Douglas-fir Research Articles

Sentient Conversations

We live in a world of reckoning. In history, in politics, in culture, oppressive paradigms are being overturned and new perspectives are unfolding. One significant site(s) of reckoning are the modern, imperial, and colonial constructions of the environment that have served to silence and limit the voice of the non-human world, and our collective understanding of it. In the spirit of this moment, I begin this conversation with a powerful reconsideration:everything is sentient—soil, plants, algae, fungi, trees, birds, worms, rocks, and more. Sophisticated and rootbound, trees cooperate with their kin and communicate their needs. Remembering past events, perceiving and mounting defenses from impending droughts and fire seasons, trees have inseparable bonds with others (Simard 2021). Similarly, lichen are mutually arranged in complex relations to help one another survive and thrive, and provide complex nutrients to the ground and tree lined canopies of Douglas fir, cedars, and spruce (Wohlleben 2016). Michael Hathaway and Willoughby Arévalo articulate how mycorrhizal networks communicate, make decisions, and learn ways to move, coordinate, and tell other fungi about lurking dangers and other events (2023). Sentient and formidable, mycelium feed one another through branched structures and tubes, releasing and responding to chemical signals using amino acids (Hathaway and Arévalo2023).

Adsorbing Volatile Organic Compounds within Bitumen Improves Colloidal Stability and Air Quality

The mass loss of bitumen due to volatilization is one of the deterioration mechanisms through which the chemical composition of bitumen deviates from its original condition, leading to change in the physical and rheological properties of bitumen. The emissions from bitumen not only accelerate its aging but also negatively impact air quality and consequently human health. Here, we characterized the molecular compositions of the volatiles emitted from bitumen in an isothermal aging process (150 °C for 24 h). We also investigated the impact of losing these compounds on the association behavior of asphaltene stacks. Based on the GC-MS results, the main mass loss of SARA (saturates, aromatics, resins, asphaltenes) fractions is attributed to the emission of lightweight nonpolar aromatic and aliphatic compounds. The most dominant volatiles are single-ring aromatics carrying short side chains, followed by saturated and unsaturated aliphatic compounds including short-chain n-alkanes, iso-alkanes, cyclic alkenes, alkenes, and dienes. Using molecular modeling in the framework of density functional theory (DFT), we showed how the reduction in aromatics and saturates can impact the colloidal stability of asphaltenes in the matrix of bitumen. Based on the DFT results, the surface adsorption of aromatics and saturates on asphaltene planes provides the steric repulsion required to maintain the asphaltene planes at a distance sufficient to inhibit their agglomeration. In addition, aromatic molecules with the least hindrance repulsion can disturb the π–π interfacial interactions between asphaltene planes, facilitating their deagglomeration. Therefore, a direct consequence of the mass loss of bitumen due to volatilization is disturbing the asphaltene distribution within the bitumen and stimulating the aggregation of asphaltenes. We also studied the merits of incorporating biochar into the bitumen surface to reduce bitumen’s mass loss. Modification of bitumen separately with each of six biochars derived from biomass feedstocks (walnut shell, peanut shell, Douglas fir, pine bark, birch, and algae) showed the efficacy of each biochar to reduce the volatiles emitted from bitumen, thereby reducing the changes in the composition of maltene with consequent colloidal stability losses. The study outcomes highlight the importance of reducing emissions from bitumen to delay its aging and minimize negative impacts on air quality and human health.

