Search

Earlier provenance research has indicated poor success even in short distance transfers (> 2â3° latitude) of silver birch (Betula pendula Roth) southward from their origin. These results may indicate poor adaptability of silver birch to a warming climate. Some of the scenarios for a warming climate in Finland suggest effective heat sums are likely to double in the north and increase 1.5 fold in the south for the period of 2070â2099. Consequently, the outlook for silver birch appears bleak. To study the acclimation of birch to this projected change we established a provenance trial in northeastern Alberta, Canada, at the temperature area currently predicted for Central Finland (lat. 64â66°N) at the turn of this century (1400 dd). Our 10-year experiment showed that all the Finnish provenances (origins 61â67°N) have acclimated well to the warmer growth conditions experienced in Alberta at 54°N. These results suggest that silver birch has the potential to acclimate to thermal conditions predicted for Finland at the end of the 21st century. Our results also indicate that silver birch has the potential as a plantation species in Canada, where the Finnish birch grew faster in the boreal forest region of Canada than local paper birch (Betula papyrifera Marsh.) provenances.

While deployment of white spruce (Picea glauca (Moench) Voss) from seed orchards is increasing in Alberta, genetic gain is only considered in pure spruce stands due to uncertainties in measuring yields in mixedwood stands. To better understand the performance of improved spruce in mixedwood stands, we compared the effects of interspecific competition on growth of improved (1.9% height gain at a 100-year rotation) and unimproved spruce in northeastern Alberta. By age 8 years the improved spruce showed no advantage over the unimproved spruce in either height (1.36 [+ or -] 0.36 m vs. 1.42 [+ or -] 0.38 m) or diameter (23.68 [+ or -] 7.33 mm vs. 25.65 [+ or -] 6.85 mm), and the largest diameter trees were found in a nutrient-poor subxeric site. A distance-independent Lorimer's index including tree size ratio, combined with a power function, accounted for most of the growth variation in diameter and height from 2016 to 2017. The unimproved and improved spruce had different growth-competition curves across ecosites, and their height growth was less sensitive to competition than diameter growth. These results highlight several considerations for managing improved spruce, including (i) deploying higher genetic worth seedlots, (ii) developing realized gain trials with a good statistical design, and (iii) developing growth and yield functions for improved spruce in mixedwood stands. Key words: white spruce, boreal forest, mixedwood stands, improved and unimproved seedlots, competition effect. Alors que le deploiement de l'epinette blanche (Picea glauca (Moench) Voss) de vergers a graines augmente en Alberta, le gain genetique est pris en consideration uniquement dans les peuplements d'epinettes purs en raison des incertitudes lors de la mesure des rendements dans les peuplements mixtes. Pour mieux comprendre la performance des epinettes ameliorees dans les peuplements mixtes, nous avons compare les effets de la competition interspecifique sur la croissance de l'epinette amelioree (gain en hauteur de 1,9 % a une rotation de 100 ans) et de l'epinette non amelioree dans le nord-est de l'Alberta. A l'age de 8 ans, l'epinette amelioree n'a montre aucun avantage par rapport a l'epinette non amelioree sur le plan de la hauteur (1,36 [+ or -] 0,36 m vs. 1,42 [+ or -] 0,38 m) ou du diametre (23,68 [+ or -] 7,33 mm vs. 25,65 [+ or -] 6,85 mm) et les arbres au plus large diametre ont ete trouves sur un site dans un site subxerique pauvre en nutriments. Un indice Lorimer independant de la distance incluant le ratio de la taille des arbres, combine a une fonction puissance, a represente la plus grande partie de la variation de la croissance en diametre et en hauteur de 2016 a 2017. L'epinette amelioree et l'epinette non amelioree avaient des courbes de competition-croissance differentes dans les ecosites et leur croissance en hauteur etait moins sensible a la competition que la croissance de leur diametre. Ces resultats mettent en evidence de nombreuses considerations pour la gestion de l'epinette amelioree, y compris : (i) le deploiement de lots de semences de valeur genetique plus elevee; (ii) le developpement d'essais de gains realises avec une bonne conception statistique; et (iii) developpement des fonctions de croissance et de rendement pour l'epinette amelioree dans les peuplements mixtes. [Traduit par la Redaction] Mots-cles: epinette blanche, foret boreale, peuplements mixtes, lots de semences ameliorees et non ameliorees, effet de competition., 1. Introduction Tree improvement is one approach available to maintain and increase ecological and economic benefits from managed forests. A tree improvement program includes a continuous cycle of population selection, [...]

