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Background: Afforestation of non-forestland is a new measure by the European Union to enhance climate mitigation and biodiversity. Hybrid aspen (Populus tremula L. × P. tremuloides Michx.) is among the suitable tree species for afforestation to produce woody biomass. However, the best performing genotypic material for intensive biomass production and its physiological adaptation capacity is still unclear. We compared 22 hybrid aspen genotypes growth and leaf physiological characteristics (stomatal conductance, net photosynthesis, intrinsic water-use efficiency) according to their geographical north- or southward transfer (European P. tremula parent from 51° to 60° N and North American P. tremuloides parent from 45° to 54° N) to hemiboreal Estonia (58° N) in a completely randomized design progeny trial. We tested whether the growth ranking of genotypes of different geographical origin has changed from young (3-year-old) to mid-rotation age (13-year-old). The gas exchange parameters were measured in excised shoots in 2021 summer, which was characterised with warmer (+ 4 °C) and drier (17% precipitation from normal) June and July than the long-term average. Results: We found that the northward transfer of hybrid aspen genotypes resulted in a significant gain in growth (two-fold greater diameter at breast height) in comparison with the southward transfer. The early selection of genotypes was generally in good accordance with the middle-aged genotype ranking, while some of the northward transferred genotypes showed improved growth at the middle-age period in comparison with their ranking during the early phase. The genotypes of southward transfer demonstrated higher stomatal conductance, which resulted in higher net photosynthesis, and lower intrinsic water-use efficiency (iWUE) compared with northward transfer genotypes. However, higher photosynthesis did not translate into higher growth rate. The higher physiological activity of southern transferred genotypes was likely related to a better water supply of smaller and consequently more shaded trees under drought. Leaf nitrogen concentration did not have any significant relation with tree growth. Conclusions: We conclude that the final selection of hybrid aspen genotypes for commercial use should be done in 10–15 years after planting. Physiological traits acquired during periods of droughty conditions may not fully capture the growth potential. Nonetheless, we advocate for a broader integration of physiological measurements alongside traditional traits (such as height and diameter) in genotype field testing to facilitate the selection of climate-adapted planting material for resilient forests. [ABSTRACT FROM AUTHOR]

This article establishes a thermodynamic model of a dual-fluidized bed biomass gasification process based on the Aspen Plus software platform and studies the operational control characteristics of the dual-fluidized bed. Firstly, the reliability of the model is verified by comparing it with the existing experimental data, and then the influence of different process parameters on the operation and gasification characteristics of the dual-fluidized bed system is investigated. The main parameters studied in the operational process include the fuel feed rate, steam/biomass ratio (S/B), air equivalent ratio (ER), and circulating bed material amount, etc. Their influence on the gasification product composition, reactor temperature, gas heat value (QV), gas production rate (GV), carbon conversion rate (ηc), and gasification efficiency (η) is investigated. The study finds that fuel feed rate and circulating bed material amount are positively correlated with QV, ηc, and η; ER is positively correlated with GV and ηc but negatively correlated with QV and η; S/B is positively correlated with GV, ηc, and η but negatively correlated with QV. The addition of CaO is beneficial for increasing QV. In actual operation, a lower reaction temperature in the gasification bed can be achieved by reducing the circulating bed material amount, and a larger temperature difference between the combustion furnace and the gasification furnace helps to further improve the quality of the gas. At the same time, GV, ηc, and η need to be considered to find the most optimized operating conditions for maximizing the benefits. The model simulation results agree well with the experimental data, providing a reference for the operation and design of dual-fluidized beds and chemical looping technology based on dual-fluidized beds. [ABSTRACT FROM AUTHOR]

Quaking aspen is an important deciduous tree species across interior western U.S. forests. Existing maps of aspen distribution are based on Landsat imagery and often miss small stands (<0.09 ha or 30 m2), which rapidly regrow when managed or following disturbance. In this study, we present methods for deriving a new regional map of aspen forests using one year of Sentinel-1 (S1) and Sentinel-2 (S2) imagery in Google Earth Engine. Using observed annual phenology of aspen across the Southern Rockies and leveraging the frequent temporal resolution of S1 and S2, ecologically relevant seasonal imagery composites were developed. We derived spectral indices and radar textural features targeting the canopy structure, moisture, and chlorophyll content. Using spatial block cross-validation and Random Forests, we assessed the accuracy of different scenarios and selected the best-performing set of features for classification. Comparisons were then made with existing landcover products across the study region. The resulting map improves on existing products in both accuracy (0.93 average F1-score) and detection of smaller forest patches. These methods enable accurate mapping at spatial and temporal scales relevant to forest management for one of the most widely distributed tree species in North America. [ABSTRACT FROM AUTHOR]

The giant noctule is a rare European bat about which we have little ecological information, but it is a priority species for which we need to determine the best conservation measures. Acoustic monitoring followed by a radio-tracking survey resulted in the localisation of two maternity colonies in different forest areas in the Western Carpathians, one in protected mixed stands in a national park (Muránska planina Mts) and the other in disturbed secondary spruce forests (Balocké vrchy Mts). The 95% home-range polygon of the roosts was about 3.5 km2 for both colonies. Eurasian aspen (Populus tremula) accounted for 100% of roosts (n = 18 trees) in mixed stands. However, even in the spruce monocultures, bats roosted in cavities of this tree whenever possible, although 76% of roosts (n = 21 trees) were still in Norway spruce (Picea abies). Regardless of forest type, the bats preferred to roost at the edges of the stands and on steep slopes that offered a free exit from the roost into open space. Small-scale salvage logging during bark beetle outbreaks can also create suitable open roosting habitats. Our observations indicate that structured stands with a higher proportion of aspen will positively affect tree-dwelling bats in mountain forests. [ABSTRACT FROM AUTHOR]

This study uses Aspen Plus simulations to explore the performance of a new flowsheet for ammonia production using Three Reactor Chemical Looping (TRCL) technology. In TRCL, the solid Oxygen Carrier continuously circulates between a Fuel Reactor, a Steam Reactor and an Air Reactor. The Oxygen Carrier is reduced in the Fuel Reactor and oxidised in the Steam and Air Reactors. Hydrogen generated in the Steam Reactor and nitrogen produced from the Air Reactor form a synthesis gas that is converted to ammonia. This study compares the TRCL process with the conventional ammonia process and a pseudo-continuous Chemical Looping Reforming (CLR) process that uses packed beds. Energy and environmental indicators are evaluated for the three processes. It was found that the energy consumed in the TRCL process is higher than the other two processes because of higher steam consumption in the Steam Reactor for generating hydrogen. However, if conversion in the Steam Reactor of greater than 67.5% can be achieved, the energy performance indicators are comparable with the conventional and CLR processes. At 67.5% conversion, the specific energy consumption becomes 21.5 GJ/t NH3. It is also noted that the Specific Energy Consumption for Carbon dioxide Avoidance (SPECCA) is much better than the conventional ammonia process at a steam conversion higher than 67.5%. Although further development is needed, this study shows that TRCL holds promise for lower energy consumption and better environmental performance than other commercial ammonia production technologies. • Aspen Plus simulations revealed viability of NH 3 generation using TRCL process. • TRCL requires lower energy (28.49 GJ/t NH3) than commercial NH 3 process. • Steam demand is higher for TRCL than for commercial and CLR-PB cases. [ABSTRACT FROM AUTHOR]

Knowledge of Eurasian aspen's (Populus tremula L.) ecological and growth characteristics is of high importance to plant and wildlife community ecology, and noncommercial forest ecosystem services. This research assessed these characteristics, identified aspen's habitat optimum, and examined causality of its current scarce distribution in central Europe. We analyzed a robust database of field measurements (4,656,130 stands) for forest management planning over 78,000 km2 of the Czech territory. Our analysis we used GIS techniques, with basic and multivariate statistics such as general linear models, ordination, and classification. Results describe a species of broad ecological amplitude that has heretofore attracted little research attention. Spatial analysis showed significant differences between aspen and other forest non-forest cover types. Additionally, we found significant association between the proportion of aspen in a stand, the size of forest property, and the forest category. The results demonstrate historic reasons for aspen's widespread presence, though contemporary occurrence is limited. This study advances the concept of a quantitatively based aspen ecological optimum (niche), which we believe may be beneficial for numerous aspen associates in the context of anticipated warming. Irrespective of local ecology (i.e., the realized aspen niche), the study confirms that profit-driven policy in forestry is chiefly responsible for historic aspen denudation in central Europe. Even so, we demonstrate that ample habitat is present. Further solutions for improving aspen resilience are provided to support these keystone systems so vital to myriad dependent flora and fauna. [ABSTRACT FROM AUTHOR]

