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Copyright of Forestry Chronicle is the property of Canadian Institute of Forestry 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 Forestry Chronicle is the property of Canadian Institute of Forestry 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.)

This study explored the key influencing factors during the flaking process of yellow birch (Betula arneghaniensis brittori) wood strands with the aim of achieving energy efficiency, improving utilization of wood resources and enhancing wood strand quality by optimizing parameters and flaking processes of the disc flaker. The impact of disc flake knife rake angle, clearance angle, knife projection, counter knife angle, wood temperature, flaking direction, and wood flaking height on the production process of yellow birch wood strands were discussed. Birch wood strand length distribution and tensile strength were evaluated as the indicators of wood strand flaking quality, while strand curl index and flaking energy consumption during the cutting process were used to evaluate the production control of high-quality yellow birch wood strands.The results showed that longitudinal flaking can obtain better wood strand quality, and increasing the wood temperature and counter knife angle can effectively improve it as well. However, the increase of counter knife tingle resulted in more energy consumption. This study was significant for guiding the flaking process of oriented strand board (OSB), improving the efficiency of wood resource utilization, and enhancing economic benefits. [ABSTRACT FROM AUTHOR]

Northern hardwoods are susceptible to a wide range of defects that can reduce the amount of sound wood with desirable qualities, such as the clear sapwood of sugar maple trees. Yet, the rate at which trees decline in quality due to the development of such defects has never been quantified in northern hardwood forests due to a dearth of repeat inventories that record the appearance of defects over time. As a result, it remains uncertain whether, and how, selection management reduces the probability of decline in quality. In this study, we quantify the rate at which trees decline in quality due to the development of defects, and we test several hypotheses regarding the influence of selection management on quality. Our results show that (1) the probability of decline in quality increases as trees grow larger; (2) crown dieback also increases the probability of decline in quality; (3) the probability of decline in quality is slightly lower in managed stands than in unmanaged stands, and (4) the probability of decline in quality increases with the mean annual temperature of the site. Finally, we combined our estimates of the probability of decline in quality with previous estimates of the probability of mortality to assess the overall risk associated with retaining trees of different species, sizes, and vigour profiles. The resulting metric can inform efforts to improve the management of northern hardwood forests by providing an integrated estimate of the risk that the value of a tree will be reduced, or eliminated, due to mortality or decline in quality. [ABSTRACT FROM AUTHOR]

The future health and productivity of tree species in the northern hardwood forest of eastern North America are uncertain considering changes in climate and pollution loading there. To better understand the trajectory of the northern hardwood forest, we studied the growth of three tree species emblematic of it: sugar maple (Acer saccharum Marsh), American beech (Fagus grandifolia Ehrh.), and yellow birch (Betula alleghaniensis Britton), plus a fourth species, red maple (Acer rubrum L.), whose abundance has increased in the region. We also analyzed the link between growth and several factors for 690 trees in 45 plots throughout Vermont, USA: tree age and size, site elevation, and climate and acid deposition variables. Throughout their chronologies (1945–2014), all four species exhibited increasing growth followed by plateaued growth indicative of a maturing forest. For all species, summer moisture was positively correlated with growth, summer temperature was negatively associated with growth, and winter moisture or snow were positively correlated with growth. This last association was expected for sugar maple. However, our data suggest that winter snowpack may be more broadly relevant in sustaining tree growth in a region where snow has historically insulated the soil from freezing that can damage roots and lead to reduced aboveground growth. Measures of pollution deposition were also correlated with growth for all species except American beech—a species with documented tolerance to pollutant inputs. Of the four species studied, red maple had the fewest associations with environmental variables, which suggests that it may be less susceptible to growth reductions as the climate changes. [ABSTRACT FROM AUTHOR]

• Temperate species can colonize boreal mixedwood stands especially in young stands. • When considering climate change on adult growth, climate change did not influence temperate species to colonize boreal mixedwood stands. • The specific dispersal, mortality, and juvenile growth abilities of temperate trees will determine their colonization of mixedwood boreal stands. • The ability of temperate trees to colonize mixedwood boreal stands will be higher in younger stands, with low influence of climate change. Temperate hardwood tree species may take advantage of climate change to migrate northward tracking their optimal growth and survival niches. Other factors than climate could constrain or facilitate their establishment north of their actual range, such as competitive interactions, their ability to disperse, and forest management. The objectives of this study were to model the ability of temperate tree species to colonize boreal mixedwood stands of Eastern Canada from a few temperate tree seeders, considering the effects of climate change, competitive interactions, and specific successional stages of the receiving stands. We used the individual based forest model SORTIE-ND with adult growth forced by four different projected climate change scenarios. To mimic the natural colonization of temperate trees from marginal populations eventually established by long-distance migration, we replaced a patch in the center of the simulated stands with temperate tree species, i.e., red maple, sugar maple or yellow birch. We then performed a sensitivity analysis on the parameters determining the growth, dispersal, and mortality of temperate tree species to determine which of these processes was critical to their expansion. All three temperate tree species were able to colonize the boreal stands with higher performance in younger stands, and greater colonization skills for yellow birch. At the 2100 horizon, the impact of the climate scenarios on the final basal area of temperate tree species was minor. Processes mostly driven by competition and species auto-ecology, including dispersion, mortality, and juvenile growth parameters, were the most important for the colonization capacity. Our results suggest that the expansion of temperate tree species from already established northern marginal populations would be minimally affected by climate change, and that forest management could have a more significant impact by rejuvenating boreal mixedwood landscapes. [ABSTRACT FROM AUTHOR]