Over 18 million hectares of lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.) forests have been affected by a massive mountain pine beetle outbreak in western Canada. The ensuing need for reforestation compels forest managers to deploy more drought-resistant stock in anticipation of a hotter and drier future climate. Recent studies suggest that naturally occurring lodgepole pine * jack pine (Pinus banksiana Lamb.) hybrids may be more drought-resistant than pure lodgepole pine. We used single-nucleotide polymorphism markers to determine the level of jack pine introgression present in the region J lodgepole pine seed orchard, in northwest Alberta, and we identified six hybrid genotypes with 10%-18% jack pine introgression for further study. We compared the performance of open-pollinated seedlings of lodgepole, jack, and hybrid pines under well-watered and drought conditions in a greenhouse experiment. Seedlings were subjected to repegated drought cycles, withholding water for either 2 or 3 weeks. We found that hybrid pines grew significantly faster than lodgepole pine under well-watered conditions while retaining the high tolerance to prolonged drought exhibited by lodgepole pine seedlings, a particularly beneficial combination of traits during the critical stage of establishment. We therefore suggest the deployment of hybrid lodgepole pine as a strategy to promote adaptation to hotter and drier future climates. Key words: tree improvement, forest genetics, seed orchards, climate change, drought response, hybridization, resilience. Plus de 18 millions d'hectares de forets de pin tordu latifolie (Pinus contorta Dougl. var. latifolia Engelm.) ont ete perdus a cause d'une epidemie severe du dendroctone du pin ponderosa dans l'ouest du Canada. Le besoin de reboisement qui s'ensuit oblige les amenagistes forestiers a deployer des stocks plus resistants a la secheresse en prevision d'un climat futur plus chaud et plus sec. Des etudes recentes indiquent que les hybrides naturels entre le pin tordu et le pin gris (Pinus banksiana Lamb.) pourraient etre plus resistants a la secheresse que le pin tordu pur. Nous avons utilise des marqueurs de polymorphisme nucleotidique simple pour determiner le niveau d'introgression du pin gris present dans le verger a graines de pin tordu de la region J, dans le nordouest de l'Alberta, et nous avons identifie six genotypes hybrides avec 10-18 % d'introgression du pin gris pour etude ulterieure. Nous avons compare la performance de semis a pollinisation libre de pins tordus, gris et hybrides bien arroses ou en conditions de secheresse dans une experience en serre. Les semis ont ete soumis a des cycles repetes de secheresse en les privant d'eau pendant 2 ou 3 semaines. Nous avons observe que les pins hybrides ont cru significativement plus vite que le pin tordu lorsqu'ils etaient bien arroses tout en conservant une grande tolerance a une secheresse prolongee caracteristique des semis de pin tordu, une combinaison de caracteres particulierement benefique durant le stade critique de l'etablissement. Nous suggerons par consequent le deploiement du pin tordu hybride comme strategie pour favoriser l'adaptation aux climats futurs plus chauds et plus secs. [Traduit par la Redaction] Mots-cles : amelioration des arbres, genetique forestiere, vergers a graines, changement climatique, reaction a la secheresse, hybridation, resilience., Introduction Climate change is expected to increase the frequency and severity of drought events in the boreal forest, thus increasing the risk of reduced productivity and mortality due to drought [...]

Strict forest renewal policies in western Canada focus on replicating the stand type that was cut and projecting the growth of young stands forward using simple models based upon past growing conditions. These policies arose from European principles of sustained yield and now limit options for adaptive management at the time of investment in forest renewal of public lands. We assert that such simple and restrictive policies, combined with long-term yield predictions, give a false sense of sustainability in times of increased drought, fires, and insect and disease attacks that accompany climate change. We must undertake comprehensive changes in forest policy that incorporate disturbance in our forest management planning. This is a large task! Options include (i) zoning public forests to vary intensities of management and minimize risk; (ii) changing stand- and forest-level models to increase the diversity of forests regenerated; (iii) widening the sphere of scientific experts that can influence forest policy and risk management; and (iv) reallocating expenditures on forest renewal, protection, and management to minimize negative impacts of disturbance. Such a comprehensive overhaul of forest management will be necessary as the current assumptions of forest sustainability come under further scrutiny by the public and investors. Key words: forest management, regeneration policy, risk of disturbance, sustained yield, fire. Resume : Des politiques strictes de renouvellement des forets dans l'ouest du Canada mettent l'accent sur le retour du type de peuplement qui a ete coupe et la projection de la croissance des jeunes peuplements a l'aide de modeles simples fondes sur des conditions de croissance passees. Ces politiques sont issues des principes europeens de rendement soutenu et limitent a present les options de gestion adaptative au moment d'investir dans le renouvellement des forets sur les terres publiques. Nous maintenons que ces politiques simplistes et restrictives, combinees aux predictions de rendement a long terme, donnent un faux sentiment de durabilite alors qu'augmentent les secheresses, les feux et les invasions d'insectes et de maladies qui accompagnent les changements climatiques. Nous devons proceder a des changements importants des politiques forestieres qui incorporent les perturbations dans notre planification de l'amenagement forestier. Il s'agit d'une tache enorme! Les options incluent (i) zoner les forets publiques pour varier l'intensite de l'amenagement et minimiser les risques; (ii) changer nos modeles a l'echelle du peuplement et de la foret pour augmenter la diversite des forets qui sont regenerees; (iii) elargir la sphere des experts scientifiques pouvant influencer les politiques forestieres et la gestion du risque; et (iv) reallouer les depenses reliees au renouvellement de la foret, a la protection et a l'amenagement pour minimiser les impacts negatifs des perturbations. Un remaniement de cette ampleur de l'amenagement forestier sera necessaire a mesure que les hypotheses courantes de durabilite de la foret seront davantage soumises a un examen rigoureux du public et des investisseurs. [Traduit par la Redaction] Mots-cles: amenagement forestier, politique de regeneration, risque de perturbation, rendement soutenu, feu., Introduction Disturbance has played a large role in the boreal forests of western Canada, especially in the last two decades. Infestations of mountain pine beetle (Dendroctonus ponderosae Hopkins, 1902) (Bentz [...]

