Search

The contribution of forest biomass to Canada's energy production is small but growing. As the forest bioenergy industry in Canada expands, there is growing interest in more sustainably managing the wood ash that is generated as a by-product. Despite being rich in nutrients, wood ash is usually landfilled in Canada. Soil applications of ash in Canadian forests could be used to mimic some of the effects of wildfire, to replace nutrients removed during harvesting, to counteract the negative effects of acid deposition, and to improve tree growth. At present, the provincial and territorial processes for obtaining regulatory approval to use wood ash as a forest soil amendment can be challenging to navigate. Furthermore, the costs for obtaining approval and transporting and applying wood ash to the soil can render landfilling a more cost-effective method of ash management. To ensure that wood ash applications in Canadian forests are conducted safely, effectively, and efficiently, experience from European countries could provide a useful starting point for developing best practices. The results of Canadian research trials will assist policy makers and forest managers in refining management guidelines that encourage soil applications of wood ash as a forest management tool while protecting the ecology, water quality, biodiversity, and productivity of Canadian forests. Key words: bioenergy, wood ash, forest soil, biomass harvesting, waste management. Au Canada, la contribution de la biomasse forestiere a la production d'energie est faible mais elle va en augmentant. A mesure que l'industrie de la bioenergie forestiere prend de l'expansion au Canada, il y a un interet croissant pour une gestion plus durable de la cendre de bois qui est generee comme sous-produit. Bien qu'elle soit riche en nutriments, la cendre de bois est generalement dirigee vers les sites d'enfouissement au Canada. L'application au sol de la cendre dans les forets canadiennes pourrait etre utilisee pour imiter certains effets des feux de foret et remplacer les nutriments preleves lors de la recolte afin de contrecarrer les effets negatifs des depots acides et ameliorer la croissance des arbres. Presentement, il peut etre difficile de s'y retrouver dans les processus territoriaux et provinciaux d'approbation reglementaire pour utiliser la cendre de bois comme amendement des sols. De plus, les couts pour obtenir l'approbation, transporter et appliquer au sol la cendre de bois peuvent faire en sorte que l'enfouissement de la cendre est une methode de gestion plus rentable. Afin de s'assurer que les applications de la cendre de bois dans les forets canadiennes soient faites de facon securitaire, efficace et efficiente, l'experience des pays europeens pourrait constituerun point de depart pour mettre au point les meilleures pratiques. Les resultats des tests canadiens aideront les decideurs politiques et les gestionnaires forestiers a raffiner les directives d'amenagement pour promouvoir l'application au sol de la cendre de bois comme outil d'amenagement tout en protegeant l'ecologie, la qualite de l'eau, la biodiversite et la productivite des forets canadiennes. [Traduit par la Redaction] Mots-cles: bioenergie, cendre de bois, sol forestier, recolte de biomasse, gestion des dechets., Introduction Canada meets its energy needs using a combination of fossil fuels, nuclear power, and renewables. Efforts to mitigate greenhouse gas emissions depend on replacing fossil fuel based energy with [...]