This paper evaluates multi-factor, non-linear dependencies of main (FC) and normal (trust) (FN) cutting forces, from chip thickness (ap), rake angle (γF) and some strength properties, namely the compression strength parallel to wood fibers (RC∥), tensile strength perpendicular to wood fibers (RT⊥), shearing strength parallel to wood fibers (RS∥) and bending strength (RB), for three North American wood species (analyzed altogether), by opened, flat, longitudinal cutting and very low cutting speed, based on work [1]. In the analyzed relations, several strong interactions were evidenced, graphically illustrated and discussed. Although a wood density (D) and a moisture content (mc), were not taken into account in this study, very good fit was obtained. The lowest influence of the RC∥ on the FC and the FN cutting forces was observed. [ABSTRACT FROM AUTHOR]

Northern hardwoods are susceptible to a wide range of defects that can reduce the amount of sound wood with desirable qualities, such as the clear sapwood of sugar maple trees. Yet, the rate at which trees decline in quality due to the development of such defects has never been quantified in northern hardwood forests due to a dearth of repeat inventories that record the appearance of defects over time. As a result, it remains uncertain whether, and how, selection management reduces the probability of decline in quality. In this study, we quantify the rate at which trees decline in quality due to the development of defects, and we test several hypotheses regarding the influence of selection management on quality. Our results show that (1) the probability of decline in quality increases as trees grow larger; (2) crown dieback also increases the probability of decline in quality; (3) the probability of decline in quality is slightly lower in managed stands than in unmanaged stands, and (4) the probability of decline in quality increases with the mean annual temperature of the site. Finally, we combined our estimates of the probability of decline in quality with previous estimates of the probability of mortality to assess the overall risk associated with retaining trees of different species, sizes, and vigour profiles. The resulting metric can inform efforts to improve the management of northern hardwood forests by providing an integrated estimate of the risk that the value of a tree will be reduced, or eliminated, due to mortality or decline in quality.

Rising interest in using wood in non-residential multi-story building structures opens up new opportunities for utilising low-grade hardwoods. The primary objective of this study was to evaluate the geographic variation in modulus of elasticity (MOE) and modulus of rupture (MOR) of sugar maple and yellow birch wood in relation to stand and tree characteristics for two regions in New Brunswick, Canada. Mixed effects statistical models were developed to test the effects of stand, tree, and wood sample variables. A second objective was to examine geographic variation in heartwood discolouration in relation to stand and tree characteristics. Between-tree differences (trees nested within sites) accounted for 44% and 35% of the total variation in yellow birch (MOE and MOR, respectively) and for 69% and 60% of total variation in sugar maple. The fixed effects explained only a very small part for the variation in MOE and MOR in the sugar maple data (10% for MOE and 5% for MOR). For sugar maple, mechanical properties (MOE and MOR) at 50% of the radius were considerably lower than those close to the bark, but this radial variation was not noteworthy for yellow birch. Discoloured heartwood proportion had no significant effect on wood mechanical properties.

Multi-cohort forest management in northern hardwood stands may well be the best way to successfully regenerate tree species of intermediate shade tolerance, such as yellow birch (Betula alleghaniensis Britt.). The creation of large enough gaps in the canopy favors increased light availability within the opening, while soil scarification provides suitable germination seedbeds. Evidence of these methods’ success nonetheless remains mostly the purview of experimental studies rather than operational tests. In Quebec, Canada, the multi-cohort methods promoted include group selection cutting and patch cutting. The present study tested their implementation at an operational scale and over a large territory in both hardwood-dominated and mixedwood stands. We assessed their efficacy in promoting natural regeneration of commercial hardwood trees, notably yellow birch and sugar maple (Acer saccharum Marsh.). We conducted regeneration surveys at 2, 5, 10, and 15 years after harvest. Overall, group selection and patch cuttings were successful in regenerating the target species. Yellow birch, for instance, showed a mean stocking around 60% and a mean sapling density around 3400 stems ha−1 after 15 years. We compared several variables for measuring regeneration in early years, and found that the relative abundance, the stocking based on one stem per sampling unit, and the mean maximum height were good predictors of the relative presence of yellow birch and sugar maple in 15-year-old canopy openings. Using smaller sampling units (6.25 m2 rather than 25 m2) and waiting until year 5 may be more useful for making such predictions. In addition, there was an important turnover in vertical dominance in these openings. Non-commercial woody competitors were frequently dominant in early years but were often replaced by commercial hardwoods, notably yellow birch. We propose certain thresholds for assessing the success of post-harvest regeneration and for evaluating the need for a cleaning treatment.

