Forests

Abiotic stresses could have complex and diverse effects on the growth and development of forest trees. In this review, we summarized the responses of morphological, physiological and anatomical traits in woody plants to abiotic stresses, including drought, flood, extreme temperature, salinity, heavy metal, microplastics and combined stresses, especially from the xylem perspective. Under most abiotic stress, xylem hydraulic conductivity decreases, which is associated with leaf stomatal regulation and the inhibition of aquaporin (AQP) activity. Meanwhile, woody plants regulate the size and morphology of their roots and leaves to balance water absorption and transpiration. The anatomical traits are also altered, such as denser leaf stomata, narrower conduits and thicker cell walls. In addition, different stresses have unique effects, such as flood-induced adventitious roots and aeration tissues, forest fire-induced irreversible xylem damage, low temperature-induced tissue freezing, salt stress-induced hinderance of ion absorption and heavy metal-induced biological toxicity. Under stresses of drought, flooding and heavy metals, woody plants’ growth may occasionally be promoted. The effects of combined stress on the physiological, morphological and anatomical traits of woody plants are not simply additive, with the related mechanism to be further studied, especially in natural or near-natural conditions. Full article

The ecological process of natural regeneration in forests is achieved by altering the relationship between community diversity and abiotic factors, thereby influencing the structure and functioning of ecosystems. Phoebe bournei is a unique and endangered tree species in China, and due to the rarity of P. bournei (Phoebe bournei) populations, there is limited research on the interaction between plant community diversity and soil environment during its natural regeneration process. Jiangxi Mingyue Mountain Forest Farm is one of the few locations where the natural regeneration of P. bournei communities occurs. From 2018 to 2021, the DBH (diameter at breast height) method was employed to define the stages of P. bournei regeneration. Community tree diversity, productivity, soil nutrients, and microbial diversity were investigated. The results showed the following: (1) P. bournei exhibits a competitive advantage compared to other tree species during natural regeneration, and it becomes the main contributor to community biomass and productivity in the later stages of regeneration. (2) The regeneration process of P. bournei has significant effects on community tree diversity and soil environment. Community diversity and biomass show a trend of initial increase followed by a decrease. Soil moisture content, available phosphorus, and bacterial diversity significantly increase. P. bournei’s competitive advantage is likely derived from its regulation of soil nutrients and microorganisms. (3) Correlation analysis reveals a significant positive correlation between soil microbial diversity and community productivity. Therefore, it is necessary to consider the composition and diversity of underground soil microorganisms in studies aimed at improving the quality of P. bournei forests. In summary, the natural regeneration of P. bournei involves the gradual removal of the original dominant evergreen species in the community by increasing its own competitive advantage and productivity, while continuously regulating community diversity, soil nutrients, and microbial diversity to facilitate the growth and development of P. bournei, ultimately establishing it as the dominant species in the forest community. Full article

Tactical planning in timber harvesting involves aspects related to forest macro-planning and, particularly, the allocation of resources and sequencing of activities, all of which affect the allocation of timber in forest yards and roads and the productivity of forest machines. Data-driven approaches encourage the use of information obtained from data to enhance decision-making efficiency and support the development of short-term strategies. Therefore, our investigation was intended to determine whether a data-driven approach can generate sufficient input for modeling forwarder productivity in timber forwarding in Pinus and Eucalyptus planted forests, to support tactical planning. We utilized 3812 instances of raw data that were generated over a 36-month period. The data were collected from 23 loggers who operated in Pinus and Eucalyptus planted forests. We applied 22 regression algorithms that applied a supervised learning method from an experimental machine learning approach to the data instances. We evaluated the fitted models using three performance metrics. Out of the tested algorithms, the default mode of light gradient boosting produced a root mean squared error of 14.80 m³ h⁻¹, a mean absolute error of 2.70, and a coefficient of determination of 0.77. Therefore, data-driven methods adequately support forwarder productivity modeling in timber forwarding in planted forests and help forest managers with tactical planning. Full article

