Search Results (78)

Forests are considered one of the most valuable natural areas in metropolitan region landscapes. Considering the sensitivity and ecosystem services provided by trees, the definition of urban forest ecosystems is nowadays based on a comprehensive understanding of the entire urban ecosystem. The effective capturing of particulate matter is one of the ecosystem services provided by urban forests. These ecosystems function as efficient biological filters. Plants accumulate pollutants passively via their leaves. Therefore, another ecosystem service provided by city forests could be the use of tree organs as bioindicators of pollution. This paper aims to estimate differences in trace metal pollution between the wooded urban areas of Vienna and Krakow using leaves of evergreen and deciduous trees as biomonitors. An additional objective of the research was to assess the ability of the applied tree species to act as biomonitors. Plant samples of five species—Norway spruce, Scots pine, European larch, common white birch, and common beech—were collected within both areas, in seven locations: four in the “Wienerwald” Vienna forest (Austria) and three in the “Las Wolski” forest in Krakow (Poland). Concentrations of Cr, Cu, Cd, Pb, and Zn in plant material were determined. Biomonitoring studies with deciduous and coniferous tree leaves showed statistically higher heavy metal contamination in the “Las Wolski” forest compared to the “Wienerwald” forest. Based on the conducted analyses and the literature study, it can be concluded that among the analyzed tree species, only two: European beech and common white birch can be considered potential indicators in environmental studies. These species appear to be suitable bioindicators, as both are widespread in urban woodlands of Central Europe and have shown the highest accumulation levels of trace metals. Full article

Betula platyphylla Sukaczev (white birch) is a cold-tolerant tree species native to northeastern Asia, valued for its ecological adaptability and economic utility. While its responses to various abiotic stresses have been studied, the physiological and biochemical mechanisms underlying its cold stress tolerance remain insufficiently explored. In this study, we investigated the effects of prolonged cold exposure (6 °C for up to 27 days) on key physiological and biochemical traits of B. platyphylla seedlings, including plant height, chlorophyll content, electrolyte leakage (EL), malondialdehyde (MDA), proline levels, and antioxidant enzyme activities (SOD, CAT, POD). Cold stress resulted in visible phenotypic changes, reduced growth, and significant declines in chlorophyll content, suggesting inhibited photosynthesis. EL and MDA levels increased with exposure duration, indicating progressive membrane damage and oxidative stress. In response, antioxidant enzyme activities and proline accumulation were significantly enhanced, reflecting a coordinated defense strategy. Correlation analyses further revealed strong associations among antioxidant enzymes, MDA, proline, and EL under cold stress. These findings advance our understanding of the adaptive responses of B. platyphylla to low-temperature stress and provide a physiological and biochemical basis for future breeding programs aimed at improving cold tolerance. Full article

Climate warming has led to more frequent soil freeze–thaw (FT) events in high-latitude and high-altitude regions, leading to significant pulse releases of greenhouse gasses (GHGs) such as nitrous oxide (N₂O) and carbon dioxide (CO₂) into the atmosphere. These pulse emissions exhibit unpredictable spatiotemporal variability, which are influenced by soil type, soil moisture and FT temperature. This study employed controlled laboratory experiments to investigate the effects of varying FT intensities (−10 °C/10 °C, −5 °C/5 °C, and a control at 0 °C/0 °C) and soil moisture levels (30%, 60%, and 90% water-filled pore space, WFPS) on the dynamics of soil N₂O and CO₂ emissions (measured daily), and the availability of carbon and nitrogen, microbial biomass, and enzyme activities (measured weekly) in the soils collected from two forest stands in the Changbai mountains of northeast China, a broadleaf and Korean pine (Pinus koraiensis Sieb. et Zucc.) mixed forest (BKPF) and an adjacent secondary white birch (Betula platyphylla Suk.) forest (WBF), where FT events frequently occur. Our findings reveal that a high FT intensity (−10 °C/10 °C) significantly increased N₂O and CO₂ emissions from BKPF and WBF soils. With increasing soil moisture, soil CO₂ emissions peaked at 60% WFPS, while soil N₂O emissions were the highest at 90% WFPS. Notably, pulse emissions of N₂O were particularly intense under a high FT intensity and high moisture (i.e., 90% WFPS) in WBF soils, persisting for nearly 8 days during FT cycles. The emissions of N₂O and CO₂ under varying FT and moisture conditions are intricately regulated by soil substrate dynamics, including dissolved organic carbon, nitrogen mineralization, and nitrate concentrations. The results improve the understanding of the high variability of soil GHG emissions during the FT process and its underlying mechanisms, which are inadequately considered in current ecological and land surface process models. Consequently, it would contribute valuable insights into the interaction between soil GHG emissions and climate change in high-latitude and high-altitude zones. Full article

