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Copyright of Fire Ecology is the property of Springer Nature 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.)

Acer negundo (Boxelder) is a common tree in eastern North America. Fruits are paired samaras that mature in late summer but persist on trees for months. We examined temporal variation in predation rates by small mammals by attaching samaras to sewing bobbins in a forest in northeastern Wisconsin. We placed samaras in groups of 5 along transects and checked them regularly across 2 fall and 2 spring seasons to determine seed fates. Of the 6702 seeds, 15.26% were consumed, 81.41% were left intact, and 3.33% were aborted. Predation rates were higher in fall than in spring. Granivorous mammals did not secondarily disperse seeds but instead acted solely as seed predators. Releasing seeds over a longer period of time than other species of maples allows trees to increase seed survival by experiencing varying soil conditions and predation rates. Retained sterile fruits may act as decoys that decrease predation rates. [ABSTRACT FROM AUTHOR]

The temperate mixedwood forests of eastern North America have been managed by partial cutting for several decades. To ensure that regeneration contributes to replacing the commercial-size stems that are removed by partial cutting, forest managers need to anticipate how saplings (i.e., regenerating trees with a diameter at breast height >1.0 cm) develop in terms of number and diameter. Using up to 20 years of monitoring data from three study sites, we developed a transition matrix model to predict the future number of saplings and their diameter distribution for mixed yellow birch (Betula alleghaniensis Britton) – conifer stands. Our results show that partial cutting allowed yellow birch, red maple (Acer rubrum L.), red spruce (Picea rubens Sarg.), and balsam fir (Abies balsamea (L.) Mill.) saplings to reach merchantable size faster and in greater numbers than in untreated control plots. We also found that fewer hardwood saplings (yellow birch and red maple) than softwood saplings (red spruce and balsam fir) were required to produce 1 m2·ha−1 of merchantable basal area after 20–40 years. Finally, our model provides a tool for forest managers to predict sapling development in mixed hardwood and softwood stands over a full cutting cycle. [ABSTRACT FROM AUTHOR]

Copyright of Berichte aus dem Julius Kühn-Institut is the property of Julius Kuehn Institut 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.)

The complex effects of global environmental changes on ecosystems result from the interaction of multiple stressors, their direct impacts on species and their indirect impacts on species interactions. Air pollution (and resulting depletion of soil base cations) and biotic invasion (e.g. beech bark disease [BBD] complex) are two stressors that are affecting the foundational tree species of northern hardwood forests, sugar maple and American beech, in northeastern North America.At the Hubbard Brook Experimental Forest in New Hampshire, a watershed‐scale calcium (Ca) addition in 1999 restored soil Ca that had been lost as a result of acid deposition in a maple‐beech forest that was severely affected by BBD beginning in the 1970s. We present historic data from the reference watershed for BBD progression, 20 years of comparative forest data from the treated and reference watersheds, and tree demographic rates for the most recent decade. We hypothesized that mitigation of soil acidification on the treated watershed in the presence of BBD would favour improved performance of sugar maple, a species that is particularly sensitive to base cation depletion.We observed significant responses of seed production, seedling bank composition, sapling survival and recruitment, and tree mortality and growth to the restoration of soil Ca, indicating that acid rain depletion of soil base cations has influenced demographic rates of maple and beech. Overall, the reduced performance of sugar maple on acidified soils may indirectly favour the persistence of diseased beech trees and a greater abundance of beech vegetative sprouts, effectively promoting the chronic presence of severe BBD in the population.Synthesis. The shifting conditions created by global change have altered long‐term demographic rates and may thereby impact competitive interactions in the current centre of these species ranges and have more profound implications for species persistence and migration potential than previously anticipated. [ABSTRACT FROM AUTHOR]

Temperate tree species are expected to expand their distribution into the boreal forest in response to climate change. However, it is becoming increasingly clear that many species will experience significant setbacks in capacity to migrate due to a series of unfavourable conditions impacting their recruitment success, and thus their ability to colonize new locations.We quantify the relative influence of a series of factors important for tree seedling recruitment at range margins: propagule dispersal, substrate favourability and the influence of the local hetero‐specific species canopy composition. We hypothesized that boreal trees are responsible for priority effects that influence the establishment of temperate tree species seedlings. To do so, we analysed two recruitment stages (first‐year seedlings and older seedlings) for seven tree species: Abies balsamea (ABBA), Acer rubrum (ACRU), Acer saccharum (ACSA), Betula papyrifera (BEPA), Betula alleghaniensis (BEAL), Populus tremuloides (POTR) and Fagus grandifolia (FAGR) commonly found within the temperate‐boreal ecotone forests of northeastern North America.Overall, we found that boreal canopy trees influence the distribution of substrates, more specifically the occurrence of needle cover and decayed wood in recruitment plots. Interestingly, decayed wood was a poor substrate in almost all cases. This association between canopy and substrate led to highly unfavourable substrates that affected the seedling densities of all temperate tree species. In addition, we found that seedling dispersion was highly localized, where the mean dispersal distance of all trees occurred in close proximity of parent trees.Synthesis. Unfavourable substrates and limited mean dispersal distance of trees due to resident boreal trees generate (strong) priority effects within the temperate‐boreal ecotone. Together, these conditions promise to cause significant lags in temperate tree species migration into the boreal forest in the future. [ABSTRACT FROM AUTHOR]

