Betula Platyphylla Research Articles

Betula platyphylla glucosyltransferase BpGT14;6 is essential for cell wall development and stress response

Glycosyltransferases (GTs) constitute a diverse family of synthetic polysaccharides with important roles in plant growth and development. This study characterized the GT14 family gene BpGT14;6 of birch (Betula platyphylla Suk.). BpGT14;6 was highly expressed in the xylem and stem of birch plants. Subcellular localization analysis suggested that BpGT14;6 was located in the Golgi apparatus. RNA interference (RNAi) silencing of BpGT14;6 revealed lower lignin, hemicellulose, and pectin contents compared to wild type (WT) plants. Following treatment with abscisic acid (ABA), compared to WT plants, RNAi-BpGT14;6 plants were more sensitive to ABA, suffered more membrane lipid damage, and accumulated more reactive oxygen species. The inhibition of BpGT14;6 expression narrowed the birch xylem and thinned the cell wall, and increased the expression of multiple ABA pathway-related genes in birch under ABA treatment. Compared to WT plants, RNAi-BpGT14;6 plants showed increased tolerance to drought stress. Promoter analysis revealed that BpGT14;6 is involved in hormone regulation and adaptation to adversity. Using the 1 156 bp BpGT14;6 promoter as bait, two potential transcription factors, BpWRKY1 and BpARF2, were identified through Y1H screening that may regulate its expression. EMSA confirmed that BpWRKY1 and BpARF2 can directly bind to the W-BOX and AuxRE cis-acting elements on the BpGT14;6 promoter, respectively. The collective results suggest that BpGT14;6 affects birch xylem and cell wall development by affecting lignin, hemicellulose, and pectin synthesis, and participates in birch adversity adaptation.

Aboveground Carbon Stock Estimation Based on Backpack LiDAR and UAV Multispectral Imagery at the Forest Sample Plot Scale

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).

Microbial community composition and co-occurrence network analysis of the rhizosphere soil of the main constructive tree species in Helan Mountain of Northwest China

To understand the microbial diversity and community composition within the main constructive tree species, Picea crassifolia, Betula platyphylla, and Pinus tabuliformis, in Helan Mountain and their response to changes in soil physicochemical factors, a high throughput sequencing technology was used to analyze the bacterial and fungal diversity and community structure. RDA (Redundancy Analysis) and Pearson correlation analysis were used to explore the influence of soil physicochemical factors on microbial community construction, and co-occurrence network analysis was conducted on the microbial communities. The results showed that the fungal and bacterial diversity was highest in B. platyphylla, and lowest in P. crassifolia. Additionally, the fungal/bacterial richness was greatest in the rhizosphere soils of P. tabuliformis and B. platyphylla. RDA and Pearson correlation analysis revealed that NN (nitrate nitrogen) and AP (available phosphorus) were the main determining factors of the bacterial community, while NN and SOC (soil water content) were the main determining factors of the fungal community. Pearson correlation analysis between soil physicochemical factors and the alpha diversity of the microbial communities revealed a significant positive correlation between pH and the bacterial and fungal diversity, while SOC, TN (total nitrogen), AP, and AN (available nitrogen) were significantly negatively correlated with the bacterial and fungal diversity. Co-occurrence network analysis revealed that the soil bacterial communities exhibit richer network nodes, edges, greater diversity, and greater network connectivity. Indicating that bacterial communities exhibit more complex and stable interaction patterns in soil. This study reveals the complex interactive relationship between microbial communities and soil physicochemical factors in forest ecosystems. By analyzing the response of rhizosphere microbial communities of major tree species in Helan Mountain to nutrient dynamics and pH changes, we can deepen our understanding of the role of microorganisms in regulating ecosystem functions and provide theoretical basis for soil improvement and ecological restoration strategies.