Background: Bitot’s spots, defined as white foamy triangular or round-shaped spots with the base located at the temporal limbus and the apex towards the lateral canthus, were initially associated with vitamin A deficiency (VAD). More recently, Bitot’s spots were also described in patients with normal vitamin A levels, associated with aniridia, dry-eye syndrome and post-thermal or chemical injury, as well as the usage of benzalkonium chloride (BAK) eyedrops. The aim of this article is to present the management of Bitot-like spots in a patient with congenital aniridia. Methods: An 8-year-old female patient with type 1 congenital aniridia, glaucoma, cataract, strabismus, congenital nistagmus and aniridia-associated keratopathy presented with changes in conjunctival appearance. The ophthalmological examination revealed Bitot-like spots with a foamy appearance, triangular shape, temporal location and proximity to the limbus. Further investigations were required in order to identify the cause of Bitot-like spots. Vitamin D deficiency, dry-eye syndrome, birch and Phleum genus pollen allergy were diagnosed. The patient underwent oral medication with vitamin D and topical treatment with steroids eye solution, preservative-free artificial tears and vitamin A ointment. Results: After three months of treatment, we observed the disappearance of the Bitot-like spots. Conclusions: Congenital aniridia, but also its complications such as glaucoma, dry-eye syndrome and the use of benzalkonium chloride topical medication, increases the risk of Bitot-like spots. Full article

Soil organic carbon (SOC) plays a critical role in regulating the global carbon (C) cycle, with forest soils serving as significant C sinks. Soil aggregate stability and the distribution of SOC in different aggregate fractions would be affected by different forest types. In this study, we investigate the distribution and dynamics of SOC within different soil aggregate fractions across three main forest types in the Huron Mountains, Michigan, USA: white birch–eastern hemlock mixed forest, eastern-hemlock-dominated forest, and sugar maple forest. We hypothesize that variations in species composition and soil depth influence SOC storage and aggregate stability through mechanisms such as root interactions, microbial activity, and soil structure development. Soil samples were collected from three depth intervals (0–20 cm, 20–40 cm, and 40–60 cm) and analyzed for aggregate size distribution and SOC content. The results showed that aggregate size distribution and SOC stocks differ significantly across forest types, with the white birch–eastern hemlock mixed forest exhibiting the highest proportion of large aggregates (>1.0 mm), which contribute to more stable soil structures. This forest type also had the highest total aggregate mass and mean weight diameter, indicating enhanced soil stability. In contrast, sugar maple forest displayed a greater proportion of smaller aggregates and a lower macroaggregate-to-microaggregate ratio, suggesting fewer stable soils. SOC stocks were closely linked to aggregate size, with macroaggregates containing the highest proportion of SOC. These differences in SOC distribution and soil aggregate stability can be attributed to several underlying mechanisms, including variations in plant root interactions, microbial activity, and the physical properties of the soil. Forests with diverse species compositions, such as the white birch–eastern hemlock mixed forest, tend to support more complex root systems and microbial communities, leading to improved soil aggregation and greater SOC storage. Additionally, forest management practices such as selective thinning and mixed-species planting contribute to these processes by enhancing soil structure, increasing root biomass, and promoting soil microbial health. These interactions play a crucial role in enhancing C sequestration and improving soil health. Our findings emphasized the importance of forest composition in influencing SOC dynamics and soil stability, offering insights into the role of forest management in C sequestration and soil health. This study provided a reference to a deeper understanding of SOC storage potential in forest ecosystems and supports the development of sustainable forest management strategies to mitigate climate change. Full article

