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Copyright of Naturaliste Canadien is the property of La Societe Provancher 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.)

Forests around the world are experiencing changes due to climate variability and human land use. How these changes interact and influence the vulnerability of forests are not well understood. In the eastern United States, well‐documented anthropogenic disturbances and land‐use decisions, such as logging and fire suppression, have influenced forest species assemblages, leading to a demographic shift from forests dominated by xeric species to those dominated by mesic species. Contemporarily, the climate has changed and is expected to continue to warm and produce higher evaporative demand, imposing stronger drought stress on forest communities. Here, we use an extensive network of tree‐ring records from common hardwood species across ~100 sites and ~1300 trees in the eastern United States to examine the magnitude of growth response to both wet and dry climate extremes. We find that growth reductions during drought exceed the positive growth response to pluvials. Mesic species such as Liriodendron tulipifera and Acer saccharum, which are becoming more dominant, are more sensitive to drought than more xeric species, such as oaks (Quercus) and hickory (Carya), especially at moderate and extreme drought intensities. Although more extreme droughts produce a larger annual growth reduction, mild droughts resulted in the largest cumulative growth decreases due to their higher frequency. When using global climate model projections, all scenarios show drought frequency increasing substantially (3–9 times more likely) by 2100. Thus, the ongoing demographic shift toward more mesic species in the eastern United States combined with drier conditions results in larger drought‐induced growth declines, suggesting that drought will have an even larger impact on aboveground carbon uptake in the future in the eastern United States. [ABSTRACT FROM AUTHOR]

The formation of a single species, recalcitrant understory vegetation layer can limit tree regeneration and, in the long term, modify the composition of forests. Few studies have investigated how recalcitrant vegetation influences competition for water resources although the formation of a dense understory is likely to modify the forest water balance. In eastern North American hardwood forests, the development of a dense understory layer of American beech (Fagus grandifolia) has been observed in stands dominated by sugar maple (Acer saccharum), a phenomenon that shares many characteristics associated with recalcitrant vegetation. Given that water availability is generally negatively correlated with stand density, we hypothesized that the formation of a dense understory beech layer increased competition for water resources, thus leading to reduced water use by sugar maple trees in beech‐dominated stands. Using thermal dissipation sensors, we measured sap flux density (Fd) of two sugar maple trees at three beech‐dominated sites and three control sites. During the growing season, Fd of sugar maple trees was significantly larger at beech‐dominated sites compared to control sites, indicating a greater rate of water use by sugar maples in stands with a dense understory beech layer. We provide two hypotheses to explain our results at the tree scale: (i) reduced cover by forest floor vegetation could limit transpiration by this layer, thus allowing increased water availability to supply transpiration by overstory trees, or (ii) increased tree transpiration rate could be a mechanism to satisfy nutrient requirements in beech‐dominated stands often associated with lower soil fertility. [ABSTRACT FROM AUTHOR]

Davidsoniella virescens is so far only known in North America. However, recently in southern Poland, blackish growth consisting of fungal mycelia and sporulation structures was found on the wood of Fagus sylvatica. As a result of isolation, 17 cultures of this fungus were obtained. All cultures produced an intense sweet odor. This fungus, both in situ and in vitro, abundantly produced perithecia with long necks and asexual stage. Particularly characteristic was the production of variable endoconidia in two types of phialophores differing mainly in the width of the collarette. The nucleotide sequences for five gene fragments of representative cultures were used in phylogenetic analyses: 18S; the internal transcribed spacer regions ITS1 and ITS2, including the 5.8S gene (ITS); 28S region of the ribosomal RNA (rRNA), β-tubulin 2 (TUB2) and translation elongation factor 1-α (TEF1). Based on morphological and phylogenetic analyses, the fungus on European beech in Poland was identified as Davidsoniella virescens. The optimal temperature for radial colony growth was 20 °C. However, the differences between colony diameter at 25 °C compared to that at the optimal temperature were not statistically significant. Six D. virescens isolates were used for pathogenicity assay. They were inoculated into wounds on stems of two-year-old seedlings of Fagus sylvatica and Acer saccharum (36 seedlings of each tree species). Final evaluation was performed 4 months after inoculation. No external symptoms were observed in any A. saccharum seedling, neither in the crown nor on the stem. However, 13.9% of F. sylvatica seedlings showed wilting symptoms throughout the entire crown within 3–6 weeks after inoculation. Moreover, after 4 months on the stems of 30.6% beech seedlings, necrotic lesions with a length of 1.3 to 7.2 cm were formed, without any symptoms of wilting. The most noticeable internal symptom was the discoloration of the wood, which was observed in all inoculated seedlings of both tree species. All D. virescens isolates caused greater wood discoloration in F. sylvatica than in A. saccharum. Most of the differences found in the extent of discoloration between host plants were statistically significant. The discoloration caused by all D. virescens isolates in F. sylvatica was significantly greater than in the control. However, none of the isolates tested on A. saccharum caused significantly greater wood discoloration compared to the control. Pathogenicity tests showed that the D. virescens isolates identified in southern Poland may pose a greater threat to native European beech than to foreign sugar maple. [ABSTRACT FROM AUTHOR]

Forests play a crucial role providing ecosystem services to humans, yet many aspects of forest dynamics remain unknown. One key area is how climate change might impact reproduction of tree species. While most studies have focused on predicting tree growth, understanding how reproduction may change will be vital to forecasting future forest communities. Of particular interest is the relationship between annual growth and reproductive output, which has often been hypothesized as a trade‐off between allocating resources to growth or to reproduction. Two proposed pathways of this trade‐off, resource accumulation, that is, storage of resources over time, and resource allocation, that is, same year allocation of resources to reproduction, have been widely explored in relation to masting events. It has also been proposed that there is no internal trade‐off between the two functions, but rather there exists one or more climate variables that are intrinsically linked to both, that is, the weather hypothesis. In this study, we use 15 years of dendrochronological data and seed rain collections from forest stands at two latitudes to determine whether one or more of these strategies are taking place in two commonly occurring tree species: red maple, Acer rubrum; and sugar maple, Acer saccharum. We found evidence of a trade‐off in both species. We also found a combination of strategies was the norm, and there appeared to be evidence to also support the weather hypothesis. However, in both species, the strategy which dictated the trade‐off switched between the northern and southern regions, indicating a degree of plasticity that could be beneficial under changing environmental conditions. By identifying the ways in which growth and reproduction are connected and how these connections vary between different populations, we can gain insights into how trees allocate resources in response to changing conditions. [ABSTRACT FROM AUTHOR]

