Sugar Maple Research Articles

Partial Structural Characterization of Complex Polysaccharide Isolated from Sugar Maple (Acer saccharum Marsh) Bark and its Anti-Inflammatory Activity

The rationale of the present novel research was to report the properties of a major complex polysaccharide from an aqueous extract of sugar maple bark obtained after catalytic organosolv pulping of the maple bark, which impacted the chemical composition of residual liquor. By using such an aqueous extract of bark, a complex polysaccharide was obtained through ultrafiltration, followed by gel filtration on Sephadex G-50, which was named WSF-3, as the third eluted polysaccharide sub-fraction. Partial polymer and structural characterization revealed that WSF-3 had an average molecular weight of 21.5 kDa and consisted of a backbone of glucose residues (87.2%) linked together by α-(1 → 6) glycosidic bonds. The presence of galactose (9.8%) and rhamnose (3.1%) units may represent polysaccharide impurities as their structures have not been confirmed belonging to the glucan structure. If this was the case, WSF-3 could be similar to dextran, polysaccharide previously reported in sugar maple sap. An anti-inflammatory assay indicated that WSF-3 along with WE and its polysaccharide-rich fraction, all at 100 μg/mL, inhibited TNF-α production in LPS-stimulated RAW 264.7 cells. These results indicate that the concentrated WSF-3 was responsible, at least in part, for the anti-inflammatory effect of WE, suggest that WSF-3 could have therapeutic implications in the treatment of inflammation and inflammatory-related diseases.

Experimental Warming of Typically Acidic and Nutrient-Poor Boreal Soils Does Not Affect Leaf-Litter Decomposition of Temperate Deciduous Tree Species

Ongoing rapid climatic changes are expected to modify the structure, composition, and functioning of forest ecosystems. Studying the influence of such changes on biogeochemical processes is thus crucial for a fuller understanding of forest response to climate change. In a temperate forest of Quebec, Canada, we emulated climate change by warming the acidic, nutrient-poor, and dry soils of two mixedwoods by 3 to 4 °C using heating cables. Leaf-litter mass loss of the local red maple, sugar maple, large-tooth aspen, and American beech were monitored to assess the ability of these tree species to condition boreal soils in the context of their northward migration under climate change. We hypothesized that decomposition rates of all leaf-litter types would be decreased equally by warming due to a drying effect of the soil and its surface, which is detrimental to microbial biomass and activity. Our results suggest differences in decomposition rates between tree species as follows: sugar maple > red maple ≥ American beech = large-tooth aspen. There was no indication of a slower turnover in these marginal soils compared to other studies conducted on typical hardwood soils. Moreover, no difference in litter mass loss was detected between treatments, likely due to a drying effect of the soil warming treatment. Results imply that climate change has a marginal influence on leaf-litter dynamics of temperate tree species on soils that are typical of the boreal forest. However, some variables that could play an important role on litter decomposition in the context of climate change were not measured (e.g., plant phenology, understory composition and density, microbes) and thus, uncertainties remain. The soil drying effect by warming also needs to be further documented and modeled. The study year was characterized by significant periods of water stress but was not considered an exceptional year in that regard. It would be relevant to test for leaf-litter dynamics during dry and wet summers and verify again our initial hypothesis of decreased leaf-litter decomposition rates due to soil warming/drying.

Genotypic variation in water relations and gas exchange of urban trees in Detroit, Michigan, USA

