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Volume 16
Issue 5
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Forests, Volume 16, Issue 5 (May 2025) – 159 articles

Cover Story (view full-size image): Mangrove forests per unit area are the most productive vascular plants on earth, occupying the crucial interface between land and sea. Until recently, there have been very few estimates of mangrove gross primary production. Wood and roots constitute a large proportion of total mangrove net primary production. Wood production is high for many species, sufficient to warrant sustainable plantation logging. The production of belowground roots assists in sediment formation and surface elevation gain, making significant contributions to carbon burial and decomposition. These forests are net autotrophic, storing large amounts of sediment carbon. Thus, mangroves contribute both locally and regionally to carbon accumulation (‘blue carbon’), placing these ecosystems at the forefront of climate change mitigation and carbon accounting mechanisms. View this paper
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12 pages, 6068 KiB  
Article
Variation in Functional Traits of Woody Plants Across Successional Stages in Subtropical Forests
by Cheng Sun, Jie Yao, Yongtao Huang and Runguo Zang
Forests 2025, 16(5), 868; https://doi.org/10.3390/f16050868 - 21 May 2025
Viewed by 367
Abstract
Variation patterns in plant functional traits and their interrelationships play a crucial role in understanding species coexistence mechanisms and ecological differentiation within local plant communities. However, the dynamic patterns of plant functional traits across different forest successional stages remain insufficiently understood. Here, we [...] Read more.
Variation patterns in plant functional traits and their interrelationships play a crucial role in understanding species coexistence mechanisms and ecological differentiation within local plant communities. However, the dynamic patterns of plant functional traits across different forest successional stages remain insufficiently understood. Here, we investigated the woody species composition of subtropical evergreen–deciduous broadleaved mixed forest across 75 plots, representing three successional stages (20-year-old secondary forest, 35-year-old secondary forest, and old-growth forest (>80 years)), in Xingdoushan and Mulinzi National Nature Reserves, Hubei Province, Central China. We measured four functional traits of woody plants: leaf area (LA), specific leaf area (SLA), leaf dry matter content (LDMC), and wood density (WD). For each different age plant community, we calculated (1) species abundance-weighted mean community trait values, and (2) species-level mean trait values. We applied trait gradient analysis to partition and assess correlations of four functional traits across communities of different successional stages, separating within-community (α components) and between-community (β components) variation. To quantify the extent to which environmental constraints influence trait expression, we used the ecological constraint index (Ci). The results revealed significant variation in the four functional traits across communities at different successional stages. Community-level mean LA and SLA decreased significantly with age, WD increased significantly with age, and there was no significant relationship between LDMC and age. The α trait components consistently varied more widely than β components at different successional stages, indicating that biological competition dominates the assembly of local forest communities across various successional stages. Correlations between the four functional traits were dynamically adjusted with the study scale (community-level and species-level) and forest age. The ecological constraints on the four functional traits varied significantly across forest successional stages, with SLA being subject to the strongest constraints. Our findings reveal that biotic competition predominantly shapes community assembly during the succession of subtropical evergreen–deciduous broadleaved mixed forests, while stronger ecological filtering in old-growth stands underscores their role in maintaining ecosystem stability. These insights support more effective conservation and restoration strategies. Full article
(This article belongs to the Special Issue Growth and Stand Dynamics of Unmanaged and Managed Forests Under Global Change)
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17 pages, 3662 KiB  
Article
Ecosystem Service Synergies and Trade-Offs in Poplar–Birch Mixed Natural Forests Across Different Developmental Stages
by Junfei Zhang, Minghao Li, Qiang Liu, Yue Pang and Zhidong Zhang
Forests 2025, 16(5), 867; https://doi.org/10.3390/f16050867 - 21 May 2025
Viewed by 258
Abstract
Forest ecosystem services are crucial for sustaining ecological balance and supporting human well-being. This study quantified and analyzed ecosystem services—carbon storage, water conservation, and productivity—across four developmental stages (I, II, III, and IV) of poplar (Populus davidiana)–birch (Betula platyphylla) [...] Read more.