As forest managers increasingly seek to develop and maintain mixedwood forests, more information is required on the potential facilitative and competitive interactions between tree species. We present data from a broadleaf thinning study established in a mixedwood stand in Central British Columbia, Canada, to examine how residual trembling aspen and paper birch competitively affect spruce growth after thinning but may also concurrently protect spruce from attack by the white pine weevil. Tree-level data collected at a stand age of 36 years, 19 years after broadleaf trees were thinned, show that spruce height and diameter growth declined with broadleaf competition, particularly from taller trees, resulting in a competition-related reduction in stand-level spruce volume yields. The fastest spruce growth occurred in treatments where all broadleaf trees were removed, but complete broadleaf removal also resulted in higher rates of weevil attack on spruce, which also caused height and diameter growth reductions. Our results suggest that maintaining a density of approximately 500 broadleaf trees per hectare may achieve a stand condition that balances spruce growth reductions from competitive interactions with broadleaf trees while providing some protection from white pine weevil attacks. Full article

Aboveground carbon stocks (AGCs) in forests play an important role in understanding carbon cycle processes. The global forestry sector has been working to find fast and accurate methods to estimate forest AGCs and implement dynamic monitoring. The aim of this study was to explore the effects of backpack LiDAR and UAV multispectral imagery on AGC estimation for two tree species (Larix gmelinii and Betula platyphylla) and to emphasize the accuracy of the models used. We estimated the AGC of Larix gmelinii and B. platyphylla forests using multivariate stepwise linear regression and random forest regression models using backpack LiDAR data and multi-source remote sensing data, respectively, and compared them with measured data. This study revealed that (1) the diameter at breast height (DBH) extracted from backpack LiDAR and vegetation indices (RVI and GNDVI) extracted from UAV multispectral imagery proved to be extremely effective in modeling for estimating AGCs, significantly improving the accuracy of the model. (2) Random forest regression models estimated AGCs with higher precision (Xing’an larch R² = 0.95, RMSE = 3.99; white birch R² = 0.96, RMSE = 3.45) than multiple linear regression models (Xing’an larch R² = 0.92, RMSE = 6.15; white birch R² = 0.96, RMSE = 3.57). (3) After combining backpack LiDAR and UAV multispectral data, the estimation accuracy of AGCs for both tree species (Xing’an larch R² = 0.95, white birch R² = 0.96) improved by 2% compared to using backpack LiDAR alone (Xing’an larch R² = 0.93, white birch R² = 0.94). Full article

Accurately measuring the moisture content (MC) of square timber is crucial for ensuring the quality and performance of wood products in wood processing. Traditional MC detection methods have certain limitations. Therefore, this study developed a one-dimensional convolutional neural network (1D-CNN) model based on the first 8 nanoseconds of ground-penetrating radar (GPR) signals to predict the MC of square timber. The study found that the mixed-species model exhibited effective predictive performance (R² = 0.9864, RMSE = 0.0393) across the tree species red spruce, Dahurian larch, European white birch, and Manchurian ash (MC range 0%–133.1%), while single-species models showed even higher accuracy (R² ≥ 0.9876, RMSE ≤ 0.0358). Additionally, the 1D-CNN model outperformed other algorithms in automatically capturing complex patterns in GPR full-waveform amplitude data. Moreover, the algorithms based on full-waveform amplitude data demonstrated significant advantages in detecting wood MC compared to those based on a traditional time–frequency feature parameter. These results indicate that the 1D-CNN model can be used to optimize the drying process and detect the MC of load-bearing timber in construction and bridge engineering. Future work will focus on expanding the dataset, further optimizing the algorithm, and validating the models in industrial applications to enhance their reliability and applicability. Full article