Increasing tree species diversity has become a key underpinning for communities to improve resilience of urban and community forests. Increasingly, urban forestry researchers are examining physiological traits to aid in selecting trees for urban sites. Knowledge of physiological responses also has implications for understanding species’ resilience to increased stresses associated with climate change. Here, we compare growth, leaf SPAD chlorophyll index, water relations, and gas exchange of seven genotypes of shade trees planted in two locations in downtown Detroit, MI, USA. Genotypes included Redpointe® maple (Acer rubrum ‘Frank Jr.’), Flashfire® maple (Acer saccharum ‘JFS-Caddo2′), Pacific Sunset® maple (Acer truncatum x platanoides ‘Warrenred’), Emerald City® tulip tree (Liriodendron tulipifera ‘JFS-Oz’), Chanticleer® pear (Pyrus calleryana ‘Glen’s Form’), swamp white oak (Quercus bicolor), and Emerald Sunshine® elm (Ulmus propinqua ‘JFS-Bieberich’). Trees were planted in either Lafayette Plaisance Park (Park), a large urban greenspace, or on the median of St. Aubin Avenue (Median), a nearby major thoroughfare. Tree height growth and leaf SPAD index were higher for trees planted in the Park location than on the Median. However, genotypic variation was larger than the effects of location or the interaction of Genotype × Location for most traits. Across measurement dates, midday leaf water potential was lowest for Pyrus trees and highest for Ulmus and Liriodendron trees. Pyrus and Quercus trees had relatively high rates of net photosynthesis (A) and stomatal conductance (gs) while Liriodendron, Acer saccharum, and Ulmus trees had low rates of A and gs. Liriodendron trees closed their stomata rapidly as leaf water potential (Ψw) declined (isohydric response), while Pyrus and Quercus trees maintained gs across a range of leaf Ψw (anisohydric response). Liriodendron trees also had the highest relative growth rates, suggesting that drought stress avoidance through isohydry is a viable drought tolerance mechanism in urban trees.

Ovipositional behaviour and larval performance ofTrichoferus campestris(Faldermann) (Coleoptera: Cerambycidae) on cut branches of four North American tree species

AbstractVelvet longhorned beetleTrichoferus campestris(Faldermann) (Coleoptera: Cerambycidae) is native to Asia. It is reported to be polyphagous in its native range, but hosts have not been screened in its introduced range in the United States.We conducted choice and no‐choice host experiments. For choice assays, gravidT. campestrisoviposited freely on cut branches of four tree species:Juglans nigra,Malus domestica,Acer saccharum, andPinus strobus. We investigated oviposition between apple branches with and without cankers. Half of the choice trials underwent winter temperatures.For no‐choice assays, eggs were placed on cut branches of these same four species. Half of these branches were later dissected to measure larval development. The rest were exposed to winter temperatures andT. campestrisemergence was quantified.Overall,Trichoferus campestrisoviposition and development occur more readily onJ. nigraandM. domesticathan onA. saccharumorP. strobus. The insect oviposited more on cankered than uncankered apple wood. Cold exposure during an overwintering period benefitted insect development in adults.The insect's high degree of polyphagy and ability to reproduce in dry wood has likely facilitated its establishment in multiple locales around the world.