Competition-based mortality and tree losses. An essential component of net primary productivity

Even-aged stands can regenerate with many thousand seedlings per hectare before the density declines to just a few hundred trees per hectare 100 years later; management practices can lead to even lower tree numbers due to quality selection and thinning. In other words, during the development of unmanaged stands, the majority of individuals die naturally due to competition. Despite the far-reaching consequences for structural and genetic diversity, dead wood and fuel wood accumulation, we have only limited quantitative knowledge about the continuous mortality of trees and the wood volume loss over longer timespans.For this study, we used a unique set of 476 unmanaged, monospecific experimental plots of Norway spruce (Picea abies (L.) H. Karst.), silver fir (Abies alba Mill.), Scots pine (Pinus sylvestris L.), European larch (Larix decidua Mill.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)), European beech (Fagus sylvatica L.), and oak (Quercus robur L. and Quercus petraea (Matt.) Liebl.) throughout Europe to analyze the competition-based mortality of trees and its dependency on age and site conditions.First, we show that the total stem volume production, standing stock, and mortality were continuously increasing until an age of 100–150 years. The accumulated competition-caused stem volume loss at that age amounted to 500–1000 m3 ha−1.Second, the net growth of the stands (share of the growth that is accumulated in the standing stock) strongly decreased with increasing age even when the gross growth was still high. The proportion of the net growth versus gross growth continuously decreased with increasing age regardless of site quality.Third, we show a degressive decrease of the annual relative tree number mortality rates from 0.05 to 0.20 in young down to 0.01–0.02 in mature stands. For some species, we found these rates to be site dependent with different directions of the site effect. The interplay of decreasing mortality rates and increasing average volume of the dead trees resulted in unimodal mortality curves over time of the annual mortality, peaking at 3–12 m3 ha−1 yr−1 at ages of about 75–150 years.Over the whole rotation, the average annual biomass loss from mortality ranged between 0.8 and 2.1 t ha−1 yr−1 with a carbon content of 0.4–1.1 t C ha−1 yr−1. We discuss the relevance of the results for measuring, understanding, modelling, and managing forest stands. Our results reveal that the withdrawal of forest management and setting aside (previously managed) forests over a rotation time of 100–150 years means that about one third of the total production in monospecific stands would flow to the debris pool rather than being exploited for carbon sequestration and related emission savings in harvested wood products. The mortality related loss fractions of above ground biomass we quantified in this study indicate the trade-off between wood production and setting aside forest to allow deadwood accumulation and associate changes in biodiversity.

Genetic and Epigenetic Mechanisms of Longevity in Forest Trees.

Trees are unique in terms of development, sustainability and longevity. Some species have a record lifespan in the living world, reaching several millennia. The aim of this review is to summarize the available data on the genetic and epigenetic mechanisms of longevity in forest trees. In this review, we have focused on the genetic aspects of longevity of a few well-studied forest tree species, such as Quercus robur, Ginkgo biloba, Ficus benghalensis and F. religiosa, Populus, Welwitschia and Dracaena, as well as on interspecific genetic traits associated with plant longevity. A key trait associated with plant longevity is the enhanced immune defense, with the increase in gene families such as RLK, RLP and NLR in Quercus robur, the expansion of the CC-NBS-LRR disease resistance families in Ficus species and the steady expression of R-genes in Ginkgo biloba. A high copy number ratio of the PARP1 family genes involved in DNA repair and defense response was found in Pseudotsuga menziesii, Pinus sylvestris and Malus domestica. An increase in the number of copies of the epigenetic regulators BRU1/TSK/MGO3 (maintenance of meristems and genome integrity) and SDE3 (antiviral protection) was also found in long-lived trees. CHG methylation gradually declines in the DAL 1 gene in Pinus tabuliformis, a conservative age biomarker in conifers, as the age increases. It was shown in Larix kaempferi that grafting, cutting and pruning change the expression of age-related genes and rejuvenate plants. Thus, the main genetic and epigenetic mechanisms of longevity in forest trees were considered, among which there are both general and individual processes.