Globally, in remaining wildlands, tree densities and forested cover have increased in grasslands and open forests since European settlement. In the southern Rocky Mountains of Colorado, United States, we determined tree composition and tree cover from historical (years 1875 to 1896) surveys and compared them to current (2002 to 2011) tree composition and current (year 2016) forested land cover for 500,000 ha of the Routt National Forest. Additionally, we examined whether changes in precipitation occurred. Regarding composition, pine (primarily lodgepole pine; Pinus contorta) decreased from 65% to 32% of all trees, with increased subalpine fir (Abies lasiocarpa) from 0.5% to 23% of all trees, and quaking aspen (Populus tremuloides) from 13% to 30% of all trees. According to 80% of 5175 survey points not in forests, the historical landscape was very open, comprised of grasslands, mountain meadows, and other open ecosystems. In contrast, 75% of the current landscape is covered by forests. Change points in the Palmer Modified Drought Index were within historical limits, indicating that forestation was not related to a change in water availability. Based on historical surveys and accounts, we envisioned a historical landscape that was open but embedded with dense lodgepole pine clusters and spruce stands at high elevations, which has now become a predominantly forested landscape of dense forests, similar to global forestation patterns. [ABSTRACT FROM AUTHOR]

Synthesis of ethanol by CO2 hydrogenation presents an efficient way to convert CO2 into value-added fuels and chemicals. For practical applications, recycling unreacted tail gas as well as CO co-feeding plays a key role to enhance CO2 conversion to ethanol. Thus, it is of great significance to study the effects of recycling unreacted tail gas and CO co-feeding on the chemical equilibrium. Herein, we perform a thermodynamic study to analyze the hydrogenation of CO2 to ethanol using Aspen Plus. The effects of recycling tail gas and CO co-feeding on CO2 conversion and ethanol selectivity at different temperatures and pressures are investigated. Both the optimal recycle ratio and CO/(CO + CO2) ratio in the feed are found to enhance ethanol synthesis from CO2 hydrogenation. [ABSTRACT FROM AUTHOR]

Hydrogen (H 2) is produced in an efficient and sustainable manner using steam reforming of glycerol in this work. Two models are used to provide anticipation about how efficiently H 2 can be produced: Model 1, a stoichiometric model, and Model 2, a thermodynamic model. Model 1 helps determine the water/glycerol molar input ratio and reaction pathway. The thermodynamic feasibility of Model 1 is examined using Model 2, which then determines the optimum conditions for maximal H 2 generation. Model 2 produced 1275 kmol/h of H 2 with an H 2 mole fraction of 0.49 at 658 °C and 1 atm of pressure. The reactor's net heat load is greatly reduced through heat integration in this study. The energy required is reduced by 29.5% as compared to when no heat integration is used. The process of separating and eliminating CO 2 is accomplished by employing the principles of mass and energy balance in the Aspen Plus. [Display omitted] • To develop an energy-efficient H 2 production model by steam reforming of glycerol. • Maximum H 2 production with minimum reformer heat duty is found by thermodynamic feasibility of stoichiometric data. • Reformer duty reductions show substantial potential for improving glycerol steam reforming efficiency. • The model also incorporates CO 2 capture, resulting in cleaner H 2 production. [ABSTRACT FROM AUTHOR]

Nitrogen can be taken up by trees in the form of nitrate, ammonium and amino acids, but the influence of the different forms on tree growth and development is poorly understood in angiosperm species like Populus. We studied the effects of both organic and inorganic forms of nitrogen on growth and wood formation of hybrid aspen trees in experimental conditions that allowed growth under four distinct steady‐state nitrogen levels. Increased nitrogen availability had a positive influence on biomass accumulation and the radial dimensions of both xylem vessels and fibers, and a negative influence on wood density. An optimal level of nitrogen availability was identified where increases in biomass accumulation outweighed decreases in wood density. None of these responses depended on the source of nitrogen except for shoot biomass accumulation, which was stimulated more by treatments complemented with nitrate than by ammonium alone or the organic source arginine. The most striking difference between the nitrogen sources was the effect on lignin composition, whereby the abundance of H‐type lignin increased only in the presence of nitrate. The differential effect of nitrate is possibly related to the well‐known role of nitrate as a signaling compound. RNA‐sequencing revealed that while the lignin‐biosynthetic genes did not significantly (FDR <0.01) respond to added NO3−, the expression of several laccases, catalysing lignin polymerization, was dependent on N‐availability. These results reveal a unique role of nitrate in wood formation and contribute to the knowledge basis for decision‐making in utilizing hybrid aspen as a bioresource. [ABSTRACT FROM AUTHOR]

Hybrid aspen Populus tremula L. × Populus tremuloides Michx. is fast-growing and a potential source of biomass for bioenergy production in Europe. However, knowledge about the phytopathological risks to hybrid aspen clones, particularly about frost crack damage as a possible infection gateway of fungal infections, is scarce. Five clones, represented by 205 trees from three trials in Latvia, were studied; two wood samples (at root collar and 1.3 m height) were obtained from each tree. Wood-inhabiting fungi were isolated and identified by the morphology and sequencing of the ITS region with fungal-specific primers, and fungal communities were compared using PERMANOVA. Fungal communities from trees with stem cracks were richer in species, especially pathogens, and species richness was higher in samples collected at 1.3 m height. Plant pathogens were isolated from 52% of all samples. Soft rot-causing Alternaria and Fusarium were dominant; Alternaria was more common at the height of 1.3 m, while Fusarium was more common at the root collar. White rot fungi were isolated from less than 2% of all samples, indicating a low degree of tree infection in the 15- to 16-year-old plantations. Clonal differences were not significant for fungal communities in general; nevertheless, for the occurrence of the genus Cladosporium, clonal differences were observed. In conclusion, the differences in fungal communities in relation to stem cracks implied only indirect clonal effects on phytopathological risks, emphasizing the resistance to stem cracking as a crucial trait for the sustainability of hybrid aspen plantations. [ABSTRACT FROM AUTHOR]

Summary: Stem bending in trees induces flexure wood but its properties and development are poorly understood. Here, we investigated the effects of low‐intensity multidirectional stem flexing on growth and wood properties of hybrid aspen, and on its transcriptomic and hormonal responses.Glasshouse‐grown trees were either kept stationary or subjected to several daily shakes for 5 wk, after which the transcriptomes and hormones were analyzed in the cambial region and developing wood tissues, and the wood properties were analyzed by physical, chemical and microscopy techniques.Shaking increased primary and secondary growth and altered wood differentiation by stimulating gelatinous‐fiber formation, reducing secondary wall thickness, changing matrix polysaccharides and increasing cellulose, G‐ and H‐lignin contents, cell wall porosity and saccharification yields. Wood‐forming tissues exhibited elevated jasmonate, polyamine, ethylene and brassinosteroids and reduced abscisic acid and gibberellin signaling. Transcriptional responses resembled those during tension wood formation but not opposite wood formation and revealed several thigmomorphogenesis‐related genes as well as novel gene networks including FLA and XTH genes encoding plasma membrane‐bound proteins.Low‐intensity stem flexing stimulates growth and induces wood having improved biorefinery properties through molecular and hormonal pathways similar to thigmomorphogenesis in herbaceous plants and largely overlapping with the tension wood program of hardwoods. [ABSTRACT FROM AUTHOR]

