Quercus Mongolica Research Articles

Linkages between intra-annual radial growth and photosynthetic production of four main species in a temperate forest in northeast China

The comprehension of the linkage between radial stem growth and photosynthesis is fundamental to gaining insight into the growth and developmental mechanisms of trees, as well as their adaptive capacity to future climate change. However, such crucial information is rarely available, particularly on short-term temporal scales. In this study, we continuously monitored the intra-annual radial stem growth of a non-porous species (Pinus koraiensis) and three ring-porous species (Quercus mongolica, Fraxinus mandshurica, Ulmus japonica) with monthly measurements in 2019 and weekly measurements from 2020 to 2022(second part in 2022) in a temperate forest of Northeast China based on microcore techniques. Concurrently, we estimated the daily photosynthetic production at the individual tree level using a photosynthetic production model developed by our research team. Subsequently, a generalized linear model was conducted to determine the temporal lag of intra-annual radial stem increment and photosynthetic production. Our results indicate significant differences in the initiation of radial growth among the observed years, while the cessation of growth remained consistent. Specifically, ring-porous species exhibited an earlier onset of radial growth compared to non-porous species, but no consistent pattern was observed for the cessation of growth across different wood types. Additionally, we found a strong coupling between radial growth increment and photosynthetic production without any day lag, particularly in different classes. Furthermore, a notable linear association was observed between relative intra-annual radial growth and photosynthetic production, further indicating a positive correlation between photosynthesis and radial growth. We concluded that the carbohydrates required for radial growth are at least partially derived from photosynthetic production produced on the same day when the leaves were available for photosynthesis. These findings enhance our understanding of the seasonal dynamics of radial growth at the cellular level and provide new insights into the relationship between radial growth and photosynthetic production on short-term temporal scales.

Macroscopic and Microscopic Anatomical Characteristics of Six Korean Oak Species

The macroscopic and microscopic anatomical characteristics of wood impact its utilization. This study investigated and compared the anatomical characteristics of six Korean oak wood species: Quercus variabilis, Quercus serrata, Quercus mongolica, Quercus dentata, Quercus aliena, and Quercus acutissima. Microscopic anatomical characteristics were evaluated according to the International Association of Wood Anatomists’ list for hardwood identification. Q. variabilis had a corky bark texture, with a color similar to that of Q. serrata. Flat ridges and shallow-fissured barks were observed in Q. serrata and Q. mongolica. The heartwood color was darker than that of sapwood in all species, with color variations. Q. variabilis had heartwood–sapwood colors similar to those of Q. acutissima, while Q. mongolica and Q. aliena presented similar heartwood–sapwood colors. Concerning microscopic features, Q. variabilis and Q. acutissima exhibited similar latewood vessel arrangements, featuring diagonal and/or radial patterns. In contrast, dendritic-to-diagonal patterns of vessels with angular outlines were observed in Q. serrata, Q. mongolica, Q. dentata, and Q. aliena. Additionally, Q. variabilis and Q. acutissima had vasicentric, confluent, and unilateral paratracheal axial parenchyma in the latewood. In summary, bark morphology, bark color, wood color, and latewood vessel characteristics can be used as identification keys for Korean oak species.

Individual and interactive effects of air warming and elevated O3 on carbon fixation and allocation in two urban tree species