Morphological Crown Attributes Contributing to Differential Height and Diameter Growth among Families in a Coastal Douglas-Fir Progeny Test: Crown Structural Evidence for Crop Ideotypes

Theoretical tree crop ideotypes have long and narrow live crowns with a high total leaf area. This crown form allows more efficient exploitation of site resources, in part by physically occupying less growing space per unit leaf area and by packing a greater number of trees into a given area. Genetic selection for crop ideotypes has been proposed as a strategy for maximizing productivity per unit area in stands managed under intensive silviculture. The primary objective of this study was to test the relationship between the relative growth performance of different families in a Douglas-fir (Pseudotsuga menziesii var. menziesii [Mirb.] Franco) progeny test and morphological crown attributes that conform to a theoretical crop ideotype. The overarching goal was to identify attributes conferring superior height and diameter growth on families and to facilitate the incorporation of these attributes and associated growth mechanisms into hybrid growth models for intensively managed plantations. Crown structural attributes were measured on destructively sampled trees and averaged for the entire crown and each third of live crown length among families. Multivariate analysis revealed that crown attributes averaged over the entire crown performed best for identifying families with different height and diameter growth, followed successively by the bottom, middle, and top crown third. Trees with relatively short branch lengths and steep branch angles tended to have higher total leaf area per unit crown length (TLACL), and this structural attribute showed a strong positive correlation with cumulative diameter growth. The ratio of crown width to crown length (CWL) was moderately and negatively correlated with cumulative height growth. The families displaying the most rapid diameter growth in this progeny test conformed to a theoretical crop ideotype, while those with the most rapid height growth displayed crown attributes with a less obvious relationship to the crop ideotype concept. TLACL implied one possible mechanism driving genetic gain in Douglas-fir families, given its high heritability and strongly positive correlation with growth performance. Incorporating TLACL as an explanatory variable in diameter growth models could at least partly represent different genetic levels. TLACL is less strongly correlated with height growth rate, so incorporating CWL may better represent genetic effects on height growth models.

Functional diversity affects tree vigor, growth, and mortality in mixed-conifer/hardwood forests in California, U.S.A, in the absence of fire

Mixed tree-species forest management can increase forest resilience by reducing the impacts of disturbances that disproportionately affect a single tree species or closely related groups of tree species. Beyond disturbance-risk reduction, tree-species diversification may foster functional-diversity effects (e.g., complementarity or facilitation) that alter the performance of a given tree species in mixed versus pure stands, potentially benefitting carbon sequestration and wildlife habitat. Tree species-mixture effects have been explored to only a limited degree in western US forests and, particularly, in California. Establishing whether vigor, growth, and mortality of common tree species vary with stand composition would help inform restoration and modeling of these forests under climate change. Using data from USDA Forest Service Forest Inventory and Analysis (FIA) plots from California, we examined how individual-tree vigor, as indicated by live crown ratio (LCR), periodic basal area increment (BAI), and mortality odds varied with functional dissimilarity (FDis). We quantified FDis using an index based on 11 traits related to resource acquisition, competition, environmental tolerances, and fire ecology. We classified major tree species into ponderosa pine (Pinus ponderosa), Jeffrey pine (Pinus jeffreyi), incense-cedar (Calocedrus decurrens), true firs (Abies spp.), Douglas-fir (Pseudotsuga menziesii), live oaks (Quercus spp.), and deciduous oaks (Quercus spp.) response groups. We tested for the main effects of FDis on tree responses, as well as for interactions with tree, site, stand, and climate factors. We found that initial tree height modulated the effects of FDis on ponderosa pine, Jeffrey pine, incense-cedar, and true fir LCR, whereas FDis interacted with climate to alter live oak and deciduous oak LCR. FDis decreased BAI in ponderosa pine and increased BAI in live oaks. FDis interacted with tree size to influence BAI for Jeffrey pine, Douglas-fir, and true firs. We found no evidence that climate or site quality modulated FDis effects on BAI for any species group. Tree mortality was not responsive to FDis, except for the true firs, where both initial tree height and competition interacted with FDis to increase and decrease mortality odds, respectively. FDis effects commonly shifted from positive to negative along gradients of stand structure and site quality, indicating that these effects vary with site and stand conditions. Our results have implications for balancing the ecosystem benefits of mixed stands, such as disturbance risk, carbon sequestration, and habitat during forest restoration projects in the region, as well as for more accurate modeling of complex stands.