There are no systematic approaches available in current specialist literature when it comes to the optimization of the process of drying out hardwood species of wood, such as birch, aspen, or black alder, all of which find industrial uses in Estonia. In order to investigate the drying of these three hardwood species, this paper has made use of an experimental and theoretical drying optimization methodology which was developed previously for pine sapwood within the framework of the EIC Grant No. 16200 project. The same methodology was used to determine the critical diffusion coefficient and corresponding critical relative humidity levels (RH) in relation to the surrounding air, with those levels being important from the point of view of drying optimization, and calculating those levels separately for each species of hardwood. For alder it was found that the critical diffusion coefficient is Dcr = 36.57 * (10−4 mm2 s−1), while for aspen the figure was Dcr = 30.71 * (10−4 mm2 s−1), and for birch it was Dcr = 16.35 * (10−4 mm2 s−1). It was found that the time dependencies for the total deformation of different tree species tend to differ considerably, although the same drying regime was used for all of those tree species which were incorporated into the experiments. [ABSTRACT FROM AUTHOR]

Hydrogen produced sustainably has the potential to be an important energy source in the short term. Biomass gasification is one of the fastest-growing technologies to produce green hydrogen. In this work, an air-blown gasification model was developed in Aspen Plus®, integrating a water–gas shift (WGS) reactor to study green hydrogen production. A sensitivity analysis was performed based on two approaches with the objective of optimizing the WGS reaction. The gasifier is optimized for carbon monoxide production (Case A) or hydrogen production (Case B). A CO2 recycling stream is approached as another intensification process. Results suggested that the Case B approach is more favorable for green hydrogen production, allowing for a 52.5% molar fraction. The introduction of CO2 as an additional gasifying agent showed a negative effect on the H2 molar fraction. A general conclusion can be drawn that the combination of a WGS reactor with an air-blown biomass gasification process allows for attaining 52.5% hydrogen content in syngas with lower steam flow rates than a pure steam gasification process. These results are relevant for the hydrogen economy because they represent reference data for further studies towards the implementation of biomass gasification projects for green hydrogen production. [ABSTRACT FROM AUTHOR]

Climate change poses a serious risk to sustainable forest management, particularly in boreal forests where natural disturbances have been projected to become more severe. In three Quebec boreal forest management units, biomass carbon storage under various climate change and management scenarios was projected over 300 years (2010–2310) with a process-based dynamic landscape model (PnET-succession for Landis-II). Several strategies varying in their use of partial cuts and clear cuts, including business as usual (BAU) (clear-cut applied on more than 95% of the managed area), were tested and compared to conservation scenarios (no-harvest). Based on simulation results at the landscape scale, the clearcut-based scenarios such as BAU could result in a decrease of biomass carbon stock by 10 tC ha−1 yr−1 compared to the natural scenario. However, this reduction in carbon stock could be offset in the long term through changes in composition, as clearcut systems promote the expansion of trembling aspen and white birch. In contrast, the use of strategies based on partial cuts on more than 75% or 50% of the managed area was closer to or better than the natural scenario and resulted in greater coniferous cover retention. These strategies seemed to be the best to maximize and stabilize biomass carbon storage and ensure wood supply under different climate change scenarios, yet they would require further access and appropriate infrastructure. Furthermore, these strategies could maintain species compositions and age structures similar to natural scenarios, and thus may consequently help achieve forest ecosystem-based management targets. This study presents promising strategies to guide sustainable forest management in Eastern Canada in the context of climate change. [ABSTRACT FROM AUTHOR]

Using multi-scale trembling aspen tree-ring width data from Alberta, we show that scaling has a profound influence on dendroecological inferencing. At all scales of sampling, there is a significant climatological signal whose strength is nevertheless superseded by the pervasive effect of insect herbivory. At the smallest spatial scale, 20 km × 20 km, we demonstrate a quasi-periodic pattern of sharp growth reductions and the existence of negative spatial correlations among successive outbreaks. At the intermediate spatial scale of 20 km × 80 km, we show that the period 1930–1963 was marked by extremely low correlations in aspen ring widths, with much higher correlations occurring both before and after, despite high variance in precipitation that might have caused ring widths to correlate under moisture limitation. At the largest spatial scale of the entire province, aspen ring widths in the boreal forest became decorrelated abruptly in 1916, after cycling synchronously for the previous 80 years. This occurred despite a warming climate that heightened moisture limitation. Something in the environment prevents some outbreak cycles from rising to maximum intensity and from spreading to maximum extent. This appears to be the key to better predictability and management of forest insects and forests at short and long time-scales. [ABSTRACT FROM AUTHOR]

Intraspecific genetic variation in foundation species such as aspen (Populus tremuloides Michx.) shapes their impact on forest structure and function. Identifying genes underlying ecologically important traits is key to understanding that impact. Previous studies, using single‐locus genome‐wide association (GWA) analyses to identify candidate genes, have identified fewer genes than anticipated for highly heritable quantitative traits. Mounting evidence suggests that polygenic control of quantitative traits is largely responsible for this "missing heritability" phenomenon. Our research characterized the genetic architecture of 30 ecologically important traits using a common garden of aspen through genomic and transcriptomic analyses. A multilocus association model revealed that most traits displayed a highly polygenic architecture, with most variation explained by loci with small effects (likely below the detection levels of single‐locus GWA methods). Consistent with a polygenic architecture, our single‐locus GWA analyses found only 38 significant SNPs in 22 genes across 15 traits. Next, we used differential expression analysis on a subset of aspen genets with divergent concentrations of salicinoid phenolic glycosides (key defense traits). This complementary method to traditional GWA discovered 1243 differentially expressed genes for a polygenic trait. Soft clustering analysis revealed three gene clusters (241 candidate genes) involved in secondary metabolite biosynthesis and regulation. Our work reveals that ecologically important traits governing higher‐order community‐ and ecosystem‐level attributes of a foundation forest tree species have complex underlying genetic structures and will require methods beyond traditional GWA analyses to unravel. [ABSTRACT FROM AUTHOR]

Although sampling the five tallest young aspen in a stand is useful for detecting the occurrence of any aspen recruitment, this technique overestimates the population response of aspen to wolf reintroduction. Our original conclusion that random sampling described a trophic cascade that was weaker than the one described by non‐random sampling is unchanged. [ABSTRACT FROM AUTHOR]

Aspen sapling recruitment increased as browsing by elk decreased, following the 1995–96 reintroduction of wolves in Yellowstone National Park. We address claims by Brice et al. (2021) that previous studies exaggerated recent aspen recovery. We conclude that their results actually supported previous work showing a trophic cascade benefiting aspen. [ABSTRACT FROM AUTHOR]

Climate change poses a serious risk to sustainable forest management, particularly in boreal forests where natural disturbances have been projected to become more severe. In three Quebec boreal forest management units, biomass carbon storage under various climate change and management scenarios was projected over 300 years (2010–2310) with a process-based dynamic landscape model (PnET-succession for Landis-II). Several strategies varying in their use of partial cuts and clear cuts, including business as usual (BAU) (clear-cut applied on more than 95% of the managed area), were tested and compared to conservation scenarios (no-harvest). Based on simulation results at the landscape scale, the clearcut-based scenarios such as BAU could result in a decrease of biomass carbon stock by 10 tC ha−1 yr−1 compared to the natural scenario. However, this reduction in carbon stock could be offset in the long term through changes in composition, as clearcut systems promote the expansion of trembling aspen and white birch. In contrast, the use of strategies based on partial cuts on more than 75% or 50% of the managed area was closer to or better than the natural scenario and resulted in greater coniferous cover retention. These strategies seemed to be the best to maximize and stabilize biomass carbon storage and ensure wood supply under different climate change scenarios, yet they would require further access and appropriate infrastructure. Furthermore, these strategies could maintain species compositions and age structures similar to natural scenarios, and thus may consequently help achieve forest ecosystem-based management targets. This study presents promising strategies to guide sustainable forest management in Eastern Canada in the context of climate change. [ABSTRACT FROM AUTHOR]