With continuous urbanization and climate warming, increased air temperature and elevated ozone (O3) concentration often co-occur in many urban areas, but we still lack information about the interactive effects of warming and elevated O3 on urban trees. In the present experiment, the single and combined effects of increased air temperature (IT, ambient air temperature + 2 °C) and elevated O3 (EO, ambient air O3 concentrations + 80 ppb) on carbon (C) fixation and allocation in Quercus mongolica and Pinus tabuliformis, which are widely used as street tree species in urban areas of China, were investigated over two consecutive growing seasons by using 13C isotope techniques. The results showed that IT increased biomass, photosynthetic gas exchange parameters and total 13C content of both tree species. Compared to ambient temperature, IT significantly increased the total 13C content labelled by 56.6 % in Q. mongolica and by 31.2 % in P. tabuliformis in 2021. Elevated O3 induced a decrease in biomass and net photosynthetic rate (Pn) in both tree species. Compared to ambient O3, elevated O3 significantly decreased Pn by 52.6 % in Q. mongolica and by 37.4 % in P. tabuliformis in 2020. The treatment EO decreased 13C allocation to roots but increased 13C content and distribution in leaves in Q. mongolica. These findings demonstrated that EO inhibited the growth and photosynthesis of the two tree species. Our results showed that Q. mongolica was more sensitive to IT and EO than P. tabuliformis, but the former has a self-repair mechanism under increased O3 stress as it is able to invest more carbon to repair leaf damage to a certain extent. Our study also found that the total biomass, relative growth rate, Pn and total 13C content remained higher under the combination of IT and EO compared to EO alone, suggesting that moderate warming may mitigate the negative effects of elevated O3 stress to some extent.

Identification of Functional Brassinosteroid Receptor Genes in Oaks and Functional Analysis of QmBRI1.

Brassinosteroids (BRs) play important regulatory roles in plant growth and development, with functional BR receptors being crucial for BR recognition or signaling. Although functional BR receptors have been extensively studied in herbaceous plants, they remain largely under-studied in forest tree species. In this study, nine BR receptors were identified in three representative oak species, of which BRI1s and BRL1s were functional BR receptors. Dispersed duplications were a driving force for oak BR receptor expansion, among which the Brassinosteroid-Insensitive-1 (BRI1)-type genes diverged evolutionarily from most rosids. In oak BRI1s, we identified that methionine in the conserved Asn-Gly-Ser-Met (NGSM) motif was replaced by isoleucine and that the amino acid mutation occurred after the divergence of Quercus and Fagus. Compared with QmBRL1, QmBRI1 was relatively highly expressed during BR-induced xylem differentiation and in young leaves, shoots, and the phloem and xylem of young stems of Quercus mongolica. Based on Arabidopsis complementation experiments, we proved the important role of QmBRI1 in oak growth and development, especially in vascular patterning and xylem differentiation. These findings serve as an important supplement to the findings of the structural, functional and evolutionary studies on functional BR receptors in woody plants and provide the first example of natural mutation occurring in the conserved BR-binding region (NGSM motif) of angiosperm BRI1s.

Nitrogen deposition alters drought-induced changes in biomass and nonstructural carbohydrates allocation patterns of Quercus mongolica seedlings

Water and nitrogen (N) are major constraints that affect plant growth and survival. N deposition can enhance plant photosynthetic capacity and drought tolerance. However, the ecophysiological processes of plants in response to N deposition associated with drought stress are unclear. We investigated the allocation patterns of biomass and nonstructural carbohydrates (NSC) among different organs in response to the addition of ammonium nitrate in Mongolian oak seedlings along a drought stress gradient. This study used pot experiment with three levels of N addition (CK: 0, LN: 5 and HN: 10 g N m−2 yr−1) in conjunction with three irrigated water volumes (W0: 36 L, W1: 25 L, reduction 30%, and W2: 18 L, reduction 50 %). The results showed drought stress, resulting in a decreasing trend in photosynthesis, had been reversed by N addition, and trends in water use efficiency also appeared to increase. Similarly, drought caused a decreasing trend in the biomass and the decreases in the ratio of root-to-shoot (R:S) and total biomass at the whole-seedling level. The enhancements in aboveground biomass were induced by N addition regardless of water conditions. Adversely, root biomass appeared to decrease under normal water conditions (W0) and increased under drought stress. In addition, leaf soluble sugar (SS) concentration and leaf SS: starch increased with N addition under W0 and decreased under severe drought (W2). When water and N availability were abundant, the carbon (C) use strategy of Mongolian oak seedlings focused on aboveground growth to get more carbohydrates. However, when water availability was in severe deficit, the C use strategy of seedlings shifted from growth to protection and defense by restoring more carbohydrates in stems or roots to survive the harsh environments, even when N availability was adequate. This study provided new insights into the understanding of C use strategy and drought survival mechanism in response to environmental change.