Maple & Rosemary by Alison James

Reviewed by: Maple & Rosemary by Alison James Sarah Sahn James, Alison Maple & Rosemary; illus. by Jennifer K. Mann. Porter/Holiday House, 2023 [48p] Trade ed. ISBN 9780823449675 $18.99 E-book ed. ISBN 9780823455140 $11.99 Reviewed from digital galleys R* 5-9 yrs Shel Silverstein’s The Giving Tree is a beloved childhood classic, but its allegory of boundless parental sacrifice has not aged especially well and has prompted a number of parodies and revisions, such as Topher Payne’s The Tree Who Set Healthy Boundaries. While this month’s Big Picture, Maple & Rosemary, doesn’t explicitly reference The Giving Tree, it, too, feels like an update to the classic—rich, warm, and bittersweet in contrast to Payne’s pointed satire, with a wisdom that will speak to both young readers and their caretakers. Maple is a sugar maple, “lovely and sweet” but lonely, as she’s the only deciduous tree in a stand of cedar and pine, and the evergreens aren’t interested in getting to know a tree that sheds its leaves. When little Rosemary climbs Maple’s branches to cry because the other children at school are mean to her, both girl and tree find the friendship they’ve been yearning for. Rosemary shares her troubles and school lessons in the shelter of Maple’s leaves, and Maple shows Rosemary the lifecycle of butterflies and rains seeds down around her. Rosemary inevitably grows up and stops visiting, leaving a desolate Maple wishing for “the winter to cover her with snow and never ever melt.” The book lingers here, with minimal text as seasons pass, visually immersing readers into the forest setting and its quiet solitude, as more trees sprout and various animals come and go. Rosemary’s eventual return as a young woman is greeted with warmth and then glee as she reveals a gift to Maple, hanging a wooden swing from Maple’s branches. She’s a teacher now, and soon she brings the children from her class to play, giggling on the swing and delighting Maple. When that, too, ends, an elderly Rosemary visits alone to read to Maple, and Maple drops a branch for her to use as a walking stick. “You have always been here for me,” Rosemary says, and Maple understands Rosemary is part of her, too, “as real as roots.” James’ gentle, straightforward prose is striking in its simplicity, capturing the strangeness and joy of new friendship as well as the ache of loneliness. During Rosemary’s long absence, “year after year, winter swept into summer. Leaves bloomed, burned, then fell.” The quiet tone invites contemplation of the power of friendship, making space for complexity as Maple and Rosemary each grow in each other’s absence and find an even more profound connection in their later years. It’s a thoughtful portrayal that honors the way relationships change over time; where Rosemary goes to Maple for comfort as a child, she in turns offers the tree care as an adult, and neither is diminished in service to the other. [End Page 181] Mann’s sweeping, digitally collaged landscapes glow in a warm welcome to young viewers, with a combination of painterly and penciled textures bringing depth. There is a sense of motion in Maple’s leaves and the grass that surrounds her, as if rustling on a gentle breeze, while Rosemary’s simple, childlike figure is more kinetic, leaping, climbing, and playing in montage-like scenes that capture the energy of their daily time together. Mann uses color and image repetition skillfully, with the dominant green-gold palettes of summer contrasted by both the fiery autumn hues and the white and brown stillness of winter. Each image centers Maple, sometimes alone, sometimes surrounded by children, as the seasons change around her. Rosemary stands out in clothes that match the crimson, red-orange, and dusty yellow of Maple’s autumn leaves, emphasizing her vibrancy but also subtly suggesting the impermanence of all living things. Adult readers will anticipate Rosemary’s death from the winter setting of the friends’ final scene, but the book only implies it, focusing instead in its final pages on Maple as she contemplates their friendship...

Four Elegies

Four Elegies

Quantifying the Probability of Decline in Quality: Implications for Selection Management in Northern Hardwood Forests

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.

Foliar chemical composition and respiration rates of sugar maple (Acer saccharum) and American beech (Fagus grandifolia) trees across a gradient of soil acidification

Foliar chemical composition and respiration rates of sugar maple (Acer saccharum) and American beech (Fagus grandifolia) trees across a gradient of soil acidification

Effects of flood duration on seedling survival and growth of potential replacement species in black ash (Fraxinus nigra Marshall) forests threatened by emerald ash borer

Within black ash (Fraxinus nigra Marshall) wetlands, black ash acts as a foundational species, resulting in high vulnerability to the invasive emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera: Buprestidae). One mitigation strategy being considered is the planting of alternative tree species to increase compositional diversity, however, there is limited understanding of how replacement tree species tolerate flooding. A greenhouse experiment was used to explore early survival and growth of eighteen tree species in response to five flooding durations (3, 6, 9, 12, or 15 weeks). Seedlings were assigned to flood tolerance groups according to their responses to the various flooding duration treatments. Taxodium distichum (L.) Rich., Ulmus americana L., and Betula nigra L. were able to survive and grow with flooding durations of up to 15 weeks. Thuja occidentalis L., Acer rubrum L., Larix laricina (Du Roi) K. Koch, Quercus bicolor Willd., and Betula alleghaniensis Britton had high survival and growth rates with flooding durations up to 6 weeks in length. Finally, Juglans nigra L. and Acer saccharum Marshall responded poorly to flooding of any duration. These results can assist managers in matching potential black ash replacement species to the hydrology of their local black ash wetlands.

Spatial patterns and climatic drivers of leaf spring phenology of maple in eastern North America