This study explores the effect of tannic acid on the corrosion of woodworking tool material W18Cr4V in a simulated wood environment. The weight loss method, potentiodynamic polarization, and electrochemical impedance spectroscopy were used to study the corrosion and the corrosion inhibition process of W18Cr4V in an environment of acetic acid solution with different concentrations of tannic acid. The results show that after continuous immersion for 20 h, low concentrations (1 wt% and 3 wt%) of tannic acid promoted the corrosion of W18Cr4V, while high concentrations (5 wt% and above) of tannic acid had a significant anti-corrosion effect, with a corrosion inhibition efficiency of about 64% for 10 wt% tannic acid. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy were used to further verify and elucidate the inhibition mechanism. It was found that tannic acid can form a dense and effective corrosion inhibition film composed of iron–tannin complexes on the surface of W18Cr4V. This study not only provides a new perspective on understanding the corrosion effect of tannic acid on woodworking tools but also offers new insights for developing effective bio-corrosion protection strategies. Full article

The tree-ring fire scar stands as a pivotal proxy for reconstructing historical wildfire occurrences, providing invaluable context for comprehending contemporary wildfire activities during the Anthropocene era. Precise identification of fire scars often necessitates sampling complete tree disks. Yet, stringent forest resource protection policies limit such collection in certain regions, thus curtailing the application of tree-ring-based fire reconstruction. While current methods based on tree-ring cores can ascertain the age range of fire events, pinpointing the exact year remains challenging. In this study, we propose a novel approach for detecting fire occurrence years by recognizing abrupt shifts in the tree-ring geometric center (TRGC). This method entails extracting a minimum of three tree-ring cores from the uninjured side of the tree and in proximity to the fire scar. We validated this method’s efficacy using samples from Transbaikal of Russia, in northeastern Asia, where fire years have already been documented. Our results show that this method accurately identified the fire year in nine fire scars with a 67 percent probability of exact agreement with the actual fire year. It is noteworthy that this method particularly excels in cases of trees with a single fire scar. We recommend employing the traditional method of collecting tree-ring cores near the fire scar to establish the age range of the fire scar. Subsequently, within this determined range, we suggest detecting the shifts in the TRGC to accurately pinpoint the exact year of the fire scar. Full article

The growth of a tree depends on the size, shape, and functioning of the crown. The length of the crown is a somewhat subjective value because the base of the crown is often difficult to determine. The aim of this study was to develop an allometric model to calculate the crown length of Pinus sylvestris L., which might serve as an alternative to the current equations used especially for stands of variable density. The model used three predictive variables, i.e., diameter at breast height, tree height, and density. The developed crown length model showed high compatibility with empirical data within the studied stands differing in diameter at breast height, height, age, biosocial position, and, above all, density (SD = 1.786). The correlation coefficient between the empirical crown length for the stand ($H_{emp}^{*}$) and the calculated model $\left(H_{cal}^{*}\right)$ was r = 0.974, with a discrepancy of (±) 3.17%. The derived crown length model can be one of the components used to estimate the mass of needles or leaf area index (LAI) and, consequently, the amount of transpiration or the amount of carbon dioxide bound, which is crucial in the context of climate change. Full article