Rapid migration of Mongolian oak into the southern Asian boreal forest.

The migration of trees induced by climatic warming has been observed at many alpine treelines and boreal-tundra ecotones, but the migration of temperate trees into southern boreal forest remains less well documented. We conducted a field investigation across an ecotone of temperate and boreal forests in northern Greater Khingan Mountains of northeast China. Our analysis demonstrates that Mongolian oak (Quercus mongolica), an important temperate tree species, has migrated rapidly into southern boreal forest in synchrony with significant climatic warming over the past century. The average rate of migration is estimated to be 12.0 ± 1.0 km decade-1 , being slightly slower than the movement of isotherms (14.7 ± 6.4 km decade-1 ). The migration rate of Mongolian oak is the highest observed among migratory temperate trees (average rate 4.0 ± 1.0 km decade-1 ) and significantly higher than the rates of tree migration at boreal-tundra ecotones (0.9 ± 0.4 km decade-1 ) and alpine treelines (0.004 ± 0.003 km decade-1 ). Compared with the coexisting dominant boreal tree species, Dahurian larch (Larix gmelinii), temperate Mongolian oak is observed to have significantly lower capacity for light acquisition, comparable water-use efficiency but stronger capacity to utilize nutrients especially the most limiting nutrient, nitrogen. In the context of climatic warming, and in addition to a high seed dispersal capacity and potential thermal niche differences, the advantage of nutrient utilization, reflected by foliar elementomes and stable nitrogen isotope ratios, is also likely a key mechanism for Mongolian oak to coexist with Dahurian larch and facilitate its migration toward boreal forest. These findings highlight a rapid deborealization of southern Asian boreal forest in response to climatic warming.

An Automated Pipeline for Extracting Forest Structural Parameters by Integrating UAV and Ground-Based LiDAR Point Clouds

In recent times, airborne and terrestrial laser scanning have been utilized to collect point cloud data for forest resource surveys, aiding in the estimation of tree and stand attributes over hectare-scale plots. In this study, an automated approach was devised to estimate the diameter at breast height (DBH) and tree height across the entire sample area, utilizing information acquired from terrestrial laser scanning (TLS) and airborne laser scanning (ULS). Centered around a meticulously managed artificial forest in Northern China, where Mongolian oak and Chinese Scots pine are the predominant species, both TLS and ULS operations were conducted concurrently on each plot. Subsequent to data collection, a detailed processing of the point cloud data was carried out, introducing an innovative algorithm to facilitate the matching of individual tree point clouds from ULS and TLS sources. To enhance the accuracy of DBH estimation, a weighted regression correction equation based on TLS data was introduced. The estimations obtained for the Chinese Scots pine plots showed a correlation of R2 = 0.789 and a root mean square error (RMSE) of 3.2 cm, while for the Mongolian oak plots, an improved correlation of R2 = 0.761 and a RMSE of 3.1 cm was observed between predicted and measured values. This research significantly augments the potential for non-destructive estimations of tree structural parameters on a hectare scale by integrating TLS and ULS technologies. The advancements hold paramount importance in the domain of large-scale forest surveys, particularly in the calibration and validation of aboveground biomass (AGB) estimations.