The resurgent frequency of extreme weather events and their strongly distinctive spatial patterns lead to a growing interest in phenology as an indicator of tree susceptibility. Using a long-term chronology of observations collected in situ, we predicted and investigated the spatial patterns and environmental drivers of spring leaf phenology across maple stand polygons dominated by Acer saccharum Marsh. and/or Acer rubra L. in eastern North America for 2000-2018. Model' calibration was based on Bayesian ordinal regressions relating the timing of the phenological events' observations to the MODIS vegetation indices EVI, NDVI and LAI. DAYMET data have been extracted to compute temperature and precipitation during spring phenology. Model accuracy increased as the season progressed, with prediction uncertainty spanning from 9 days for bud swelling to 4 days for leaf unfolding. NDVI and LAI were the best predictors for the onset and ending of spring phenology, respectively. Bud swelling occurred at the end of March in the early stands and at the onset of May in the late stands, while leaf unfolding was completed at the beginning of April for the early and in mid-June for the late stands. Early and late stands polarized towards a south-west-north-east gradient. In the south-western regions, which are also the driest, total precipitation and minimum temperature explained respectively 73 % and 25 % of the duration of spring phenology. In the north-eastern regions, precipitation and minimum temperature explained 62 % and 26 % of the duration of spring phenology. Our results suggest high vulnerability to extreme weather events in stands located in the south-west of the species distribution. The increasing incidence of drought in these locations might affect spring phenology, decreasing net primary production in these stands. Warmer nights might expose the buds to late frosts, events that are expected to become more frequent in the coming years.

Eight decades of compositional change in a managed northern hardwood landscape

We analyzed over 8 decades of change in forest composition (represented by species proportion of basal area) and size class from more than 400 permanent plots located on the Bartlett Experimental Forest in the White Mountains of New Hampshire. These data represent one of the longest-term landscape-scale records of forest change based on permanent plots in North America. We analyzed the plots based on elevation class, land type indicating assumed successional direction (grouped into coniferous and deciduous), and inventory period within managed and unmanaged portions of the forest. An ongoing shift from small- to large-diameter stems is clear across all species, in response to the overall aging of the forest following exploitative harvesting in the 19th century. Major compositional changes include a continuing decline in shade-intolerant species (paper birch and aspen), along with the mid-tolerant yellow birch. An increase in red maple abundance through the early 1990s has leveled off or reversed. Among shade-tolerant species, increases in beech and red spruce were largely consistent with assumed land type on unmanaged plots, but heavy marking against diseased beech on managed plots restricted increase of that species. Sugar maple declined in abundance except where silvicultural intervention helped maintain it. By contrast, eastern hemlock showed a continuing expansion at all elevations below 600 m. The data continue to show little or no evidence of upward migration of species, despite evidence of recent regional change in climate. However, the BEF is poised for substantial changes when emerald ash borer and hemlock woolly adelgid, both of which are known to infest nearby areas, do arrive.

Visual assessment of tree vigour in Canadian northern hardwood forests: The need for a simplified system

Northern hardwood forests include many degraded stands dominated by trees of low vigour due to past management. To facilitate the implementation of stand improvement, several classification systems have been developed to help tree markers visually assess tree vigour at time of harvest based on the presence of individual defects. Because very few studies have tried to empirically validate such systems, it remains uncertain whether many of these defects should be used to guide the tree marking process. In this study, we assess tree vigour using repeated measurements collected as part of long-term silvicultural trials conducted in 615 permanent plots throughout the northern hardwood forest of Quebec, Canada. We aimed to determine whether the defects that are commonly used for classification have a significant effect on both growth and survival over three decades, using 9,338 sugar maple and 1,316 yellow birch trees. We also conducted a retrospective analysis to quantify the rate at which vigorous trees develop defects. Our results confirmed that crown dieback is by far the best indicator of vigour for both sugar maple and yellow birch trees. Conversely, our results revealed that stem defects did not contribute much to explaining the variation in vigour, except for the presence of cankers and fungi, which had modest effects. Consequently, stem defects should not be used as the main indicators of tree vigour, and existing classification systems should be simplified by reducing the number of stem defects under consideration for this purpose. Lastly, our results showed that the rate that vigorous trees develop defects increased with increasing diameter, more so than the probability of surviving. Thus, assessing the risk of retaining large trees should not only be based on survival, but also on the risk of developing defects that reduce the growth and value of trees.

Tree variability limits the detection of nutrient treatment effects on sap flux density in a northern hardwood forest.