Rhizosphere soils receive a substantial input of plant carbon (rhizosphere C flux, RCF), and therefore support larger microbial populations and higher decomposing activity compared to bulk soils. The relative difference between rhizosphere and bulk soils (rhizosphere effect) may be sensitive to the effects of soil nutrient availability on plant belowground C allocation and RCF. However, it is not known whether rhizosphere effects are similarly responsive to availability of different nutrients, such as N or P, or to a combination of N and P. We tested the effects of elevated nitrogen (N) and phosphorus (P), alone and in combination, on microbial activity and abundance in bulk and rhizosphere soils associated with two tree species, red maple and yellow birch, in young, possibly N-limited northern hardwood forests in a long-term fertilization study in New Hampshire, USA. We found that N addition increased microbial respiration, soluble inorganic N, and potential net N mineralization and nitrification, and decreased fungal abundance and fungal:bacterial ratios in red maple soils, but decreased microbial respiration, fungal abundance and the F:B ratio in yellow birch soils. Positive rhizosphere effects were observed for microbial respiration, potential net N mineralization, and microbial abundance for both tree species. Nitrogen addition suppressed rhizosphere effects on microbial activity and abundance in red maple soils but did not alter rhizosphere effects in yellow birch soils. Our results show strong effects of N and some interactions with P on soil processes, microbial abundance and rhizosphere effects in these forests. Nitrogen effects strongly depended on tree species, suggesting the importance of differential responses to nutrients between arbuscular and ectomycorrhizal associations, and indicating the importance of belowground processes to species-specific effects on C and mineral nutrient transformations. Highlights • We tested effects of elevated N and P on rhizosphere effects in two tree species. • Microbial respiration and fungi increased in response to N in red maple soils. • Microbial respiration and fungi declined in response to N in yellow birch soils. • Elevated N decreased rhizosphere effects in soils of red maple but not yellow birch. • Bacterial abundance rhizosphere effects responded to interactions of P and N. [ABSTRACT FROM AUTHOR]

Abstract: Sapwood area is an important parameter for estimating transpiration at whole‐tree and watershed scales, given that it is used for scaling up point sap flow measurements. However, its determination may be difficult, particularly for large‐diameter trees of diffuse‐porous, broad‐leaved species. By delineating only the highly conductive sapwood, electrical resistivity tomography (ERT) may be more appropriate than sapwood dyeing for estimating tree sapwood area. We compared sapwood area measurements made with ERT with those that were obtained from wood dyeing, assuming that the more adequate measure was that which was best correlated with tree leaf area. To achieve this objective, we sampled 31 sugar maple (Acer saccharum Marsh.) and 20 yellow birch (Betula alleghaniensis Britt.) trees covering a large range of tree diameters and leaf areas from one site located in eastern Canada. Also, 79 sugar maple trees were sampled in two other sites to document the estimation of tree leaf area over a large territory. The sapwood area that was determined from ERT appeared to be the best method for scaling up point sap flow measurements to whole‐tree transpiration. The predictive ability of ERT was particularly greater than that of wood dyeing when they were both measured at 1 m. If the objective is to estimate tree leaf area rather than sapwood area, the crown surface area would provide a useful substitute for the ERT method because it is rapid and easy to measure while serving a robust predictor applicable over a large territory. [ABSTRACT FROM AUTHOR]

Today, scattered disjunct stands of two temperate species, yellow birch and white pine, are present north of their continuous distributional range in southern Quebec (Canada) at topographical locations that offer protection from severe fires. This study tested whether these species had populations more numerous and widespread millennia ago when the climate was presumably warmer. Specifically, this research involved the analyses of pollen, plant macrofossils, and charcoal fragments of two sites within the western part of Quebec's balsam fir - paper birch bioclimatic domain: a forest humus deposit from a yellow birch stand (local scale), and a peatland (regional scale). Fossil data suggest that white pine was more abundant regionally between 7500 and 5000 cal. BP, before coming rare under subsequent cooler conditions. Likewise, yellow birch was more abundant regionally between 7700 and 1500 cal BP. Its subsequent decline and the local disappearance of white pine by ∼200 cal. BP may both be explained by the severe fires that occurred in recent centuries, as well as the rarity of suitable habitats for these species. The sustained presence of temperate species in mixed boreal forests is the result of the combined action of climate, natural disturbances and habitat characteristics. [ABSTRACT FROM AUTHOR]

