Academic literature on the topic 'Bouleau jaune – Composition'

Forest successions following a forest fire that occurred in 1932 were studied on mesic sites of the boreal mixedwood forest of the Bas-Saint-Laurent region of Quebec, Canada. Physiographic, soil and vegetation data were collected in 28 ecosystems distributed on a topographic gradient. The vegetation composition of the main canopy, 64 years after the fire, varied according to topographic situation. The proportion of tolerant hardwood species (yellow birch (Betula alleghaniensis Britton), sugar maple (Acer saccharum Marsh.), red maple (Acer rubrum L.)) increased toward upper slopes whereas it was the opposite for coniferous species (white spruce (Picea glauca [Moench] Voss), balsam fir (Abies balsamea [L.] Mill.)), as their proportion increased toward lower slopes. Intolerant hardwood species (white birch (Betula papyrifera Marsh.), trembling aspen (Populus tremuloides Michx.)) were abundant in all ecosystems. The distribution pattern of regeneration density and stocking of tolerant hardwoods and conifers was similar to that of the main canopy. The majority of commercial species, including tolerant species, established rapidly after the fire. Only eastern white cedar (Thuya occidentalis L.), which is a species typical of late succession, did not grow back. Ten years after the fire, 78% of the sampled dominant trees were established. Competition caused by mountain maple (Acer spicatum Lam.) did not seem to be as important after fire compared with the situation after clearcutting. Results showed that after the elimination of intolerant species, the vegetation composition should evolve toward the potential vegetation (climax) of the toposequence, that is, the sugar maple - yellow birch type on upper slopes, the balsam fir - yellow birch type on midslopes and the balsam fir - yellow birch - cedar type on lower slopes. Key words: succession, fire, yellow birch, balsam fir, mountain maple.

A total of 48 plots originating from clearcuts were studied in the balsam fir-yellow birch ecological domain of the province of Quebec, Canada, using dendrochronology. The aim of the study was to assess the effect of pre-cut stand type, structure and abundance of regeneration after logging, and soil type on stand dynamics. Results indicate a relationship between pre-cut stand type and the composition of second-growth stands. Ecological characteristics must be taken into account in order to estimate the abundance of advance regeneration and predict the evolution of stocking. Results also show that the structure of regeneration, described by a diameter index, can help in predicting yield at age 38. Devastation by the spruce budworm played a major role in second-growth stand dynamics making it difficult to predict balsam fir yield. The study has also shown an increase in intolerant hardwoods and a low softwood production on rich sites. Black spruce stands came back to black spruce.Key words: mixedwoods, succession, regeneration survey, yield, Choristoneura fumiferana

The effect of careful logging to preserve advance growth was studied in mixedwood stands of the balsam fir (Abies balsamea (L.) Mill.) - yellow birch (Betula alleghaniensis Britton) eco-climatic domain in eastern Quebec, Canada. The study is based on 19 sites harvested five years earlier. In each cutover, 50 sample plots have been established to quantify the abundance of regeneration five years after logging. This cutting method proved to be ineffective in limiting the invasion of competiting species such as mountain maple (Acer spicatum Lam.) and pin cherry (Prunus pensylvanica (L.), which fully occupied the sites with 25 092 and 5619 stems ha−1 respectively. Balsam fir was abundant after five years in the study area with 13 500 stems ha−1 but two thirds of the seedlings were smaller than 30 cm. Soil disturbance was minimal, probably limiting the establishment of yellow birch, which reached a density of 1416 stems ha−1 five years after logging. Height growth projection of regeneration over five years showed that competiting species should still dominate the sites. Commercial species should improve their position but would still account for only 40% of dominant stems. It is therefore unlikely that this regeneration method will be successful in bringing back the initial stand composition in a short period of time. The next stands will probably contain a high proportion of intolerant species with a dominance of paper birch (Betula papyrifera Marsh.) over yellow birch. In the near future, cleaning operations should be conducted to reduce the impact of competing vegetation and make sure that balsam fir will remain in the main canopy.