Phytosociological characteristics of Betula davurica–Quercus crispula forests in Japan based on a comparison with summergreen broad-leaved forests in Northeast Asia

Betula davurica and deciduous Quercus forests are among the principal forest types in Northeast Asia. They are found throughout continental Northeast Asia and in some mountainous regions of Central Honshu and eastern Hokkaido in the Japanese Archipelago. B. davurica–Quercus crispula forests in Japan are significant for understanding the phytogeography of Japan and Northeast Asia. However, their relationships with B. davurica–Quercus mongolica forests in continental Northeast Asia remain poorly understood. We compared the species composition of B. davurica–Q. crispula forests of Japan, with those of Q. crispula dominant forests and B. davurica–Q. mongolica forests using phytosociological methods. The results suggested that B. davurica–Q. crispula forests of Japan had a significant number of species common to the order Lespedezo bicoloris–Quercetalia mongolicae and the class Querco mongolicae–Betuletea davuricae in continental Northeast Asia than in other associations in Japan. Furthermore, our results showed that associations between B. davurica and Q. crispula forests in Central Honshu and Hokkaido are related to different orders in continental Northeast Asia. The relations of the associations between Japan and the continent are considered to have been caused by the environmental similarities, the histories of taxa, and the changes in vegetation distribution.

Individual Tree Height Increment Model for Quercus mongolica Secondary Forest in the Northeastern China Using Generalized Nonlinear Two-Level Mixed-Effects Model

(1) Background: Mongolian oak secondary forest is widely distributed in the northeast of China, and most of these forests are formed after the overcutting of broad-leaved Pinus koraiensis mixed forest. Most of the forest productivity is low and the ecological function is degraded, due to insufficient understanding of Mongolian oak and lack of scientific management. Deepening the research on exploring reasonable management measures of Mongolian oak secondary forest to an improved stand status is the basis for improving its quality and promoting its forward succession process. (2) Methods: Twelve permanent plots with an area of 1 ha were established in the Mongolian oak secondary forest on Tazigou forest farm in Wangqing, Jilin Province of northeastern China. The response of tree height increment of Mongolian oak secondary forest is studied based on the survey data of 2013 and 2018. Two-level nonlinear mixed-effects models were constructed to predict the height of a single tree using sample plots and tree species as random effects, combined with a variety of tree size factors, site factors, and competitive factors as independent variables. (3) Results: The significant factors related to the height increment of Mongolian oak secondary forest are the initial diameter at breast height as the size of the tree itself (DBH), height (H), crown height ratio (CR), and site productivity index reflecting site quality (SPI). The distance-dependent and distance-independent competition indexes have no significant effect on tree height increment. The fitting accuracy of the two-level mixed-effects model that introduces plots and tree species as random effects has been greatly improved (coefficient of determination R2 increased by 51.8%). The prediction results show that the two trees with the largest DBH have the strongest prediction ability. (4) Conclusions: The generalized nonlinear two-level mixed-effects model constructed in this study can describe the height increment of an individual tree in the Mongolian oak secondary forest. Two sample trees, namely the two largest trees in each sub-plot, were applied for estimating the random effects when both measurement cost and potential errors of prediction were balanced.

Forest Fire Spread Hazard and Landscape Pattern Characteristics in the Mountainous District, Beijing

Objective: This study established an index system for assessing forest fire spread hazards and conducted a forest fire spread hazard assessment in the mountainous district of Beijing (including Fangshan, Mentougou, Changping, Yanqing, Huairou, Miyun, and Pinggu). The relationship between forested landscape spatial pattern and forest fire spread hazard was explored; this method provided the basis for the establishment of a landscape forest fire security guarantee system. Methods: The forest fire spread hazard assessment index system was constructed from four aspects: forest fuel, meteorological factors, topographic factors, and fire behavior. The weighted comprehensive evaluation method and area-weighted average method were used to calculate the forest fire spread hazard indices at the subcompartment scale and township scale. Moran’s I index was selected as the spatial autocorrelation index to analyze the autocorrelation degree and spatial distribution of the forest fire spread hazard index. Eleven representative landscape pattern indices were selected to analyze the main landscape spatial pattern affecting forest fire spread hazard by correlation analysis and principal component analysis. Results: (1) The areas with high, medium–high, medium-low, and low forest fire spread hazard grades accounted for 39.87%, 33.10%, 11.37%, and 15.66% of the study area, respectively, at the subcompartment scale and for 52.36%, 22.58%, 18.39%, and 6.67% of the study area, respectively, at the township scale. (2) The forest fire spread hazard index results obtained at the subcompartment and township scales in the Mountainous District of Beijing showed a spatial agglomeration distribution law. (3) The forest fire spread hazard was influenced mainly by landscape diversity (SHDI and PRD), landscape aggregation (AI, CONTAG, and PD), and landscape area (TA). Conclusions: The overall forest fire spread hazard in the mountainous district of Beijing showed a gradual increase from plains to mountainous areas. The land types of the high-spread hazard subcompartment mainly included general shrubbery and coniferous forestlands, and the dominant species in the high-spread hazard arbor forest subcompartment were mainly Platycladus orientalis, Pinus tabuliformis, and Quercus mongolica.