The effect of climate change on forest dynamics is likely to increase in importance in the forthcoming decades. For this reason, it is essential to predict the extent to which changes in temperature, precipitation, and atmospheric CO₂ might affect the development of forest ecosystems and successional pathways. The gap model ZELIG-CFS was used to simulate the potential long-term effects of climate change on species-specific annual change in mean basal area and stand density under two scenarios of representative concentration pathways (RCP), 4.5 and 8.5, for the boreal forest region of Ontario, Canada, where mean temperature, precipitation, and atmospheric CO₂ are expected to increase. Forest ecosystems in this boreal region included pure and mixed stands of black spruce (Picea mariana [Mill.] B.S.P.), paper birch (Betula papyrifera Marsh.), balsam fir (Abies balsamea [L.] Mill.), jack pine (Pinus banksiana Lamb.), trembling aspen (Populus tremuloides Michx.), white spruce (Picea glauca [Moench] Voss), northern white cedar (Thuja occidentalis L.), American larch (Larix laricina [Du Roi] K. Koch), and balsam poplar (Populus balsamifera L.). Simulation results under climate change generally predicted a decline in the basal area and stand density for black spruce, balsam fir, jack pine, and white spruce, but an increase for paper birch, trembling aspen, American larch, and balsam poplar. However, the extent of change differed regionally among species. Forest composition is expected to change over the long term. Simulation results indicated that shade-intolerant deciduous and conifer species will increase their dominance over the 100-year time horizon. This transition toward the increasing presence of deciduous forests is likely explained by more favorable temperature conditions for their growth and development. Full article

Bent wood has the advantages of visually appealing and ergonomic shapes and the disadvantage of processing failure. Understanding how water and temperature influence wood bending is critical to avoid processing failure. Compared with softwood, saturated hardwood has been seldom reported in terms of bending performance at various temperature levels. In this paper, white birch and ash wood were studied in bending using a universal testing machine and a program-controlled water bath. White birch wood exhibited lower proportional limit stress, smaller modulus of elasticity (MOE), and lower failure stress, but higher proportional strain and failure strain than ash wood. At 20 °C, bending of air-dried wood on the tangential direction exhibited much smaller mechanical variation than that on the radial direction. The proportional limit stress, MOE, and failure stress of water-saturated wood were much smaller than those of air-dried wood, while failure strain was much higher. Evidenced by the almost constant proportional limit strain, plastic bending deformation of water-saturated wood happened to a great extent. As the temperature elevated at 20–100 °C, MOE, proportional limit stress, and failure stress of water-saturated wood decreased while proportional limit strain, failure strain, and wood toughness increased. Variation in proportional limit strain resulting from temperature change was ignorable, evidencing that elevated temperature enhanced wood plastic deformation. Furthermore, white birch wood was more susceptible to temperature over 40 °C than ash wood in terms of toughness. Under water-saturated condition, both species exhibited excellent bending performance at relatively high temperature. Full article

Diameter at breast height (DBH) is a unique attribute used to characterize forest growth and development for forest management planning and to understand forest ecology. Forest managers require an array of DBHs of forest stands, which can be reconstructed using selected probability distribution functions (PDFs). However, there is a lack of practices that fit PDFs of sub-dominating species grown in natural mixed forests. This study aimed to fit PDFs and develop predictive models for PDF parameters, so that the predicted distribution would represent dynamic forest structures and compositions in mixed forest stands. We fitted three of the simplest forms of PDFs, log-normal, gamma, and Weibull, for the DBH of eight tree species, namely balsam fir (Abies balsamea [L.] Mill.), eastern white pine (Pinus strobus L.), paper birch (Betula papyrifera Marshall), red maple (Acer rubrum L.), red pine (Pinus resinosa Aiton), sugar maple (Acer saccharum Marshall), trembling aspen (Populus tremuloides Michx), and white spruce (Picea glauca [Moench] Voss), all grown in natural-origin mixed forests in Ontario province, Canada. We estimated the parameters of the PDFs as a function of DBH mean and standard deviation for these species. Our results showed that log-normal fit the best among the three PDFs. We demonstrated that the predictive model could estimate the recovered parameters unbiasedly for all species, which can be used to reconstruct the DBH distributions of these tree species. In addition to prediction, the cross-validated R² for the DBH mean ranged between 0.76 for red maple and 0.92 for red pine. However, the R² for the regression of the standard deviation ranged between 0.00 for red pine and 0.69 for sugar maple, although it produced unbiased predictions and a small mean absolute bias. As these mean and standard deviations are regressed with dynamic covariates (such as stem density and stand basal area), in addition to climate and static geographic variables, the predicted DBH distribution can reflect change over time in response to management or any type of disturbance in the regime of the given geography. The predictive model-based DBH distributions can be applied to the design of appropriate silviculture systems for forest management planning. Full article