Cordiaceae is a family comprising more than 400 species in the order Boraginales. The classification of this family has undergone changes over time, transitioning between family and subfamily status. In the present study, the complete chloroplast (cp) genomes of Cordia monoica and Cordia sinensis were sequenced, and their cp genomes were then characterized, analyzed, and compared to those of closely related taxa. The lengths of the cp genomes of C. monoica and C. sinensis were 151,813 bp and 152,050 bp, respectively. Both genomes consisted of 114 genes, divided into 4 ribosomal RNA genes, 30 transfer RNA genes, and 80 protein-coding genes. We observed a unique gene inversion in the trnM-rbcL region of both Cordia species. The long repeats analysis revealed that both species’ chloroplast genomes contained forward and palindromic repeats. The simple sequence repeats (SSRs) analysis detected 155 microsatellites in each genome, with the majority being mononucleotide repeats (A/T). Phylogenetic analysis based on maximum likelihood and Bayesian analyses confirmed two major clades in the order Boraginales: clade I comprised Boraginaceae, while clade II included Cordiaceae, Ehretiaceae, and Heliotropiaceae. This study expands our knowledge of the evolutionary relationships across the order Boraginales and offers useful genetic resources. Full article

Gleditsia sinensis Lam. (Fam. Leguminosae; Gen.: Gleditsia) has various uses, including for medicinal, edible, chemical, and material purposes, and is widely distributed in China. However, the extent of graft compatibility and its impact on growth when using different Gleditsia species as rootstocks for grafting G. sinensis scions is not yet clear. This study examined homologous and heterologous grafting between different Gleditsia species, measuring the survival rate, morphology, photosynthesis, physiology, and hormones of the grafted plants. The results showed that G. sinensis and other Gleditsia seedlings have survival rates of over 86%. The more distant the genetic relationship between species, the lower the grafting survival rate. The grafting of fast-growing G. fera as a rootstock increased the accumulation of photosynthetic products in the grafted plants, while the grafting of slow-growing G. microphylla as a rootstock slowed down the growth rate of the longitudinal extension of the leaves of the grafted plants. Heterografted rootstocks increased the contents of IPA, PP333, ACC, and DZ but decreased the levels of GA₄, iP, and SA hormones. Some hormone levels that can be highly expressed in seedlings were used as rootstocks, and the corresponding hormone levels in the grafted seedlings were still highly expressed. This study lays a material and theoretical basis for the development of new resources for the breeding and rootstock selection of G. sinensis. Full article

Sentinel-2 serves as a crucial data source for monitoring forest cover change. In this study, a sub-pixel mapping of forest cover is performed on Sentinel-2 images, downscaling the spatial resolution of the positioned results to 2.5 m, enabling sub-pixel-level forest cover monitoring. A novel sub-pixel mapping with edge-matching correction is proposed on the basis of the Sentinel-2 images, combining edge-matching technology to extract the forest boundary of Jilin-1 images at sub-meter level as spatial constraint information for sub-pixel mapping. This approach enables accurate mapping of forest cover, surpassing traditional pixel-level monitoring in terms of accuracy and robustness. The corrected mapping method allows more spatial detail to be restored at forest boundaries, monitoring forest changes at a smaller scale, which is highly similar to actual forest boundaries on the surface. The overall accuracy of the modified sub-pixel mapping method reaches 93.15%, an improvement of 1.96% over the conventional Sub-pixel-pixel Spatial Attraction Model (SPSAM). Additionally, the kappa coefficient improved by 0.15 to reach 0.892 during the correction. In summary, this study introduces a new method of forest cover monitoring, enhancing the accuracy and efficiency of acquiring forest resource information. This approach provides a fresh perspective in the field of forest cover monitoring, especially for monitoring small deforestation and forest degradation activities. Full article

Palm leaf manuscripts were a prevalent literary medium from South Asia and Southeast Asia prior to the widespread use of paper. This study focuses on the analysis of historical palm leaf manuscripts from South and Southeast Asia. Sample palm leaf manuscripts from Burma were used as a case study; simulated palm leaf manuscripts were also created as a reference for comparison. The anatomy, chemical composition, and mechanical properties of the manuscripts were analyzed to find various forms of deterioration, including damage, fractures, pollution, acidification, and microbial deterioration. Specifically, the S₁–S₃ layers of the cell walls exhibited complete cracking, and the S₂ layer showed numerous circular or nearly circular cavities caused by microbial erosion, while the middle lamella remained intact. The severe degradation of polysaccharides and pectin, accompanied by an increase in the relative content of lignin, caused the historical manuscripts to become more brittle. Additionally, the tensile strengths of historical palm leaf manuscripts were markedly reduced; their longitudinal tensile strength was significantly greater than their transverse tensile strength. This study can contribute to a better understanding of the deterioration process of historical palm leaf manuscripts and provide valuable insights for their restoration and preservation. Full article