Forest ecosystem services are crucial for sustaining ecological balance and supporting human well-being. This study quantified and analyzed ecosystem services—carbon storage, water conservation, and productivity—across four developmental stages (I, II, III, and IV) of poplar (Populus davidiana)–birch (Betula platyphylla) mixed natural secondary forests (MPB) in Weichang County, China, over the year 2022 using the InVEST and biomass models. Synergies and trade-offs between these ecosystem services were assessed using the constraint line method. The results showed that as the stand developed, carbon storage values gradually increased, while productivity remained relatively low during the initial three stages but exhibited a significant upward trend by Stage IV (p < 0.05). In contrast, water conservation did not exhibit a clear pattern with stand development. Across all stages, carbon storage exhibited a synergistic relationship with productivity, but a trade-off was observed with water conservation. In the first three stages, productivity and water conservation were in trade-off, yet by Stage IV, this relationship shifted to a weak synergy. The constraint line analysis revealed dynamic trade-offs between productivity, carbon storage, and water conservation. The findings emphasize the importance of adopting adaptive management strategies for MPB at different developmental stages to maximize the synergistic effects among ecosystem services. Full article
(This article belongs to the Section Forest Ecology and Management)
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18 pages, 3103 KiB  
Article
Multi-Source Remote Sensing-Based High-Accuracy Mapping of Helan Mountain Forests from 2015 to 2022
by Wenjing Cui, Yang Hu and Yun Wu
Forests 2025, 16(5), 866; https://doi.org/10.3390/f16050866 - 21 May 2025
Viewed by 323
Abstract
This study develops an optimized approach for small-scale forest area extraction in mountainous regions by integrating Landsat multispectral and ALOS PALSAR-2 radar data through threshold-based classification methods. The threshold fusion method proposed in this study achieves innovations in three key aspects: First, by [...] Read more.
This study develops an optimized approach for small-scale forest area extraction in mountainous regions by integrating Landsat multispectral and ALOS PALSAR-2 radar data through threshold-based classification methods. The threshold fusion method proposed in this study achieves innovations in three key aspects: First, by integrating Landsat NDVI with PALSAR-2 polarization characteristics, it effectively addresses omission errors caused by cloud interference and terrain shadows. Second, the adoption of a decision-level (rather than feature-level) fusion strategy significantly reduces computational complexity. Finally, the incorporation of terrain correction (slope > 20° and aspect 60–120°) enhances classification accuracy, providing a reliable technical solution for small-scale forest monitoring. The results indicate that (1) the combination of Landsat multispectral remote sensing data and PALSAR-2 radar remote sensing data achieved the highest classification accuracy, with an overall forest classification accuracy of 97.62% in 2015 and 96.97% in 2022. The overall classification accuracy of Landsat multispectral remote sensing data alone was 93%, and that of PALSAR radar data alone was 85%, which is significantly lower than the results obtained using the combined data for forest classification. (2) Between 2015 and 2023, the forest area of Helan Mountain experienced certain fluctuations, primarily influenced by ecological and natural factors as well as variations in the accuracy of remote sensing data. In conclusion, the method proposed in this study enables more precise estimation of the forest area in the Helan Mountain region of Ningxia. This not only meets the management needs for forest resources in Helan Mountain but also provides valuable reference for forest area extraction in mountainous regions of Northwest China. Full article
(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)
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17 pages, 2402 KiB  
Article
Effects of Different Vegetation Types on Soil Quality in Golden Huacha (Camellia petelotii) National Nature Reserve
by Yong Jiang, Sheng Xu, Weiwei Gu, Siqi Wu, Jian Qiu, Wenxu Zhu and Nanyan Liao
Forests 2025, 16(5), 865; https://doi.org/10.3390/f16050865 - 21 May 2025
Viewed by 267
Abstract
Natural and planted forests differentially regulate soil quality through vegetation–soil interactions. The effects of four types of planting covers on soil nutrients, enzyme activities, and microbial communities in the Guangxi Camellia nitidissima National Nature Reserve were studied, revealing the multi-dimensional influences of natural [...] Read more.