The effect of postfire regeneration pattern on soil respiration in the boreal forest of China

BackgroundAs the second largest carbon flux between the atmosphere and terrestrial ecosystems, soil respiration involves multiple components of ecosystem production. Revealing soil respiration in forests with different postfire regeneration patterns is critical for determining appropriate restoration strategies in response to increasing wildfire disturbances. Here, we examined the influence of five postfire regeneration patterns (L: Larix gmelinii monocultures, LB: L. gmelinii and Betula platyphylla mixed plantations, P: Pinus sylvestris var. mongolica monocultures, PB: P. sylvestris var. mongolica and B. platyphylla mixed plantations, N: naturally regenerated forests) on soil heterotrophic respiration (Rh) and total respiration (Rs).MethodsTrenching was implemented to monitor soil heterotrophic respiration. We used partial least squares path modeling methods to estimate the different environmental factors regulating soil respiration across forest types.ResultsThe results showed that forest type and season had significant effects on Rs and Rh. Rh was the dominant part of Rs for all forest types (68.84 ~ 90.20%). Compared to naturally regenerated forests, Rs and Rh under L, LB, and PB had higher rates (P < 0.05), while Rs and Rh under P had lower rates (P < 0.05). The temperature sensitivities of Rs under different forest types were 2.316 (L), 1.840 (LB), 1.716 (P), 1.665 (PB), and 2.096 (N).ConclusionsForests regenerated with artificial participation established their plant communities visibly faster than naturally regenerated forests. Mixed species plantation regeneration demonstrated an improvement in soil respiration compared to naturally regenerated forests but had a lower temperature sensitivity of soil respiration than their respective monocultures. Soil temperature and moisture dominated the influence factors on soil respiration throughout the broader seasonal shifts. However, for a single season, forest productivity and soil properties have a greater impact on soil respiration. This study extends our knowledge of the interaction mechanism between soil respiration and environmental variables in boreal forests and contributes to improving confidence in global carbon cycling model predictions.

Patterns of Soil Stoichiometry Driven by Mixed Tree Species Proportions in Boreal Forest

Soil stoichiometry is essential for determining the ecological functioning of terrestrial ecosystems. Understanding the stoichiometric relationships in mixed forests could enhance our knowledge of nutrient cycling. In a mixed forest zone of Larix principis-rupprechtii (LP) and Betula Platyphylla (BP) in Hebei China, we conducted a study at six different sites with varying levels of tree species mixing. The proportion of L. principis-rupprechtii ranged from 0% to 100%, with intermediate values of 8.58%, 10.44%, 18.62%, and 38.32%. We compared soil stoichiometry, including carbon (C), nitrogen (N), and phosphorus (P), as well as chemical and physical properties across these sites. Piecewise structural equation modeling (piecewiseSEM) was used to assess the direct and indirect links between key ecosystem factors and their effects on soil stoichiometry. In mixed forests, the soil exhibited higher contents of soil organic matter (SOM), total nitrogen (TN), and total phosphorus (TP) compared to those in pure LP forests. Additionally, the soil C: N ratio in the 8.58% and 18.62% mixed forests as well as pure BP forests was significantly higher than that in LP forests. Structural equation modeling (SEM) revealed that the contents and ratios of soil C, N, and P exhibited different responses to mixed species proportions. The effect of mixed species proportions on soil nutrients was predominantly indirect, mediated primarily by variations in soil-available nutrients and, to a lesser extent, by physical properties and pH. Specifically, an increase in the proportion of LP in mixed forests had a direct negative effect on soil-available nutrients, which in turn had a positive effect on the content of SOM, TN, and TP and their respective ratios. Based on these findings, we can predict that soil nutrient limitation becomes more pronounced with increasing proportions of Larix principis-rupprechtii in the mixed forest. Our results emphasized the significance of changes in mixed species proportions on soil stoichiometry, providing valuable references for the sustainable development of forests.

The BpPP2C-BpMADS11-BpERF61 signaling confers drought tolerance in Betula platyphylla.

Plant MADS-box proteins are vital for abiotic stress tolerance, yet their mechanisms for responding to drought remain poorly understood. Here, we investigated the drought tolerance mechanism of a MADS-box protein (BpMADS11) from birch (Betula platyphylla) using immunoprecipitation, Western blotting, yeast two-hybrid, yeast one-hybrid, ChIP, RNA-seq, and dual-luciferase assays to explore post-translational modifications, protein interactions, and gene regulation. Birch plants overexpressing BpMADS11 exhibited enhanced drought tolerance, while knockout lines displayed reduced tolerance. Under drought conditions, BpMADS11 interacts with protein phosphatase 2C22 (BpPP2C22), which dephosphorylates BpMADS11. Birch plants that overexpress BpMADS11 and lack BpPP2C22 show significantly reduced drought tolerance compared with those that only overexpress BpMADS11. BpMADS11 regulates the expression of BpERF61 by binding to CArG-box in its promoter. The dephosphorylated BpMADS11 exhibits increased DNA binding ability and increased expression of BpERF61. Like BpMADS11, birch plants overexpressing BpERF61 show improved drought tolerance, while those with BpERF61 knockout exhibit decreased tolerance. BpERF61 binds to specific DNA motifs including 'CACGTG' (G-box), 'GGGCCCC', and 'TTGGAT' to regulate the genes related to drought stress. Collectively, BpMADS11 undergoes dephosphorylation through its interaction with BpPP2C22, prompting the expression of BpERF61. Subsequently, BpERF61 regulates downstream genes by binding to specific DNA motifs, thereby enhancing drought tolerance.