Teaching English in the Muslim World against the Backdrop of 9/11 and Resurgent Nationalism: A Case Study of Bangladeshi ELT

AbstractThis article examines English language teaching (ELT) policy, textbooks, and pedagogy in the neo‐nationalist era that followed 9/11 in Muslim‐majority Bangladesh. Informed by the Douglas Fir Group's transdisciplinary framework of second language learning, the examination substantiates the ideologies of economization, de‐Islamization and awamization, which coalesce into the overarching ideology of secularization of ELT as a response to the global war on terror and the rise of neo‐nationalism in South Asia. This secular response to forces and developments in global, regional, and local contexts marks the distinctiveness of Bangladeshi ELT compared with other Muslim societies, which have sought to develop students' awareness of religious and cultural values while teaching English. The secularization of ELT can be explained by the rise of Hindutva nationalism in India and the latter's influence on the ruling Bangladesh Awami League government which has been in power for over 14 years. The article attests to the complex, multilayered ELT ideology shaped by local, regional, and global forces and interests, suggesting the formation of a national/social imaginary that seeks alliance with secular Muslims and non‐Muslim communities at home and in the region and excludes practicing Muslims in both contexts.

Particle size and shape effect of Crumbler® rotary shear-milled granular woody biomass on the performance of Acrison® screw feeder: A computational and experimental investigation

Physical experiments and discrete element model (DEM) simulations are conducted to evaluate particle characteristics and operation parameter effects on screw feeding performance for rotary shear-milled Douglas fir. Three performance metrics are used: mass flow rate, shaft driving torque, and specific energy consumption. The impact of particle size, particle size distribution (PSD), shaft rotational speed (rpm), and hopper dimensions on the performance are investigated. All employed performance metrics reveal the superior flowability of the 2-mm particles in contrast to the larger 6-mm counterpart. Remarkably, wider PSD results in poorer flowability than the two mono-sized particles, proving the flowability enhancement achieved by narrower PSD of the woody feedstock. More importantly, DEM simulations unveil PSD-induced degradation in flowability is attributed to mechanical interlocking and particle segregation effects. Furthermore, higher shaft rpm causes higher mass flow rate at the cost of higher specific energy consumption due to viscous dissipation and changes in flow pattern.

Unpacking the ‘black box’: Improving ecological interpretation of regression‐based models

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

Sustaining Critical Approaches to Translanguaging in Education: A Contextual Framework

AbstractTranslanguaging remains a timely and important topic in bi/multilingual education. The most recent turn in translanguaging scholarship involves attention to translanguaging in context in response to critiques of translanguaging as a universally empowering educational practice. In this paper, seven early career translanguaging scholars propose a framework for researching translanguaging “in context,” drawing on the Douglas Fir Group's (2016) transdisciplinary framework for language acquisition. Examining translanguaging in context entails paying attention to who in a classroom wields power, as a result of their greater proficiency in societally valued languages, their more “standard” ways of speaking these languages, their greater familiarity with academic literacies valued at school, and/or their more “legitimate” forms of translanguaging. In our framework for researching translanguaging in context, we propose three principles. The first principle is obvious: (1) not to do so apolitically. The other two principles describe a synergy between ethnographic research and teacher‐researcher collaborative research: (2) ethnographic research can assess macro‐level language ideologies and enacted language hegemonies at the micro‐ and meso levels, and (3) teacher‐researcher collaborations must create and sustain inclusive, equitable classroom social orders and alternative academic norms different from the ones documented to occur in context if left by chance.