The relation between bordering tree forest composition, seed rain and tree seedling establishment was estimated in a powerline corridor of southern Quebec (Canada). Red maple was the most important tree species in the bordering forests, accounting for nearly half of the 18 tree species found, in terms of basal area. Seeds from 10 tree species were found in the seed traps, the large majority of which being from gray birch, followed by red maple, paper birch, and white ash. A good proportion of seeds from gray birch and eastern hemlock were dispersed in winter. Seedlings from 14 tree species were sampled in the right-of-way, the large majority being from red maple and gray birch. The relation between nearby bordering tree, seed and seedling abundances varied among tree species. Seed abundance collected within a single year appeared to be poorly related to tree representation and seedling abundance, suggesting high interannual variation in seed production. Distance to seed source was weakly related to seedling establishment for some species such as gray birch. However, for many species, tree composition in the neighboring forest was a good predictor of nearby seedling establishment, implying that dispersal limitation may be an important factor in determining tree composition. [ABSTRACT FROM AUTHOR]

We carried out a study to determine if bark type could reflect the growth potential of yellow birch (Betula alleghaniensis Britt.) and sugar maple (Acer saccharum Marsh.) at the northern limit of their range in Québec, Canada (47°N, 75°W). We measured a large sample of 266 trees that ranged in size from 95 to 712 mm in diameter at breast height, on two independent study sites. Our results suggest that trees with smooth bark type had mean 5-year diameter increment 8 and 11 mm higher than trees with rough bark type, depending upon the study site. Differences in growth of 8 and 11 mm represented 85% of the overall rough bark type increment in the first site and 78% of the overall rough bark type increment in the second site. The rapid identification of a tree’s growth potential using bark type could be of great use to practitioners because it avoids the need to bore trees to collect increment cores, which injures trees and may serve as an entry point for disease. Moreover, the proposed method helps protect or release the smallest trees with high growth potential and remove trees with low growth potential. While the proposed method is valuable to practitioners operating in uneven-aged forests, its applicability still needs to be tested in even-aged forests. [ABSTRACT FROM AUTHOR]

Many second growth forests have poor regeneration and in some spatial and economic context, such as post-agricultural forests, it may be beneficial to increase tree diversity. We planted seedlings of yellow birch (Betula alleghaniensis) and bur oak (Quercus macrocarpa) in strip openings of 3, 6 and 9 m width to control light. Individual mesh sleeves were used to reduce browsing pressure but they also reduced available light for seedlings: a large mesh and a small mesh sleeves were tested in each opening. Available light for seedlings ranged from 5 to 46% of full sunlight. First year growth was almost non-responsive to all treatments for both species, but birch showed strong responses during second year. Birches in the large mesh sleeve and the 9 m opening had the largest height and diameter increments, while those in the small mesh sleeve and the 3 m opening had the smallest increments. Small mesh sleeves increased the height over stem diameter ratio for both species. Treatments affected several other morphometric variables of birch but none of the oak. More time is needed to assert if bur oak can be a candidate species for enrichment planting. We recommend strip openings of 9 m width and large mesh sleeves, for protection against deer browsing, while controlling neighbouring competition, to promote artificial regeneration of hardwood species. [ABSTRACT FROM AUTHOR]

Northern hardwood stands, notably those with American beech ( Fagus grandifolia Ehrh), sugar maple ( Acer saccharum Marsh.), and yellow birch ( Betula alleghaniensis Britton), are abundant across the forested landscapes of northeastern USA and southeastern Canada. Recent studies have reported an increasing dominance of American beech in the understory and midstory of these forests. Beech is a commercially less desirable tree species due to its association with beech-bark disease, and because it commonly interferes with the regeneration of other more desirable tree species. We examined hardwood regeneration characteristics nine years after application of a 3 × 4 factorial combination of glyphosate herbicide (0.56, 1.12, and 1.68 kg ha) and surfactant concentrations (0.0, 0.25, 0.5, and 1.0% v v) to release sugar maple regeneration from beech-dominated understories using three stands that received shelterwood seed cutting in central Maine. Measurements nine years after treatment showed that glyphosate rate increased both absolute ( AD) and relative density ( RD) of sugar maple regeneration, but not its height ( HT). In contrast, beech AD, RD, and HT were all significantly reduced with increasing glyphosate rate. Post-release browsing by ungulates and a high residual overstory basal area resulted in reduced sugar maple HT. Our results indicated that glyphosate herbicide applied in stands that have been recently shelterwood seed cut can significantly increase the abundance of sugar maple regeneration. However, subsequent browsing damage combined with the negative influence of the residual overstory cover can limit the longer-term benefit of understory herbicide treatments. Subsequent removal of the overstory and browsing-control measures may be needed to promote sugar maple regeneration over beech in similar northern hardwood stands. [ABSTRACT FROM AUTHOR]