Les forêts du sud-ouest de la province de Québec, Canada, sont riches en essences feuillues dites nobles telles que le bouleau jaune (Betula alleghaniensis) et l’érable à sucre (Acer saccharum). Leur exploitation antérieure a généralement été basée sur une coupe à diamètre limite visant la récupération des billes de grande valeur. Une telle pratique, avec le temps, a amené une diminution générale de la vigueur des arbres sur pied en forêt. La réglementation actuelle oblige les exploitants forestiers à récolter préférentiellement les arbres de faible vigueur de manière à rétablir la qualité des forêts. Ces arbres de faible vigueur, souvent de faible qualité, possèdent généralement une faible valeur économique. La pertinence de l’ajout d’une étape d’extraction chimique à l’éthanol des tissus de bois et de l’écorce dans les procédés de transformation de la matière déjà existants a été étudiée dans ce mémoire. Plus spécifiquement, les travaux visaient à évaluer le potentiel d’une telle stratégie appliquée à la transformation des arbres de faible vigueur. Du bois et de l’écorce provenant d’arbres vigoureux (références) et non-vigoureux mourants (infectés par des champignons ou séchant du houppier) ont été extraits à l’éthanol à l’aide de deux méthodes différentes : par macération et par extraction assistée aux ultrasons. D’une part, les extraits ont été étudiés pour leur contenu en polyphénols (phénols totaux, taux de proanthocyanidines, de flavonoïdes et d’acides hydroxycinnamiques) et en triterpènes et phytostérols. D’autre part, les tissus ont été étudiés avant et après extraction pour leur pouvoir calorifique supérieur, leur composition chimique organique, leur contenu en cendres, ainsi que la composition chimique des cendres. Bien qu’une variation soit observée entre les différents arbres, les extractions n’affectent pas les capacités de combustion des tissus. Elles peuvent en outre constituer un apport notable de polyphénols, de triterpènes et de stérols possédant un potentiel économique dans les domaines nutraceutique, pharmaceutique ou cosméceutique, et ce, peu importe la vigueur des arbres à la source des tissus ou la méthode d’extraction utilisée. L’extraction du bois et de l’écorce de bouleaux jaunes et d’érables à sucre de faible vigueur peut donc être envisagée dans une stratégie de transformation à valeur ajoutée de la ressource.
Forests of South-West Québec, Canada, are rich in yellow birch (Betula alleghaniensis) and sugar maple (Acer saccharum). Past forest practices were aiming to harvest the superior quality and higher value logs via selective cuttings, which resulted in a decrease of the general vigor of the trees left standing in the forests. Current regulations require the foresters to harvest preferentially low vigor trees in order to restore the quality of the forests. These low vigor trees, which are often less suitable for value-added products such as flooring or furniture, are also generally of a low economic value. The addition of an ethanolic extraction of the wood and bark tissues to a currently applied processing approach was studied in order to assess its feasibility with trees of different vigor. Wood and bark tissues were collected from vigorous (references) and non-vigorous dying trees (fungus infected or with very poor foliage) and were extracted with ethanol using two different methods: maceration assisted and an ultrasound assisted extraction. The extracts were characterized for their total phenols, proanthocyanidins, flavonoids, hydroxycinnamic acids, triterpenes and phytosterols content. Tissues were characterized before and after extraction for their calorific value, organic composition, ash content and ash mineral composition. While much variation was observed between trees, the ethanolic extractions did not affect the combustion properties of the tissues, while bringing a significant contribution in polyphenols, triterpenes and phytosterols - all molecules having potential applications in nutraceutics, pharmaceutics or cosmeceutics - no matter the vigor of the tree at the source of the tissues or the extraction method employed. The ethanolic extraction of wood and bark coming from low vigor yellow birch and sugar maple can be considered as a mean to add value to the resource.