The Variations in Tracheid Length of Pseudotsuga menziesii (Mirb.) Franco Wood in Relation to Cambium Age, Site, and Growth

This study investigated the variations in tracheid length of Pseudotsuga menziesii (Mirb.) Franco from three sites in Croatia in relation to cambium age, within- and between-site differences, and growth rate. Tracheids are the main structural element in P. menziesii wood, varying in length following different patterns that should be precisely determined. After the maceration procedure, earlywood tracheid length (EWTL), latewood tracheid length (LWTL), annual growth ring tracheid length (RTL), earlywood ring width (EWW), latewood ring width (LWW), and annual ring width (ARW) were measured in selected annual growth rings. The significant effect of annual growth rings and zone interaction for EWTL and LWTL, as well as of annual growth rings, trees, and sites for RTL, was determined. The results conclude on the differences between the trends in EWTL and LWTL from pith toward the bark. In addition, the correlation analysis between the tracheid length and different growth patterns was investigated, and very weak or no association between the variables was detected. This research contributes to better understanding the degree of wood uniformity of P. menziesii from the technological perspective, as well as the variability factor in the optimization of forest management with favoring overall wood quality.

Decomposition of green tea and rooibos tea across three monospecific temperate forests: Effect of litter type and tree species

We studied the effect of different forest covers on carbon (C) and nitrogen (N) dynamics of two standardised litters during decomposition in soil. For this purpose, commercially available bags containing green tea or rooibos tea were incubated in close monospecific stands of Fagus sylvatica, Pseudotsuga menziesii, and Quercus cerris, in the Apennines range, Italy, and then analysed at different intervals for up to two years. We also investigated the fate of various C functional groups in both types of litter under beech by nuclear magnetic resonance spectroscopy. After two years of incubation, green tea had not changed its original C/N ratio of 10, while rooibos tea had nearly halved its original value of 45, because of different C and N dynamics. Both litters progressively lost C, about fifty per cent of the initial content in the case of rooibos tea, and a little more for green tea, most of the loss occurring in the first three months. In terms of N, green tea behaved as for C, while rooibos tea in the early stage lost part of its N stock, fully recovering it by the end of the first year. Under beech, both litters showed a preferential loss in carbohydrates during the first trimester of incubation and, consequently, an indirect enrichment in lipids. Later on, the relative contribution of the various C forms remained practically constant.Our results overall support that the decay rate and compositional changes of litter depend strongly on the litter type and little on the tree cover of the soil in which the litter is incubated.

Yield and Toxin Analysis of Leaf Protein Concentrate from Common North American Coniferous Trees

In the event of an abrupt sunlight reduction scenario, there is a time window that occurs between when food stores would likely run out for many countries (~6 months or less) and ~1 year when resilient foods are scaled up. A promising temporary resilient food is leaf protein concentrate (LPC). Although it is possible to extract LPC from tree biomass (e.g., leaves and needles), neither the yields nor the toxicity of the protein concentrates for humans from the most common tree species has been widely investigated. To help fill this knowledge gap, this study uses high-resolution mass spectrometry and an open-source toolchain for non-targeted screening of toxins on five common North American coniferous species: Western Cedar, Douglas Fir, Ponderosa Pine, Western Hemlock, and Lodgepole Pine. The yields for LPC extraction from the conifers ranged from 1% to 7.5%. The toxicity screenings confirm that these trees may contain toxins that can be consumed in small amounts, and additional studies including measuring the quantity of each toxin are needed. The results indicate that LPC is a promising candidate to be used as resilient food, but future work is needed before LPCs from conifers can be used as a wide-scale human food.

Finite element modeling of biomass hopper flow

Hoppers are widely used biomass handling devices that channel bulk biomass from storage to subsequent handling equipment. Jenike’s longstanding approach, based on the Mohr-Coulomb model, has been successfully used to design hoppers handling cohesionless granular materials such as grains and other agricultural produces. However, designing a hopper to ensure reliable biomass flow is found to be challenging due to cohesion, irregular particle shape, and bulk material elastoplasticity. This study aims to address the biomass handling engineering challenge with alternative constitutive material models concerning the flow behavior of bulk solids. Finite element modeling is an approach that allows for implementation of different material models, whose underlying constitutive theories assist in investigating the origin and manifestation of bulk mechanical behavior of granular materials. This study focuses on the incipient gravity hopper flow of two types of biomass feedstocks, i.e., ground corn stover and Douglas fir wood. Three widely used constitutive material models, i.e., Mohr-Coulomb model, modified Cam-Clay model, and Drucker-Prager/Cap model, are implemented. Using the flow pattern represented by the volume of biomass exhibiting more than 7% of axial strain (Kamath and Puri, 1999), the finite element model predicts that the bulk corn stover particulate material forms an arch, which represents a hampered transition from the static state to the dynamic flow-state out of the hopper, whereas bulk Douglas fir wood particulate material develops a reliable mass flow pattern. A laboratory scale hopper was used to experimentally determine the biomass flow conditions, which were subsequently compared with the predicted onset of flow by a finite element model (FEM). The developed FEM was found to correctly predict the initiation of mass flow for the milled Douglas fir wood, whereas corn stover was predicted to establish a strong core flow suggesting an unreliable handling characteristic. This observation aligns with the reported poor handling of milled corn stover.