In tolerant hardwood forests of eastern North America, multiple-aged silvicultural systems rely on advanced regeneration to restock the forests. Evaluation of the long-term influence of advanced regeneration on the mature stand is critical for improving management practices. We used a retrospective approach to evaluate the influence of advanced regeneration present at the time of harvest on the current (2012) stand structure and the quality of the growing stock. The study was carried out in partially harvested stands in northwestern New Brunswick, Canada. Trees were sampled from stands with varying degrees of harvest intensities, times since harvest, and site characteristics. Pre-existing advanced regeneration contributed the bulk of trees in the 10-19 cm diameter class across the stands. In stands with low-intensity harvest, the overstory was dominated by sugar maple ( Acer saccharum Marsh.) that originated as advanced regeneration. In stands with high-intensity harvest, however, yellow birch ( Betula alleghaniensis Britt.) pre-existing advanced regeneration dominated the overstory. The probability of sugar maple and yellow birch being acceptable growing stock peaked at a diameter at breast height (DBH) of about 30-40 cm, while other species combined peaked at a DBH of around 20-25 cm. Our results suggest that harvest intensities based on the dominant advanced regeneration composition and harvesting systems that minimize the risk of physical damage to advanced regeneration are required to achieve partial harvesting objectives. [ABSTRACT FROM AUTHOR]

We resampled a research trial 20 years after applying acidifying or liming compounds (−16 to +16 kmol(+) ha −1 of acid-neutralizing capacity [ANC]) in a northern hardwood stand. Although soil properties showed no statistical changes after this period, foliar calcium (Ca) concentrations of sugar maple ( Acer saccharum Marsh.), yellow birch ( Betula alleghaniensis Britt.) and American beech ( Fagus grandifolia Ehrh.) were still related to the treatment ANC. The three species showed distinct growth responses to treatments. Over the two decades following treatment, basal area increment (BAI) of sugar maple increased by 138% in limed plots compared with controls, while it decreased by 25% in acidified plots. The BAI of yellow birch in limed plots increased mainly during the second decade, while in acidified plots, it remained comparable to that of the controls. As for American beech, the BAI increased by 133% over two decades in acidified plots, but not significantly in limed plots. Results support the hypothesis that liming improves the foliar calcium status of these hardwood species, and that acid input: (1) leads to long-term nutritional imbalance for calcium that could explain, at least in part, the positive growth response of sugar maple and yellow birch to liming, and (2) contributes to slow the growth of sugar maple relative to that of American beech in northern hardwood stands located on acid soils in northeastern North America. [ABSTRACT FROM AUTHOR]

In the northeastern United States, tree declines associated with acid deposition induced calcium depletion have been documented, notably for red spruce ( Picea rubens Sarg.) and sugar maple ( Acer saccharum Marsh.). There is conflicting evidence concerning whether co-occurring tree species capitalized on these declines or suffered similar growth reductions and on how growth has fluctuated relative to environmental variables. We examined five species along three elevational transects on Mt. Mansfield, Vermont: sugar maple, red spruce, red maple ( Acer rubrum L.), yellow birch ( Betula alleghaniensis Britton), and balsam fir ( Abies balsamea (L.) Mill.). We found baseline differences in growth. Red maple and yellow birch had the highest growth, sugar maple and red spruce had intermediate growth, and balsam fir had the lowest growth. While some year-to-year declines were associated with specific stress events, protracted patterns such as recent increases in red spruce and red maple growth were correlated with increased temperature and cooling degree days (heat index). For most species and elevations, there was a positive association between temperature and growth but a negative association with growth in the following year. Based on our comparisons, for some species, growth at Mt. Mansfield aligns with regional trends and suggests that patterns assessed here may be indicative of the broader region. [ABSTRACT FROM AUTHOR]

This study was conducted with the aim of converting low quality hardwoods into high quality fuel pellets by using hot water as a pretreatment method. Hardwood particles from sugar maple and yellow birch trees were first pretreated with hot water at 150 °C, 175 °C and 200 °C for 30 min in a batch reactor. The solid fractions following hot water treatment were then compacted into pellets using a single pelletizer. The produced pellets exhibited a number of enhanced properties as compared to those obtained from untreated wood particles. The increases in density and energy content of pellets reached approximately 30% and 40%, respectively. Compressive strength was increased by three times or more. Results also indicated that pellets of high water resistance were obtained using material treated with hot water at a temperature of about 200 °C for both sugar maple and yellow birch wood. In addition, considerable reduction in friction in the die was observed when treated wood particles were used. [ABSTRACT FROM AUTHOR]