The influence of nutrient availability on transpiration is not well understood, in spite of the importance of transpiration to forest water budgets. Soil nutrients have the potential to affect tree water use through indirect effects on leaf area or stomatal conductance. For example, following addition of calcium silicate to a watershed at Hubbard Brook, in New Hampshire, streamflow was reduced for 3 years, which was attributed to a 25% increase in evapotranspiration associated with increased foliar production. The first objective of this study was to quantify the effect of nutrient availability on sap flux density in a nitrogen, phosphorus, and calcium addition experiment in New Hampshire in which tree diameter growth, foliar chemistry, and soil nutrient availability had responded to treatments. We measured sap flux density in American beech (Fagus grandifolia, Ehr.), red maple (Acer rubrum L.), sugar maple (Acer saccharum Marsh.), white birch (Betula papyrifera Marsh.), or yellow birch (Betula alleghaniensis Britton.) trees, over five years of experiments in five stands distributed across three sites. In 2018, 3 years after a calcium silicate addition, sap flux density averaged 36% higher in trees in the treatment than the control plot, but this effect was not very significant (p = 0.07). Our second objective was to determine whether this failure to detect effects with greater statistical confidence was due to small effect sizes or high variability among trees. We found that tree-to-tree variability was high, with coefficients of variation averaging 39% within treatment plots. Depending on the species and year of the study, the minimum difference in sap flux density detectable with our observed variability ranged from 46% to 352%, for a simple ANOVA. We analyzed other studies reported in the literature that compared tree water use among species or treatments and found detectable differences ranging from 16% to 78%. Future sap flux density studies could benefit from power analyses to guide sampling intensity. Including pretreatment data, in the case of manipulative studies, would also increase statistical power.

No stress memory pattern was detected in sugar maple and white spruce seedlings subjected to experimental droughts

AbstractAn increase in the frequency and magnitude of drought events threatens the health of forests and the economic, ecological, and societal services they provide. It has been widely demonstrated that trees undergoing a succession of stresses may accumulate lesions that in turn lead to a decrease in their vigor and eventually to death. However, recent studies have shown that a nonlethal stress should also initiate a stress memory, which triggers a faster and stronger plant defensive response when a new stress occurs. Although this mechanism is well understood in many herbaceous plants, a better understanding in trees is needed. The aim of our study was to explore the capacity of two forest tree species to develop a stress memory. A greenhouse experiment was conducted to evaluate the tree seedlings' vigor after one or two consecutive droughts separate from a rehydration period during the same growing season. No stress memory pattern was observed for the two tree species as, on the contrary, we even observed a stress accumulation pattern in sugar maple. It remains possible that some individuals in our study developed stress memory, but that we were not able to detect it. The fine‐tuning of experimental parameters and the conducting of longitudinal studies would be helpful to detect individual capacity in stress memory activation.

Growth trends and environmental drivers of major tree species of the northern hardwood forest of eastern North America

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.

Is foliar tissue drying and grinding required for reliable and reproducible extraction of total inorganic nutrients? A comparative study of three tissue preparation methods.

In response to abiotic and biotic stress or experimental treatment(s), foliar concentrations of inorganic nutrients and metabolites often change in concert to maintain a homeostatic balance within the cell's environment thus allowing normal functions to carry on. Therefore, whenever possible, changes in cellular chemistry, metabolism, and gene expressions should be simultaneously evaluated using a common pool of tissue. This will help advance the knowledge needed to fill the gaps in our understanding of how these variables function together to maintain cellular homeostasis. Currently, foliar samples of trees for total inorganic nutrients and metabolic analyses are often collected at different times and are stored and processed in different ways before analyses. The objective of the present study was to evaluate whether a pool of wet (previously frozen) intact tissue that is used for metabolic and molecular work would also be suitable for analyses of foliar total inorganic nutrients. We compared quantities of nutrients extracted from wet-intact, dried-intact, and dried-ground tissues taken from a common pool of previously frozen foliage of black oak (Quercus velutina L.), sugar maple (Acer saccharum Marshall), red spruce (Picea rubens Sarg.), and white pine (Pinus strobus L.). With a few exceptions in the case of hardwoods where concentrations of total Ca, Mg, K, and P extracted from wet-intact tissue were significantly higher than dry tissue, data pooled across all collection times suggest that the extracted nutrient concentrations were comparable among the three tissue preparation methods and all for species. Based on the data presented here, it may be concluded that drying and grinding of foliage may not be necessary for nutrient analyses thus making it possible to use the same pool of tissue for total inorganic nutrients and metabolic and/or genomic analyses. To our knowledge, this is the first report on such a comparison.