Changes of vegetation in coniferous monocultures in the context of conversion to mixed forests in 30 years – Implications for biodiversity restoration

The understorey vegetation of temperate forests harbours a major proportion of terrestrial biodiversity and fulfills an important role in ecosystem functioning. Over the past decades, temperate forest understoreys were found to change in species diversity and composition due to several anthropogenic and natural drivers. Currently, the conversion and restoration of even-aged coniferous monocultures into more diverse and mixed broad-leaved forests are major objectives of sustainable forest management in Central Europe. This forest conversion alters understorey communities and abiotic site conditions but the underlying patterns and processes are not yet fully understood. Therefore, we investigated changes in the Bavarian Spessart mountains in southwest Germany, where we re-sampled 108 semi-permanent plots from four different coniferous stand types (i.e., Norway spruce, Scots pine, Douglas fir, European larch) about 30 years after the initial assessment. On these plots, we recorded understorey vegetation and forest structure, and derived abiotic site conditions based on ecological indicator values of understorey vegetation, followed by multivariate analysis. We found changes in plant communities that point towards a decrease of soil acidity and a “thermophilization” of forest understoreys. Understorey species richness remained constant, while understorey's Shannon and Simpson diversity increased. The observed changes in forest structure explained the temporal shifts in understorey species composition. The understorey species composition did not experience a significant floristic homogenization since the 1990s. However, plant communities exhibited a reduction in species characteristic of coniferous forests and a simultaneous increase in species associated with broad-leaved forests. The increase of specialist species (closed forests and open sites) may have compensated for the detected decrease in generalist species. We conclude that the forest conversion towards mixed broad-leaved forest in the Spessart mountains of the past decades might have masked homogenization trends that are increasingly reported from Central European forest understoreys.

Tree diversity reduces co-infestation of Douglas fir by two exotic pests and pathogens

The number of non-native invasive pests and pathogens has increased dramatically in recent years, with disastrous consequences for the health of forests worldwide. Multiple studies have shown that mixed forests may suffer less damage from insect pests than single species forest. This “associational resistance” can be notably explained by the fact that heterospecific neighbours make it more difficult for herbivores to locate and then exploit their host tree. However, the validity of these findings in the case of non-native, invasive pests and pathogens remains to be demonstrated. In this study, we monitored over two hundred Douglas firs in pure and mixed plots of a tree diversity experiment to assess the damage from the non-native gall midge Contarinia pseudotsugae and the non-native needle cast Nothophaeocryptopus gaeumannii. The probability of Swiss needle-cast infection was lower in Douglas fir trees surrounded by heterospecific neighbours. Gall midge damage was lower on Douglas firs surrounded by taller neighbours, consistent with the hypothesis of reduced host Apparency. Douglas fir trees that were more damaged by C. pseudotsugae were also more often infected by N. gaeumannii. Our study thus provides partial support of the associational resistance hypothesis of mixed forests against exotic pests and pathogens. Promoting forest species diversity at the stand level could, therefore, offer interesting prospects for reducing the impact of biological invasions, especially those involving both pests and pathogens.