As the use of forest harvesting residues for energy production gains popularity, debate continues regarding the long-term sustainability of whole tree harvesting (WTH). This practice removes nutrient-rich twigs that only account for a small fraction of harvest residues, emphasising the need to develop nutrient-efficient alternatives to WTH. This study assessed N, P, K, Ca, and Mg distributions within sugar maple (Acer saccharum Marshall) and yellow birch (Betula alleghaniensis Britton) branches of various sizes in order to determine the branch diameter threshold that would represent the best compromise between the quantity of harvested biomass and nutrient losses that were generated. Quantities of nutrients that were exported with harvesting were then modelled at the stand level using different biomass harvest scenarios to explore what factors ultimately drove total quantities of nutrients exported with harvest. We found that the branch diameter threshold for biomass harvesting should be set at 2 cm for most nutrients in both tree species. An exception was Mg in yellow birch, for which the harvesting of branches larger than 10 cm would always generate larger nutrient export than gains in terms of biomass. At the stand scale, we provide evidence that the intensity of biomass harvest (i.e., the number of branch compartments harvested) is the principal factor responsible for the quantity of nutrient that is exported with harvesting. [ABSTRACT FROM AUTHOR]

A useful approach to monitor tree response to climate change and environmental extremes is the recording of long-term time series of stem radial variations obtained with precision dendrometers. Here, we study the impact of environmental stress on seasonal growth dynamics and productivity of yellow birch (Betula alleghaniensis Britton) and sugar maple (Acer saccharum Marsh.) in the Great Lakes, St Lawrence forest region of Ontario. Specifically, we research the effects of a spring heat wave in 2010, and a summer drought in 2012 that occurred during the 2005-14 study period. We evaluated both growth phenology (onset, cessation, duration of radial growth, time of maximum daily growth rate) and productivity (monthly and seasonal average growth rates, maximum daily growth rate, tree-ring width) and tested for differences and interactions among species and years. Productivity of sugar maple was drastically compromised by a 3-day spring heat wave in 2010 as indicated by low growth rates, very early growth cessation and a lagged growth onset in the following year. Sugar maple also responded more sensitively than yellow birch to a prolonged drought period in July 2012, but final tree-ring width was not significantly reduced due to positive responses to above-average temperatures in the preceding spring. We conclude that sugar maple, a species that currently dominates northern hardwood forests, is vulnerable to heat wave disturbances during leaf expansion, which might occur more frequently under anticipated climate change. [ABSTRACT FROM AUTHOR]

In the late 1980s, large forest companies began precommercial thinning (PCT) operations in young northern hardwood cutovers in New Brunswick, Canada. To provide supporting growth and yield information, an industrial experiment was established at residual stand densities of 1300, 1600, 1900, and 2200 stems ha−1. Stand responses were examined for measurements recorded at 0 (1987), 5 (1992), 10 (1997), 16 (2003), and 23 (2010) years after establishment. Average diameter at breast height, quadratic mean diameter, stand basal area, and stand total volume growth increased as stem density decreased from PCT. There were significant linear differences for many of these variables between treatments and time periods (year). No significant differences were detected in tree height between treatments. In 2010, the four PCT thinning treatments did not exhibit any differences in potential sawlogs at 2.4 m (8 ft) and 3.6 m (12 ft) lengths. Significant differences were observed for 4.9 m (16 ft) sawlogs that were produced at the least dense spacing (1300 stems ha−1). Results from this study and recommendations from the European literature suggest that value-added timber products may be produced from more intense PCT treatments than are currently being practiced on sites dominated by yellow birch (Betula alleghaniensisBritt.). [ABSTRACT FROM AUTHOR]

The traditional wood industry has gone through an important crisis over recent years due to a decline in demand for certain traditional products coupled with a decreased demand due to competing developing economies, among others. In this context, the production of high value-added products and the exploration of new markets could promote the transition to a more resilient forest industry. One of the up and coming markets involves the plant-based extracts, which can be used in several industries, such as pharmaceuticals, cosmetics and nutraceuticals. In order to better understand the potential that biorefining products from yellow birch ( Betula alleghaniensis ) have to produce high value-added extracts, this study evaluated the relationship between total phenols, major triterpenes and phytosterols content in wood and bark of the studied species and selected tree characteristics. Results showed that the majority of the studied chemical compounds were related to tree health. The wood of non-vigorous trees presented the highest total phenols content among the three vigour classes, with an average of 394.9 ± 138.6 mg GAE g −1 of oven-dry extract, while presenting the lowest β-sitosterol content (3.0 ± 0.9 mg g −1 ). The bark of moribund trees contained the lowest total phenols content (317.6 ± 46.8 mg GAE g −1 ), but the highest betulin content (6.6 ± 4.2 mg g −1 ). Variations in bark compounds were also frequently correlated with the presence of fungal fruiting bodies on the stem, being associated with lower extract values for the betulin, lupeol and lupenone. Tree vigour and the presence of sporocarps in the stem explained a significant part of the variation in the studied chemical compounds from wood and bark. A remaining unexplained variation may be attributed to stand-level conditions. [ABSTRACT FROM AUTHOR]