Net primary productivity of Betula platyphylla woodland and the response of current-year shoots to vegetation degradation in Mongolian forest steppe

At the southern margin of forest steppe vegetation in Mongolia, Betula platyphylla woodlands occur on north-facing slopes and hill tops, where congeneric shrub Betula fusca often coexists. Woodland degradation results in B. fusca scrub with scattered B. platyphylla trees. We studied structure and productivity of a B. platyphylla woodland and the current-year shoot allometry in the Hustai National Park of central Mongolia. For the B. platyphylla woodland examined, stand basal area and estimated aboveground biomass for stems ≥ 3 cm diameter were 3.9 m2 ha–1 and 13.3 Mg dry mass ha–1, respectively. Leaf area index was 0.93 indicating open canopy layer. Aboveground net primary productivity as the sum of coarse wood production and current-year shoot mass amounted to 1.89 Mg dry mass ha–1 year–1, which was high relative to small aboveground biomass. Analysis of current-year shoot allometry demonstrated that B. platyphylla had more xeromorphic shoots in the scrub, with smaller specific leaf area, lower mass ratio of leaf laminae to supporting parts, and smaller lamina mass against sum of petiole basal area, than in the woodland. Our results indicate that current-year shoot allometry characterizes tree response to woodland degradation at the dry margin of forest steppe.

BpTCP19 targets BpWRKY53 to negatively regulate jasmonic acid- and dark-induced leaf senescence in Betula platyphylla

TCP (TEOSINTE-LIKE1, CYCLOIDEA, and PROLIFERATING CELL FACTOR1) is a plant-specific transcription factor that has garnered significant attention due to its wide-ranging involvement in the regulation of plant growth or developmental processes. However, the molecular mechanisms through which TCP genes orchestrate leaf senescence have not been extensively elucidated. BpTCP19, a member of the PCF subfamily in Betula platyphylla, and has high homology to AtTCP19. BpTCP19 displayed pronounced downregulation in response to methyl jasmonate (MeJA) and dark treatment. Overexpressing BpTCP19 in Betula platyphylla led to a delay in leaf senescence, resulting in prolonged leaf greenness under both MeJA and dark conditions. Transcriptome analysis revealed that overexpression of BpTCP19 induced alterations in the expression levels of genes linked to cell proliferation, hormone signaling transduction, and leaf senescence, including the early responsive factor BpWRKY53. Furthermore, through Yeast one-hybrid assays and GUS analysis, BpTCP19 was shown to bind to the promoter region of BpWRKY53, suppressing its expression and thereby retarding leaf senescence. This study elucidates the physiological and molecular functions of BpTCP19 as a central transcriptional regulatory module in leaf senescence and provides a potential target gene for delaying leaf senescence by mitigating sensitivity to external aging signals such as Jasmonic acid (JA) and darkness.

A process-based model of climate-driven xylogenesis and tree-ring formation in broad-leaved trees (BTR).

The process-based xylem formation model is an important tool for understanding the radial growth process of trees and its influencing factors. While numerous xylogenesis models for conifers have been developed, there is a lack of models available for non-coniferous trees. In this study, we present a process-based model designed for xylem formation and ring growth in broad-leaved trees, which we call the Broad-leaved Tree-Ring (BTR) model. Climate factors, including day length, air temperature, soil moisture, and vapor pressure deficit, drive daily xylem cell production (fibers and vessels) and growth (enlargement, wall deposition). The model calculates the total cell area in the simulated zone to determine the annual ring width. The results demonstrate that the BTR model can basically simulate inter-annual variation in ring width and intra-annual changes in vessel and fiber cell formation in Fraxinus mandshurica (ring-porous) and Betula platyphylla (diffuse-porous). The BTR model is a potential tool for understanding how different trees form wood and how climate change influences this process.