Atmospheric CO₂ levels have been increasing, and likewise, increasing drought events have been following increasing temperatures. There is very little literature on the effects of climate change factors on early-successional deciduous species used for ecological restoration. Thus, morphological and allometric variation in four coppiced early-successional deciduous species was examined in response to a 2 × 2 factorial of ambient CO₂ (aCO₂, 400 ppm) and elevated CO₂ (eCO₂, 800 ppm), as well as well-watered and drought treatments with 15%–20% and 5%–10% volumetric moisture content, respectively, grown in sandy soil with low soil nitrogen (N) under greenhouse conditions. The four species examined were as follows: green alder (Alnus viridis subsp. crispa (Ait.) Turrill), speckled alder (A. incana subsp. rugosa (Du Roi) R.T. Clausen), gray birch (Betula populifolia (Marshall)), and white birch (B. papyrifera (Marshall)), and all are from the same phylogenetic family, Betulaceae. Genus differences in morphological and growth traits were large, especially in response to the environmental treatments used. Alders upregulated all growth traits under eCO₂ because of the strong coppicing sink effect and the additional foliar N provided by the actinorhizal ability of the genus, whereas birches remained the same or slightly decreased under eCO₂. As a result, alders have a significantly greater foliar N than birches, with 2.8 and 1.0%, respectively. All species reduced growth under drought, and green alder had the greatest stem dry mass growth, followed by speckled alder and then the birches. Under drought, eCO₂ not only mitigated the alder drought dry mass but, in fact, doubled the stem dm, whereas eCO₂ only just mitigated the birches drought response. When corrected for size using stem height, alders allocated more to stem and leaf and less to root dry mass than birches. Atmospheric CO₂ and soil moisture treatments changed organ biomass allocation. The tallest stem height was the best predictor of total (above and below) dry mass. With increasing atmospheric CO₂, particularly on low nutrient sites, the results show alders are capable of sequestering far more carbon than birches. In addition, with more atmospheric CO₂, alders can mitigate against drought conditions better compared to birches. Full article

The WRKY family of transcription factors (TFs) is one of the most diverse families in plants, playing crucial roles in various plant growth and stress response processes. Asian white birch (Betula platyphylla) is a globally distributed tree species that holds ecological, medical, and economic significance. However, the regulatory mechanisms of WRKY TFs in birch remain poorly understood. Herein, we cloned and characterized the BpWRKY49 gene from birch. Through bioinformatics analyses, we revealed the potential involvement of BpWRKY49 in both biotic and abiotic stress responses. In addition, BpWRKY49 was found to be localized in the nucleus and exhibited transcriptional activity in yeast. Transactivation assays further confirmed that BpWRKY49 exhibited transcriptional activity at its C-terminal end. Notably, our binding specificity assays demonstrated the specific interaction of BpWRKY49 with the W-box cis element in vitro. Furthermore, tissue-specific expression analysis demonstrated that BpWRKY49 exhibited the highest expression level in the roots. Real-time quantitative PCR (RT-qPCR) analysis of birch plants subjected to salt and drought treatments revealed that BpWRKY49 displayed significant 30-fold and 10-fold upregulations under salt and drought stress conditions, respectively. DAP-seq analysis of BpWRKY49 identified a total of 21,832 peaks, with 3477 occurring in the promoter region of genes. Gene ontology (GO) enrichment analysis highlighted prominent terms related to defense against biotic stress, followed by terms associated with abiotic stress and development. Y1H assays of three genes provided evidence for the binding ability of BpWRKY49 to the promoters of BpPUB21, BpBTL15, and BpHIP47 in vitro. Collectively, our findings strongly suggest that BpWRKY49 possesses diverse functions and may activate multiple genes to contribute to various biological processes, including salt stress tolerance, in birch. Full article