Over the last century, nonnative earthworms have invaded forests of the Great Lakes region of North America. Although a growing body of scientific research has documented short-term changes associated with invasive earthworms, there is little research describing the effects of invasive earthworms over multiple decades. To investigate the long-term effects of invasive earthworms on forests, sites sampled in the past need to be classified as wormed or unwormed when originally sampled. However, this is often difficult to accomplish because field methods for sampling earthworms have only recently been developed, and the few historical permanent sites available for resampling largely do not have past information about earthworm presence or absence. Although historic sites lack data on invasive earthworm presence, many of these sites do have information about soil horizon thickness. Therefore, soil horizons can potentially be used as an indicator of the presence or absence of invasive earthworms. In this paper we developed a logistic regression generalized linear model to classify 40 sugar maple-basswood sites in the Chippewa National Forest of Northern Minnesota as wormed or unwormed (i.e., presence or relative absence of earthworms, respectively). A model using the thickness of the O horizon as a predictor variable correctly classified 93% of sites resampled in 2017 as wormed or unwormed. This result suggests we can predict which sugar maple-basswood stands in the Chippewa National Forest were wormed in the past. By comparing historic conditions to those present today, we can then analyze the long-term effects of invasive earthworms. [ABSTRACT FROM AUTHOR]

Background: Invasive species affect community dynamics and ecosystem functions, but the mechanisms of their impacts are poorly understood. Hypotheses on invasion impact range from Superior Competitor to Novel Function, from Enemy Escape to Microbial Mediation. In this study, we examined the effects of an urban tree invader, Acer platanoides (Norway maple, NM), on a mesic deciduous forest in contrast to its native congener Acer rubrum (red maple, RM) with a split-plot design experiment. A total of 720 maple seedlings were transplanted to 72 plots under 24 trees of three canopy types. The three experimental treatments were removal of resource competition at above- and belowground and removal of leaf-litter effect. Soil moisture and nitrogen-related microbial activities were followed for each plot. Results: We found that partial canopy removal increased canopy openness and light transmission to the forest floor, but to a greater extent under NM than under RM trees. NM seedlings were more shade tolerant than RM seedlings in height growth. During the reciprocal transplantation in the mixed forest, biomass accumulation of NM seedlings under RM trees were twice as much as under NM, while that of RM seedlings under NM trees was 23.5% less than under RM. Soil net nitrification and relative nitrification were significantly higher, but mineralization rate was much lower under NM than under RM trees, which would lead to faster N leaching and lower N availability in the soil. Plots with litter removal had significantly higher seedling mortality due to herbivory by the end of 2 years, especially for NM seedlings under NM trees. Trenching enhanced soil water availability but there was no difference among canopy types. Conclusions: Our results demonstrated that invasion of NM not only altered forest canopy structure but also changed herbivory rate for seedlings and N dynamics in the soils. NM seedlings were more shade tolerant under NM canopies than RM seedlings and were more protected by NM litter under NM canopies than under RM canopies. These altered biotic and abiotic environments will likely facilitate further invasion of NM in the forests, hence positive feedbacks, and make it an increasingly serious tree invader in North America. [ABSTRACT FROM AUTHOR]

• Group-selection openings modestly increase tree diversity in uneven-aged hardwoods. • Large openings (22 m radius) have highest regeneration richness and diversity. • Shade-tolerant Acer saccharum dominant in regeneration layers 15 years post-harvest. Group selection has been proposed as a complementary system to conventional, uneven-aged management in temperate hardwoods (i.e. single-tree selection) to counteract declines in overstory diversity and growing importance of shade-tolerant species caused largely by past management activities. Mixed results from experimental group selection harvests in eastern North America and growing interest in retention forestry have led some scientists and managers to apply ideas from retention forestry into group selection systems. The Yellow Birch Legacy-Tree Project is a group selection experiment established in 2003, which incorporates single, dominant/co-dominant yellow birch (Betula alleghaniensis Britt.) legacy-trees into the centers of harvested canopy gaps in a northern hardwoods forest in the Upper Peninsula of Michigan. Group selection openings (n = 49) in three size classes based upon radii—small (11 m, n = 16), medium (16.5 m, n = 17), and large (22 m, n = 16)—were surveyed alongside single-tree selection reference sites (n = 20) 15 years post-harvest. Our goals were to (1) examine long-term trends in seedling and sapling abundance and diversity, (2) evaluate the initial and contemporary effects of gap size on regeneration, and (3) assess the overall efficacy of group-selection with legacy-tree retention in regenerating mid-tolerant and intolerant species, especially yellow birch. At 15 years post-harvest, we found that shade-tolerant sugar maple (Acer saccharum Marsh.) dominated regeneration layers across all treatments, but we observed modest increases in seedling and sapling diversity within openings that may alter long-term canopy composition over several cutting cycles. We found that gains in diversity and evenness in canopy gaps persisted through time and that large gaps (22 m radius) had the most species-rich and diverse regeneration compared to reference sites. Canopy gaps contained significantly higher densities of shade-intolerant and mid-tolerant seedlings and saplings compared to reference sites, namely red maple (Acer rubrum L.), black cherry (Prunus serotina Ehrh.), and yellow birch; however, most diversity occurred in shorter height classes. Nevertheless, legacy retention within group selection systems holds promise for maintaining ecological memory and structural complexity through time, but further treatments such as scarification may be necessary to shift compositional trajectories in favor of shade-intolerant and mid-tolerant species. [ABSTRACT FROM AUTHOR]