Identification of BpEXP family genes and functional characterization of the BpEXPA1 gene in the stems development of Betula platyphylla

Expansins (EXPs) are unique plant cell wall proteins with the ability to induce cell wall expansion and play potential roles in xylem development. In the present study, a total of 25 BpEXP genes were identified in Betula platyphylla. Results of bioinformatics analysis described that BpEXP gene family was highly conserved in the process of evolution. All these genes were clustered into four groups, EXPA (Expansin A), EXPB (Expansin B), EXLA (Expansin-like A) and EXLB (Expansin-like B), according to phylogenetic analysis and BpEXPA1 was highly homologous to PttEXP1 and PttEXP2. The results of RT-qPCR showed that BpEXPA1 was expressed higher in stems and preferentially expressed in the first internodes, followed by apical buds and the third internodes, promoter expression analysis with GUS assay demonstrated that it was expressed in developing xylem, suggesting that BpEXPA1 might be involved in the development of the primary stems of birch. Overexpression of BpEXPA1 can promote cortex cell expansion and then enlarge the cortex cell area and layer, however inhibit the secondary cell wall deposition and result in the thinner cell wall and larger lumens of xylem fiber in transgenic plants. This study will provide information for investigating the regulation mechanism of BpEXP family genes and gene resources for birch genetics improvement.

Genome-wide identification and expressional analysis of carotenoid cleavage oxygenase (CCO) gene family in Betula platyphylla under abiotic stress

BackgroundCarotenoid cleavage oxygenases (CCOs) are a group of enzymes that catalyze the oxidative cleavage of carotenoid molecules. These enzymes widely exist in plants, fungi, and certain bacteria, and are involved in various biological processes. It would be of great importance and necessity to identify CCO members in birch and characterize their responses upon abiotic stresses.ResultsA total of 16 BpCCOs, including 8 BpCCDs and 8 BpNCEDs were identified in birch, and phylogenetic tree analysis showed that they could be classified into six subgroups. Collinearity analysis revealed that BpCCOs have the largest number of homologous genes in Gossypium hirsutum and also have more homologous genes in other dicotyledons. In addition, promoter analysis revealed that the promoter regions of BpCCOs contained many abiotic stress-related and hormone-responsive elements. The results of qRT-PCR showed that most of the BpCCOs were able to respond significantly to ABA, PEG, salt and cold stresses. Finally, the prediction of the interacting proteins of BpCCOs by STRING revealed several proteins that may interact with BpCCOs and be involved in plant growth and development/abiotic stress processes, such as HEC1 (bHLH), ATABA1, ATVAMP714, etc.ConclusionIn this study, the CCO members were identified in birch in a genome-wide scale. These results indicate that BpCCO genes may play important roles in the abiotic stress responses of birch plants.

Analysis of PM2.5 Concentration Released from Forest Combustion in Liangshui National Natural Reserve, China

(1) Background: In recent years, forest fires have become increasingly frequent both domestically and internationally. The pollutants emitted from the burning of fuel have exerted considerable environmental stress. To investigate the influence of forest fires on the atmospheric environment, it is crucial to analyze the variations in PM2.5 emissions from various forest fuels under differing fire conditions. This assessment is essential for evaluating the effects on both the atmospheric environment and human health. (2) Methods: Indoor simulated combustion experiments were conducted on the branches, leaves, and bark of typical tree species in the Liangshui National Natural Reserve, including Pinus koraiensis (PK), Larix gmelinii (LG), Picea koraiensis (PAK), Betula platyphylla (BP), Fraxinus mandshurica (FM), and Populus davidiana (PD). The PM2.5 concentrations emitted by six tree species under various combustion states were measured and analyzed, reflecting the impact of moisture content on the emission of pollutants from fuel combustion, as indicated by the emission factors for pollutants. (3) Results: Under different fuel loading and moisture content conditions, the mass concentration values of PM2.5 emitted from the combustion of different organs of various tree species exhibit variability. (4) Conclusions: Among the various tree species, broad-leaved varieties release a greater quantity of PM2.5 compared to coniferous ones. A positive correlation exists between the moisture content of the fuel and the concentration of PM2.5; changes in moisture content notably influence PM2.5 levels. The emission of PM2.5 from fuel with varying loads increases exponentially. Utilizing the Response Surface Methodology (RSM) model for simulation, it was determined that both moisture content and fuel load exert a significant combined effect on the release of PM2.5 during combustion.