During a survey of culturable microfungi from the bark of sugar maple (Acer saccharum), Atrocalyx glutinosus and Nigrograna rubescens, two novel species of Pleosporales (Dothideomycetes) were isolated from several locations in eastern Ontario, Canada. Formal species descriptions are presented based on unique colony phenotypes and micromorphological characteristics and supported using multi-locus molecular phylogenetic comparisons with similar species. Both A. glutinosus and N. rubescens produce pycnidial asexual morphs in culture. As their names imply, under specific culture conditions, A. glutinosus excretes large amounts of the glutinous polysaccharide pullulan and N. rubescens produces a dark red naphthoquinone pigment that diffuses in the culture medium. [ABSTRACT FROM AUTHOR]

We evaluated shoot nonstructural carbohydrate (NSC) concentrations, stem wound closure, and radial growth of sugar maple (Acer saccharum Marsh.) and red maple (Acer rubrum L.) trees in a novel ice storm experiment in which five storm treatments (0, 6.4, 12.7, and 19.1 mm of radial ice accretion in 1 year and 12.7 mm of ice in two consecutive years) were applied within a mature northern hardwood forest. We tested for changes in physiology at two levels: (1) associated with plot-level ice treatments and (2) with crown damage classes of individual trees. Few differences in NSC or wound closure associated with treatment were found. Growth decreased for red maple in the medium and high treatments and sugar maple in the high treatment but no other treatments. Changes in physiology were more evident when assessed using crown damage classes. Two NSC components were elevated in sugar and red maples with high (≥50%) crown damage. Wound closure was less for red maples with high damage, and separation among damage classes was even greater for sugar maple. Red maples with moderate (<50%) and high crown damage showed gradually declining growth, whereas sugar maples with high damage showed ∼80% reduction in growth the first year after injury. [ABSTRACT FROM AUTHOR]

Wood densification is a technique to enhance wood density and hardness, presenting a promising solution to expand wood use across various applications. However, current densification methods have cost and environmental impact limitations. This project introduces a potential environmentally friendly approach involving surface chemical densification through in-situ polymerization, using carbon Michael addition reaction between biobased acrylate and malonate monomers. This reaction, conducted in mild conditions with low energy and solvent consumption, aims to enhance wood densification while minimizing environmental impact. Various malonate-acrylate systems were formulated, and were optimized based on their viscosity, conversion rate, glass transition temperature, crosslinking density, and hardness. Then, sugar maple wood samples were densified with the best formulations. Monomers with lower viscosity demonstrated higher chemical retention. Density profile and penetration depth were also higher for the samples impregnated with lower viscosity formulations, which was confirmed by scanning electron microscopy. Confocal Raman spectroscopy confirmed that formulations successfully filled lumens and vessels without reacting with the cell wall components. Brinell hardness was used to determine the hardness of natural and densified woods. One-way ANOVA data analysis showed a significant increase in hardness of densified samples compared to untreated wood; however, based on TUKEY Anova analysis, no noticeable difference was reported between impregnated samples with different formulations. Overall, results showed the potential of the Michael addition reaction in wood impregnation. [ABSTRACT FROM AUTHOR]

Sap exudation is the process whereby trees such as sugar (Acer saccharum Marsh.) and red maple (Acer rubrum L.) generate unusually high positive stem pressure in response to repeated cycles of freeze and thaw. This elevated xylem pressure permits the sap to be harvested over a period of several weeks and hence is a major factor in the viability of the maple syrup industry. The extensive literature on sap exudation documents competing hypotheses regarding the physical and biological mechanisms that drive positive pressure generation in maple, but to date, relatively little effort has been expended on devising mathematical models for the exudation process. In this paper, we utilize an existing model of Graf et al. (J Roy Soc Interface 12:20150665, 2015) that describes heat and mass transport within the multiphase gas–liquid–ice mixture in the porous xylem tissue. The model captures the inherent multiscale nature of xylem transport by including phase change and osmotic transport in wood cells on the microscale, which is coupled to heat transport through the tree stem on the macroscale. A parametric study based on simulations with synthetic temperature data identifies the model parameters that have greatest impact on stem pressure build-up. Measured daily temperature fluctuations are then used as model inputs and the resulting simulated pressures are compared directly with experimental measurements taken from mature red and sugar maple stems during the sap harvest season. The results demonstrate that our multiscale freeze–thaw model reproduces realistic exudation behavior, thereby providing novel insights into the specific physical mechanisms that dominate positive pressure generation in maple trees. [ABSTRACT FROM AUTHOR]

Background: Temperate forests of eastern North America will be increasingly affected by chronic atmospheric nitrogen deposition, elevated temperatures, and drought events that will expose trees to moisture‐stressed conditions in non‐nitrogen‐limited soils. Yet, little is known regarding the response of sugar maple‐dominated forests to moisture stress under non‐nitrogen‐limiting conditions. Aims: The objective of this greenhouse study was to analyze the effects of moisture stress on the nutrition and growth of sugar maple seedlings growing on base‐poor forest soils that were strongly fertilized with nitrogen. Methods: One‐year‐old sugar maple seedlings were grown with and without water stress on soils from a sugar maple stand that had been fertilized for 15 years at a rate of 85 kg N ha−1 y−1. Results: Decreased moisture availability decreased total, leaf, root and stem biomass, and root/stem ratio. Leaf concentrations of N, P, Ca, and Mg and root concentrations of K, Ca, and Mg were 6% to 23% significantly lower under stressed versus unstressed conditions despite no changes in N, P, K, and Mg concentrations in the soil. Only soil Ca concentration was negatively affected by the moisture stress treatment. Soil and leaf δ15N and the k‐factor (i.e., isotopic discrimination effect of 15N‐labeled sources of N between roots and soil) that was used to assess N‐use efficiency of sugar maple seedlings did not differ between water stress treatments. Conclusions: Our results indicate that decreasing root biomass of sugar maple seedlings under moisture stress in non‐nitrogen‐limiting situations would decrease their ability to take up nutrients that are necessary for growth and induce lower concentrations in leaves and roots. Expected severe drought events could substantially limit nutrient uptake capacity of sugar maple seedlings on sites that are subject to chronic atmospheric N‐deposition, which would contribute to dieback in sugar maple stands. [ABSTRACT FROM AUTHOR]