Alternative states defined by tree‐canopy dominance result in different ecosystem functioning and shape habitat conditions for the understory vegetation. One example in the boreal forest is the alternation between broadleaf deciduous and coniferous forests. Disturbances related to natural fires and human land uses have produced changes in tree‐canopy dominance in the boreal region where coniferous forests change to broadleaved forests, affecting understory community dynamics and their related ecosystem processes and functions. To analyze the factors driving changes in understory vegetation and the resistance of its vegetation to shifts between alternative states, we compared the effects of changes in the system between two contrasting boreal forest types (black spruce vs. trembling aspen) in adjacent stands with similar topoedaphic conditions. We performed a 5‐year in situ experiment using alternative states as a theoretical framework including two approaches: (1) the ecosystem approach, manipulating environmental conditions of light, litter, and nutrients in each forest type to determine the main mechanisms associated with tree‐canopy dominance that affect the diversity and composition of understory communities; and (2) the community approach, physically exchanging understory communities between alternative states, to determine their resistance under a new tree‐canopy dominance through time, as well as the resilience of the forest understory after a small‐scale disturbance. Results indicate that the understory vegetation of trembling aspen forests were resistant through time both after changes in local conditions in the ecosystem approach and in the new black spruce‐dominated alternative state in the community approach. In contrast, mosses and ericaceous plants that typically dominate the forest floor of black spruce forests were negatively affected by the physical effect of broadleaf litter addition in our ecosystem approach and they were not resistant when transplanted to trembling aspen forests in the community approach, as they decreased in abundance and were invaded by aspen understory community species over time. The understory vegetation is a key forest ecosystem driver that can contribute to maintain the resilience of the boreal system and help to preserve their ecosystem services, which is a key aspect to consider in forest management faced with the effects of climate change. [ABSTRACT FROM AUTHOR]

Boreal mixed forests of trembling aspen (Populus tremuloides) and white spruce (Picea glauca) can provide higher outputs of many ecosystem goods and services, combined with resilience for changing environmental conditions. In this study, we examine the growth of white spruce and aspen over a range of stand compositions created by spot and broadcast treatments of broadleaves using manual and chemical means, aspen spacing, and untreated control. Twenty-two growing seasons postharvest, treatment responses created a range of broadleaf densities and spatial arrangements, reflected in significant differences in heights and diameters of the spruce mixedwood component. At this early seral stage, treatments have generated diversity in both tree species composition and stand structure. Modeling of the stand structures created by the different treatments provided outcomes ranging from pure conifer to broadleaf dominated when assessed by merchantable volumes. Broadleaf manipulations changed the relative proportion of spruce and broadleaf species in a mixture, achieving a variety of potential landscape and stand-level goals. Treatment differences were often not statistically significant until at least 16 years after stand initiation. Monitoring the achievement of mixedwood management goals will require longer time periods than currently employed for broadleaf or conifer monocultures. [ABSTRACT FROM AUTHOR]

The American bison (Bison bison) is a species that strongly interacts with its environment, yet the effects of this large herbivore on quaking aspen (Populus tremuloides) have received little study. We documented bison breaking the stems of aspen saplings (young aspen >2 m tall and ≤5 cm in diameter at breast height) and examined the extent of this effect in northern Yellowstone National Park (YNP). Low densities of Rocky Mountain elk (Cervus canadensis) after about 2004 created conditions conducive for new aspen recruitment in YNP's northern ungulate winter range (northern range). We sampled aspen saplings at local and landscape scales, using random sampling plots in 87 randomly selected aspen stands. Across the YNP northern range, we found that 18% of sapling stems had been broken. The causal attribution to bison was supported by multiple lines of evidence: (1) most broken saplings were in areas of high bison and low elk density; (2) saplings were broken in summer when elk were not foraging on them; (3) we directly observed bison breaking aspen saplings; and (4) mixed‐effects modeling showed a positive association between scat density of bison and the proportion of saplings broken. In a stand heavily used by bison, most aspen saplings had been broken, and portions of the stand were cleared of saplings that were present in previous sampling in 2012. Bison numbers increased more than fourfold between 2004 and 2015, and their ecosystem effects have similarly increased, limiting and in some places reversing the nascent aspen recovery. This situation is further complicated by political constraints that prevent bison from dispersing to areas outside the park. Thus, one important conservation goal, the preservation of bison, is affecting another long‐term conservation goal, the recovery of aspen and other deciduous woody species in northern Yellowstone. [ABSTRACT FROM AUTHOR]

Aspen mosaic-associated virus (AsMaV) is a newly identified Emaravirus, in the family Fimoviridae, Bunyavirales, associated with mosaic symptoms in aspen trees (Populus tremula). Aspen trees are widely distributed in Europe and understanding the population structure of AsMaV may aid in the development of better management strategies. The virus genome consists of five negative-sense single-stranded RNA (–ssRNA) molecules. To investigate the genetic diversity and population parameters of AsMaV, different regions of the genome were amplified and analyzed and full-length sequence of the divergent isolates were cloned and sequenced. The results show that RNA3 or nucleoprotein is a good representative for studying genetic diversity in AsMaV. Developed RT–PCR–RFLP was able to identify areas with a higher number of haplotypes and could be applied for screening the large number of samples. In general, AsMaV has a conserved genome and based on the phylogenetic studies, geographical structuring was observed in AsMaV isolates from Sweden and Finland, which could be attributed to founder effects. The genome of AsMaV is under purifying selection but not distributed uniformly on genomic RNAs. Distant AsMaV isolates displayed amino acid sequence variations compared to other isolates, and bioinformatic analysis predicted potential post-translational modification sites in some viral proteins. [ABSTRACT FROM AUTHOR]

This simulation study presents the municipal solid waste gasification, along with a detailed design of CO 2 capturing unit using monoethanolamine (solvent). The gasifier's operational parameters, such as pressure, temperature, and equivalence ratio, are chosen to optimize the gasified H 2 -enriched product stream. At optimal operational parameters, such as temperature (800 °C), pressure (1 bar), and equivalence ratio (0.2), a maximum H 2 content of 27.9% could be attained. Following that, 39.5% H 2 is found at the high-temperature shift reactor's exit, followed by 42.1% at the low-temperature shift reactor's output. It is observed that the absorber (16.5 m) and stripper (6 m) packing heights are required to capture 95% CO 2 from the product effluent obtained after shift reactors, along with column diameters of 2.70 and 3.61 m, respectively. Hence, the proposed model can give vital information for large-scale gasifier and CO 2 capture unit design, operation, and optimization with respect to different flue gases. [Display omitted] • Effective utilization of MSW for renewable fuel production. • MSW gasification followed by CO 2 capturing model is proposed. • Maximum of 42.1% H 2 content was obtained using a gasifier and WGSRs. • Design of standalone absorber and stripper to optimize the system. • Greater than 90% of CO 2 capture is possible using 30% MEA solvent. [ABSTRACT FROM AUTHOR]

Fast growing hardwoods are one of the major renewable resources available to produce bio-based materials, platform chemicals and biofuels. However, the industrial processing of lignocellulosic biomass is hindered by the complex molecular structure of the cell wall components and their supramolecular organization. This highlights the necessity of improving green processing strategies to enhance biomass conversion to valuable products from industrial wood production species. In the present study, we implemented a hydrothermal step by sequential subcritical water (SW) in aspen wood prior to saccharification and validated the process for trees grown in greenhouse and field conditions. Subcritical water enables extraction of non-cellulosic cell wall polysaccharides in native polymeric form. A major part of the pectic fraction was easily extracted within the first 10 min, while acetylated xylan was enriched in the subsequent extracts after 20- and 30-min rounds. Prolonged extraction (above 60 min) resulted in partial deacetylation and a reduction of the molar mass of xylan. The analysis of the residues enriched with cellulose and lignin showed several micromorphological changes caused by subcritical water treatment, such as an increased porosity, a loosening of the fibre matrix and a decrease in the macrofibrillar dimensions. These morphological and molecular changes in the organization of cell wall polymers after SW treatment significantly enhanced saccharification yields compared to those of non-treated aspen wood chips from both field and greenhouse conditions. Our study demonstrates that SW can be implemented as pretreatment prior to saccharification reducing the requirements for chemical acid pretreatments. This process enables the extraction of native non-cellulosic cell wall polymers for potential material applications and promotes the subsequent biochemical conversion of the residual biomass into fermentable sugars and platform chemicals in future biorefineries. [ABSTRACT FROM AUTHOR]