Does the photosynthetic response of Asimina triloba to low light contribute to its competitive advantage in forest understories compared with Acer saccharum and Fraxinus quadrangulata? 1

Does the photosynthetic response of Asimina triloba to low light contribute to its competitive advantage in forest understories compared with Acer saccharum and Fraxinus quadrangulata? 1

Hydraulic integrity of plant organs during drought stress and recovery in herbaceous and woody plant species.

The relationship between root, stem, and leaf hydraulic status and stomatal conductance during drought (field capacities: 100-25%) and drought recovery was studied in Helianthus annuus and five tree species (Populus×canadensis, Acer saccharum, A. saccharinum, Picea glauca, and Tsuga canadensis). Measurements of stomatal conductance (gs), organ water potential, and vessel embolism were performed and the following was observed: (i) cavitation only occurred in the petioles and not the roots or stems of tree species regardless of drought stress; (ii) in contrast, all H. annuus organs exhibited cavitation to an increasing degree from root to petiole; and (iii) all species initiated stomatal closure before cavitation events occurred or the expected turgor loss point was reached. After rewatering: (i) cavitated vessels in petioles of Acer species recovered whereas those of P. ×canadensis did not and leaves were shed; (ii) in H. annuus, cavitated xylem vessels were refilled in roots and petioles, but not in stems; and (iii) despite refilled embolisms in petioles of some species during drought recovery, gs never returned to pre-drought conditions. Conclusions are drawn with respect to the hydraulic segmentation hypothesis for above- and below-ground organs, and the timeline of embolism occurrence and repair is discussed.

Effects of helix angle and feed per knife on the surface quality of sugar maple and black spruce boards produced by planing

ABSTRACT A conventional straight knife cutterhead and three helical knife cutterheads were tested for planing sugar maple (Acer saccharum Marsh.) and black spruce (Picea mariana (Mill.) B.S.P.) woods. The effects of helix angle and feed per knife (FK) on roughness, tactical perception, and anatomical features of the planed surfaces were evaluated. Rk and Rpk parameters were found to be more descriptive in evaluating the roughness of these woods and proved to be good indicators of tactile perception. Roughness increased as the helix angle and feed per knife increased for both wood species. Sugar maple showed smoother surface than black spruce. Surfaces planed with helical knives showed a fuzzy texture resulting from cell-wall fibrillation. For sugar maple wood, the differences in roughness between straight and 40° helical knives were small. Therefore, the latter must be preferred for planing this species. Roughness of planed black spruce also increased as helix angle increased and in this case its effect depended on FK. The straight knife produced the lowest roughness, for all studied FKs. Planing with helical knives produced higher roughness as a result of cell-wall fibrillation. This defect was more pronounced than that of sugar maple, and by far more present with helical knives of 50° and 60°. Therefore, straight knives working at low FK (1.3 mm) should be preferred for planing black spruce wood when roughness is a critical concern. Possible benefits provided by rougher surfaces planed by helical knives are discussed.

Daily timings of sap production in sugar maple in Quebec, Canada.

Global warming is affecting plant phenology, with potential consequences on the dynamics of growth reactivation of sugar maple and the timings of maple syrup production. In this study, we assess the temperatures inducing the daily reactivation or cessation of sap production. We selected 19 sugarbushes across Quebec, Canada, using a tapping method associated with the tubing system, we recorded the daily timings of onset and ending of sap production during winter and spring 2018, and we associated the hourly temperatures at each site. Sap production occurred from mid-February to the end of April, starting on average between 10 and 11 AM, and ending from 6 to 8 PM. We observed a seasonal pattern in the onset and ending of sap production during spring, with the onset showing a greater change than the ending. Onset and ending of sap production occurred mostly under temperatures ranging between -2 and 2°C. The production of sap in maple is closely related to circadian freeze-thaw cycles and occurs under nighttime and daytime temperatures fluctuating below and above 0°C. The daily lengthening of the duration of sap production mirrors the changes in the timings of freeze and thaw events and can be explained by the physical properties of the water and the physiological processes occurring during growth reactivation. The ongoing warming will result in earlier and warmer springs, which may anticipate the cycles of freeze and thaw and advance sap production in sugar maple.