DNA methylation is critical to the regulation of transposable elements and gene expression and can play an important role in the adaptation of stress response mechanisms in plants. Traditional methods of methylation quantification rely on bisulfite conversion that can compromise accuracy. Recent advances in long‐read sequencing technologies allow for methylation detection in real time. The associated algorithms that interpret these modifications have evolved from strictly statistical approaches to Hidden Markov Models and, recently, deep learning approaches. Much of the existing software focuses on methylation in the CG context, but methylation in other contexts is important to quantify, as it is extensively leveraged in plants. Here, we present methylation profiles for two maple species across the full range of 5mC sequence contexts using Oxford Nanopore Technologies (ONT) long‐reads. Hybrid and reference‐guided assemblies were generated for two new Acer accessions: Acer negundo (box elder; 65x ONT and 111X Illumina) and Acer saccharum (sugar maple; 93x ONT and 148X Illumina). The ONT reads generated for these assemblies were re‐basecalled, and methylation detection was conducted in a custom pipeline with the published Acer references (PacBio assemblies) and hybrid assemblies reported herein to generate four epigenomes. Examination of the transposable element landscape revealed the dominance of LTR Copia elements and patterns of methylation associated with different classes of TEs. Methylation distributions were examined at high resolution across gene and repeat density and described within the broader angiosperm context, and more narrowly in the context of gene family dynamics and candidate nutrient stress genes. [ABSTRACT FROM AUTHOR]

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.)

Quantifying uncertainty is important to establishing the significance of comparisons, to making predictions with known confidence, and to identifying priorities for investment. However, uncertainty can be difficult to quantify correctly. While sampling error is commonly reported based on replicate measurements, the uncertainty in regression models used to estimate forest biomass from tree dimensions is commonly ignored and has sometimes been reported incorrectly, due either to lack of clarity in recommended procedures or to incentives to underestimate uncertainties. Even more rarely are the uncertainty in predicting individuals and the uncertainty in the mean both recognized for their contributions to overall uncertainty. In this paper, we demonstrate the effect of propagating these two sources of uncertainty using a simple example of calcium concentration of sugar maple foliage, which does not require regression, then the mass of foliage and calcium content of foliage, and finally an entire forest with multiple species and tissue types. The uncertainty due to predicting individuals is greater than the uncertainty in the mean for studies with few trees—up to 30 trees for foliar calcium concentration and 50 trees for foliar mass and calcium content in the data set we analyzed from the Hubbard Brook Experimental Forest. The most correct analysis will take both sources of uncertainty into account, but for practical purposes, country-level reports of uncertainty in carbon stocks can safely ignore the uncertainty in individuals, which becomes negligible with large enough numbers of trees. Ignoring the uncertainty in the mean will result in exaggerated confidence in estimates of forest biomass and carbon and nutrient contents. [ABSTRACT FROM AUTHOR]

Community assembly is influenced by environmental niche processes as well as stochastic processes that can be spatially dependent (e.g. dispersal limitation) or independent (e.g. priority effects). Here, we sampled senesced tree leaves as unit habitats to investigate fungal community assembly at two spatial scales: (i) small neighborhoods of overlapping leaves from differing tree species and (ii) forest stands of differing ecosystem types. Among forest stands, ecosystem type explained the most variation in community composition. Among adjacent leaves within stands, variability in fungal composition was surprisingly high. Leaf type was more important in stands with high soil fertility and dominated by differing tree mycorrhizal types (sugar maple vs. basswood or red oak), whereas distance decay was more important in oak-dominated forest stands with low soil fertility. Abundance of functional groups was explained by environmental factors, but predictors of taxonomic composition within differing functional groups were highly variable. These results suggest that fungal community assembly processes are clearest for functional group abundances and large spatial scales. Understanding fungal community assembly at smaller spatial scales will benefit from further study focusing on differences in drivers for different ecosystems and functional groups, as well as the importance of spatially independent factors such as priority effects. [ABSTRACT FROM AUTHOR]

Non-industrial wood ash may be an effective forest soil nutrient supplement but its use in Canada is largely restricted because of unknown concentrations of trace metal contaminants. Sugar maple (Acer saccharum Marshall) is particularly sensitive to low soil calcium (Ca) levels, and though maple syrup is of great economic importance in Canada, it is unknown how wood ash could affect sap chemistry. Non-industrial wood ash (NIWA; 6 Mg·ha−1) applied to experimental plots in Muskoka, Ontario was rich in Ca (27%), while metal concentrations were well below provincial regulatory limits. One-year post-application, significant increases were observed in the treated plots in the soil pH and base cations (Ca, K, and Mg) in the surface soil horizons, and metal concentrations in the litter. Sap yield in the control plots was significantly lower in the first-year post-application than in the second year, but no other differences were found. In both tapping years, sap sweetness remained similar and differences in nutrient and metal concentrations between treatments were generally small and inconsistent. Foliar chemistry remained largely unchanged 1 year following application, except for K that was twice as high in the treated plots. Ultimately, NIWA is unlikely to significantly alter sugar maple sap chemistry, indicating that it is a viable nutrient supplement that can enhance soil fertility in sugar bushes with no impact on sap sweetness. [ABSTRACT FROM AUTHOR]