Natural and planted forests differentially regulate soil quality through vegetation–soil interactions. The effects of four types of planting covers on soil nutrients, enzyme activities, and microbial communities in the Guangxi Camellia nitidissima National Nature Reserve were studied, revealing the multi-dimensional influences of natural (broadleaf, shrubland) and planted forests (bamboo, pine) on soil quality. Surface soils (0–10 cm depth) were characterized for physicochemical properties (pH, TC, TN, NO3−-N, AP), enzyme activities (α-amylase, urease, phosphatase, β-glucosidase), and microbial composition (using 16S rRNA and ITS region sequencing). Mantel tests and PLS–PM modeling were employed to investigate interactions among vegetation, soil variables, and microbes. Natural forests exhibited higher pH, nitrate nitrogen, and enzymatic activities (urease, phosphatase, β-glucosidase) alongside enhanced carbon–nitrogen accumulation and reduced acidification. Planted forests showed elevated available phosphorus and nutrient supply but lower organic matter retention. Microbial communities displayed higher similarity within natural forests, with fungal composition strongly linked to total carbon/nitrogen (p < 0.05). Vegetation type positively influenced bacterial diversity but negatively affected fungal communities. Natural forests maintained critical soil–microbe–plant interactions supporting ecosystem resilience through carbon–nitrogen cycling, while planted forests fostered divergent microbial functionality despite short-term nutrient benefits. These findings underscore natural forests’ unique role in preserving ecological stability and reveal fundamental limitations of artificial systems in mimicking microbially-mediated biogeochemical processes. Conservation policy should prioritize the protection of natural forests while simultaneously integrating microbial community management with vegetation restoration efforts to enhance long-term ecosystem functionality and nutrient cycling efficiency. Full article
(This article belongs to the Special Issue Soil Organic Matter Dynamics and Microbial Roles in Biogeochemical Cycles in Forestry)
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14 pages, 2641 KiB  
Article
Evaluation of the Process of Steaming Beech Sapwood and False Heartwood with Saturated Water Steam in Terms of Acidity Changes and Color Wood
by Michal Dudiak
Forests 2025, 16(5), 864; https://doi.org/10.3390/f16050864 - 21 May 2025
Viewed by 288
Abstract
The paper presents changes in the color and acidity of beech wood with false heartwood in the process of pressure steaming at the temperature interval t = 105 °C and 125 °C during τ = 6 to 24 h. The light white-gray color [...] Read more.
The paper presents changes in the color and acidity of beech wood with false heartwood in the process of pressure steaming at the temperature interval t = 105 °C and 125 °C during τ = 6 to 24 h. The light white-gray color of sapwood with a yellow tint changes to pale pink and red-brown to brown-red color during the steaming process. The color of beech wood with false heartwood changed to brown-gray color shades during 24 h of steaming with saturated water steam. From the measured data, as well as the visual evaluation of the color of the wood, I can conclude that, in the process of steaming beech wood with false heartwood, we can achieve color unification between false heartwood and sapwood in mode at temperature t = 105 °C for time τ = 18 h and in mode at temperature t = 125 °C for time τ = 12 h. Due to the influence of hemicellulose hydrolysis, the acidity of beech wood changes in the process of steaming. The decrease in acidity of beech wood in the temperature interval t = 105–125 °C and time τ = 6–24 h is in the range of values pHsapwood = 5.2 to 3.6 and pHfalse heartwood = 5.0 to 3.9. The relationship between the total color difference ∆E and the acidity change in beech sapwood and false heartwood is expressed by a second-degree polynomial function. The above mathematical relations represent a useful tool for evaluating the achieved color shade before further technological processing. Full article
(This article belongs to the Special Issue Advances in Sustainable Processing of Wood and Lignocellulosic Materials: From Molecular Engineering to Industrial Implementation)
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19 pages, 4931 KiB  
Article
A Hybrid Deep Learning Model for Early Forest Fire Detection
by Akhror Mamadmurodov, Sabina Umirzakova, Mekhriddin Rakhimov, Alpamis Kutlimuratov, Zavqiddin Temirov, Rashid Nasimov, Azizjon Meliboev, Akmalbek Abdusalomov and Young Im Cho
Forests 2025, 16(5), 863; https://doi.org/10.3390/f16050863 - 21 May 2025
Viewed by 713
Abstract
Forest fires pose an escalating global threat, severely impacting ecosystems, public health, and economies. Timely detection, especially during early stages, is critical for effective intervention. In this study, we propose a novel deep learning-based framework that augments the YOLOv4 object detection architecture with [...] Read more.