It is important to clarify the distribution of pyrolysis products from lignocellulosic biomass for its thermal transformation to produce high-quality bio-oil. Influences of the reaction temperature and catalysts on the pyrolysis product distribution from aspen wood (AW) and rice husk (RH) were studied by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The difference in components from the lignocellulosic biomass results in different pyrolysis characteristics of the biomass raw materials. The reaction temperature significantly influences the product distribution from AW and RH pyrolysis. In all AW catalysis experiments, acids (8.35%), ketones (3.79%), phenols (4.73%), and esters (1.50%) have the lowest content while carbohydrates (48.75%) demonstrate the highest content when taking zinc chloride (ZnCl2) as the catalyst; the HZSM-5 molecular sieve (HZSM-5) promotes the generation of esters (7.97%) and N-compounds (22.43%) while inhibiting production of aldehydes (2.41%); addition of an MCM-41 molecular sieve (MCM-41) is conducive to increasing the contents of aldehydes (21.29%), furans (5.88%), ketones (22.30%), acids (20.46%), and hydrocarbons (4.85%), while reducing the contents of alcohols (0) and carbohydrates (0). In all RH catalysis experiments, the addition of ZnCl2 helps increase the content of carbohydrates (39.16%) and decrease the contents of ketones (3.89%), phenols (5.20%), alcohols (2.34%), esters (1.13%), and N-compounds (3.09%); when applying HZSM-5 as the catalyst, hydrocarbons (18.28%) and alcohols (6.66%) reach their highest content while acids (13.21%) have the lowest content; MCM-41 promotes the generation of aldehydes (25.33%) and furans (5.55%) while inhibiting that of carbohydrates (1.42%). [ABSTRACT FROM AUTHOR]

The health risks impact of heavy metal contamination in the environment has prompted researchers to study its mitigation in an efficient and cost-friendly approach. Recently, simulated continuous biosorption using agricultural wastes is gaining popularity because it offers cheaper and faster alternative study methods using efficient large-scale removal of lead, which is known to cause adverse effects even at low concentrations. Bamboo shoots (Bambusa spp.), a delicacy known in Southeast Asia, are recognized worldwide, but the inedible sheath husks are thrown. This study evaluated the continuous Pb2+ biosorption performance of Bambusa spp. using Aspen Adsorption V8.4 by varying bed height, influent concentration, and volumetric flow rate. Linear driving force model was used to simplify, according to a separate batch biosorption study, ion exchange mechanism and Langmuir isotherm for equilibrium conditions. The backward differencing method was used to solve the resulting differential equation. Results showed that increasing the volumetric flowrate from 4.00x10-5 to 8.00x10-5 m³ /s, the bed height from 0.2 to 1.0 m, and influent concentration from 80 to 120 ppm resulted in changes in the breakthrough time by a factor of 0,5, 4.0, and 0.67 respectively. Analysis of the breakthrough curves showed that increasing volumetric flow rate shortens breakthrough time due to reduced contact time, and increasing Pb2+ concentration facilitated ion exchange by increasing concentration difference. Bed height provides more binding sites available hence, higher Pb2+ removal. [ABSTRACT FROM AUTHOR]

Purpose: Natural and anthropogenic causes have produced changes in tree dominance from coniferous to broadleaf deciduous forests, generating shifts in litter inputs and plant understory composition. The impact of changes in canopy-associated factors on belowground microbial communities remain poorly understood. The objective of this study was to better understand how abiotic and biotic factors in black spruce and trembling aspen forests shape soil microbial community structure. Methods: With high throughput sequencing, we first analyzed differences in microbial communities between microhabitats (tree phyllosphere vs. soil microbiome) and forest types (black spruce vs. trembling aspen). Second, we analyzed how shifts in factors related to each forest type (litter deposition and understory vegetation) affected soil microbial community composition. Results: We found a high microhabitat specificity of bacterial communities interacting with forest type. Shifts in litter deposition and understory vegetation between forest types did not influence microbial community composition, but the legacy effects of each forest type defined soil bacterial and fungal communities. Fungal community composition was more strongly influenced by forest type compared with bacterial communities, and both were correlated with several soil physicochemical properties that differed among forest types. Conclusion: This study expands our knowledge of the microbial composition of tree phyllosphere and soil microbial communities in black spruce and trembling aspen forests and their correlation with abiotic and biotic factors in each forest type. Our study demonstrates the resistance of microorganisms to variation in canopy-related factors and the importance of legacy effects of forest type in defining soil microbial community composition. [ABSTRACT FROM AUTHOR]

Summary: Intraspecific variation in functional traits may mediate tree species' drought resistance, yet whether trait variation is due to genotype (G), environment (E), or G×E interactions remains unknown. Understanding the drivers of intraspecific trait variation and whether variation mediates drought response can improve predictions of species' response to future drought.Using populations of quaking aspen spanning a climate gradient, we investigated intraspecific variation in functional traits in the field as well as the influence of G and E among propagules in a common garden. We also tested for trait‐mediated trade‐offs in growth and drought stress tolerance.We observed intraspecific trait variation among the populations, yet this variation did not necessarily translate to higher drought stress tolerance in hotter/drier populations. Additionally, plasticity in the common garden was low, especially in propagules derived from the hottest/driest population. We found no growth–drought stress tolerance trade‐offs and few traits exhibited significant relationships with mortality in the natural populations, suggesting that intraspecific trait variation among the traits measured did not strongly mediate responses to drought stress.Our results highlight the limits of trait‐mediated responses to drought stress and the complex G×E interactions that may underlie drought stress tolerance variation in forests in dry environments. [ABSTRACT FROM AUTHOR]

A new method for extractive-catalytic fractionation of aspen wood to produce microcrystalline (MCC), microfibrillated (MFC), nanofibrilllated (NFC) celluloses, xylan, and ethanollignin is suggested in order to utilize all of the main components of wood biomass. Xylan is obtained with a yield of 10.2 wt.% via aqueous alkali extraction at room temperature. Ethanollignin was obtained with a yield of 11.2 wt.% via extraction with 60% ethanol from the xylan-free wood at 190 °C. The lignocellulose residue formed after the extraction of xylan and ethanollignin was subjected to catalytic peroxide delignification in the acetic acid-water medium at 100 °C in order to obtain microcrystalline cellulose. MCC is hydrolyzed with 56% sulfuric acid and treated with ultrasound to produce microfibrillated cellulose and nanofibrillated cellulose. The yields of MFC and NFC were 14.4 and 19.0 wt.%, respectively. The average hydrodynamic diameter of NFC particles was 36.6 nm, the crystallinity index was 0.86, and the average zeta-potential was 41.5 mV. The composition and structure of xylan, ethanollignin, cellulose product, MCC, MFC, and NFC obtained from aspen wood were characterized using elemental and chemical analysis, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) analyses, Gas chromatography (GC), Gel permeation-chromatography (GPC), Scanning electron microscopy (SEM), Atomic force microscopy (AFM), Dynamic light scattering (DLS), Thermal gravimetric analysis (TGA). [ABSTRACT FROM AUTHOR]

Summary: Spatiotemporal patterns of phenology may be affected by mosaics of environmental and genetic variation. Environmental drivers may have temporally lagged impacts, but patterns and mechanisms remain poorly known.We combine multiple genomic, remotely sensed, and physically modeled datasets to determine the spatiotemporal patterns and drivers of canopy phenology in quaking aspen, a widespread clonal dioecious tree species with diploid and triploid cytotypes.We show that over 391 km2 of southwestern Colorado: greenup date, greendown date, and growing season length vary by weeks and differ across sexes, cytotypes, and genotypes; phenology has high phenotypic plasticity and heritabilities of 31–61% (interquartile range); and snowmelt date, soil moisture, and air temperature predict phenology, at temporal lags of up to 3 yr.Our study shows that lagged environmental effects are needed to explain phenological variation and that the effect of cytotype on phenology is obscured by its correlation with topography. Phenological patterns are consistent with responses to multiyear accumulation of carbon deficit or hydraulic damage. [ABSTRACT FROM AUTHOR]