Three-Year Effects of Crown Removal by Clipping or Burning on Beargrass (Xerophyllum tenax) Size and Biomass

Beargrass (Xerophyllum tenax), an evergreen perennial herb of the northern Rocky Mountains, Pacific Northwest, and northern California, is used in Native American basketry and commercial floral greens. We studied beargrass size and biomass responses to crown removal by clipping or burning over three years in a coast Douglas-fir (Pseudotsuga menziesii var. menziesii) woodland with variable shrub cover in the southeastern Olympic Peninsula of Washington State. Clipping forested plants resulted in 28% mortality, mostly from smaller plants growing under 26% more total cover than the surviving plants; however, only 3% of completely crown-scorched open-grown plants died. Three years after treatment, crown width of surviving plants was only 61% of the pre-treatment size for clipped plants, compared to 88% for completely crown-scorched plants. Regression analyses indicated that the percentage of crown scorch accounted for only 16% and 27% of crown width and foliar height variation, respectively, one year post-burn, decreasing to 10% and 19% at three years post-burn. During the three years after burning, percentage flowering increased linearly to 64% of plants. Three years post-burn, foliar browse was higher on crown-scorched than on non-crown-scorched plants. Although shade tolerant, long-term survival of lowland beargrass is likely limited by combined competition from shrubs and trees. Stand density management is needed to maintain healthy, reproducing populations in the lowlands of western Washington.

An insight into novel therapeutic potentials of taxifolin.

Taxifolin is a flavonoid compound, originally isolated from the bark of Douglas fir trees, which is often found in foods such as onions and olive oil, and is also used in commercial preparations, and has attracted the interest of nutritionists and medicinal chemists due to its broad range of health-promoting effects. It is a powerful antioxidant with excellent antioxidant, anti-inflammatory, anti-microbial and other pharmacological activities. This review focuses on the breakthroughs in taxifolin for the treatment of diseases from 2019 to 2022 according to various systems of the human body, such as the nervous system, immune system, and digestive system, and on the basis of this review, we summarize the problems of current research and try to suggest solutions and future research directions.

The effectiveness of filter material for respiratory protection worn by wildland firefighters

During a wildland fire event, firefighters often receive significant exposure to smoke consisting of particulate matter (PM) and gaseous emissions. Major respiratory and cardiovascular health concerns are related to inhalation of smoke and respiratory protection (RP), such as masks, are one of the most important pieces of personal protective equipment (PPE) that can be used to mitigate this exposure. One barrier to RP implementation is that the effectiveness of different PPE worn by firefighters is not well studied in the literature. In this study, six different filtering materials were tested against simulated wildland fire smoke produced by smoldering Douglas fir needles in a custom-made lab-scale apparatus. Both PM and gases were measured with and without the filter material and their effectiveness is reported in this study. As expected, cloth bandanas, currently the most worn RP material, provided little benefit in terms of both PM and gaseous emissions reduction, while all other filter materials provided significant benefits. N95, P95 and P100 filters were very effective at removing PM and somewhat effective at filtering some gaseous species, especially those with nuisance VOC capabilities, although this effect may not be sustained for longer durations.

Mechanical performance of engineered bamboo subjected to accelerated aging with single and multiple durability exposures

Durability is a critical concern for engineered bamboo structures. The results of an experimental study of the mechanical performance of engineered glue laminated bamboo, bamboo scrimber and Douglas fir specimens subjected to accelerated aging under single and multiple durability exposures are presented. In total, nineteen specimen groups comprising almost 1200 samples were prepared and tested under conditions of ultraviolet radiation, alternating wet-dry cycles, alternating hot–cold cycles, and a combination of all three exposures. Specimen density, dimensional stability and discoloration were reported. Mechanical properties assessed were longitudinal compressive strength and modulus, and bending strength and modulus. Durability exposure related damage of the laminated bamboo and Douglas fir was greater than that of the bamboo scrimber under single and multiple durability exposures; the bamboo scrimber exhibited a better durability resistance. Analysis of variation of the results of the single and multiple exposures indicated that exposure to ultraviolet radiation had the greatest contribution to the durability performance of the three materials.