We used data on a forest-based ecosystem service, sugar maple (Acer saccharum) sap, spanning sugar maple's latitudinal range to predict the role of climate variation on two aspects of sap productivity: sugar content and sap flow. The sugar in maple sap is derived from carbohydrate stores influenced by growing season conditions in the prior year, while sap flow is tied to freeze/thaw cycles during early spring. Our findings suggest optimal regions for sap production will move northward, with lower average production across nearly the entire range except for the far north, and provide spatially-explicit projections for forest managers and syrup producers making decisions on the location and viability of management for maple syrup production. Climate change is affecting the benefits society derives from forests. One such forest ecosystem service is maple syrup, which is primarily derived from Acer saccharum (sugar maple), currently an abundant and widespread tree species in eastern North America. Two climate sensitive components of sap affect syrup production: sugar content and sap flow. The sugar in maple sap derives from carbohydrate stores influenced by prior year growing season conditions. Sap flow is tied to freeze/thaw cycles during early spring. Predicting climate effects on syrup production thus requires integrating observations across scales and biological processes. We observed sap at 6 sugar maple stands spanning sugar maple's latitudinal range over 2–6 years to predict the role of climate variation on sugar content and sap flow. We found that the timing of sap collection advanced by 4.3 days for every 1 °C increase in March mean temperature, sap volume peaked at a January-May mean temperature of 1 °C, and sap sugar content declined by 0.1 °Brix for every 1 °C increase in previous May-October mean temperature. Using these empirical relationships, we projected that the sap collection season midpoint will be 1 month earlier and sap sugar content will decline by 0.7 °Brix across sugar maple's range by the year 2100 in an RCP 8.5 climate change scenario. The region of maximum sap flow is expected to shift northward by 400 km, from near the 43rd parallel to the 48th parallel by 2100. Our findings suggest climate change will have profound effects on syrup yield across most of sugar maple's range; drastic shifts in the timing of the tapping season accompanied by flat to moderate increases in syrup yield per tap in Canada contrast with declines in syrup yield and higher frequencies of poor syrup production years across most of the U.S. range. [ABSTRACT FROM AUTHOR]

Copyright of Agronomy Journal / Agronomski Glasnik (0002-1954) is the property of Croatian Society of Agronomists 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.)

Red maple often dominates tree regeneration following the harvest of upland oak stands in eastern North America. An open question is whether the oak component of the new stands will eventually reassert dominance (delayed oak dominance hypothesis) or whether red maple will succeed as a major, new overstory component on these sites (red maple dominance hypothesis). We examined changes between the 3rd and 4th decades of growth (mean interval 13 years) in 46 stands on formerly oak-dominated sites in the Blue Ridge (BlRi), Ridge and Valley (RiVa), and Appalachian Plateau (ApPl) physiographic provinces of the central Appalachians. Almost without exception, the new stands in their 4th decade (mean age 38 yrs) had less oak and more red maple than did their predecessors. All ApPl stands had failed to develop a substantial component of oak early in stand development, and most were dominated by red maple in their 4th decade. Most BlRi stands had become dominated by oak by their 4th decade, and changes between the 3rd and 4th decades show that oak is progressively becoming more dominant by displacing the relatively minor component of red maple that remains. The success of oak was generally intermediate in the RiVa, where red maple retained an approximately co-equal position of dominance with oak between the 3rd and 4th decades and in some stands advanced in dominance against oak. We suggest a nuanced interpretation of delayed oak dominance as an emergent and contingent property of individual trees and their neighborhoods. Both this and red maple dominance accurately describe developmental trajectories that are co-occurring in most of our stands, with one predominating over the other depending upon physiographic region and site-related characteristics. In general, development favored oaks where growth rates were slower and where species composition was more xerophytic. Red maple was favored on better sites, where delayed oak dominance appears to be a longer and ultimately less successful process. [ABSTRACT FROM AUTHOR]