Perennial para‐ and endo‐dormancy are seasonally separate phenomena. Whereas para‐dormancy is the suppression of axillary buds (AXBs) by a growing shoot, endo‐dormancy is the short‐day elicited arrest of terminal and AXBs. In hybrid aspen (Populus tremula x P. tremuloides) compromising the apex releases para‐dormancy, whereas endo‐dormancy requires chilling. ABA and GA are implicated in both phenomena. To untangle their roles, we blocked ABA biosynthesis with fluridone (FD), which significantly reduced ABA levels, downregulated GA‐deactivation genes, upregulated the major GA3ox‐biosynthetic genes, and initiated branching. Comprehensive GA‐metabolite analyses suggested that FD treatment shifted GA production to the non‐13‐hydroxylation pathway, enhancing GA4 function. Applied ABA counteracted FD effects on GA metabolism and downregulated several GA3/4‐inducible α‐ and γ‐clade 1,3‐β‐glucanases that hydrolyze callose at plasmodesmata (PD), thereby enhancing PD‐callose accumulation. Remarkably, ABA‐deficient plants repressed GA4 biosynthesis and established endo‐dormancy like controls but showed increased stress sensitivity. Repression of GA4 biosynthesis involved short‐day induced DNA methylation events within the GA3ox2 promoter. In conclusion, the results cast new light on the roles of ABA and GA in dormancy cycling. In para‐dormancy, PD‐callose turnover is antagonized by ABA, whereas in short‐day conditions, lack of GA4 biosynthesis promotes callose deposition that is structurally persistent throughout endo‐dormancy. Summary statement: This study untangles the so far undetermined nature of para‐ and endo‐dormancy. Using the model tree hybrid aspen, we show that para‐dormancy is caused by ABA antagonizing GA4, whereas endo‐dormancy is due to repression of GA4 biosynthesis, likely by short‐day induced methylation of the GA3ox2 promoter. [ABSTRACT FROM AUTHOR]

Disturbances are ubiquitous in ecological systems, and species have evolved a range of strategies to resist or rebound following disturbance. Understanding how the presence and complementarity of regeneration traits will affect community responses to disturbance is increasingly urgent as disturbance regimes shift beyond their historical ranges of variability. We define "disturbance niche" as a species' fitness across a range of disturbance sizes and frequencies that can reflect the fundamental or realized niche, that is, whether the species occurs alone or with other species. We developed a model of intermediate complexity (i.e., a Goldilocks model) to infer the disturbance niche. We parameterized the model for subalpine forests in Yellowstone National Park (USA) adapted to infrequent stand‐replacing fires and included the three major tree‐regeneration strategies: (1) obligate seeders that rely on ex situ seeding into burned areas (non‐serotinous lodgepole pine, Pinus contorta var. latifola), (2) obligate seeders that depend on in situ seedbanks (serotinous lodgepole pine, Pinus contorta var. latifola), and (3) species that can resprout from surviving roots following fire (quaking aspen, Populus tremuloides). Our results showed which regeneration strategies increase or decrease in prevalence as fire rotation declines. Non‐serotinous pines were extirpated when fire rotation was below 50 years in a monoculture and 100 years in a mixed forest; serotinous pines were extirpated when fire rotation was below 20 years; and aspen was extirpated when fire rotation fell below 6 years. The fundamental and realized disturbance niches pinpointed the key mechanisms limiting regeneration for each strategy, namely, increasing fire size for non‐serotinous pine (ex situ seeders), decreasing fire frequency for serotinous pine (in situ seeders), and interspecific competition for aspen (resprouters). In a mixed forest, the three regeneration strategies were complementary and each dominated at different combinations of fire size and frequency. Consequently, diversity of regeneration strategies enhanced forest resilience to declining fire rotations. Despite its simplicity, our Goldilocks model produced realistic dynamics and could be readily adapted to other disturbance‐prone ecosystems to explore the generality of these results. The disturbance niche is a key concept for anticipating community resilience to changing disturbance regimes. [ABSTRACT FROM AUTHOR]

Nearby mature forests sites are dominated by I A. saccharum i and I T. americana i , with I Quercus i spp. and I Ulmus i spp. (elm) also common before I Ophiostoma i spp. (Dutch elm disease) killed many of the large elms. Of the species added since 1990, I Ulmus i spp. became more common, making up 4.7% of the trees in 2020, and shade intolerant species I P. tremuloides i , I P. americana i , I Prunus serotina i (black cherry), and I C. cordiformis i , filled in forest gaps ([1], [2], [21]). A notable change over time was the increase in species richness, from 11 planted species in 1990 to 15 species in 2013 and 19 species in 2020. Our data suggest that it would be better to initially plant species with low shade tolerance and higher growth rates such as I Fraxinus i spp. I Prunus i spp. and I Quercus i spp. [Extracted from the article]

Condensed tannins (CTs) are abundant, ecologically-relevant secondary metabolites in many plants, which respond to variables associated with anthropogenic environmental change. While many studies have reported how genetic and environmental factors affect CT concentrations, few have explored how they influence CT molecular structure. Here, using trembling aspen (Populus tremuloides) as a model organism, we report how foliar CT concentrations, polymer sizes, representation of procyanidins and prodelphinidins, and stereochemistry vary in response to changes in air temperature (warming and freeze damage), air composition (elevated CO2 and O3), soil quality (nutrients and microbiome), and herbivory (mammal and lepidopteran). Use of multiple aspen genotypes enabled assessment of genetic influences on aspen CTs. CT concentration and composition were analyzed by thiolysis-ultra high performance liquid chromatography/mass spectrometry in archived leaf samples from prior experiments. All environmental variables explored except for soil microbiome influenced both CT quantity and quality, with climate factors appearing to have larger effect magnitudes than herbivory. Climate, soil, and herbivory effects varied among genotypes, while air composition effects were consistent across genotypes. Considering that CT properties (concentrations and molecular structures) mediate functions at the organismal through ecosystem scales, intraspecific variation in responses of CT properties to environmental factors could provide a pathway through which environmental change exerts selective pressure on Populus populations. Future studies are needed to identify the molecular-level mechanisms by which environmental factors influence CT concentrations and structures, and to establish their ecological and evolutionary significance. [ABSTRACT FROM AUTHOR]

Trembling aspen (Populus tremuloides) is arguably the most important deciduous tree species in the Intermountain West of North America. There, as elsewhere in its range, aspen exhibits remarkable genetic variation in observable traits such as morphology and phenology. In contrast to Great Lakes populations, however, relatively little is known about phytochemical variation in western aspen. This survey of phytochemistry in western aspen was undertaken to assess how chemical expression varies among genotypes, cytotypes (diploid vs. triploid), and populations, and in response to development and mammalian browsing. We measured levels of foliar nitrogen, salicinoid phenolic glycosides (SPGs) and condensed tannins (CTs), as those constituents influence organismal interactions and ecosystem processes. Results revealed striking genotypic variation and considerable population variation, but minimal cytotype variation, in phytochemistry of western aspen. Levels of SPGs and nitrogen declined, whereas levels of CTs increased, with tree age. Browsed ramets had much higher levels of SPGs, and lower levels of CTs, than unbrowsed ramets of the same genotype. We then evaluated how composite chemical profiles of western aspen differ from those of Great Lakes aspen (assessed in earlier research). Interestingly, mature western aspen trees maintain much higher levels of SPGs, and lower levels of CTs, than Great Lakes aspen. Phenotypic variation in chemical composition of aspen – a foundation species – in the Intermountain West likely has important consequences for organismal interactions and forest ecosystem dynamics. Moreover, those consequences likely play out over spatial and temporal scales somewhat differently than have been documented for Great Lakes aspen. [ABSTRACT FROM AUTHOR]