Genome-wide identification of R2R3-MYB transcription factors in Betula platyphylla and functional analysis of BpMYB95 in salt tolerance

The Myeloblastosis (MYB) transcription factor (TF) family is one of the largest transcription factor families in plants and plays an important role in various physiological processes. At present, there are few reports on birch (Betula platyphylla Suk.) of R2R3-MYB-TFs, and most BpMYBs still need to be characterized. In this study, 111 R2R3-MYB-TFs with conserved R2 and R3 MYB domains were identified. Phylogenetic tree analysis showed that the MYB family members of Arabidopsis thaliana and birch were divided into 23 and 21 subgroups, respectively. The latter exhibited an uneven distribution across 14 chromosomes. There were five tandem duplication events and 17 segmental duplication events between BpMYBs, and repeat events play an important role in the expansion of the family. In addition, the promoter region of MYBs was rich in various cis-acting elements, and MYB-TFs were involved in plant growth and development, light responses, biotic stress, and abiotic stress. RNA-sequencing (RNA-seq) and quantitative Real-Time Polymerase Chain Reaction (qRT-PCR) results revealed that most R2R3-MYB-TFs in birch responded to salt stress. In particular, the expression of BpMYBs in the S20 subfamily was significantly induced by salt, drought, abscisic acid, and methyl jasmonate stresses. Based on the weighted co-expression network analysis of physiological and RNA-seq data of birch under salt stress, a key MYB-TF BpMYB95 (BPChr12G24087), was identified in response to salt stress, and its expression level was induced by salt stress. BpMYB95 is a nuclear localization protein with transcriptional activation activity in yeast and overexpression of this gene significantly enhanced salt tolerance in Saccharomyces cerevisiae. The qRT-PCR and histochemical staining results showed that BpMYB95 exhibited the highest expression in the roots, young leaves, and petioles of birch plants. Overexpression of BpMYB95 significantly improved salt-induced browning and wilting symptoms in birch leaves and alleviated the degree of PSII photoinhibition caused by salt stress in birch seedlings. In conclusion, most R2R3-MYB-TFs found in birch were involved in the salt stress response mechanisms. Among these, BpMYB95 was a key regulatory factor that significantly enhanced salt tolerance in birch. The findings of this study provide valuable genetic resources for the development of salt-tolerant birch varieties.

Genome-wide identification and expression analysis of the GST gene family of Betula platyphylla

Glutathione-S-transferase (GST, EC2.5.1.18) multifunctional protease is important for detoxification, defense against biotic and abiotic stresses, and secondary metabolic material transport for plant growth and development. In this study, 71 members of the BpGST family were identified from the entire Betula platyphylla Suk. genome. Most of the members encode proteins with amino acid lengths ranging from 101 to 875 and were localized to the cytoplasm by a prediction. BpGSTs can be divided into seven subfamilies, with a majority of birch U and F subfamily members according to gene structure, conserved motifs and evolutionary analysis. GST family genes showed collinearity with 22 genes in Oryza sativa L., and three genes in Arabidopsis thaliana; promoter cis-acting elements predicted that the GST gene family is functional in growth, hormone regulation, and abiotic stress response. Most members of the F subfamily of GST (BpGSTFs) were expressed in roots, stems, leaves, and petioles, with the most expression observed in leaves. On the basis of the expression profiles of F subfamily genes (BpGSTF1 to BpGSTF13) during salt, mannitol and ABA stress, BpGSTF proteins seem to have multiple functions depending on the type of abiotic stress; for instance, BpGSTs may function at different times during abiotic stress. This study enhances understanding of the GST gene family and provides a basis for further exploration of their function in birch.