Background and aims: Changes in water availability during the growing season are becoming more frequent due to climate change. Our study aimed to compare the fine-root acclimation capacity (plasticity) of six temperate tree species aged six years and exposed to high or low growing season soil water availability over five years. Methods: Root samples were collected from the five upper strata of mineral soil to a total soil depth of 30 cm in monoculture plots of Acer saccharum Marsh., Betula papyrifera Marsh., Larix laricina K. Koch, Pinus strobus L., Picea glauca (Moench) Voss and Quercus rubra L. established at the International Diversity Experiment Network with Trees (IDENT) field experiment in Sault Ste. Marie, Ontario, Canada. Four replicates of each monoculture were subjected to high or low water availability treatments. Results: Absorptive fine root density increased by 67% for Larix laricina, and 90% for Picea glauca, under the high-water availability treatment at 0–5 cm soil depth. The two late successional, slower growing tree species, Acer saccharum and Picea glauca, showed higher plasticity in absorptive fine root biomass in the upper 5 cm of soil (PIv = 0.36 & 0.54 respectively), and lower plasticity in fine root depth over the entire 30 cm soil profile compared to the early successional, faster growing tree species Betula papyrifera and Larix laricina. Conclusion: Temperate tree species show contrasting acclimation responses in absorptive fine root biomass and rooting depth to differences in water availability. Some of these responses vary with tree species successional status and seem to benefit both early and late successional tree species. [ABSTRACT FROM AUTHOR]

Stomatal density, stomatal length and carbon isotope composition can all provide insights into environmental controls on photosynthesis and transpiration. Stomatal measurements can be time-consuming; it is therefore wise to consider efficient sampling schemes. Knowing the variance partitioning at different measurement levels (i.e. among stands, plots, trees, leaves and within leaves) can aid in making informed decisions around where to focus sampling effort. In this study, we explored the effects of nitrogen (N), phosphorus (P) and calcium silicate (CaSiO3) addition on stomatal density, length and carbon isotope composition (δ13C) of sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton). We observed a positive but small (8%) increase in stomatal density with P addition and an increase in δ13C with N and CaSiO3 addition in sugar maple, but we did not observe effects of nutrient addition on these characteristics in yellow birch. Variability was highest within leaves and among trees for stomatal density and highest among stomata for stomatal length. To reduce variability and increase chances of detecting treatment differences in stomatal density and length, future protocols should consider pretreatment and repeated measurements of trees over time or measure more trees per plot, increase the number of leaf impressions or standardize their locations, measure more stomata per image and ensure consistent light availability. [ABSTRACT FROM AUTHOR]

Sugar maple (Acer saccharum) wood chips were pretreated with aqueous sodium hydroxide, sodium borohydride, and hydrogen peroxide pretreatments, and the characterization (i.e., amount, molar masses, and molar mass distributions) of the lignin dissolved during the pretreatments was performed. Of the applied pretreatments, especially borohydride pretreatments were efficient in dissolving lignin from this feedstock, as 20% to 28% of the dissolved organics were found to consist of dissolved lignin, contributing to 3.4% to 9.0% of the initial wood lignin. Corresponding values for 2.5% and 5.0% alkaline peroxide pretreatments were from 5.9% to 9.2% dissolved lignin of the total dissolved organics and from 1.1% to 3.2% of the initial wood lignin. Additionally, determined molar masses and molar mass distributions indicated that borohydride pretreatments generally led to the formation of smaller-molar-mass lignin fragments when compared to reference pretreatments and to pretreatments conducted with alkaline peroxide process, indicating more efficient lignin degradation caused by borohydride addition. For example, Mn and Mw values of the analyzed reference effluents were 54%-62% and 66%-71% higher when compared to the corresponding borohydride effluents, respectively. [ABSTRACT FROM AUTHOR]

Wood is a preferred material for constructing staircases due to its appealing aesthetic features. The use of wood, especially hardwoods such as red oak (Quercus rubra), white oak (Quercus alba), yellow poplar (Liriodendron tulipifera), and hard maple (Acer saccharum), has been the main construction material for staircases over the years. Staircase designs have evolved because of the flexibility of wood and working with specialized manufacturing machinery. A stair guard system connection must be designed to resist rotational and translational movements whenever a force is applied to the handrail. The demand for structural design values in wooden stair guards has been steadily increasing, driven by the needs of engineers, designers, builders, and end-users alike. This paper presents experimental data for four stair guard connections (post-to-rail, infill-to-footing, infill-to-rail, and rail-to-rail) encountered in a hardwood stairway handrail guard system. The data generated from this research could be useful for modeling the structural behavior of the connections. [ABSTRACT FROM AUTHOR]

Fundamental understanding of paleoecological proxies is necessary when attempting to compare, complement, or contrast two or more methods, and lack thereof may lead to erroneous conclusions. This comment addresses three such misunderstandings found in a recently published paper by Paillard et al. regarding soil macrofossil charcoal analysis (SMCA) and its relationship to lacustrine sediment analysis. The aim is to correct some misinformation associated with the following three assertions: (1) Broadleaved tree species produce fewer charcoal fragments than coniferous species. Although coniferous stands are more fire-prone, experimental burning shows that species with denser wood, that is, broadleaves, produce greater amounts of charcoal under similar fire conditions. (2) Preservation of charcoal particles is poor at the referenced study site. Once buried in the mineral soil compartment, charcoal particles remain quite stable. As such, SMCA has revealed Late Pleistocene marginal stands of broadleaved species. (3) Underestimating the importance of range-edge dynamics on the results of SMCA reconstructions. SMCA offers a stand-scale historical reconstruction that has proven well-suited to study peripheral stands and to reflect the heterogeneity of a landscape mosaic. By attempting to reconcile the SMCA (in situ) and lake sediments (ex situ) narratives, Paillard et al. missed one key aspect of comparing complementary proxies: they show different aspects of the past. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Forest Research is the property of Canadian Science Publishing 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.)