• Cumulative impact of atmospheric nitrogen (N) deposition is a concern for forest ecosystems. • N doses (0, 3, 10 times ambient rate) were applied during a 13-year period in a sugar maple stand. • N concentrations in foliage and organic soil remained similar between treatments after 13 years. • Soil nitrate increased and Ca, Mg, and K (top organic layers) decreased in the high N treatment. • Foliar N:P ratio increased while Ca and Mn decreased with increasing levels of N addition. • Sugar maple dieback rate increased over time in the high N treatment. Cumulative effects of nitrogen (N) deposition are a matter of concern in temperate forests of northeastern North America. Increased N deposition may stimulate forest growth and carbon sequestration while also causing N saturation, which may lead to soil cation depletion, particularly in base-poor systems. We applied ammonium nitrate for 13 years in a sugar maple (Acer saccharum; SM) stand at the rates of 3 (Low N, LN) and 10 times (High N, HN) the ambient N deposition rate. N concentrations in soil layers were similar among treatments, except for a nitrate increase in the top B horizon in the HN treatment. Exchangeable Ca2+, Mg2+, and K+ were significantly lower than for the Control, at least in one of the top organic soil layers in the HN treatment. The temporal dynamics of foliar chemistry revealed that N:P ratio increased and both Ca and Mn decreased in the early years following treatment initiation, but that they did not change much thereafter. Foliar Ca values in the HN treatment are the lowest reported in the literature. This probably explains why the proportion of crown dieback steadily increased over time, reaching values as high as 80% in the HN treatment in 2017. [ABSTRACT FROM AUTHOR]

• Maple sugaring is an important and rapidly expanding industry in eastern North America with a long and rich history, yet there is to-date no review on the mechanisms of sap runs and how they are affected by tree and tap characteristics. • Here, we review the mechanisms underlying sap runs in the leafless-state of maple species. • We also review knowledge on the importance of tap and tree characteristics, such as tap hole depth and tree size in maple sugaring. • Additionally, we conducted a meta -analysis on compiled data including about 15 000 data points on sap yield and the sap's sugar content from eleven tapping years across ten sites to test various hypothesis. • The meta -analysis revealed that tree and site characteristics are the primary sources of variability in both sap yield and the sap's sugar content. Maple sugaring mainly uses sugar and red maples (Acer saccharum and Acer rubrum) by tapping them for sap in the leafless-state across large portions of their ranges. How much sap exudes from a tap hole and how sweet this sap is, can vary substantially. Year-to-year variation in sap yield and sugar content can be primarily traced to differences in meteorological conditions that drive sap runs. Yet, how much of the total variation in sap yield and sugar content is linked to the year, site, species, tree, or tap has not been investigated systematically. Here, we reviewed the literature and also compiled a dataset of sap yield and sugar content from gravity taps on 324 red and sugar maples. The compiled data originates from multiple studies at ten sites across a large proportion of the ranges of sugar and red maple and stretches over eleven years. Using about 15 000 data points on sap yield and sap sugar content, we analysed the importance of tap and tree characteristics, such as height of the tap hole on the stem or diameter at breast height. We also review previous research on the importance of tap and tree characteristics in maple sugaring. Moreover, we partition variability in the data to attribute it to species, site, tree, year, and tap characteristics. Our results indicate that species, site and tree characteristics are the three largest sources of variability with regards to sap yield and the sap's sucrose concentration. However, differences between years and tap characteristics, which were found to be comparatively minor sources of variability in sap yield and the sap's sucrose concentration, have attracted far more attention in the past. We advocate for the continuation and expansion of systematic measurements of sap characteristics across a network of sites to further improve our understanding of maple sugaring. Such an understanding will be instrumental to prepare maple sugaring operations against the imminent effects of the climate and biodiversity crises and ensure their sustainability to perpetuate this traditional activity. [ABSTRACT FROM AUTHOR]