The Impact of Urbanization on Tree Growth and Xylem Anatomical Characteristics.

In the context of the intensification of global urbanization, how urbanization (urban heat island effect and air pollution) affects urban tree growth is not fully understood. In this paper, the radial growth and xylem anatomical characteristics of three different tree species (Quercus mongolica, Fraxinus mandshurica, and Pinus sylvestris var. mongolica) in urban and rural areas of Harbin were compared by means of tree-ring anatomy. The results showed that there were significant differences in the growth of both broadleaf trees and conifers between urban and rural areas. The vessel number, cumulative area of vessels, and theoretical hydraulic conductivity of all tree species in rural areas were higher than those in urban areas, indicating that urbanization may have the effect of slowing down growth. However, broadleaf trees in urban areas had higher vessel density and a greater percentage of a conductive area within xylem and theoretical xylem-specific hydraulic conductivity. The thickness of cell walls and cell wall reinforcement index of P. sylvestris var. mongolica were strongly reduced by air pollution, implying that it may be more sensitive to urbanization. Compared to Q. mongolica, F. mandshurica showed less sensitivity to urbanization. Warming and drying climate in Harbin may be an important factor affecting tree growth.

Evolution of vegetation of the Lake Khanka Depression in the southernmost of the Russian Far East in the Holocene

This paper presents recently obtained palynological results regarding to the evolution of vegetation of the Khanka Depression in the Holocene. Radiocarbon-dated pollen records evidence that the evolution of vegetation in this area was more complicated than one has previously thought. As a result of a rapid increase in heat supply in the Early Holocene, the plants of the Manchurian flora, primarily Ulmus davidiana, Ulmus laciniata, Quercus mongolica, and Pinus koraiensis, began to expand to the Khanka Depression. However, Sphagnum mires with Betula grandulosa, Betula pubescens, and sparse forests of Larix, still remained in plains and valleys. Picea jezoensis, Pinus pumila, Betula grandulosa, Betula alnobetula, Betula pubescens, Pinus pumila and Larix were widespread in the mountains. During the Middle Holocene these cold-tolerant plants of the north-boreal flora, completely disappeared. Broad-leaved and fir-pine forests have become widespread. The vegetation of the Khanka Depression compared with modern one was characterized by great diversity of broad-leaved plants. At the beginning of the Late Holocene cooling has caused the expansion of Betula grandulosa, Betula alnobetula, Abies nephrolepis, Picea jezoensis, Betula pubescens, Betula costata, and Alnus hirsuta. The areas of forb meadows expanded on the plains. Larch sparse forests, thickets with domination of Betula grandulosa and Sphagnum mires reappeared. However, some thermophilic plants, such as Pinus koraiensis, Abies nephrolepis, Quercus mongolica, Juglans mandshurica, Ulmus davidiana, and Ulmus laciniata have survived. Since 1 300 cal BP, vegetation of the Khanka Depression began to degrade due to fires, plowing of the land, and deforestation.