With the growing demand for high-quality timber, selection processes for both growth and wood properties are needed for multi-trait breeding programs in Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.). The present study examined the variation and correlation of growth (tree height, diameter at breast height, stem volume, crown-width) and wood properties (wood basic density, hygroscopicity, and heart-wood ratio) traits of 201 Chinese fir breeding parents, aiming to select better parents for future multi-trait improvement. The results showed that significant differences (p < 0.01) regarding growth and wood property traits were observed among clones in an individual site and in a two-site joint analysis. The repeatability of the tested traits varied from 0.22 to 0.87. Strong and positive (p < 0.01) correlations were detected among the four growth traits, while wood basic density had a significant negative correlation (p < 0.01 or 0.05) with the growth traits. A set of parent clones was shortlisted with substantial realized gains (ranging from 4.59% to 83.77%) in growth and wood traits. It was suggested that these selected parents could be used to improve the growth and wood quality of Chinese fir. Full article

To study the softening bending properties and mechanism of teakwood, it was extractively pretreated by using superheated steam, the triethanolamine compound was used as a softening solution, which was infiltrated into the wood by vacuum impregnation and synergistically softened through saturated steam to improve the bending properties of teakwood. Analysis by Fourier transform infrared spectroscopy (FTIR), Carbon 13 nuclear magnetic resonance (¹³C NMR), and X-ray photoelectron spectroscopy (XPS) showed that the synergistic softening treatment elevated the content of O and N elements in the softening solution and together with the C elements in the wood, formed C-NH₂ and C-N bonds, which increased the molecular activity and improved the softening properties of teakwood. Scanning electron microscope (SEM) observations revealed that the outer conduits, cell walls, and fibrous tissue structures of the teakwood were stretched after softening and bending, and even microcracks of different degrees were formed between the cell walls. According to the load–deformation relationship of teakwood softening bending, the stress–strain relationship was theoretically derived and the bifold constitutive model of teakwood bending was constructed after fitting the constitutive relationship data, the integrated correlation coefficient R² was 96.25%, which proved that the present model can better simulate the constitutive relationship of teakwood in bending. Full article

A superhydrophobic wood surface was produced by employing the solvothermal method to form shuttle-like, well-crystallized MIL-88(Fe) on the surface of wood and assembling a Octadecylphosphonic acid (OPA) reagent. The nanosized MIL-88(Fe) molecule caused the wood’s surface to take on a nano mastoid shape. In addition, MIL-88(Fe) provides metal sites to capture OPA molecules, preventing the long-chain alkane hydrophobic group from contacting the surface of the wood. They both make a considerable difference in the growth of a hydrophobic wood surface. The results of the experiment indicate that the water contact angle (WCA) increases with reactant concentration. The WCA of the samples prepared with 5.0 × 10⁻² M FeCl₃ was 140.57°. When the reactant concentration was 10.0 × 10⁻² M, the greatest WCA = 153.69° reading was obtained. The research’s findings present a novel technique for producing superhydrophobic wood surfaces. Full article