Ethnopharmacological relevance The genus Acer (Aceraceae), commonly known as maple, comprises approximately 129 species that primarily grow in the northern hemisphere, especially in the temperate regions of East Asia, eastern North America, and Europe. These plants have been traditionally used to treat a wide range of diseases in East Asia and North America. Moreover, clinical studies have shown that medicinal plants belonging to Acer are highly effective in the treatment of rheumatism, bruises, hepatic disorders, eye disease, and pain, and in detoxification. This review provides a systematic and constructive overview of the traditional uses, chemical constituents, and pharmacological activities of plants of the genus Acer . Material and methods This review is based on a literature study of scientific journals and books from libraries and electronic sources such as SciFinder, ScienceDirect, Springer, PubMed, CNKI, Google Scholar, Baidu Scholar, and Web of Science. The literature in this review related to chemical constituents and pharmacological activities dates from 1922 to the end of October 2015. Furthermore, ethnopharmacological information on this genus was obtained from libraries and herbaria in China and USA. Results In traditional medicine, 40 species, 11 subspecies, and one varieta of the genus Acer are known to exhibit a broad spectrum of biological activities. To date, 331 compounds have been identified from 34 species of the genus Acer , including flavonoids, tannins, phenylpropanoids, diarylheptanoids, terpenoids, benzoic acid derivatives, and several other types of compounds, such as phenylethanoid glycosides and alkaloids. Preliminary pharmacological studies have shown that the extracts and compounds isolated from this genus exhibit a broad spectrum of biological activities such as antioxidant, antitumor, anti-inflammatory, antidiabetic, hepatoprotective, and antiobesity activities, as well as promoting osteoblast differentiation. To date, reports on the toxicity of Acer species to humans are very limited, and the major safety concern of these plants is in the veterinary field. Conclusions Based on our systematic review, Acer species can be used to treat rheumatism, hepatic disorders, eye disease, pain, etc. effectively. Some indications from ethnomedicine have been validated by pharmacological activities, such as the anti-inflammatory and hepatoprotective activities of the species. The available literature showed that most of the activities of these species can be attributed to flavonoids and tannins. To ensure the safety and efficacy in clinical practice in the future, studies identifying active molecules and clarifying their pharmacological mechanisms as well as toxicity are needed. [ABSTRACT FROM AUTHOR]

Liming, the application of carbonate materials (e.g., CaCO3, CaMg(CO3)2) to soils and surface waters, has been used extensively in Europe, and to a lesser extent in Canada and the United States, to mitigate the effects of acid deposition on forest and aquatic ecosystems. This literature review was conducted to assess the effects of liming on ecologically and economically important sugar maple dominated ecosystems of northeastern North America, where it is increasingly used to treat sugar maple dieback. Potential direct and indirect effects were considered to determine whether the use of liming to revitalize these forests could negatively affect other ecological parameters, including those in adjacent aquatic habitats. Based on current scientific literature, it is not anticipated that liming at rates of 1-3 t ha−1 would have major detrimental effects on these ecosystems. However, liming could have negative effects on northern hardwood forests with regard to earthworm invasions. The choice of liming as a mitigation tool should be made not only after weighing the potentially negative effects against the benefits of restoring sugar maple dominated stands in poorly buffered soils, but also after considering ecological components that could be lost or never recovered if an acidified forest ecosystem is not limed. [ABSTRACT FROM AUTHOR]

Long-term effects of alley cropping on soils in the temperate zone are not widely known. Management, landscape, and soil depth effects on soil physical and biological properties were examined in a silver maple (Acer saccharinum L.) no-till corn (Zea mays L.)- soybean (Glycine max L.) rotation established in 1990 in northeast Missouri. Soils from crop alleys and tree rows were collected along transects traversing upper to lower landscape positions at three depths. Fluorescein diacetate hydrolase (FDA), β-glucosidase, β-glucosaminidase, and dehydrogenase activities were measured. Soil bulk density, aggregate stability, carbon (C), nitrogen N), and enzyme activities decreased with soil depth in alley and tree rows except for glucosaminidase. Soil physical and biological parameters did not differ significantly between alley and tree row. Landscape position effects were not significant for management or depth. Tree establishment improves soil quality in the crop alley as the system matures with improvements extended throughout the soil profile. [ABSTRACT FROM PUBLISHER]

1. Acer platanoides (Norway maple) is an important non-native invasive canopy tree in North American deciduous forests, where native species diversity and abundance are greatly reduced under its canopy. We conducted a field experiment in North American forests to compare planted seedlings of A. platanoides and Acer saccharum (sugar maple), a widespread, common native that, like A. platanoides, is shade tolerant. Over two growing seasons in three forests we compared multiple components of seedling success: damage from natural enemies, ecophysiology, growth and survival. We reasoned that equal or superior performance by A. platanoides relative to A. saccharum indicates seedling characteristics that support invasiveness, while inferior performance indicates potential barriers to invasion. 2. Acer platanoides seedlings produced more leaves and allocated more biomass to roots, A. saccharum had greater water use efficiency, and the two species exhibited similar photosynthesis and first-season mortality rates. Acer platanoides had greater winter survival and earlier spring leaf emergence, but second-season mortality rates were similar. 3. The success of A. platanoides seedlings was not due to escape from natural enemies, contrary to the enemy release hypothesis. Foliar insect herbivory and disease symptoms were similarly high for both native and non-native, and seedling biomass did not differ. Rather, A. platanoides compared well with A. saccharum because of its equivalent ability to photosynthesize in the low light herb layer, its higher leaf production and greater allocation to roots, and its lower winter mortality coupled with earlier spring emergence. Its only potential barrier to seedling establishment, relative to A. saccharum, was lower water use efficiency, which possibly could hinder its invasion into drier forests. 4. The spread of non-native canopy trees poses an especially serious problem for native forest communities, because canopy trees strongly influence species in all forest layers. Success at reaching the canopy depends on a tree's ecology in previous life-history stages, particularly as a vulnerable seedling, but little is known about seedling characteristics that promote non-native tree invasion. Experimental field comparison with ecologically successful native trees provides insight into why non-native trees succeed as seedlings, which is a necessary stage on their journey into the forest canopy. [ABSTRACT FROM AUTHOR]

Reviews the diagnostic characters of the fruits of two extant Dipteronia species as a basis for recognizing fossil remains of Sapindaceae from western North America. Similarities between Dipteronia and its sister genus, Acer; Description of Dipteronia fruits; Phylogeny of Dipteronia and Acer.