Forest fires pose an escalating global threat, severely impacting ecosystems, public health, and economies. Timely detection, especially during early stages, is critical for effective intervention. In this study, we propose a novel deep learning-based framework that augments the YOLOv4 object detection architecture with a modified EfficientNetV2 backbone and Efficient Channel Attention (ECA) modules. The backbone substitution leverages compound scaling and Fused-MBConv/MBConv blocks to improve representational efficiency, while the lightweight ECA blocks enhance inter-channel dependency modeling without incurring significant computational overhead. Additionally, we introduce a domain-specific preprocessing pipeline employing Canny edge detection, CLAHE + Jet transformation, and pseudo-NDVI mapping to enhance fire-specific visual cues in complex natural environments. Experimental evaluation on a hybrid dataset of forest fire images and video frames demonstrates substantial performance gains over baseline YOLOv4 and contemporary YOLO variants (YOLOv5–YOLOv9), with the proposed model achieving 97.01% precision, 95.14% recall, 93.13% mAP, and 92.78% F1-score. Furthermore, our model outperforms fourteen state-of-the-art approaches across standard metrics, confirming its efficacy, generalizability, and suitability for real-time deployment in UAV-based and edge computing platforms. These findings highlight the synergy between architectural optimization and domain-aware preprocessing for high-accuracy, low-latency wildfire detection systems. Full article
(This article belongs to the Special Issue Forest Fires Prediction and Detection—2nd Edition)
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14 pages, 5063 KiB  
Article
Can Forest Management Improve Water Retention Conservation Under Climate Change? A Case Study of the Republic of Korea
by Mina Hong, Youngjin Ko, Sujong Lee, Minkyung Song and Woo-Kyun Lee
Forests 2025, 16(5), 862; https://doi.org/10.3390/f16050862 - 21 May 2025
Viewed by 398
Abstract
This study aimed to analyze changes in water retention conservation in response to climate change and forest management strategies and to propose methods for securing sustainable water resources. The KO-G-Dynamic model, a Korean forest growth model, was utilized alongside aboveground and belowground water [...] Read more.
This study aimed to analyze changes in water retention conservation in response to climate change and forest management strategies and to propose methods for securing sustainable water resources. The KO-G-Dynamic model, a Korean forest growth model, was utilized alongside aboveground and belowground water resource prediction models to evaluate changes in water retention conservation under various climate change scenarios and forest management strategies. The analysis revealed that under climate change and current forest management levels, water retention conservation was projected to reach 37.553 billion tons per year in the 2030s, 38.274 billion tons per year in the 2050s, and 40.306 billion tons per year in the 2080s. Under optimal forest management policies, the water yield and storage were expected to increase to 37.863 billion tons per year in the 2030s, 38.877 billion tons per year in the 2050s, and 41.495 billion tons per year in the 2080s. Notably, watershed-based forest management offers a more practical management unit than conventional legal boundaries, as it reflects hydrological flow and the ecological characteristics of forest environments. Furthermore, the watershed-based forest management scenario demonstrated greater feasibility in securing water resources. This study provides foundational data for climate change adaptation and sustainable forest management and may aid national and local forest planning. The findings underscore the critical role of forest management in mitigating climate change impacts and ensuring long-term water sustainability. Full article
(This article belongs to the Section Forest Hydrology)
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10 pages, 1604 KiB  
Article
Foraging Guilds of Birds in Continuous and Fragmented Forests of Southeast China
by Yuan Wang, Jiawen Liu, Shuai Gao, Sichun Tong, Zheng Wang and Ning Li
Forests 2025, 16(5), 861; https://doi.org/10.3390/f16050861 - 21 May 2025
Viewed by 299
Abstract
Habitat fragmentation is one of the main factors leading to changes in bird foraging behavior. Therefore, studying bird diversity, foraging groups, and spatial utilization in fragmented habitats is of great significance for forest bird conservation. This experiment was conducted in the continuous and [...] Read more.