Drivers and spatiotemporal patterns of post-drought growth resilience of four temperate broad-leaved trees

With the intensification of climate warming, more frequent and hotter droughts are a significant risk to forest ecosystems around the globe, including temperate biomes. To accurately predict the response of forests to drought, it is necessary to provide comprehensive information on the resilience of tree growth, its spatiotemporal changes and drivers. This information is often lacking for broadleaf species in temperate regions. To fulfill this aim, we analyzed 3177 ring-width series from 1981 trees covering 40 sites for four dominant broad-leaf tree species (Fraxinus mandshurica, Phellodendron amurense, Juglans mandshurica, and Quercus mongolica) in temperate forests in northeastern China. We quantified the resilience (resistance and recovery) of tree growth to extreme droughts. Minimum temperatures in most seasons and warm conditions and drought stress in early summer were the main factors limiting growth. Among the four tree species, Q. mongolica had the weakest growth resistance to drought and the fastest growth recovery from drought. Juglans mandshurica had a significantly (p < 0.05) higher drought resilience than F. mandshurica and P. amurense. Tree resilience presented a clear spatial pattern driven by differences in site condition and local climate. The resistance (recovery) to drought decreased (increased) with increasing latitude and longitude, and increased (decreased) with elevation. Q. mongolica exhibited a decrease in resistance and increase in recovery through time, whereas the other three tree species showed the opposite pattern. Fraxinus mandshurica, J. mandshurica, and Q. mongolica had high resistance (recovery) in warmer-wetter (colder-drier) regions. In contrast, P. amurense had reduced recovery in cold sites and low resistance in warm sites. The resistance and recovery indices of these sympatric tree species confirmed that different tree species have distinct strategies to cope with drought that is influenced by tree condition and local environment. The influence of biogeographical factors is often more important than other factors and should be considered when studying forest resilience to drought.

Variation and drivers of soil fungal and functional groups among different forest types in warm temperate secondary forests

Soil fungal communities play a crucial role in maintaining and regulating ecosystem functions. The soil fungal structure of different plant communities in forests has been widely studied. However, the drivers of changes in soil fungal community dynamics in warm temperate secondary forests and the pathways influencing them remain to be explored. The Illumina high-throughput sequencing and FUNGuild platform were used to characterize the soil fungal diversity and community composition of six typical plant communities (JM, Juglans mandshurica; PD, Populus davidiana; QM, Quercus mongolica; MB, mixed broadleaf forest; MC, mixed conifer forest; PT, Pinus tabuliformis) in warm temperate secondary forests. The drivers of structural changes in dominant fungal taxa and functional groups were also explored. The pathways through which forest type, soil properties, altitude, climate, and plant diversity affected fungal community structure were further clarified. The results suggested that Ascomycota, Basidiomycota, and Zygomycota dominated the soil fungal communities in warm temperate secondary forests. Except for symbiotic fungi, there was no significant difference in soil fungal α-diversity among forest types. However, there were significant differences in total fungi and functional group community composition. The drivers of diversity and community composition of different soil fungal taxa in warm temperate secondary forests differed. In addition, the partial least squares path model indicated that the composition of soil fungal community in warm temperate secondary forests was directly influenced by forest type and was less dependent on soil properties. Collectively, our study highlights the importance of forest type, soil properties, and other factors (climate, altitude, plant diversity) in driving changes in soil fungal community structure.

Integrated physiological and metabolomic analyses reveal changes during the natural senescence of Quercus mongolica leaves.