The integration of functional traits into vulnerability assessments is a promising approach to quantitatively capture differences in species sensitivity and adaptive capacity to climate change, allowing the refinement of tree species distribution models. In response to a clear need to identify traits that are responsive to climate change and applicable in a management context, we review the state of knowledge of the main mechanisms, and their associated traits, that underpin the ability of boreal and temperate tree species to persist and (or) shift their distribution in a changing climate. We aimed to determine whether current knowledge is sufficiently mature and available to be used effectively in vulnerability assessments. Marshalling recent conceptual advances and assessing data availability, our ultimate objective is to guide modellers and practitioners in finding and selecting sets of traits that can be used to capture differences in species' ability to persist and migrate. While the physiological mechanisms that determine sensitivity to climate change are relatively well understood (e.g., drought-induced cavitation), many associated traits have not been systematically documented for North American trees and differences in methodology preclude their widespread integration into vulnerability assessments (e.g., xylem recovery capacity). In contrast, traits traditionally associated with the ability to migrate and withstand fire are generally well documented, but new key traits are emerging in the context of climate change that have not been as well characterized (e.g., age of optimum seed production). More generally, lack of knowledge surrounding the extent and patterns in intraspecific trait variation, as well as co-variation and interaction among traits, limit our ability to use this approach to assess tree adaptive capacity. We conclude by outlining research needs and potential strategies for the development of trait-based knowledge applicable in large-scale modelling efforts, sketching out important aspects of trait data organization that should be part of a coordinated effort by the forest science community. Key words: vulnerability assessment, drought tolerance, fire tolerance, migration ability, intraspecific variation in trait, species persistence. L'utilisation des traits fonctionnels dans l'evaluation de la vulnerabilite est une approche prometteuse pour integrer de maniere quantifiable les differences de sensibilite des especes et leur capacite d'adaptation aux changements climatiques, ameliorant ainsi les modeles de repartition des arbres. Afin d'identifier dans un contexte d'amenagement les traits cles qui sont affectes par les changements climatiques, nous examinons l'etat des connaissances sur les principaux mecanismes - ainsi que leurs traits associes--qui regissent la capacite des arbres des forets boreales et temperees a persister ou a migrer. Nous avons tente de determiner si les connaissances actuelles sont suffisamment matures et disponibles pour etre utilisees efficacement dans le contexte des evaluations de vulnerabilite. En synthetisant les avancees conceptuelles les plus recentes et en evaluant la disponibilite des donnees, nous avons comme objectif principal de guider les modelisateurs et autres intervenants dans la selection de traits fonctionnels pouvant servir a caracteriser les differences dans la capacite des especes a persister et a migrer face a un climat en changement. Par exemple, malgre que l'on comprenne assez bien les mecanismes physiologiques qui determinent la sensibilite aux changements climatiques (ex., cavitation induite par la secheresse), un grand nombre de traits associes a ces mecanismes n'ont pas ete systematiquement documentes pour les arbres d'Amerique du Nord. Nous constatons egalement des differences dans les methodologies utilisees pour mesurer ces traits (ex., capacite de retablissement des xylemes), ce qui nuit a l'integration des traits dans l'evaluation de la vulnerabilite. Pour leur part, les traits traditionnellement associes a la capacite de migrer et de resister au feu sont generalement bien documentes; cependant, de nouveaux traits cles emergeant dans le contexte des changements climatiques demeurent peu documentes (ex., l'age de la production optimale de graines). De facon generale, le manque de connaissance entourant la variabilite intraspecifique des traits, ainsi que sur la covariation et l'interaction entre traits, est limitant dans nos evaluations de la capacite adaptative des arbres. Nous concluons en soulignant des besoins precis en matiere de recherche et en identifiant certaines avenues possibles pour le developpement des connaissances liees aux traits applicables dans des projets de modelisation a grande echelle. Nous soulignons finalement l'importance de certains aspects de la gestion de donnees de traits qui devraient faire partie de tout effort coordonne de documentation par la communaute scientifique du milieu forestier. Mots-cles : evaluation de la vulnerabilite, tolerance a la secheresse, tolerance au feu, capacite de migration, variabilite intraspecifique des traits, persistance de l'espece., 1. Introduction Recent years have seen a marked increase in efforts to assess potential effects of climate change on the distribution and abundance of forest plant species (Thuiller et al. [...]

A method has been developed and used in the direct determination of the primary quantum yield of OH in the laser photolysis of nitric acid at 222 nm. The amount of laser light absorbed was determined with a calibrated disk calorimeter. The amount of OH produced was determined by absorption spectroscopy using the resonance line at 308.3 nm and a published value of its line strength. The primary quantum yield of OH at 296 K was found to be 0.89±0.08 (95% confidence interval) with an uncertainty of +17%, -8% due to potential systematic errors. Within the experimental uncertainty, this result is consistent with a previous determination of a quantum yield of unity for the other product of photolysis, NO2. [ABSTRACT FROM AUTHOR]

Although it is known that [O.sub.2] inhibits and represses denitrification, few studies have examined the effect of [O.sub.2] on NO production. Our objectives were to measure [O.sub.2] inhibition, repression, and derepression of NO and [N.sub.2]O production by denitrifying microorganisms in soil columns continuously purged by [N.sub.2] or various constant (0.074-15%) [O.sub.2]-[N.sub.2] mixtures. Net rates of NO and [N.sub.2]O production were measured under successive anaerobic, partially aerobic, and anaerobic conditions. Oxygen inhibition was rapid and reversible. Within 5 min after exposure to [is greater than] 5% [O.sub.2], NO production was reduced to [approximately equals] 50 to 58% and [N.sub.2]O rates to [approximately equals] 29 to 32% of their maximum anaerobic rates. Maintaining [O.sub.2] at [is greater than or equal to]5% in soil without added C or at [is greater than] 10% 02 in C-amended soil decreased (repressed) NO production rates by a factor of [approximately equals] 1.5 to 1.8 [d.sup.-1]. Rates of [N.sub.2]O repression remained constant at [approximately equals] 0.07 [d.sup.-1] for all C and [O.sub.2] treatments. Restoration of anoxic conditions following the aerobic phase reversed inhibition; within 5 min, NO production rates by the nonrepressed denitrifiers increased to 55 to 101% of their respective anaerobic rates and [N.sub.2]O production rates increased to 26 to 62%. The rates of NO and [N.sub.2]O production then increased more slowly (derepression) during this anaerobic period. This research supports previous observations for [O.sub.2] effects on [N.sub.2]O production and apparently is the first systematic study of [O.sub.2] inhibition, repression, and derepression of NO production.