Habitat fragmentation is one of the main factors leading to changes in bird foraging behavior. Therefore, studying bird diversity, foraging groups, and spatial utilization in fragmented habitats is of great significance for forest bird conservation. This experiment was conducted in the continuous and fragmented forests of Meihua Mountain National Nature Reserve in southeast China. We collected bird foraging behavior data using the distance sampling method and compared the composition of bird foraging groups in the two habitats between October and December 2020 and 2021. The 46 bird species observed in the fragmented habitat belonged to 3 orders and 24 families, forming a total of 8 bird foraging groups. In contrast, the continuous habitat had 45 bird species belonging to 3 orders and 19 families, forming 7 bird foraging groups. Using principal component analysis and log-linear analysis, we demonstrated significant differences in foraging location, foraging substrate, foraging height, and foraging mode between the fragmented and continuous habitats during autumn and winter. Birds in the fragmented habitat tended to pick up food from high tree crown layers, while those in the continuous habitat preferred picking up or exploring food from low shrubs and ground levels. This study revealed that the separation of foraging variables among different groups allows for efficient utilization of foraging space, and foraging behavior is influenced by habitat type. Consequently, there are notable differences in resource utilization within evergreen broad-leaved forests. These results provide valuable scientific insights into how habitats with varying degrees of fragmentation affect biodiversity and species spatial utilization. Full article
(This article belongs to the Special Issue Wildlife Ecology and Conservation in Forest Habitats)
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19 pages, 13505 KiB  
Article
Genome-Wide Resequencing Revealed the Genetic Diversity of Fraxinus platypoda Oliv. in Northwestern China
by Ying Liu, Wanting Ge, Qiuling Zhao, Jing Zhang, Xiaolong Guo and Wenjun Ma
Forests 2025, 16(5), 860; https://doi.org/10.3390/f16050860 - 21 May 2025
Viewed by 316
Abstract
Fraxinus platypoda Oliv. (Oleaceae), an ecologically and economically valuable tree species with key distribution areas in northwestern China, faces conservation challenges due to its fragmented groups and scarce individual numbers. To investigate the genetic consequences of this demographic crisis, we analyzed 65 individuals [...] Read more.
Fraxinus platypoda Oliv. (Oleaceae), an ecologically and economically valuable tree species with key distribution areas in northwestern China, faces conservation challenges due to its fragmented groups and scarce individual numbers. To investigate the genetic consequences of this demographic crisis, we analyzed 65 individuals from 11 natural groups in this region using whole-genome resequencing. We identified a total of 60,503,092 single nucleotide polymorphisms (SNPs), and after further filtering, retained 3,394,299 SNPs for subsequent analysis. Population structure analysis (Neighbor-Joining tree, STRUCTURE, and kinship coefficients) revealed two distinct genetic clusters (K = 2), with principal component analysis (PCA) confirming this subdivision. Cluster I, composed of eight individuals from Groups 3, 5, 8, and 11, is highly differentiated from Cluster II and may be ancestral to it. Among the 11 groups, Groups 3 and 11 show a high genetic diversity and differentiation, with Tajima’s D > 0, indicating a long evolutionary history and balancing selection. The remaining nine groups have a low diversity, low differentiation, and frequent gene flow, with Tajima’s D < 0, suggesting directional selection. A mantel test showed no significant link between genetic variation and geographic isolation (p = 0.460). The high differentiation of Cluster I and gene flow of Cluster II are maintained by factors like evolutionary history and reproductive systems. Groups 3 and 11 are highlighted as important genetic resources deserving priority protection. This study offers key genomic data for conserving fragmented tree species and future adaptability research. Full article
(This article belongs to the Section Genetics and Molecular Biology)
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17 pages, 1854 KiB  
Article
The Effect of Selected Operation Factors on Cutter Deflection Angles, Instantaneous Speeds, and Accelerations While Cutting Wood with a Petrol Chainsaw
by Adam Maciak and Magda Kubuśka-Orłowska
Forests 2025, 16(5), 859; https://doi.org/10.3390/f16050859 - 21 May 2025
Viewed by 277
Abstract
The aim of this study was to determine the influence of initial chain tension, feed force, and wood hardness on the variability of the cutter’s deflection angle during petrol chainsaw operation. Cutting wood with a chainsaw is a complex process that has not [...] Read more.
