés sous serre chauffée pendant 11 semaines, pendant et après l'induction de la dormance, avec les 3 modalités suivantes : (1) longueur naturelle du jour (latitude 46° 31' N) et chauffage à une température égale ou supérieure à 20 °C (NDW); (2) comme le traitement 1, mais avec fertilisation (NDWF); (3) comme le traitement 1 mais en jours courts (SD). Pour le quatrième traitement (OD) les plants ont été endurcis à l'extérieur avec la baisse de température et la diminution de la longueur des jours des conditions naturelles, sans faire appel à une fertilisation. Les plants issus des traitements comportant une phase sous serre chaude présentaient des bourgeons ayant davantage d'ébauches foliaires et des pousses plus résistantes à la dessication que les plants du traitement OD. Dans un premier stade, l'endurcissement au froid des plants SD tendait à être plus élevé. Ultérieurement celui des plants OD est devenu équivalent à celui des SD. Fin novembre, tous les plants étaient à l'extérieur, les plants NDW étaient moins résistants au froid. Le potentiel de croissance racinaire au printemps était moins élevé pour les plants OD. endurcissement pour la résistance au froid / dessication / ébauche racinaire / transpiration / potentiel hydrique
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