Traditionally, fine roots were grouped using arbitrary size categories, rarely capturing the heterogeneity in physiology, morphology and functionality among different fine root orders. Fine roots with different functional roles are rarely separated in microbiome‐focused studies and may result in confounding microbial signals and host‐filtering across different root microbiome compartments. Using a 26‐year‐old common garden, we sampled fine roots from four temperate tree species that varied in root morphology and sorted them into absorptive and transportive fine roots. The rhizoplane and rhizosphere were characterized using 16S rRNA gene and internal transcribed spacer region amplicon sequencing and shotgun metagenomics for the rhizoplane to identify potential microbial functions. Fine roots were subject to metabolomics to spatially characterize resource availability. Both fungi and bacteria differed according to root functional type. We observed additional differences between the bacterial rhizoplane and rhizosphere compartments for absorptive but not transportive fine roots. Rhizoplane bacteria, as well as the root metabolome and potential microbial functions, differed between absorptive and transportive fine roots, but not the rhizosphere bacteria. Functional differences were driven by sugar transport, peptidases and urea transport. Our data highlights the importance of root function when examining root‐microbial relationships, emphasizing different host selective pressures imparted on different root microbiome compartments. Summary Statement: Functionally discrete fine roots are often homogenized in microbiome studies. Here, we show that the microbial composition, potential microbial functions and the root metabolome differ with root functional type for four temperate tree species: Liriodendron tulipifera, Pinus strobus, Acer saccharum and Quercus rubra. [ABSTRACT FROM AUTHOR]

In northern hardwood forests, selection silviculture aims to remove low-vigor trees that are likely to die or grow slowly to increase the growth of the remaining high-vigor trees, particularly those afforded more exposure to direct light. However, few studies have quantified the relative importance of crown position and vigor in determining growth and mortality. In this article, we did so for the most common species, sugar maple (Acer saccharum Marsh.), and we quantified the difference in growth and mortality between each of four crown classes to determine whether fewer classes can be used to describe competition-related variation in growth. Our results show that mortality is primarily determined by vigor, competition reduces growth more than the defects used to assess vigor, and there is only a modest difference in growth between dominant and co-dominant trees, indicating that these two classes can be merged because they are effectively released, unlike trees that are surrounded by competitors. Based on these results, we conclude that stand improvement should not be prioritized over crown spacing, and that tree markers should release surrounded trees to whatever extent possible, including as many trees as possible and low-vigor trees where necessary. Study Implications : We identified three ways to balance stand improvement and crown spacing in selection-managed northern hardwood forests. First, tree markers should not only release high-vigor trees, but also low-vigor trees that will be retained. Second, tree markers should focus on releasing trees surrounded by competitors rather than dominant and co-dominant trees. Third, rather than maximizing lateral light exposure for a few select trees, tree markers should release trees to whatever extent possible, including as many trees as possible and low-vigor trees where necessary. Finally, we provide a heuristic method for classifying crown position and implementing our spacing recommendations. [ABSTRACT FROM AUTHOR]

1. Though not often examined together, both plant-soil feedbacks (PSFs) and functional traits have important influences on plant community dynamics and could interact. For example, seedling functional traits could impact seedling survivorship responses to soils cultured by conspecific versus heterospecific adults. Furthermore, levels of functional traits could vary with soil culturing source. In addition, these relationships might shift with light availability, which can affect trait values, microbe abundance, and whether mycorrhizal colonization is mutualistic or parasitic to seedlings. 2. To determine the extent to which functional traits mediate PSFs via seedling survival, we conducted a field experiment. We planted seedlings of four temperate tree species across a gradient of light availability and into soil cores collected beneath conspecific (sterilized and live) and heterospecific adults. We monitored seedling survival twice per week over one growing season, and we randomly selected subsets of seedlings to measure mycorrhizal colonization and phenolics, lignin, and NSC levels at three weeks. 3. Though evidence for PSFs was limited, Acer saccharum seedlings exhibited positive PSFs (i.e., higher survival in conspecific than heterospecific soils). In addition, soil microbes had a negative effect on A. saccharum and Prunus serotina seedling survival, with reduced survival in live versus sterilized conspecific soil. In general, we found higher trait values (measured amounts of a given trait) in conspecific than heterospecific soils and higher light availability. Additionally, A. saccharum survival increased with higher levels of phenolics, which were higher in conspecific soils and high light. Quercus alba survival decreased with higher AMF colonization. 4. We demonstrate that functional trait values in seedlings as young as three weeks vary in response to soil source and light availability. Moreover, seedling survivorship was associated with trait values for two species, despite both drought and heavy rainfall during the growing season that may have obscured survivorship-trait relationships. These results suggest that seedling traits could have an important role in mediating the effects of local soil source and light levels on seedling survivorship and thus plant traits could have an important role in PSFs. [ABSTRACT FROM AUTHOR]

Much remains unknown regarding the linkages between forest structure and microclimate as they regulate detrital decomposition. In this study, we use a factorial field experiment that included canopy gap creation and downed woody material (DW) additions conducted in a mature northern hardwood forest. Our objectives were to (1) test the individual and combined effects of canopy gaps and DW additions on detrital mass loss; (2) determine whether the factors regulating mass loss are similar among leaf litter, experimental wood stakes, and coarse DW; and (3) assess the microclimatic variables that most strongly influence mass loss of these detrital types. After three years, leaf litter mass loss within gaps, without or with DW additions, was significantly greater than that of any non-gap treatments. Mass loss of stakes was significantly greater in gaps, intermediate in gaps with DW additions, and lowest in non-gap treatments. Mass loss of wood stakes after 8 years varied by species, with aspen (Populus tremuloides) losing up to 93% and sugar maple (Acer saccharum) up to 82% of its original mass. Fourteen years following treatment, the experimental logs lost 55–70% of their original mass, with ash (Fraxinus spp.) decaying faster than maple. Gap creation and DW additions individually, but not in combination, increased mass loss of coarse DW. For most substrates tested, gaps were consistently and positively related to mass loss, with approximately 10% greater mass loss in gaps compared to non-gaps. The presence of deadwood strongly moderated litter decomposition, had minimal effect on small woody substrates in the short-term after gap creation, but was influential on longer-term decay patterns of larger DW. Predictive models for each substrate varied, though shared some similar drivers. Litter mass loss was positively correlated to increasing gap size, canopy openness, and soil moisture. Stake mass loss was positively correlated to increasing gap size and canopy openness for maple, but soil temperature for aspen. Mass loss for logs was driven by increasing DW volume and gap size for ash, but soil temperature for maple. Smaller-sized materials may be more sensitive to environmental conditions as opposed to logs for which microclimatic influence may lag or remain a minor driver for at least the initial decade of decomposition. Regardless of substrate type, the findings of this work highlight the potential for greater rates of detrital mass loss from forest systems under predicted increases in canopy disturbance rates with climate change and invasive insects and diseases. [ABSTRACT FROM AUTHOR]