Quercus mongolica is a common landscape, afforestation, and construction timber species in northern China with high ecological, economic, and ornamental value. Leaf senescence is a complex process that has important implications for plant growth and development. To explore changes of metabolites during the ageing of Quercus mongolica leaves, we investigated physiological responses and metabolite composition in ageing leaves harvested from 15-20-year-old Quercus mongolica. Leaf samples of Q. mongolica were collected when they were still green (at maturity) (stage 1), during early senescence (stage 2), and during late senescence (stage 3). These leaves were then subjected to physiological index and metabolome sequencing analyses. The physiological analysis showed that the leaves of Q. mongolica changed from green to yellow during senescence, which induced significant accumulation of soluble sugar and significant reductions in the concentration of soluble protein and chlorophyll. Peroxidase and catalase were the main antioxidant enzymes mitigating leaf senescence. Metabolomic analysis identified 797 metabolites during leaf senescence. Compared to stage 1, 70 differential metabolites were screened in stage 2 and 72 were screened in stage 3. Differential metabolites in the two senescent stages were principally enriched in amino acid metabolism, lipid metabolism and secondary metabolite biosynthesis. The contents of N-oleoylethanolamine and N, N-dimethylglycine were significantly increased only in stage 2, while the contents of trifolin, astragalin, valine, isoleucine, leucine, and citric acid were significantly increased only in stage 3. Histidine, homoserine, tryptophan, tyrosine, phenylalanine, proline, norleucine, N-glycyl-L-leucine, linoleic acid, linolenic acid, gallic acid, 3-indoleacrylic acid, 3-amino-2-naphthoic acid, 3-hydroxy-3-methylpentane-1,5-dioic acid, 2,3,4-trihydroxybenzoic acid, trifolin, astragalin, DL-2-aminoadipic acid, pinoresinol dimethyl ether, dimethylmatairesinol, and lysophosphatidylcholine increased during both stage 2 and stage 3. Increasing contents of these metabolites may constitute the main mechanism by which Q. mongolica leaves adapt to senescence.

Understory fuel loads and the impact factors of Quercus mongolica natural secondary forest in Hebei Pro-vince, China.

We investigated understory fuel loads of Quercus mongolica natural secondary forests in Hebei Province, China. We analyzed the effects of stand factors, topographic factors, and ground cover factors on the quantity and composition of fuel, established the dynamic models of understory fuel loads, and proposed management measures. The results showed that the understory total fuel load in Q. mongolica natural secondary forests was 11.68 t·hm-2, which exceeded the forest fire potential threshold (10 t·hm-2). The understory dead fuel load was mainly humus, and the understory living fuel load was mainly shrubs. The 1 h time-lag fuel load increased significantly with increasing canopy density, stand density, stand age, and litter thickness. The 10 h time-lag fuel load increased signi-ficantly with increasing stand density, average tree height, and litter thickness. Humus load decreased significantly with increasing altitude and increased significantly with increasing humus thickness. Herb load increased significantly with increasing sunny slope orientation and herbal coverage. Shrub load increased significantly with increasing slope degree, shrub coverage, and humus thickness. Understory total fuel load decreased significantly with increasing altitude, and increased significantly with increasing stand density, humus thickness, and litter thickness. The results of stepwise regression analysis indicated that stand density, humus thickness, and altitude could better predict the understory total fuel load (Radj2=0.775). Therefore, more attention should be paid on the control of stand density of Q. mongolica natural secondary forest in Hebei Province. Cleaning of litters and humus on the ground would help prevent forest fires scientifically and effectively.

신갈나무(Quercus mongolica) 입자 크기에 따른 화학조성 및 전처리 효율 변화

신갈나무(Quercus mongolica) 입자 크기에 따른 화학조성 및 전처리 효율 변화

Transcriptomic Determination of the Core Genes Regulating the Growth and Physiological Traits of Quercus mongolica Fisch. ex Ledeb