Hydraulic conductivity regulates tree growth and drought resistance in semi-arid mixed forests of northern China

With the intensification of climate warming, drought has become increasingly severe. Drought seriously impacts tree growth and may even result in tree mortality. However, our understanding of how the hydraulic structure of xylem in different tree species regulates growth and drought resistance remains incomplete. Here, we collected tree-ring samples from three semi-arid natural Chinese pine (Pinus tabuliformis)-broadleaf mixed forests in northern China. We selected Chinese pine (non-porous wood), white birch (Betula platyphylla, diffuse-porous wood), and Liaodong oak (Quercus liaotungensis, ring-porous wood) as target tree species. Using dendrochronology and wood anatomy methods, we evaluated interspecies differences in tree growth, climate sensitivity, and drought resistance, and analyzed the relationships between tree growth, drought resistance, and theoretical xylem-specific hydraulic conductivity (Ks). Our findings revealed distinct differences in the hydraulic structure of xylem among these three tree species as well as their resilience to drought. Liaodong oak exhibited less sensitive to drought compared to Chinese pine and white birch. Meanwhile both Chinese pine and Liaodong oak demonstrated greater resistance to drought than white birch. The positive correlation between specific xylem hydraulic conductivity and both tree growth and drought resistance were observed for Chinese pine, but Liaodong oak was the opposite. This suggested that specific hydraulic conductivity of xylem cannot serve as a consistent or robust predictor of tree growth or drought resistance across different species. As climate warming intensifies, it is anticipated that white birch may experience severe and significant irreversible decline in growth, while Liaodong oak may exhibit the highest potential growth performance. Given the projected intensification of future warming trends along with more frequent extreme climate events, safeguarding biodiversity and productivity within semi-arid Chinese pine-broadleaf mixed forests may hinge on the prioritizing protection efforts for Chinese pine.

NRT2.1 mediates the reciprocal regulation of nitrate and NO/SNO in seedling leaves of Fraxinus mandshurica and Betula platyphylla

Nitric oxide (NO) and S-nitrosothiol (SNO) are signal molecules and the products of nitrogen metabolism. Nitrate (NO3−) is the main nitrogen source, and nitrate transporters (NRTs) are responsible for NO3− absorption or transport. However, the interactive effect between NO3−/NRT and NO/SNO in tree plants remains ambiguous. In the present study, 25 mmol L−1 NO3− and 1 mmol L−1 NO donor sodium nitroprusside (SNP) treatment that was conducted for 24 h enhanced NO/SNO and NO3− metabolism, whereas 2.5 mmol L−1 NO3− and 80 μmol L−1 N6022 (a compound that increases SNO content) treatment reduced them in seedling leaves of Fraxinus mandshurica and Betula platyphylla. Among the nine NRT family members examined, the gene expression level of NRT2.1 had a greater response to NO/SNO and NO3− treatment in the seedling leaves of F. mandshurica and B. platyphylla. Meanwhile, FmNRT2.1 mediated NO and SNO production in seedling leaves of F. mandshurica using Agrobacterium-mediated transient transformation. These findings shed light on the reciprocal regulation between NO3− and NO/SNO in seedlings of F. mandshurica and B. platyphylla, and NRT2.1 may act as a key regulatory hub.

Diversity of Microbial Functional Genes Promotes Soil Nitrogen Mineralization in Boreal Forests.

Soil nitrogen (N) mineralization typically governs the availability and movement of soil N. Understanding how factors, especially functional genes, affect N transformations is essential for the protection and restoration of forest ecosystems. To uncover the underlying mechanisms driving soil N mineralization, this study investigated the effects of edaphic environments, substrates, and soil microbial assemblages on net soil N mineralization in boreal forests. Field studies were conducted in five representative forests: Larix principis-rupprechtii forest (LF), Betula platyphylla forest (BF), mixed forest of Larix principis-rupprechtii and Betula platyphylla (MF), Picea asperata forest (SF), and Pinus sylvestris var. mongolica forest (MPF). Results showed that soil N mineralization rates (Rmin) differed significantly among forests, with the highest rate in BF (p < 0.05). Soil properties and microbial assemblages accounted for over 50% of the variability in N mineralization. This study indicated that soil environmental factors influenced N mineralization through their regulatory impact on microbial assemblages. Compared with microbial community assemblages (α-diversity, Shannon and Richness), functional genes assemblages were the most important indexes to regulate N mineralization. It was thus determined that microbial functional genes controlled N mineralization in boreal forests. This study clarified the mechanisms of N mineralization and provided a mechanistic understanding to enhance biogeochemical models for forecasting soil N availability, alongside aiding species diversity conservation and fragile ecosystem revitalization in boreal forests.