The spatial effects of vegetation control on early tree growth were investigated in central Alberta, Canada, for four years after the establishment of hybrid poplar plantations including the two clones Walker (Populus deltoides x (P. laurifolia x P. nigra)) and its progeny Okanese (Walker x (P. laurifolia x P. nigra)). Tree survival and growth, herbaceous vegetation cover, soil nutrient availability, moisture, temperature, and light availability were assessed. Tree growth in the first two years after establishment was improved through selective in-row vegetation control close (within 50 cm) to trees for both aboveground (mechanical) and above- and below-ground (chemical) control. This was associated with increased light availability for trees. In contrast, growth in the third and fourth years benefitted from control of aboveground vegetation within 140 cm of the stem, and this was associated with increased nutrient availability. These findings suggest that the effects of neighbouring vegetation on trees shift from aboveground competition near the tree stem to belowground competition further (>50 cm) away; thus between-row vegetation control is more important starting in the third year after establishment. Okanese outperformed Walker poplar across all treatments and was more responsive to vegetation control, reflecting its superior performance, higher plasticity, and greater potential for short-rotation intensive-culture plantations. Key words: hybrid poplar, tree growth, aboveground and belowground competition, resource availability, vegetation management. Les effets de nature spatiale de la maitrise de la vegetation sur la croissance precoce des arbres ont ete etudies dans le centre de l'Alberta, au Canada, pendant quatre ans suivant l'etablissement de plantations de peupliers hybrides incluant les deux clones Walker (Populus deltoides x (P. laurifolia x P. nigra)) et sa descendance Okanese (Walker x (P. laurifolia x P. nigra)). La survie et la croissance des arbres, le couvert de vegetation herbacee, la disponibilite des nutriments dans le sol, l'humidite, la temperature, et la disponibilite de la lumiere ont ete evalues. Durant les deux premieres annees suivant l'etablissement, la croissance des arbres a ete amelioree par la maitrise selective de la vegetation dans les rangs pres (a moins de 50 cm) des arbres tant dans le cas de la maitrise aerienne (mecanique) qu'aerienne et souterraine (chimique). Cela etait associe a plus grande disponibilite de la lumiere pour les arbres. Par contre, durant les troisieme et quatrieme annees la croissance a beneficie de la maitrise aerienne de la vegetation en dedans de 140 cm de la tige et cela etait associe a une plus grande disponibilite des nutriments. Ces resultats indiquent que les effets de la vegetation avoisinante passent de la competition aerienne pres du tronc des arbres a la competition souterraine plus loin (>50 cm). Par consequent, la maitrise de la vegetation entre les rangs est plus importante a partir de la troisieme annee suivant l'etablissement. Le clone Okanese a ete plus performant que le clone Walker peu importe le traitement et reagissait mieux a la maitrise de la vegetation, refletant sa performance superieure, sa plus grande plasticite et son potentiel plus eleve pour les plantations a culture intensive et courte rotation. [Traduit par la Redaction] Mots-cles: peuplier hybride, croissance des arbres, competition aerienne et souterraine, disponibilite des ressources, gestion de la vegetation., Introduction Plantations of fast-growing hybrid poplar trees play a significant role in wood and fibre production and as a supplier of biomass for energy, alternative fodder sources, and ecosystem services [...]

In this paper we hypothesize that farmers with a stronger valuation of family farming will be more resistant to converting farmland to tree plantations. Our survey data analysis from 106 farmers in northern Alberta reveals that general opposition to trees on farmland is the strongest predictor of farmers' resistance to the establishment of poplar tree plantations on privately-owned land. Valuation of family farming is the strongest determinant of resistance to trees on farmland. Among the potential intervening variables influencing support for tree plantations, including county, age, gender, number of children, and percent of income from farming, number of children and percent of income from farming had significant direct effects on valuation of family farming. This study suggests that economic incentives alone are unlikely to influence farmers' willingness to convert their land to non-traditional uses, and that intergenerational transfer of land, and its relationship to valuation of family farming, deserves further attention in rural sociological scholarship. (Contains 3 figures, 4 tables, and 5 footnotes.)