• Health of sugar maple (SM) is still a concern in many areas of NE North America. • The effect of liming on SM health was evaluated 20 years after a single application. • Lime still had a positive effect on the nutrition, stem growth and crown vigor. • Dieback decreased from 44% (control) to <5% (lime rates ≥5 t·ha−1). • Stem growth increased by 93% and 144% for SM that received lower and higher doses, respectively. Despite the decrease in acid deposition observed over the last decades, the health of sugar maple (SM; Acer saccharum Marshall), a species known as sensitive to base cation availability, is still a concern in many areas of northeastern North America. Twenty years after a single application of dolomitic lime, a widely available soil amendment, the effect of liming was evaluated on SM nutrition, vigor and growth in a declining stand affected by acid deposition. Lime doses of 0–50 t·ha−1 were applied over a 5 m radius around each selected tree. This experiment is unique in that it monitors the effects of doses that are economically feasible ("lower doses"; 0, 0.5, 1, 2 and 5 t·ha−1) and of higher ones (10, 20, 50 t·ha−1). We found that lime still had a positive effect on all variables studied after 20 years. In addition, SM nutrition, stem growth and crown vigor improved as lime dose increased. On average, foliar Ca and Mg concentrations increased by 35% and 46% for trees that received the 2 and 5 t·ha−1 doses, respectively, and by as much as 70% and 95% for those that received the 50 t·ha−1 dose. Crown dieback decreased from 44% for the control trees to less than 5% for those that received lime doses ≥5 t·ha−1. Basal area increment increased by 93% and 144% for trees that received lower and higher doses, respectively, compared to non-limed trees. Results indicate that a lime dose of approximately 5 t·ha−1, which is both potentially economic and operationally feasible, can have a beneficial effect on SM nutrition, vigor and growth for at least 20 years on such acidic and base-poor soils. Preserving SM tree health in this changing world is important to ensure its sustainability in maple forests. [ABSTRACT FROM AUTHOR]

• Flammability differences were more pronounced when drying rates were incorporated. • White oak absorbed the least water, dried the fastest, and was the most flammable. • Red maple absorbed the most water, dried the slowest, and was the least flammable. • Drying rates and curling of litter best explained differences in flammability. • Poor flammability of red maple litter provides mechanistic support of mesophication. Global change has contributed to substantial vegetation shifts across many ecosystems through altered fire-vegetation feedbacks, but the direction, strength, and mechanism of these processes vary considerably. Most prior studies have focused on fire-vegetation feedbacks that enhance community flammability with less emphasis on examples of feedbacks resulting from dampened flammability. Widespread fire exclusion in many deciduous forests and woodlands of eastern North America has caused substantive changes in overstory species composition. These changes have led to feedbacks that are hypothesized to decrease community flammability (i.e. mesophication) to the detriment of fire-dependent "pyrophytes". Mesophytic species, such as maple (Acer spp.), are implicated in these fire regime changes and have extensively invaded many oak (Quercus spp.) landscapes across the region. To date, only limited circumstantial evidence is available in support of dampened flammability as the mechanism contributing to mesophication. Here we use laboratory experiments to determine whether red maple (A. rubrum) and sugar maple (A. saccharum) could reduce forest floor flammability through the input of their leaf litter. Wetting, drying, and burning characteristics of three pyrophytic oaks, white oak (Q. alba) , northern red oak (Q. rubra) , and chestnut oak (Q. montana), and the two mesophytic maples revealed the strong potential for red maple to reduce community flammability. Red maple absorbed the greatest amount of water, was the slowest to dry, and was the least flammable among these species while white oak was the most resistant to water absorption, the fastest to dry, and the most flammable. Northern red oak, chestnut oak, and sugar maple were intermediate in their moisture dynamics and flammability. The moisture and flammability responses of the species examined were a result of their corresponding leaf traits, with drying rate and curling having the strongest influence. Our findings provide substantial evidence that vegetation shifts resulting from an altered fire regime could result in dampened litter flammability that further limit fire and reinforce on-going changes. [ABSTRACT FROM AUTHOR]