Past silvicultural treatments have resulted in the high-grading mixed temperate forests of Québec, Canada. Despite recognition of this issue, the low occurrence of yellow birch (Betula alleghaniensis Britton) within current stands raises questions about the potential of the species to grow and eventually constitute a high-quality forest resource. The objective of this study was to assess this potential using tree characteristics, forest structure and additional site and climatic conditions as predictors. A total of 145 trees were sampled in two areas located in the same bioclimatic zone. Lower-Saguenay-Charlevoix was chosen as an area where a restoration plan could be implemented, whereas Portneuf was selected as a reference. We used nonlinear mixed models to investigate which environmental factors are likely to influence the radial growth and stem quality of yellow birch sample trees. Our results suggest that topographic and climatic conditions, as well as the competitive environment of the trees, are important factors to consider in the evaluation of yellow birch production. Despite the limited occurrence of yellow birch, the potential for growth and quality was high in the Lower-Saguenay-Charlevoix area. For equivalent topographic, climatic, and competitive environment conditions, there was no significant difference in either radial growth or stem quality with Portneuf. We suggest that the economic interest of producing high quality timber should be used to justify the implementation of a restoration strategy in the Lower-Saguenay-Charlevoix area.

Many northern hardwood stands include several low-vigor trees as a result of past management. To restore these degraded stands, partial cuts are applied with partly validated tree classification systems that are based upon apparent stem defects. We sampled 214 sugar maple (Acer saccharum Marsh.) and 84 yellow birch (Betula alleghaniensis Britt.) trees from six sites covering the northern hardwood forest zone of the Province of Quebec, Canada. We evaluated their vigor with a four-class system, and quantified the growth efficiency index and several indices that were based solely upon radial growth. The growth efficiency index increased non-significantly with increasing tree vigor class. The five-year basal area increment (BAI-1-5) was significantly different between the lowest and highest tree vigor classes. Yet, temporal changes in BAI-1-5 helped classify correctly only 16% of high-vigor trees that became poorly vigorous 8–10 years later. Overall, these results suggest that the tree classification system is weakly related to actual tree vigor and its application likely generates few significant gains in future stand vigor. Modifying and simplifying the tree vigor system must be considered to facilitate the tree marking process that is required to improve the vigor of degraded stands.

In the context of the predicted increasing frequency of summer droughts in the northeastern deciduous forest of North America due to climate change, we investigated the acclimation capacity of yellow birch, an economically important native tree species, to soil water deficit. We carried out an integrated examination of allocation of biomass, leaf physiology, branching pattern and in situ 3D crown display. Potted seedlings were subjected to moderate soil water deficit for four consecutive months during their second growing season. Individuals under soil water deficit showed a 40% decrease in biomass accumulation but no change in the relative allocation of biomass to the different plant compartments. Net CO2 assimilation rates at leaf level decreased under water deficit (∼15%) but could not alone explain the total reduction in growth, excluding the carbon starvation hypothesis. The observed reduction in net CO2 assimilation rates was related to a decrease in stomatal conductance and chlorophyll content. STARzen (in situ silhouette to total leaf area ratio; a proxy for light interception efficiency) decreased under soil water deficit due to shifts in biomass allocation within the branch compartment from long upper axes to short bottom axes. Despite the fact that the understanding of the processes involved in growth reduction and branching pattern alteration will need more attention in future research, we conclude that under water deficit yellow birch at young stages will: (i) experience a substantial loss of growth and biomass; and (ii) acclimate through architectural plasticity rather than through changes in the relative allocation of root biomass to enhance its water management. [ABSTRACT FROM AUTHOR]