In forest ecosystems, most of the soil organic matter is derived from trees, as deadwood lignocellulose and wood-decaying basidiomycetes are the most important decomposers of lignin and cellulose. Fomes fomentarius is one of the most common white-rot fungi colonizing angiosperm trees and is often found in birch deadwood but seldom in pine deadwood. To reveal the mechanism through which F. fomentarius selects angiosperms as its preferred host trees, birch and pinewood sticks were selected for culturing for two months. The weight loss, cellulose and lignin degradation rates, activities of degrading enzymes, and transcriptome analyses of two degradation models were compared and analyzed. The results showed that F. fomentarius-degraded birchwood with higher efficiency than pinewood. A GO enrichment analysis found that more upregulated genes related to the top 30 terms showed a molecular function related to degradation, and most genes belonged to the CAZymes family in F. fomentarius-degraded birchwood. However, pinewood degradation did not show these phenomena. A KEGG pathway analysis also indicated that, for the same pathway, more upregulated genes were involved in birchwood degradation caused by F. fomentarius than in pinewood degradation. Full article

Barren sites that lack soil are exposed to some of the harshest elements, which include high temperatures, solar radiation, wind, extreme temperature changes, and low soil moisture and nutrient conditions. An ecological restoration experiment was conducted using three site-preparation treatments, straw (S), Meri-Crusher (MC), and coarse woody debris (CWD), in a site-/no site-preparation 2 × 2 × 2 factorial on sites that had been barren for 25 years. In addition, four early successional deciduous species, white birch (WB, Betula papyrifera Marshall), gray birch (GB, Betula populifolia Marshall), green alder (GA, Alnus viridis Vill. subsp. crispa Ait), and speckled alder (SA, Alnus incana L. subsp. rugosa Du Roi), were examined. The two- and three-way interactions were almost all magnitude effects and not rank changes. Gray birch had the greatest overall first-year height growth, followed by GA, SA, and WB, with 12.1, 9.7, 9.6, and 5.6 cm, respectively. Straw doubled first-year growth, while CWD and MC increased first-year height growth by 43 and 31%, respectively. Straw’s ability to retain moisture in the dry summer provided the greatest benefit. In the second year, GA had the greatest height growth, followed by SA, GB, and WB, with 42.5, 30.5, 13.4, and 13.0 cm, respectively. Alders form symbiotic relationships with N-fixing bacteria and, although this was observed in some first-year roots, they did not fully express this advantage at these severely degraded sites until the second year, which allowed them to surpass birches in growth. Site-preparation treatments furthered their height growth affect, with S, and CWD doubling second-year height growth and MC, with an increase of 25%. Alders and birches had, on average, three and one stems, respectively, and the mean stem number of alders increased under S and CWD. After two years, overall stem dry mass had very large genus and species differences with GA, SA, GB, and WB, with 58.4, 30.3, 5.4, and 4.0 g, respectively. The N-fixing ability of alders under these conditions resulted in a 13-fold stem dry mass production increase compared with birches. Straw tripled, CWD doubled, and MC increased stem dry mass by 40%. For WB, site-preparation combinations had an additive effect, whereas GB, GA, and SA had several combined site-preparation treatments showing synergistic results, which were greater than the additive effects of single treatments. Under the control (no site prep.), second-year stem dry masses for WB, GB, GA, and SA were 0.7, 1.4, 17.8, and 0.5 g, respectively. Under the three combined treatments, MC × S × CWD, WB, GB, GA, and SA had 6.6, 12.3, 115.7, and 70.6 g stem dry masses, respectively. SA is ecologically a lowland species, hence the low 0.5 g under the control; however, the result under the three combined treatments demonstrates their combined effectiveness on these barren sites. Green alder seems to be the best adapted to the sites, having the greatest stem dry mass under control, although that was considerably magnified under the site-preparation treatments. This study using combinations of treatments with these early successional species introduces a novel research concept, and similar studies in the literature are currently lacking, creating an opportunity for future exploration. Full article