The aim of this study was to determine the influence of initial chain tension, feed force, and wood hardness on the variability of the cutter’s deflection angle during petrol chainsaw operation. Cutting wood with a chainsaw is a complex process that has not been fully elucidated to date. During operation, the position of cutters with respect to the workpiece may vary. The situation is additionally complicated by the fact that chainsaws are powered by one-cylinder gasoline engines characterized by highly variable instantaneous rotational speeds. The experiments involved two types of wood (pine and oak), two initial tension values (tight vs. slack chain), and two feed forces (20 N and 80 N). The cutting process was recorded with a high-speed camera at 12,000 fps to determine cutter deflection angles, instantaneous speeds, and accelerations for all the aforementioned cases. It was found that at the lower feed force the cutter deflection differed depending on the initial chain tension, and a greater cutter deflection angle was observed in pine wood processing. It was also found that speed and acceleration in the Y axis were much lower than in the X axis. Additionally, the rear part of the cutter revealed greater speed variation in the X axis. Full article
(This article belongs to the Section Wood Science and Forest Products)
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24 pages, 3819 KiB  
Article
SF-UNet: An Adaptive Cross-Level Residual Cascade for Forest Hyperspectral Image Classification Algorithm by Fusing SpectralFormer and U-Net
by Xinggui Xu, Xuyang Li, Xiangsuo Fan, Qi Li, Hong Li and Haotian Yu
Forests 2025, 16(5), 858; https://doi.org/10.3390/f16050858 - 20 May 2025
Viewed by 316
Abstract
Traditional deep learning algorithms struggle to effectively utilize local spectral info in forest HS images and adequately capture subtle feature differences, often causing model confusion and misclassification. To tackle these issues, we present SF-UNet, a novel pixel-level classification network for forest HS images. [...] Read more.
Traditional deep learning algorithms struggle to effectively utilize local spectral info in forest HS images and adequately capture subtle feature differences, often causing model confusion and misclassification. To tackle these issues, we present SF-UNet, a novel pixel-level classification network for forest HS images. It integrates the strengths of SpectralFormer and U-Net. First, the HGSE module generates semicomponent spectral nesting, strengthening local info element connections via spectral embedding. Next, the CAM within SpectralFormer serves as an auxiliary U-Net encoder. This allows cross-level jump connections and cascading through interlayer soft residuals, enhancing feature representation via cross-regional adaptive learning. Finally, the U-Net decoder is used for pixel-level classification. Experiments on forest Sentinel-2 data show that SF-UNet outperforms mainstream frameworks. While Vision Transformer has an 88.29% classification accuracy, SF-UNet achieves 95.28%, a significant 6.99% improvement. Moreover, SF-UNet excels in land cover change analysis using multi-temporal Sentinel-2 images. It can accurately capture subtle land use changes and maintain classification consistency across seasons and years. These results highlight SF-UNet’s effectiveness in forest remote sensing image classification and its potential application value in deep learning-based forest HS remote sensing image classification research. Full article
(This article belongs to the Topic Challenges, Development and Frontiers of Smart Agriculture and Forestry—2nd Volume)
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23 pages, 1407 KiB  
Article
How Does the Development of Forestry Service Outsourcing Organizations Affect Households’ Forestland Leasing?
by Yingxue Wen, Ying Liu and Linping Wang
Forests 2025, 16(5), 857; https://doi.org/10.3390/f16050857 - 20 May 2025
Viewed by 234
Abstract
The fragmented nature of Chinese households’ forestland hinders the realization of economies of scale in forestry production. Understanding the role of forestry service outsourcing organizations in mitigating this fragmentation provides a critical foundation for the exploration of pathways to scaled forestry management. Based [...] Read more.