Summary: Trees constitute promising renewable feedstocks for biorefinery using biochemical conversion, but their recalcitrance restricts their attractiveness for the industry. To obtain trees with reduced recalcitrance, large‐scale genetic engineering experiments were performed in hybrid aspen blindly targeting genes expressed during wood formation and 32 lines representing seven constructs were selected for characterization in the field. Here we report phenotypes of five‐year old trees considering 49 traits related to growth and wood properties. The best performing construct considering growth and glucose yield in saccharification with acid pretreatment had suppressed expression of the gene encoding an uncharacterized 2‐oxoglutarate‐dependent dioxygenase (2OGD). It showed minor changes in wood chemistry but increased nanoporosity and glucose conversion. Suppressed levels of SUCROSE SYNTHASE, (SuSy), CINNAMATE 4‐HYDROXYLASE (C4H) and increased levels of GTPase activating protein for ADP‐ribosylation factor ZAC led to significant growth reductions and anatomical abnormalities. However, C4H and SuSy constructs greatly improved glucose yields in saccharification without and with pretreatment, respectively. Traits associated with high glucose yields were different for saccharification with and without pretreatment. While carbohydrates, phenolics and tension wood contents positively impacted the yields without pretreatment and growth, lignin content and S/G ratio were negative factors, the yields with pretreatment positively correlated with S lignin and negatively with carbohydrate contents. The genotypes with high glucose yields had increased nanoporosity and mGlcA/Xyl ratio, and some had shorter polymers extractable with subcritical water compared to wild‐type. The pilot‐scale industrial‐like pretreatment of best‐performing 2OGD construct confirmed its superior sugar yields, supporting our strategy. [ABSTRACT FROM AUTHOR]

Purpose: Most plants interact with soil biota that positively or negatively affect seedling performance. These plant-soil feedbacks (PSFs) can strongly affect recruitment, potentially for years after death. We tested whether PSFs persisted following death for Populus tremuloides Michx. (aspen) and if these effects were environment dependent using soils collected from live and dead aspen and heterospecific Picea glauca (Moench) Voss in 24 stands across two ecosystems. Methods: We conducted a greenhouse experiment using soils from 24 aspen stands. At each stand, we collected soil from three trees of each tree type and used live and sterilized versions of these soils to inoculate aspen seedlings. We then recorded mortality and growth of the seedlings over three months. Results: Live inocula reduced aspen survival and growth relative to sterilized inocula, suggesting that pathogens drive PSF. Plant responses to live and dead aspen inocula were correlated across environments; however, responses to aspen and heterospecific Picea inocula were uncorrelated, suggesting that specialized pathogens may drive PSF. Conclusions: Pathogen-driven negative PSFs can persist for multiple years irrespective of the environment, potentially limiting the regeneration of aspen stands following dieback. Persistent PSFs thus have potential to cause lagged effects on population and community dynamics. [ABSTRACT FROM AUTHOR]

The use of the commercial simulator Aspen Plus® could bring an amelioration in the accuracy of the predictions of the chemical species composition in the output streams of the anaerobic digestion process. Compared to the traditionally employed lumped models, which are elaborated from scratch, the models implemented in Aspen Plus® have access to a broad library of thermodynamic and phenomena transport properties. In the present investigation, a process simulation model for anaerobic digestion has been prepared by including a stoichiometric-equilibria reactor to calculate the extent of the ionization of the molecules present in the anaerobic digestate. The model characterizes the technical feasibility of anaerobic digestate stabilization, by means of biomass ash-based treatment, for the production of an organic fertilizer and potential biogas upgradation with the synthesis of ammonium carbonate. First of all, the titration of the manure digestate with the hydrochloric acid showed that a dose of 3.18 mEq/g would be required to attain the targeted pH of zero-point charge, upon addition of the sewage sludge ash in a ratio to the manure digestate of 0.6 ± 0.2%. Secondly, the profiles of ammonia, carbon dioxide, and methane found in the biogas agree with the pH of the treated digestate and enable the upgrading of the biogas with the production of NH4HCO3. The model needs to be further developed to ensure the standards are attained in all output streams of stabilized anaerobic digestate, biomethane, and isolated added-value chemical fertilizers. [ABSTRACT FROM AUTHOR]

Currently, 90% of Kazakhstan's oil is situated in 15 oil and gas fields where simple cycle gas turbines are utilized for electricity generation. The need for developing techniques to enhance the efficiency and eco-friendliness of fuel consumption in Kazakhstan's oil fields is imperative. In this article, methods for improving the energy efficiency of a simple gas turbine power plant functioning in an oil field are discussed, with consideration given to the impact of ambient temperature and specific environmental constraints, such as water scarcity and high temperatures. Two schemes to increase efficiency are evaluated: the first involves the utilization of a waste heat boiler for steam production intended for technological purposes, while the second involves electricity generation through a combination of a waste heat boiler and a steam turbine. Models based on Aspen HYSYS were formulated, with actual gas turbine power plant operation taken into account. Analysis indicated that a waste heat boiler scheme could generate up to 350 t/h of steam, completely replacing power boilers. Im plementation of the combined cycle power plant (CCPP) system resulted in the production of up to 262.42 MW of electricity. Environmental analyses demonstrated that both schemes exhibit comparable specific emissions in terms of power generation, with 0.56 kgCO2/kWh for HRSG and 0.53 kgCO2/kWh for CCPP. Technological, environmental, and economic analyses were conducted to determine the most promising technology, considering the specifics of the oil fields in Kazakhstan. Based on the payback period for HRSG (4 years) and CCPP (7 years) options, it was deduced that the former is the most favorable for implementation [ABSTRACT FROM AUTHOR]

Evaluation of the acoustic properties of objects using the results as an informative parameter in determining the physical and mechanical characteristics of a material, is widely used in modern science and technology, as well as in the field of nondestructive testing. In the present paper the possibility of using this approach is considered in relation to the woodworking industry in order to estimate the characteristics of sawn timber modified by the ultrasonic method. The results of previous studies have shown the effectiveness of this technology for increasing the surface density and hardness of wood; therefore, one urgent task is to find criteria that allow evaluating the achieved modification parameters, as well as optimizing the settings of the corresponding technological equipment. In this paper the research results of the acoustic properties of ultrasonic modified aspen wood (Populus tremula) are presented and their applicability as a criterion for estimating the degree of lumber modification is determined. [ABSTRACT FROM AUTHOR]

Electricity is essential in human life. It is generated from power plants fuelled by fossil resources that have threatened the environment. Greener resources, such as biomass, are becoming imperative to utilize for their eco-friendly, renewable, and sustainable properties. One of the potential biomass is bamboo leaves because of their high calorific value (15–19 MJ/kg), high ash content (up to 25.86%-wt), and silica content in the ash (bio-silica) of 90–92%-wt. Unfortunately, the study on their valorization is still rarely disclosed, and hence, this study aims to discuss the simulation of bamboo leaves valorization to electricity and bio-silica. In this study, 2 tonnes/day of bamboo leaves are combusted at 700 °C and the produced heat is then fed to the organic Rankine cycle (ORC) systems to generate small-scale electricity. Depending on several case studies, the specific electricity is generated in the range of 0.156–0.160 kWh/kg and can electrify 24 households in rural areas. Furthermore, the produced ash from combustion is undergone alkaline extraction processes to gain bio-silica with a yield of 17.5%-wt and purity of 92%-wt. Based on the simulation, bio-silica is obtained at the highest amount of 3.3 kg/h. Finally, this study concludes that bamboo leaves valorization is promising. [ABSTRACT FROM AUTHOR]