The January 1998 ice storm broke off tree crowns across a wide geographic area in northeastern North America, and forest tent caterpillar (Malacosoma disstria Hubner) defoliated some of the same stands in 2004–2007. We assessed the post-event growth responses of upper canopy sugar maples (Acersaccharum Marsh.) in previously thinned and recently rehabilitated even-aged northern hardwood stands in New York State, USA. Cores from ice-storm-damaged trees showed an initial radial growth reduction, a recovery after one year, and an increase to or above pre-storm levels after three years. A later forest tent caterpillar defoliation in the same stand caused a second reduction of growth, and another recovery after one year. We observed greater post-storm radial growth on trees released by a post-ice storm rehabilitation treatment than in the untreated control, with growth exceeding pre-storm rates. Cores from another site thinned 38 years earlier and impacted only by the forest tent caterpillar showed a more moderate growth reduction, and a prompt but smaller post-defoliation growth response than among trees affected by both the ice storm and defoliation. Findings reflect the potential for growth of upper canopy sugar maple trees to recover after a single or two closely occurring crown disturbances, and provide guidance to managers who must decide about removing or continuing to manage stands after similar kinds of ice storm damage or defoliation. [ABSTRACT FROM AUTHOR]

Research highlights: The availability of global distribution data and new, fossil-calibrated phylogenies has made it possible to compare the climatic niches of the temperate maple (Acer L.) taxa and assess phylogenetic and continental patterns in niche overlap. Background and Objectives: The maples have radiated from East Asia into two other temperate continental bioregions, North America and Eurasia (Europe and West Asia), over a roughly 60-million-year period. During this time, the Earth's climate experienced pronounced cooling and drying, culminating in cyclic periods of widespread temperate glaciation in the Pliocene to Pleistocene. The objective of this study is to use newly available data to model the climatic niches of 60% of the temperate maples and assess patterns of niche divergence, constraint, and conservatism in the genus's radiation out of East Asia. Materials and Methods: I assembled global occurrence data and associated climatic information for 71 maple taxa, including all species endemic to temperate North America and Eurasia and their closely related East Asian congeners. I constructed Maxent niche models for all taxa and compared the climatic niches of 184 taxa pairs and assessed phylogenetic signal in key niche axes for each taxon and in niche overlap at the continental and global scale. Results: Maxent models define a fundamental climatic niche for temperate maples and suggest that drought-intolerant taxa have been lost from the Eurasian maple flora, with little continental difference in temperature optima or breadth. Niche axes and niche overlap show minimal evidence of phylogenetic signal, suggesting adaptive evolution. Pairwise niche comparisons reveal infrequent niche overlap continentally and globally, even among sister pairs, with few taxa pairs sharing ecological niche space, providing evidence for constrained divergence within the genus's fundamental climatic niche. Evidence of niche conservatism is limited to three somewhat geographically isolated regions of high maple diversity (western North America, the Caucasus, and Japan). Conclusions: Over 60 million years of hemispheric radiation on a cooling and drying planet, the maple genus experienced divergent, though constrained, climatic niche evolution. High climatic niche diversity across spatial and phylogenetic scales along with very limited niche overlap or conservatism suggests that the radiation of the genus has largely been one of adaptive diversification. [ABSTRACT FROM AUTHOR]

• Numerical model is consistent with experimentally measured tree temperatures. • Frequency of freeze-thaw cycles increases with decreasing stem diameter. • Plantation method a promising strategy for maple syrup production in mild climates. Freeze-thaw cycles, where temperatures fluctuate above and below 0 °C, are the cause of elevated stem pressures that drive sap flow from within the sugar maple. This temperature-dependency has historically limited the production of maple syrup to select regions of North America. The plantation method of sap harvesting (which uses densely planted saplings instead of mature trees) now raises the possibility of a New Zealand-based maple syrup industry. In this study, a transient 2D heat transfer model was developed to predict freeze-thaw events in trees, and thereby evaluate potential plantation locations based on their climate. The heat transfer phenomena which have been modelled are bulk thermal diffusion, diffusion across discrete wood layers, convection, infrared radiation and solar radiation. Through experimental validation the model was found capable of predicting temperatures in real-life trees with high accuracy. Sensitive parameters were the bark absorptivity and sapwood diffusivity. Simulation results also indicate that the frequency of freeze-thaw cycles increase dramatically in saplings, as compared to mature trees, making maple syrup production potentially viable in locations that would otherwise fail when using traditional methods. [ABSTRACT FROM AUTHOR]