The fragmented nature of Chinese households’ forestland hinders the realization of economies of scale in forestry production. Understanding the role of forestry service outsourcing organizations in mitigating this fragmentation provides a critical foundation for the exploration of pathways to scaled forestry management. Based on tracking data from 500 households across 10 counties in Fujian Province between 2013 and 2018, this study examines an unbalanced panel containing six periods and 2780 valid observations. It constructs a panel Logit model to examine the influence of forestry service outsourcing organizations on the likelihood of forestland transfer by households, and it employs a panel Tobit model to analyze the relationship between these organizations and the scale of forestland transferred. To capture potential heterogeneity, the analysis incorporates households’ part-time status and the forestland terrain conditions. The results indicate that the duration of establishment of county-level forestry project teams and forestry companies in households’ regions significantly reduces the tendency of households to lease out their forestland, especially for those in plain and hilly regions and part-time forestry producers. Furthermore, the longer the establishment history of township-level forestry project teams, the more inclined households are to retain their family forestland management rights. Our study demonstrates that, when specialized forestry service outsourcing organizations emerge in the market, households are less likely to lease out their forestland, thereby retaining management rights, avoiding the risk of forestland loss, and reducing forestland abandonment. As forestry service outsourcing organizations continue to develop and expand—with improvements in service levels and production efficiency—forestry production is gradually transitioning toward a new stage of service-oriented scale operations. Full article
(This article belongs to the Topic Biophilic Cities and Communities: Human-Environment Interaction and Sustainable Governance)
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11 pages, 714 KiB  
Article
Chemical and Energetic Evaluation of Densified Biomass of Quercus laurina and Quercus rugosa for Bioenergy Production
by María Elena Jiménez-Mendoza, Faustino Ruiz-Aquino, José Guadalupe Rutiaga-Quiñones, Rossy Feria-Reyes, Wenceslao Santiago-García, Mario Ernesto Suárez-Mota, Ramiro Puc-Kauil and Rosalío Gabriel-Parra
Forests 2025, 16(5), 856; https://doi.org/10.3390/f16050856 - 20 May 2025
Viewed by 1018
Abstract
Fuels obtained from woody forest resources such as oaks have been traditionally used in various regions due to their availability and energy properties. In the search for sustainable bioenergy sources and the transition towards cleaner alternatives, biomass-derived fuels, such as charcoal and pellets, [...] Read more.
Fuels obtained from woody forest resources such as oaks have been traditionally used in various regions due to their availability and energy properties. In the search for sustainable bioenergy sources and the transition towards cleaner alternatives, biomass-derived fuels, such as charcoal and pellets, represent a relevant option for rural and urban communities. This study determines the chemical composition, physical and mechanical properties, and energy quality of pellets from two oak species (Quercus laurina and Q. rugosa) in San Sebastián Coatlán, Miahuatlán, Oaxaca. The chemical composition was determined in an Ankom fiber analyzer; the energetic, physical, and mechanical analysis was carried out with UNE-EN ISO and ASTM standards. On average, 56.18% and 54.63% cellulose, 17.81% and 17.87% lignin, and 13.96% and 13.78% hemicelluloses were obtained for Quercus laurina and Q. rugosa, respectively. Mechanical durability ranged from 87% to 95% for Q. laurina stump and Q. rugosa stem, respectively; for calorific value, values from 19.79 MJ Kg−1 to 20.31 MJ Kg−1 were recorded for Q. laurina stem and Q. rugosa stump, respectively. The forest biomass of both oak species is viable for pellet production. Full article
(This article belongs to the Special Issue Forest-Based Biomass for Bioenergy)
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20 pages, 3407 KiB  
Review
A Critical Review: Unearthing the Hidden Players—The Role of Extremophilic Fungi in Forest Ecosystems
by Muhammad Talal, Xiaoming Chen, Irfana Iqbal and Imran Ali
Forests 2025, 16(5), 855; https://doi.org/10.3390/f16050855 - 20 May 2025
Viewed by 356
Abstract
Often thought of as a mesic paradise, forest ecosystems are a mosaic of microhabitats with temporal oscillations that cause significant environmental stresses, providing habitats for extremophilic and extremotolerant fungi. Adapted to survive and thrive under conditions lethal to most mesophiles (e.g., extreme temperatures, [...] Read more.