In tree canopies, incoming solar radiation interacts with leaves and branches to generate temperature differences within and among leaves, presenting thermal opportunities and risks for leaf‐dwelling ectotherms. Although leaf biophysics and insect thermal ecology are well understood, few studies have examined them together in single systems. We examined temperature variability in aspen canopies, Populus tremuloides, and its consequences for a common herbivore, the leaf‐mining caterpillar Phyllocnistis populiella. We shaded leaves in the field and measured effects on leaf temperature and larval growth and survival. We also estimated larval thermal performance curves for feeding and growth and measured upper lethal temperatures. Sunlit leaves directly facing the incoming rays reached the highest temperatures, typically 3–8°C above ambient air temperature. Irradiance‐driven increases in temperature, however, were transient enough that they did not alter observed growth rates of leaf miners. Incubator and ramping experiments suggested that larval performance peaks between 25 and 32°C and declines to zero between 35 and 40°C, depending on the duration of temperature exposure. Upper lethal temperatures during 1‐h heat shocks were 42–43°C. When larvae were active in early spring, temperatures generally were low enough to depress rates of feeding and growth below their maxima, and only rarely did estimated mine temperatures rise beyond optimal temperatures. Observed leaf or mine temperatures never approached larval upper lethal temperatures. At this site during our experiments, larvae thus appeared to have a significant thermal safety margin; the more pressing problem was inadequate heat. Detailed information on mine temperatures and larval performance curves, however, allowed us to leverage long‐term data sets on air temperature to estimate potential future shifts in performance and longer‐term risks to larvae from lethally high temperatures. This analysis suggests that, in the past 20 years, larval performance has often been limited by cold and that the risk of heat stress has been low. Future warming will raise mean rates of feeding and growth but also the risk of exposure to injuriously or lethally high temperatures. [ABSTRACT FROM AUTHOR]

In this study, hemicelluloses of aspen wood (Pópulus trémula) were obtained by oxidative delignification in an acetic acid-water-hydrogen peroxide medium at temperatures of 70–100 °C and a process time of 1–4 h. The maximum polysaccharide yield of up to 9.68 wt% was reported. The composition and structure of the hemicelluloses were studied using a complex of physicochemical methods: gas and gel permeation chromatography, Fourier-transform infrared spectroscopy, 2D nuclear magnetic resonance spectroscopy, and thermogravimetric analysis. The xylose, mannose, galactose, and glucose monomer units were identified in the hemicelluloses by gas chromatography. The weight average molecular weight Mw of the products determined by gel permeation chromatography was found to range within 8932–33,142 g/mol. The reported Fourier-transform spectra of the hemicelluloses contain all the bands characteristic of heteropolysaccharides; a weak lignin absorption signal in the spectra at 1500–1510 cm−1 is attributed to a minor content of phenolic fragments in the structure of the obtained hemicelluloses. The use of thermogravimetric analysis established that the hemicelluloses isolated from aspen wood are resistant against heating to temperatures of up to 90–100 °C and, upon further heating up to 400 °C, start destructing at an increasing rate. The antioxidant activity of the hemicelluloses was examined using the compounds that mimic free radicals (1,1-diphenyl-2-picrylhydrazyl) and hydroxyl radicals (salicylic acid). It was found that the activity of all polysaccharides in neutralizing DPPH and hydroxyl radicals is lower than the absorption capacity of vitamin C at all the tested concentrations (0.5, 2, and 5 mg/mL) and attains 81.7 and 82.9%, respectively. [ABSTRACT FROM AUTHOR]

Diverse geographic, environmental, and ecological factors affect gene flow and adaptive genomic variation within species. With recent advances in landscape ecological modelling and high‐throughput DNA sequencing, it is now possible to effectively quantify and partition their relative contributions. Here, we use landscape genomics to identify determinants of genomic differentiation in the forest tent caterpillar, Malacosoma disstria, a widespread and irruptive pest of numerous deciduous tree species in North America. We collected larvae from multiple populations across Eastern Canada, where the species experiences a diversity of environmental gradients and feeds on a number of different host tree species, including trembling aspen (Populus tremuloides), sugar maple (Acer saccharum), red oak (Quercus rubra), and white birch (Betula papyrifera). Using a combination of reciprocal causal modelling (RCM) and distance‐based redundancy analyses (dbRDA), we show that differentiation of thousands of genome‐wide single nucleotide polymorphisms (SNPs) among individuals is best explained by a combination of isolation by distance, isolation by environment (spatial variation in summer temperatures and length of the growing season), and differences in host association. Configuration of suitable habitat inferred from ecological niche models was not significantly related to genomic differentiation, suggesting that M. disstria dispersal is agnostic with respect to habitat quality. Although population structure was not discretely related to host association, our modelling framework provides the first molecular evidence of host‐associated differentiation in M. disstria, congruent with previous documentation of reduced growth and survival of larvae moved between natal host species. We conclude that ecologically mediated selection is contributing to variation within M. disstria, and that divergent adaptation related to both environmental conditions and host association should be considered in ongoing research and management of this important forest pest. [ABSTRACT FROM AUTHOR]

A novel method was tested for improving tree breeding strategies that integrate quantitative and population genetics based on range‐wide reciprocal transplant experiments. Five reciprocal common garden tests of Populus tremuloides were investigated including 6450 trees across western Canada focusing on adaptation traits and growth. Both genetic parameters and home‐site transplant models were evaluated. We found a genetic trade‐off between growth and early spring leaf flush and late fall senescence. Coefficients of phenotypic variation (CVp) of cell lysis (CL), a measure of freezing injury, shrank from 0.28 to 0.10 during acclimation in the fall, and the CVp slope versus the freezing temperature was significantly different from zero (R2 = 0.33, p =.02). There was more between‐population genetic variation in fall phenology than in spring leaf phenology. We suggest that P. tremuloides demonstrated a discrepancy between the ecological optimum and the physiological optimum minimum winter temperature. The sub‐optimal growing condition of P. tremuloides is potentially caused by the warmer ecological optimum than the physiological optimum. Assisted migration and breeding of fast growers to reforest cooler plantation sites can improve productivity. Transferring the study populations to less than 4°C of extreme minimum temperature appears safe for reforestation aligning with the historical recolonization direction of the species. This is equivalent to a 5–10° latitudinal northward movement. Fall frost hardiness is an effective criterion for family selection in the range tested in this study. [ABSTRACT FROM AUTHOR]

Upland aspen (Populus spp.) forests contribute significantly to biodiversity in their circumboreal role as keystone species. As aspen ecosystems flourish or diminish, myriad dependent species follow suit. The 43‐hectare Pando aspen (Populus tremuloides Michx.) clone in Utah, USA, is thought to be the largest living organism on earth, but is faltering due to chronic herbivory. Long‐term resilience in aspen communities, including Pando, rests on successful recruitment of vegetative suckers that are nutritiously desirable to browsing ungulates. Here, I evaluate aspen reproduction alongside numerous vital indicators of Pando's status in the first trend assessment of this embattled iconic forest. I remeasured 64 plots from 2017 using 19 indicators to determine current conditions. Findings show that the genetically uniform Pando is "breaking up" because of herbivory and fencing. Initial successes within fenced zones are tempered by nearly half of Pando that remains unprotected from chronic wild and domestic herbivory. I propose a strategy of process‐based stewardship informed by adaptive monitoring to restore this famed "one‐tree forest." Lessons from Pando may be applied to struggling, often species rich, aspen systems facing similar challenges globally. [ABSTRACT FROM AUTHOR]

Upland aspen (Populus spp.) forests contribute significantly to biodiversity in their circumboreal role as keystone species. As aspen ecosystems flourish or diminish, myriad dependent species follow suit. The 43‐hectare Pando aspen (Populus tremuloides Michx.) clone in Utah, USA, is thought to be the largest living organism on earth, but is faltering due to chronic herbivory. Long‐term resilience in aspen communities, including Pando, rests on successful recruitment of vegetative suckers that are nutritiously desirable to browsing ungulates. Here, I evaluate aspen reproduction alongside numerous vital indicators of Pando's status in the first trend assessment of this embattled iconic forest. I remeasured 64 plots from 2017 using 19 indicators to determine current conditions. Findings show that the genetically uniform Pando is "breaking up" because of herbivory and fencing. Initial successes within fenced zones are tempered by nearly half of Pando that remains unprotected from chronic wild and domestic herbivory. I propose a strategy of process‐based stewardship informed by adaptive monitoring to restore this famed "one‐tree forest." Lessons from Pando may be applied to struggling, often species rich, aspen systems facing similar challenges globally. [ABSTRACT FROM AUTHOR]