The ten most frequently isolated fungi from the wood of the dead branches of Acer pseudoplatanus L. were tested in dual cultures to evaluate their in vitro antagonistic activity against Eutypella parasitica R.W. Davidson and R.C. Lorenz, the causative agent of a destructive disease of maples in Europe and North America. The tested fungi, treated also as challenge isolates, were Diaporthe sp., Eutypa sp., Eu. maura, E. parasitica, Fusarium avenaceum, Neocucurbitaria acerina, Neonectria sp., Peniophora incarnata, Petrakia irregularis, and Phomopsis pustulata. The antagonistic ability of each challenge isolate was evaluated by calculating an index of antagonism (AI) based on the interaction type in the dual cultures. The results of competition between the fungal isolates were quantified after re-isolations from the interaction zone (s). The dual cultures revealed two main types of competitive interactions: Deadlock, consisting of mutual inhibition after mycelial contact or at a distance, and replacement, reflecting in the inhibition of E. parasitica, followed by partial overgrowth by the replacing fungus. Statistical analysis showed significant differences in average AI and s of challenge isolates between different dual culture assays. Based on the results of the antagonism index, Eutypa sp., Eu. maura, Neonectria sp., and P. incarnata had the highest inhibitory effect on E. parasitica growth and were recognized as the most promising candidates for further biocontrol studies of E. parasitica. The mycelium of E. parasitica at the interaction zones remained mostly viable, except in dual cultures with Eutypa sp., F. avenaceum, and Neonectria sp., where re-isolations did not yield any colony of the E. parasitica isolate. Based on the results, we assume that E. parasitica is a weak competitor, which invests less energy in direct mycelial competition. We discuss the potential of the observed antagonists as a possible biocontrol of Eutypella canker of maple. Nevertheless, additional experiments should be performed for a solid conclusion about competitive ability of E. parasitica and usefulness of antagonists as biocontrol. [ABSTRACT FROM AUTHOR]

• Physicochemical composition of maple syrup samples from North America was analysed. • Maple syrup pH, color, Brix and sugars significantly differ based on the location. • Major phenolics were protocatechuic acid, coniferyl alcohol and vanillin. • Higher amounts of phenolics, minerals were observed in late-season maple syrup. • Darker color with more phenolics and minerals were observed in late-season syrup. Maple syrup is produced by concentrating the maple tree sap. The physicochemical profile of maple syrup can be varied depending on the processing method, microbial contamination, seasonal and geographical variations etc. Apart from being a better alternative to refined sugar, the minerals and phenolics in maple syrup may provide additional health benefits owing to their bioactivities. We studied the physicochemical profiles of maple syrup samples from North America and the seasonal compositional changes of the syrup from Nova Scotia (NS). Syrup pH, color, Brix were significantly differ depending on the location. Brix values ranged from 61.6 to 70.2°. Thirteen different phenolics including protocatechuic acid, coniferyl alcohol, vanillin, and syringic aldehyde were identified and quantified. The total mineral content ranged from 2.6 to 4.8 g/L of syrup. Potassium was the most abundant, followed by calcium, magnesium, phosphorus, manganese, and zinc. Analyses of NS syrup during early, mid and late seasons revealed that, total phenolics and minerals increased and the syrup color became darker towards late season. Syrup pH, brix and sugars did not differ among the seasons. Interestingly, vanillin, syringic acid and syringic aldehyde were the main phenolics in early maple syrup samples while protecatechuic acid was the predominant in late season. [ABSTRACT FROM AUTHOR]

Oak regeneration failures have been causing a slow decline in the occurrence of oak forest ecosystems in eastern North America. Accordingly, our study sought to determine a means of creating more vigorous and competitive oak seedlings by the addition of manganese (Mn) fertilizers. Seeds of northern red oak (Quercus rubra L.), chestnut oak (Quercus prinus L.), and red maple (Acer rubrum L.), one of oak's major competitors in North America oak forest ecosystems, were sown in 0.7 liter pots that contained a growing medium mixture of peat moss, perlite, and sand in a ratio of 2:1:2, and germinated in a greenhouse. Three different chemical compound Mn fertilizer treatments—manganese chloride (0.16 mg L−1 Mn, MnCl2·4H2O), nanoparticle manganese in the form of manganese hydroxide (0.01 mg/L Mn, nanoparticle Mn(OH)2), and manganese hydroxide (0.01 mg L−1 Mn, Mn(OH)2)—and a treatment of Hoagland solution were applied to the planted seed. These treatments were compared to a control consisting of water, and treatments were applied twice a week over a 12 week period. Germination rates and seedling growth were measured over this period of time. At the end of 12 weeks seedlings were harvested, separated into roots, stem, and foliage for the purpose of biomass and nutrient analysis by seedling component. Northern red oak displayed a 100% germination success rate with MnCl2·4H2O and Mn(OH)2 treatments, while red maple germination was reduced with the MnCl2·4H2O and nanoparticle Mn(OH)2 treatments with only a 32% and 24% germination rate, respectively. The MnCl2·4H2O treatment produced the largest overall seedling size (basal diameter squared times the seedling height) of red maple with a 191.6% increase; however, the MnCl2·4H2O treatment produced the largest overall seedling size (basal diameter squared times the seedling height) of northern red oak and chestnut oak with an increase of 503.7% and 339.5%, respectively. The greatest increase in overall seedling size for northern red oak was with the Mn(OH)2 treatment at 507.2%, and 601.2% for chestnut oak with the nanoparticle Mn(OH)2 treatment. MnCl2·4H2O treatment significantly increased the oak foliar nitrogen (N) content. It appears that the application of Mn fertilizer can increase the germination and growth of these oak species while suppressing or having a lesser effect on red maple, thus creating a competitive advantage for oak over its competitor. [ABSTRACT FROM AUTHOR]