Recent severe ice storms across the United States severely damaged trees resulting in extensive electrical power outages. Furthermore, trees and branches can fall on nearby roads, blocking traffic flow and reducing the safety of drivers. In this study, trees subjected to ice loads were analyzed using the finite element method and Monte Carlo simulation to develop analytical fragility curves. Two-dimensional, fractal trees were constructed with randomly generated geometric and mechanical parameters for four deciduous tree species: Acer saccharum, Tilia americana, Fagus grandifolia, and Quercus alba. Two load case scenarios were considered – with and without the effects of leaves – which were then subjected to varying ice accumulation thicknesses. The resulting fragility curves suggest that leaves have a substantial impact on tree branch damage under ice loads, which is significant because of the increase in unseasonably early ice storms due to climate change. [ABSTRACT FROM AUTHOR]

Silvicultural regeneration methods focus on manipulating the forest canopy, but success can depend on the use of site preparation to control competing vegetation, including the density of advance regeneration, and create suitable microsite conditions for germination and seedling establishment. Tip-up mounds are known to provide favorable conditions for some tree species, but the creation of tip-up mounds as a method of site preparation has scarcely been investigated. We assessed effects of artificial tip-up mounds on tree seedling composition across a gradient of regeneration methods and residual overstory densities 2–4 years post-implementation. We found that tree seedling communities on mounds in some treatments were compositionally distinct from untreated reference plots. However, no tree species exhibited a strong affinity for mounds when analyzed independently from the regeneration method, and much of the difference in composition was associated with lower dominance of maples (Acer spp. L.) on mounds. As maples are strong competitors in forests regenerated with selection systems, reduced maple competition on artificial mounds could advantage desired under-represented species and aid in natural regeneration over time. Therefore, in stands where promoting tree species diversity is desirable, implementing artificial tip-up mounds as part of a long-term strategy may be beneficial. [ABSTRACT FROM AUTHOR]

New methodologies have enabled viable sap yields from juvenile sugar maple trees. To further improve yields, a better understanding of sap exudation is required. To achieve this, the anatomy of the xylem must first be fully characterised. We examine juvenile maple saplings using light optical microscopy (LOM) and scanning electron microscopy (SEM), looking at sections cut along differing orientations as well as macerations. From this we measure various cell parameters. We find diameter and length of vessel elements to be 28 ± 8 μm and 200 ± 50 μm, for fibre cells 8 ± 3 μm and 400 ± 100 μm, and for ray parenchyma cells 8 ± 2 μm and 50 ± 20 μm. We also examine pitting present on different cell types. On vessel elements we observe elliptical bordered pits connecting to other vessel elements (with major axis of 2.1 ± 0.7 μm and minor 1.3 ± 0.3 μm) and pits connecting to ray parenchyma (with major axis of 4 ± 2 μm and minor 2.0 ± 0.7 μm). We observe two distinct pit sizes on fibres with circular pits 0.7 ± 0.2 μm in diameter and ellipsoidal pits 1.6 ± 0.4 μm by 1.0 ± 0.3 μm. We do not observe distinct pitting patterns on different fibre types. The various cell and pit measurements obtained generally agree with the limited data available for mature trees, with the exception of vessel element and fibre length, both of which were significantly smaller than reported values. [ABSTRACT FROM AUTHOR]

Aside from the larger question of which traits make introduced species invasive, there is the practical concern of understanding the ecology of established invasives. An ecological understanding of invaders allows us to better identify invasible habitats and know the advantages and disadvantages an invader holds in relation to natives. This gives insights on how the invader will interact with natives, and how it might fare over time. Throughout eastern North America Amur honeysuckle (Lonicera maackii (Rupr.) Maxim) is a notorious invader of forests and forest edges. The species inflicts harm on individual species, communities, and ecosystem functions. Lonicera appears in forests across a continuum of light conditions. It possesses considerable shade tolerance, although the extent and nature of this trait has been rarely contrasted with native species. Lonicera appears to be less abundant and slower growing under the closed canopy of the forest interior. Forests on mesic sites, especially those with closed sugar maple (Acer saccharum Marshall.) canopies or dense subcanopies have especially dim understories, perhaps posing a significant limitation on carbon gain in Lonicera. I compared the photosynthetic responses, leaf characteristics, and leaf area ratios (LAR) of Lonicera to two shade tolerant native understory shrubs, Asimina triloba Adans. (pawpaw) and Lindera benzoin Thunb. (spicebush). Lonicera had comparable light responses measured on a leaf area basis, but mass-based measurements show it is less efficient paying back carbon invested in leaf tissue. This arises because Lonicera does not adjust specific leaf mass downward to the level of Asimina and Lindera in deep shade. LAR is distinctly higher in Asimina and Lindera, suggesting higher rates of carbon gain in the native species. Because photosynthesis is only one of many other physiological, demographic, and community-level processes in play, we should not necessarily assume lesser success for Lonicera in deep shade. [ABSTRACT FROM AUTHOR]

Decades of acidic deposition and timber harvesting have depleted calcium (Ca) stocks in soils, especially at base-poor soils characterized by low base cation weathering rates. One approach to tracking Ca sources from soil is by using Ca/Sr ratios in vegetation, while 87Sr/86Sr ratios have also been used to estimate mineral weathering rates. To evaluate the uses of Ca/Sr ratios and Sr isotopes in identifying Ca sources in sugar maple (Acer saccharum Marsh.) trees, three base-poor sites on the Canadian Shield and three limestone sites in southern Ontario were sampled for Ca, Sr, and 87Sr/86Sr ratios. Higher Ca/Sr ratios in soil extracts and sugar maple tissues at base-rich sites compared with base-poor sites reflect different minerology among regions, while the Ca/Sr discrimination factor between roots and foliage indicated that internal cycling exerts a major control on Ca/Sr ratios in sugar maple. At the three off-shield sites, 87Sr/86Sr ratios in soil and tree tissues were higher than precipitation but were indistinguishable for off-shield sites. Mixing models using a 1.0 mol L−1 HCl soil extract as the weathering endmember indicated that a lower proportion of weathering Ca compared with other geochemical approaches. One potential explanation is that the extraction method dissolves more recalcitrant minerals to a greater extent than under field conditions, leading to a higher weathering rate endmember value used in the mixing model. [ABSTRACT FROM AUTHOR]

Copyright of Centrosur is the property of Instituto Corporativo Edwards Deming 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.)