In terrestrial ecosystems, a large portion (20-80%) of the dissolved Si ( DSi) in soil solution has passed through vegetation. While the importance of this 'terrestrial Si filter' is generally accepted, few data exist on the pools and fluxes of Si in forest vegetation and the rate of release of Si from decomposing plant tissues. We quantified the pools and fluxes of Si through vegetation and coarse woody debris ( CWD) in a northern hardwood forest ecosystem (Watershed 6, W6) at the Hubbard Brook Experimental Forest ( HBEF) in New Hampshire, USA. Previous work suggested that the decomposition of CWD may have significantly contributed to an excess of DSi reported in stream-waters following experimental deforestation of Watershed 2 (W2) at the HBEF. We found that woody biomass (wood + bark) and foliage account for approximately 65% and 31%, respectively, of the total Si in biomass at the HBEF. During the decay of American beech ( Fagus grandifolia) boles, Si loss tracked the whole-bole mass loss, while yellow birch ( Betula alleghaniensis) and sugar maple ( Acer saccharum) decomposition resulted in a preferential Si retention of up to 30% after 16 yr. A power-law model for the changes in wood and bark Si concentrations during decomposition, in combination with an exponential model for whole-bole mass loss, successfully reproduced Si dynamics in decaying boles. Our data suggest that a minimum of 50% of the DSi annually produced in the soil of a biogeochemical reference watershed (W6) derives from biogenic Si ( BSi) dissolution. The major source is fresh litter, whereas only ~2% comes from the decay of CWD. Decay of tree boles could only account for 9% of the excess DSi release observed following the experimental deforestation of W2. Therefore, elevated DSi concentrations after forest disturbance are largely derived from other sources (e.g., dissolution of BSi from forest floor soils and/or mineral weathering). [ABSTRACT FROM AUTHOR]

The fuel properties of wood obtained from sugar maple (SM) and yellow birch (YB) of temperate hardwood stands located in the Province of Québec, Canada were studied to see how tree vigor affects the chemical composition and calorific value of the wood. This study focused on the physical and chemical properties of wood with the aim of using the material for the production of solid biofuels. Specific items measured included the wood's calorific values, and the levels of extractives, ash, and lignin. Changes in chemical composition were found among tree vigor classes. The low vigor trees had higher extractives, ash, and lignin contents than the vigorous trees. Total extractives ranged between 4.88 and 7.32% in SM, and between 3.35 and 5.12% in YB. Klason lignin ranged between 21.46 and 23.53% in SM, and between 18.60 and 21.51% in YB. Ash content ranged between 0.38 and 0.97% in SM, and between 0.26 and 0.47% in YB. The combined effects of higher lignin content that could contribute to a better self-bonding of particles and of higher extractives content that could facilitate the pelletization process makes the low vigor trees more suitable for conversion into solid biofuels. The higher amounts of extractives and lignin present in the low vigor sugar maple and yellow birch trees could also have a positive role in maintaining the high calorific values of this wood despite higher ash content. [ABSTRACT FROM AUTHOR]

Historical deposition of nitrogen (N) and sulfur (S) over the Eastern United States has impacted ecosystem structure and function. The potential for recovery of ecosystems is relatively uncertain, with deposition paired with future climate change contributing to this uncertainty. The impacts of N and S deposition and climate change (from 1900 to 2100) on two sugar maple-beech-yellow birch sites in the Northeastern United States were evaluated using the paired biogeochemical-vegetation response model ForSAFE-Veg at two research sites, Hubbard Brook Experimental Forest and Bear Brook Watershed. Deposition was found to be the dominant stressor, causing changes in soil acid-base chemistry, N enrichment, and shifts in understory species composition. Responses of the two sites varied due primarily to differences in buffering capacity and levels of deposition. However, at both sites, recovery of soil and plant community properties to 1900 conditions was approached only when future deposition to 2100 was returned to pre-industrial levels. Policy-based reductions in deposition generally halted further damage to soils and plants and resulted in no or only partial recovery. Increased temperatures and precipitation according to Intergovernmental Panel on Climate Change (IPCC) climate futures stimulated soil and plant response, thereby accelerating changes in plant communities and N enrichment and counteracting the acidifying impacts of N and S deposition on soil acid-base chemistry. [ABSTRACT FROM AUTHOR]

Rising interest in using wood in non-residential multi-story building structures opens up new opportunities for utilising low-grade hardwoods. The primary objective of this study was to evaluate the geographic variation in modulus of elasticity (MOE) and modulus of rupture (MOR) of sugar maple and yellow birch wood in relation to stand and tree characteristics for two regions in New Brunswick, Canada. Mixed effects statistical models were developed to test the effects of stand, tree, and wood sample variables. A second objective was to examine geographic variation in heartwood discolouration in relation to stand and tree characteristics. Between-tree differences (trees nested within sites) accounted for 44% and 35% of the total variation in yellow birch (MOE and MOR, respectively) and for 69% and 60% of total variation in sugar maple. The fixed effects explained only a very small part for the variation in MOE and MOR in the sugar maple data (10% for MOE and 5% for MOR). For sugar maple, mechanical properties (MOE and MOR) at 50% of the radius were considerably lower than those close to the bark, but this radial variation was not noteworthy for yellow birch. Discoloured heartwood proportion had no significant effect on wood mechanical properties. [ABSTRACT FROM AUTHOR]