WRKY proteins are key transcription factors involved in a range of physiological processes and environmental adaptations. Yet, little is known about the role WRKY genes play in Cyclocarya paliurus (Batal.) Iljinskaja (C. paliurus) a significant medicinal plant belonging to the Juglandaceae family. Leveraging the recently released whole-genome sequence of C. paliurus, we conducted an in-depth, genome-wide study on the expression of WRKY genes under environmental stresses. We identified 80 CpWRKY genes, classifying them into distinct groups and subgroups based on their structural and phylogenetic characteristics. Synteny analysis and phylogenetic comparison provided insights into the evolutionary traits of these genes. We further investigated the response of the WRKY gene family to salinity stress in combination with the following specific stressors: Methyl jasmonate (MeJA), sodium hydrosulfide (NaHS), and sodium nitroprusside (SNP), which induce the production of signaling molecules jasmonates (JA), hydrogen sulfide (H₂S), and nitric oxide (NO), respectively. Our comprehensive analysis of CpWRKY gene expression patterns under various conditions revealed that combined treatments were more effective in inducing up-regulation of CpWRKY gene expression than individual treatments. Full article

Since the COVID-19 pandemic, urban forests have become important restorative environmental spaces for which demand-customized management based on users’ experiences is needed. We collected 21,557 data points from blogs from January 2020 to December 2021. For data analysis, keyword frequency, term frequency–inverse document frequency, and sentiment analyses were conducted using TEXTOM 4.0, and a semantic linkage network was established and analyzed using Gephi 0.92. In the analyses, the restorative environment components of “being away”, “fascination”, “extent”, and “compatibility” were derived from users’ experiences. Fascination, which stems from natural objects such as rocks, valleys, and trails, was derived the most frequently, and being away and compatibility, representing leisure activities such as climbing and walking, formed the largest cluster in cluster analysis. Sentiment analysis revealed a high positive word rate of 91.6%, with favorable feelings accounting for 87.5%, whereas the proportion of joy and interest (12.5%) was relatively low. In addition, this study showed that hard fascinations such as sports, entertainment, and education are required to improve the experience quality in urban forests as restorative environments. Hence, the necessity of local government policies and projects is emphasized. Full article

The ecological resilience of forests is the ability to return to a stable state after being subjected to external disturbances, and it is among the critical indicators of forest status. Climate change has significant effects on forest ecological resilience and diversity. In this research, we selected Mao County as the study region, and employed the forest landscape model LANDIS-II to simulate the effect of different climate scenarios on the ecological resilience of alpine forests in western Sichuan during the next 300 years from the forest composition and structure perspective. The findings revealed that: (1) climate change will favor an increase in forest ecological resilience values in short simulations, but future climate scenarios will negatively impact the ecological resilience of forests as the simulation progresses through the middle and long term. (2) The rate of change of forest ecological resilience in the MTDF and SCF ecotones, which have a higher proportion of Fir (Abies fabri) and Spruce (Picea asperata), was greater than that in the rest of the ecotones in the short-term simulation. In contrast, it was the opposite in the medium-term simulation. The rate of change of forest ecological resilience was more significant in the long-term simulation in all four ecotones. (3) The high values of forest ecological resilience in the short- and medium-term simulations were primarily concentrated within the MTDF and SCF ecotones among the midwestern and northern parts of the study region. When the simulation proceeded to a later stage, the ecological resilience of the forests decreased significantly throughout the study region, with high values occurring only in some areas within the western parts of the study region. The research results can grasp the influence of future climate on the ecological resilience of high mountain forests within western Sichuan and provide an essential reference for the sustainable development of local forests. Full article

The measurement of plant sap flow has long been a traditional method for quantifying transpiration. However, conventional direct measurement methods are often costly and complex, thereby limiting the widespread application of tree sap flow monitoring techniques. The concept of a Virtual Measurement Instrument (VMI) has emerged in response to this challenge by combining simple instruments with Artificial Intelligence (AI) algorithms to indirectly assess specific measurement objects. This study proposes a tree sap flow estimation method based on environmental factors and AI algorithms. Through the acquisition of environmental factor data and the integration of AI algorithms, we successfully achieved indirect measurement of tree sap flow. Accounting for the time lag response of the flow to environmental factors, we constructed the Magnolia denudata sap flow estimation model using the K-Nearest Neighbor (KNN), Random Forest (RF), Backpropagation Neural Network (BPNN), and Long Short-Term Memory network (LSTM) algorithms. The research results showed that the LSTM model demonstrated greater reliability in predicting sap flow velocity, with R² of 0.957, MAE of 0.189, MSE of 0.059, and RMSE of 0.243. The validation of the target tree yielded an R² of 0.821 and an error rate of only 4.89% when applying the model. In summary, this sap flow estimation method based on environmental factors and AI provides new insights and has practical value in the field of tree sap flow monitoring. Full article