An isolated sugar maple (Acer saccharum Marsh.) stand is located in the boreal forest of Abitibi, about 75 km beyond its present northern range limit. When did this relatively thermophilous tree species establish after ice retreat? Were its populations more abundant than now sometimes in the past? If so, when and how did they expand then retracted? How did the species persist in boreal forest over time? What could have been the role of fire on this stand? To answer those questions, we reconstructed the postglacial fire and vegetation history from three lacustrine sediment sequences distributed along a c. 180 km latitudinal transect from southern boreal forests to the northern portion of deciduous forests. From north to south, those are lakes Labelle, Chasseur and Fur. We explored a procedure based on pollen accumulation rates in order to detect the probable presence of sugar maple within the lakes' watershed. The procedure successfully indicates a sugar maple establishment c. 7800–5100 cal. BP at Fur, 5500–4400 cal. BP at Chasseur and c. 4000–2700 cal. BP at Labelle, in the north. At Fur, the subsequent sugar maple expansion happened 1 to 2 thousand years after establishment, during colder and moister climatic conditions favoring Pinus strobus L. replacement by Betula spp. c. 6000–5000 cal. BP. Sugar maple establishment, persistence or expansion is apparently not linked to a change in fire activity at Fur and Chasseur, but at Labelle, the species was more abundant during periods of shorter fire return intervals from 2000 to 500 years ago. Our study suggests that northern (Chasseur and Labelle) sugar maple establishment and possible expansion was probably more controlled by a complex interaction of inhibition and facilitation dynamics than by climate alone, a process reliant on the dominant vegetation's composition and structure. [ABSTRACT FROM AUTHOR]

Aims: Climate change is expected to shift climatic envelopes of temperate tree species into boreal forests where unsuitable soils may limit range expansion. We studied several edaphic thresholds (mycorrhizae, soil chemistry) that can limit seedling establishment of two major temperate tree species, sugar maple (arbuscular mycorrhizal, AM) and American beech (ectomycorrhizal, EM). Methods: We integrate two field surveys of tree seedling density, mycorrhizal colonization, and soil chemistry in montane forests of the Adirondack and Green Mountains (Mtns) in the northeastern United States. We conducted correlation and linear breakpoint analyses to detect soil abiotic and biotic thresholds in seedling distributions across edaphic gradients. Results: In the Green Mtns, sugar maple seedling importance (an index of species relative density and frequency, IV) declined sharply with low pH (< 3.74 in mineral soil) and low mycorrhizal colonization (< 27.5% root length colonized). Sugar maple importance was highly correlated with multiple aspects of soil chemistry, while beech was somewhat sensitive to pH only; beech mycorrhizal colonization did not differ across elevation. Mycorrhizal colonization of sugar maple was positively correlated with soil pH and conspecific overstory basal area. In the Adirondacks, sugar maple importance, but not beech, plateaued above thresholds in soil calcium (~ 2 meq/100 g) and magnesium (~ 0.3 meq/100 g). Conclusions: The establishment of sugar maple, but not beech, was impeded by both biotic and abiotic soil components in montane conifer forests and by soil acidity in temperate deciduous forests. These differences in species sensitivity to edaphic thresholds will likely affect species success and future shifts in forest composition. [ABSTRACT FROM AUTHOR]

Bacteria from the leaf surface and the leaf tissue have been attributed with several beneficial properties for their plant host. Though physically connected, the microbial ecology of these compartments has mostly been studied separately such that we lack an integrated understanding of the processes shaping their assembly. We sampled leaf epiphytes and endophytes from the same individuals of sugar maple across the northern portion of its range to evaluate if their community composition was driven by similar processes within and across populations differing in plant traits and overall abiotic environment. Leaf compartment explained most of the variation in community diversity and composition across samples. Leaf epiphytic communities were driven more by host and site characteristics than endophytic communities, whose community composition was more idiosyncratic across samples. Our results suggest a greater importance of priority effects and opportunistic colonization in driving community assembly of leaf endophytes. Understanding the comparative assembly of bacterial communities at the surface and inside plant leaves may be particularly useful for leveraging their respective potential for improving the health of plants in natural and anthropized ecosystems. [ABSTRACT FROM AUTHOR]

With global change already enhancing drought frequency and severity, there is a critical need to determine if temperate forests will continue to act as carbon (C) sinks. The degree to which belowground strategies sustain tree growth under water stress remains uncertain. We examined differences between two temperate forest tree species in their belowground response to experimentally reduced precipitation over three years. We chose trees that are dominant in temperate forests and have different belowground resource acquisition strategies. We tested our hypothesis that in response to reduced precipitation, sugar maple trees would reduce belowground C investment while oak trees would show resiliency belowground. We found that oak trees maintained belowground C investment at the same level, likely reflecting an ability to leverage a higher baseline level of investment to enhance water and nutrient uptake. By contrast, sugar maple trees initially responded with increased investment in roots and mycorrhizae, but mycorrhizal colonization faded over time. Moreover, the treatment reduced rhizodeposition belowground by sugar maple trees, suggesting that the belowground C investment we observed does not lead to increased mobilization of nutrients. Our findings indicate that there are species specific responses of C investment in roots, mycorrhizae, and rhizodeposits to reduced precipitation. [ABSTRACT FROM AUTHOR]