Quercus mongolica is a multipurpose forest species of high economic value that also plays an important role in the maintenance and protection of its environment. Consistent with the wide geographical distribution of Q. mongolica, differences in the growth and physiological traits of populations of different provenances have been identified. In this study, the molecular basis for these differences was investigated by examining the growth, physiological traits, and gene expression of Q. mongolica seedlings from six provenances in northern China. The results showed that there were significant differences in growth and physiological traits, except for the ground diameter (p &lt; 0.05), and identified abscisic acid (ABA), indole-3-acetic acid (IAA), and soluble sugar contents as important physiological traits that distinguish Q. mongolica of different provenances. The transcriptome analysis showed that the largest difference in the total number of differentially expressed genes (DEGs) was between trees from Jilin and Shandong (6918), and the smallest difference was between trees from Heilongjiang and Liaoning (1325). The DEGs were concentrated mainly in the Gene Ontology entries of metabolic process, catalytic activity, and cell, and in the Kyoto Encyclopedia of Genes and Genomes metabolic pathways of carbohydrate metabolism, biosynthesis of other secondary metabolites, signal transduction, and environmental adaptation. These assignments indicated that Q. mongolica populations of different provenances adapt to changes in climate and environment by regulating important physiological, biochemical, and metabolic processes. A weighted gene co-expression network analysis revealed highly significant correlations of the darkmagenta, grey60, turquoise, and plum1 modules with ABA content, IAA content, soluble sugar content, and soluble protein content, respectively. The co-expression network also indicated key roles for genes related to the stress response (SDH, WAK5, APA1), metabolic processes (UGT76A2, HTH, At5g42100, PEX11C), signal transduction (INPS1, HSD1), and chloroplast biosynthesis (CAB13, PTAC16, PNSB5). Functional annotation of these core genes implies that Q. mongolica can adapt to different environments by regulating photosynthesis, plant hormone signal transduction, the stress response, and other key physiological and biochemical processes. Our results provide insight into the adaptability of plants to different environments.

The effects of forest types and age groups on forest provisioning and supporting service value in Sanhu Nature Reserve, Northeast China

The promotion of forest resource protection and sustainable development relies greatly on the value of forest ecosystem services. In Jilin Songhuajiang Sanhu National Nature Reserve in Northeast China, a total of 169 sample plots were examined and analyzed to evaluate the provisioning and supporting services provided by the forest ecosystem. The study revealed that the near-mature and over-mature Fraxinus mandshurica forest have relatively high timber supply and species resources conservation values per unit area, respectively. Furthermore, the mature Betula platyphylla forest has the highest forest nutrient retention value, while the near-mature Juglans mandshurica forest has the highest soil conservation value, with the nitrogen fixation value accounting for the highest proportion. The forest ecosystem services in the reserve have a total value of 659.07 million $⋅y–1. The main contributors to the value are the services of soil fertilizer conservation, timber supply, and species resources conservation, with the mixed broad-leaved forest and Quercus mongolica forest being the main contributors, accounting for 63.1 and 18.8% of the total value, respectively. Nonetheless, the service value of per unit area in J. mandshurica forest is the highest. Near-mature and mature forests are the main contributors to the total value, accounting for 42.3 and 34.9%, respectively. Forest lands exhibit significant variations in the values of provisioning and supporting services across different stand types and age groups.

Sensitivity of isoprene emission rate to ozone in greening trees is concurrently determined by isoprene synthesis capacity and stomatal conductance

The sensitivity of isoprene emission rate (ISOrate) to ozone (O3) in plant suggests potentially large changes in future isoprene emissions, which will have important consequences for atmospheric chemistry. However, the interspecific variation of ISOrate sensitivity to O3 and its key drivers remain largely unknown. In this study, four urban greening tree species were exposed to two O3 treatments (charcoal-filtered air, CF; and non-filtered ambient air plus 60 ppb extra O3, EO3) in open-top chambers for one growing season. We aimed to compare the interspecific variation in O3 inhibitory effect on ISOrate and explore its physiological mechanism. EO3 decreased the ISOrate by on average 42.5 % across species. According to absolute effect size ranking, the highest ISOrate sensitivity to EO3 was observed in Salix matsudana, followed by Sophora japonica and hybrid poplar clone ‘546’, while Quercus mongolica ISOrate was the least sensitive. Leaf anatomical structures differed in tree species but did not respond to EO3. Furthermore, the ISOrate sensitivity to O3 was driven by the concurrent effects of O3 on ISO synthesis ability (i.e., dimethylallyl diphosphate and isoprene synthase contents) and stomatal conductance. Overall, the mechanistic understanding grained from this study may promote the integrity of O3 effect into process-based ISO emission models.