Magnolia wufengensis is a newly discovered rare and endangered species endemic to China. The primary objective of this study is to find the most suitable species distribution models (SDMs) by comparing the different SDMs to predict their habitat distribution for protection and introduction in China under climate change. SDMs are important tools for studying species distribution patterns under climate change, and different SDMs have different simulation effects. Thus, to identify the potential habitat for M. wufengensis currently and in the 2050s (2041–2060) and 2070s (2061–2080) under different climate change scenarios (representative concentration pathways RCP2.6, RCP4.5, RCP6.0, and RCP8.5) in China, four SDMs, Maxent, GARP, Bioclim, and Domain, were first used to compare the predicted habitat and explore the dominant environmental factors. The four SDMs predicted that the potential habitats were mainly south of 40° N and east of 97° E in China, with a high distribution potential under current climate conditions. The area under the receiver operating characteristic (ROC) curve (AUC) (0.9479 ± 0.0080) was the highest, and the Kappa value (0.8113 ± 0.0228) of the consistency test and its performance in predicting the potential suitable habitat were the best in the Maxent model. The minimum temperature of the coldest month (−13.36–9.84 °C), mean temperature of the coldest quarter (−6.06–12.66 °C), annual mean temperature (≥4.49 °C), and elevation (0–2803.93 m), were the dominant factors. In the current climate scenario, areas of 46.60 × 10⁴ km² (4.85%), 122.82 × 10⁴ km² (12.79%), and 96.36 × 10⁴ km² (10.03%), which were mainly in central and southeastern China, were predicted to be potential suitable habitats of high, moderate, and low suitability, respectively. The predicted suitable habitats will significantly change by the 2050s (2040–2060) and 2070s (2060–2080), suggesting that M. wufengensis will increase in high-elevation areas and shift northeast with future climate change. The comparison of current and future suitable habitats revealed declines of approximately 4.53%–29.98% in highly suitable habitats and increases of approximately 6.45%–27.09% and 0.77%–21.86% in moderately and lowly suitable habitats, respectively. In summary, these results provide a theoretical basis for the response to climate change, protection, precise introduction, cultivation, and rational site selection of M. wufengensis in the future. Full article

Image-based morphometric technology is broadly applicable to generate large-scale phenomic datasets in ecological, genetic and morphological studies. However, little is known about the performance of image-based measuring methods on plant morphological characters. In this study, we presented an automatic image-based workflow to obtain the accurate estimations for basic leaf characteristics (e.g., ratio of length/width, length, width, and area) from a hundred Populus simonii pictures, which were captured on Colony counter Scan1200. The image-based workflow was implemented with Python and OpenCV, and subdivided into three parts, including image pre-processing, image segmentation and object contour detection. Six image segmentation methods, including Chan-Vese, Iterative threshold, K-Mean, Mean, OSTU, and Watershed, differed in the running time, noise sensitivity and accuracy. The image-based estimates and measured values for leaf morphological traits had a strong correlation coefficient (r² > 0.9736), and their residual errors followed a Gaussian distribution with a mean of almost zero. Iterative threshold, K-Mean, OSTU, and Watershed overperformed the other two methods in terms of efficiency and accuracy. This study highlights the high-quality and high-throughput of autonomous image-based phenotyping and offers a guiding clue for the practical use of suitable image-based technologies in biological and ecological research. Full article