One of the principal inputs of organic matter to forest soils is turnover of tree fine roots, but the process of decomposition of fine root litter and its conversion into stable soil organic matter (SOM) has received limited study. We labeled fine roots of sugar maple (Acer saccharum Marsh.) with 13C and traced the label for 7 years into four contrasting soils to improve understanding of this process. After 7 years we recovered an average of 8.9% of the 13C label, with about two-thirds recovered as coarse particulate organic matter and one-third in microaggregates and on silt and clay particles. No differences in 13C recovery were detected between 1–2 and 3–4 order fine roots. Most of the 13C in microaggregates (53–250 µm, 58%) was occluded within macroaggregates, and the recovery in this fraction increased significantly from year 2 to 7, illustrating the role of fine root detritus in the formation of microaggregates. This process was most pronounced in the A horizon of a higher pH soil (pH = 5.5) with high iron oxide content. Conversely, the lowest 13C recovery in this fraction was observed in the A horizon of an acidic, fine-textured Inceptisol (Cambisol—World Reference Base). We estimate that annual input into relatively stable fractions of SOM represents about 14% of the total annual accumulation in these fractions; thus, our results support recent evidence that fine root litter is only a moderate contributor to stable SOM in acid temperate forest soils. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Host affiliation and entomopathogenic infections play a major role in shaping population dynamics of the forest tent caterpillar (FTC), Malacosoma disstria Hübner (Lepidoptera: Lasiocampidae). The effect of these individual factors has been studied, but it is unknown whether interactions between these factors significantly impact FTC life history traits. In the laboratory, we investigated a tritrophic interaction among larval diet, larval microsporidian infection, and FTC life history traits. Larvae were reared on foliage of trembling aspen, Populus tremuloides Michx (Malpighiales: Salicaceae) or sugar maple, Acer saccharum Marshall (Sapindales: Sapindaceae), or an artificial diet. Natural levels of microsporidian infection were assessed through microscopy and categorized as none (0 spores), low (1–100 spores), or high (>100 spores). Microsporidian infection and larval diet individually, but not interactively, impacted FTC life history traits. Moths with high infection had smaller wings, but infection did not increase the probability of wing malformations. Wings of FTC reared on fresh maple foliage were significantly smaller, had a higher probability of wing malformation, and a lower likelihood of cocoon production than FTC reared on other diets, but displayed higher overall survival. While microsporidian infection did not influence FTC-diet interactions, we provide further evidence on how these main effects may individually contribute to shaping FTC adult life history traits, and, ultimately, cyclical population dynamics. Future research should consider how larval mortality, distinct infection levels, and geographical source of FTC populations affect this tritrophic interaction. [ABSTRACT FROM AUTHOR]

Glycobius speciosus (Say) was studied in New York State to elucidate poorly known aspects of its biology. Head capsule size from excavated larvae coupled with gallery lengths measured at the time of excavation was used to characterize larval development. Partial life tables indicated nearly 20% of G. speciosus survive to adulthood. Larvae experienced 30% of their mortality during early development, 27% during mid-larval development, and 43% during late larval development. Predation by hairy woodpeckers, Dryobates villosus (Linnaeus) (Piciformes: Picidae), the only unambiguous source of mortality, accounted for 43% mortality in naturally infested trees located and followed 2004–2009, and 74% late instar mortality. One parasitoid, Dolichomitus irritator (Fabricius) (Hymenoptera: Ichneumonidae), was recovered from a single larva. Beetles emerged between 316 accumulated DD (base 10 °C) and 648 DD. Males emerged prior to, or simultaneously with, females and lived longer. Female fecundity averaged 41.3 ± 6 eggs. Larval eclosion occurred 7–10 days after oviposition. Non-functional ovipositors observed in 16% of females represented an appreciable reproductive loss. In 77% of infested trees 1 oviposition site was located and in 70% of oviposition sites examined only 1 or 2 larvae successfully eclosed, penetrated the bark to the phloem-xylem interface, and began feeding. Beetles preferred southern and eastern aspects for oviposition which occurred preferentially on the lower bole (<20 cm). Male beetles had longer and wider antennae than females, pronotal pits containing gland pores, and a straight to concave posterior margin of the terminal sternite compared to the more rounded margin of females. [ABSTRACT FROM AUTHOR]

Copyright of Megadrilogica is the property of Megadrilogica 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.)

Few previous studies have described the patterns of leaf characteristics in response to nutrient availability and depth in the crown. Sugar maple has been studied for both sensitivity to light, as a shade-tolerant species, and sensitivity to soil nutrient availability, as a species in decline due to acid rain. To explore leaf characteristics from the top to bottom of the canopy, we collected leaves along a vertical gradient within mature sugar maple crowns in a full-factorial nitrogen (N) by phosphorus (P) addition experiment in three forest stands in central New Hampshire, USA. Thirty-two of the 44 leaf characteristics had significant relationships with depth in the crown, with the effect of depth in the crown strongest for leaf area, photosynthetic pigments and polyamines. Nitrogen addition had a strong impact on the concentration of foliar N, chlorophyll, carotenoids, alanine and glutamate. For several other elements and amino acids, N addition changed patterns with depth in the crown. Phosphorus addition increased foliar P and boron (B); it also caused a steeper increase of P and B with depth in the crown. Since most of these leaf characteristics play a direct or indirect role in photosynthesis, metabolic regulation or cell division, studies that ignore the vertical gradient may not accurately represent whole-canopy performance. [ABSTRACT FROM AUTHOR]

Aim: Many tree species distribution models use black‐box machine learning techniques that often neglect interpretative aspects and instead focus mainly on maximizing predictive accuracy. In this study, we outline an interpretative modelling framework to gain better ecological insights while mapping abundance patterns of six North American species. Location: Continental United States and Canada. Methods: We develop an innovative procedure using regression trees by stabilizing variance, and mapping dominant rules which we term 'optimized regression tree bagging for interpretation and mapping' (ORTBIM). We apply this technique to understand ecological features influencing the abundance patterns of three eastern (Pinus strobus, Acer saccharum and Quercus montana), and three western (Picea engelmannii, Pinus ponderosa and Pseudotsuga menziesii) tree species in North America. For these species, we assess and map the dominant climate–terrain interactions that partly determine abundance patterns in the eastern and western regions. In the process, we examine the role of varying responses and scales and explore finer‐scale species climate–terrain niches and non‐linear relationships. Results: Our study emphasizes the prominent role of elevation and heat–moisture variables in the west and the greater importance of seasonal precipitation and seasonal temperature in the east. The abundance patterns under future climate (SSP5‐8.5) show climate–terrain habitats shifting northward and westward into Canada and Alaska for the eastern species, and predominantly north‐westward for the western species. Conclusion: Our interpretative modelling framework can be used to gain a more comprehensive understanding of the abundance patterns across the full species range, formulate better predictive models and facilitate improved management practices under climate change. [ABSTRACT FROM AUTHOR]