Effects of Fuel Removal on the Flammability of Surface Fuels in Betula platyphylla in the Wildland–Urban Interface

This paper aimed to provide technical support for fuel management by exploring different strengths of fuel removal on the physical and chemical properties and flammability of Betula platyphylla forests in the wildland–urban interface. After investigating the northeastern region during the forest fire prevention period in May 2023, a typical WUI area was selected, and three different treatment strengths, combined with a control, were set up to carry out indoor and outdoor experiments for 27 weeks. Compared with previous studies, this study mainly investigated and analyzed the dynamic changes in the physical and chemical properties and fuel flammability after different intensities of treatments on a time scale. By processing and analyzing the data, the following results were obtained. Significant differences existed in the fuel loading of different time-lag fuels over time (p &lt; 0.05). The ash and ignition point of 1 h time-lag fuel after different treatment intensities generally increased first and then decreased, and the higher heat value and ash-free calorific value generally decreased first and then increased. The physical and chemical properties of 10 h and 100 h time-lag fuel fluctuated with time, but the overall change was insignificant. The indicator that had the greatest impact on the combustion comprehensive score for different time-lag fuels was fuel loading. The change in the flammability of dead surface fuel with time varied significantly, and different treatment intensities effectively reduced the fuel’s flammability. The reduction effects, presented in descending order, were as follows: medium-strength treatment &gt; low-strength treatment &gt; high-strength treatment &gt; control check. In conclusion, different treatment intensities have significant effects on the flammability of the fuel, and the medium-strength treatment has the best effect. Considering the ecological and economic benefits, adopting the medium-strength treatment for the WUI to regulate the fuel is recommended.

Bending and compressive properties of glued-laminated timber composed of Japanese white birch wood using casein adhesive

ABSTRACT Size-reduced model glued-laminated timber (GLT) (1/8 cross-sectional size, six layers, 11 by 18 by 430 mm) was manufactured using birch (Betula platyphylla) wood and a casein adhesive to evaluate the possibility of producing the structural GLT without petrochemical-based adhesives in Mongolia. The same-sized solid lumber and GLT using aqueous vinyl polymer solution-isocyanate adhesives (API) that can be used for structural GLT production in Japan was prepared to evaluate the mechanical performance of GLT using casein adhesive. The effects of lamination configuration and patterns on the mechanical properties (dynamic Young's modulus, modulus of elasticity [MOE], modulus of rupture [MOR], bending work [energy until broken, W], and compressive strength [CS]) were also evaluated using mixed-effect model. Almost no significant differences in the bending and compressive properties were found between GLT using casein and API adhesives, suggesting that, in dry conditions, the bonding performance of casein adhesives closely matches that of API. Modeling results showed that lamina configuration influenced the W and CS even in the Young’s modulus was almost the same, suggesting that the basic wood properties, such as load and deflection characteristics, are important to enhance the mechanical properties of birch GLT with casein adhesive by laminae configurations.

A putative Na+/H+ antiporter BpSOS1 contributes to salt tolerance in birch

White birch (Betula platyphylla Suk.) is an important pioneer tree which plays a critical role in maintaining ecosystem stability and forest regeneration. The growth of birch is dramatically inhibited by salt stress, especially the root inhibition. Salt Overly Sensitive 1 (SOS1) is the only extensively characterized Na+ efflux transporter in multiple plant species. The salt-hypersensitive mutant, sos1, display significant inhibition of root growth by NaCl. However, the role of SOS1 in birch responses to salt stress remains unclear. Here, we characterized a putative Na+/H+ antiporter BpSOS1 in birch and generated the loss-of-function mutants of the birch BpSOS1 by CRISPR/Cas9 approach. The bpsos1 mutant exhibit exceptional increased salt sensitivity which links to excessive Na+ accumulation in root, stem and old leaves. We observed a dramatic reduction of K+ contents in leaves of the bpsos1 mutant plants under salt stress. Furthermore, the Na+/K+ ratio of roots and leaves is significant higher in the bpsos1 mutants than the wild-type plants under salt stress. The ability of Na+ efflux in the root meristem zone is found to be impaired which might result the imbalance of Na+ and K+ in the bpsos1 mutants. Our findings indicate that the Na+/H+ exchanger BpSOS1 plays a critical role in birch salt tolerance by maintaining Na+ homeostasis and provide evidence for molecular breeding to improve salt tolerance in birch and other trees.