Often thought of as a mesic paradise, forest ecosystems are a mosaic of microhabitats with temporal oscillations that cause significant environmental stresses, providing habitats for extremophilic and extremotolerant fungi. Adapted to survive and thrive under conditions lethal to most mesophiles (e.g., extreme temperatures, pH, water potential, radiation, salinity, nutrient scarcity, and pollutants), these species are increasingly recognized as vital yet underappreciated elements of forest biodiversity and function. This review examines the current understanding of the roles of extremophilic fungi in forests, scrutinizing their presence in these ecosystems with a critical eye. Particularly under severe environmental conditions, extremophilic fungi play a crucial role in forest ecosystems, as they significantly enhance decomposition and nutrient cycling, and foster mutualistic interactions with plants that increase stress resilience. This helps to maintain ecosystem stability. We examine the definition of “extreme” within forest settings, survey the known diversity and distribution of these fungi across various forest stress niches (cold climates, fire-affected areas, acidic soils, canopy surfaces, polluted sites), and delve into their possible ecological functions, including decomposition of recalcitrant matter, nutrient cycling under stress, interactions with plants (pathogenesis, endophytism, perhaps mycorrhizae), bioremediation, and contributions to soil formation. However, the review stresses significant methodological difficulties, information gaps, and field-based natural biases. We recommend overcoming cultural constraints, enhancing the functional annotation of “omics” data, and planning investigations that clarify the specific activities and interactions of these cryptic creatures within the forest matrix to further advance the field. Here, we demonstrate that moving beyond simple identification to a deeper understanding of function will enable us to more fully appreciate the value of extremophilic fungi in forest ecosystems, particularly in relation to environmental disturbances and climate change. Full article
(This article belongs to the Section Forest Ecology and Management)
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21 pages, 8045 KiB  
Article
A GIS-Based Decision Support Model (DSM) for Harvesting System Selection on Steep Terrain: Integrating Operational and Silvicultural Criteria
by Benno Eberhard, Zoran Trailovic, Natascia Magagnotti and Raffaele Spinelli
Forests 2025, 16(5), 854; https://doi.org/10.3390/f16050854 - 20 May 2025
Viewed by 294
Abstract
The goal of this study was to develop a GIS-based Decision Support Model for selecting the best timber harvesting systems on steep terrain. The model combines multiple layers, each representing an important factor in mechanized logging. These layers are used to create a [...] Read more.
The goal of this study was to develop a GIS-based Decision Support Model for selecting the best timber harvesting systems on steep terrain. The model combines multiple layers, each representing an important factor in mechanized logging. These layers are used to create a final map that functions as a spatially explicit Decision Support Model that helps decide which machines are best suited for different forest areas. A key idea of this study is to consider not only operational criteria (slope, ruggedness, wetness, and road accessibility), but also a fundamental silvicultural aspect, i.e., the assessment of tree growth classes to enable the integration of silvicultural deliberations into timber harvest planning. The data used for this model come from orthophoto image and a Digital Terrain Model (DTM). The operational factors were analyzed using GIS tools, while the silvicultural aspects were assessed using the deep learning algorithm DeepForest and tree growth equations (allometric functions). The model was tested by comparing its results with field data taken in a Norway Spruce stand in South Tyrol/Italy. The findings show that the model reliably evaluates operational factors. For silvicultural aspects, it tends to underestimate the number of small trees, but provides a good representation of tree size classes within a forest stand. The innovation of this method is that it relies on low-cost, open-source tools instead of expensive 3D scanning devices. Full article
(This article belongs to the Section Forest Operations and Engineering)
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14 pages, 6773 KiB  
Article
Preparation and Characterization of a Novel Eco-Friendly Acorn-Based Wood Adhesive with High Performance
by Liu Yang, Manli Xing, Xiaobo Xue, Xi Jin, Yujie Wang, Fei Xiao, Cheng Li and Fei Wang
Forests 2025, 16(5), 853; https://doi.org/10.3390/f16050853 - 20 May 2025
Viewed by 462
Abstract
With the concept of sustainable development gaining increasing traction, the high-value utilization of forest biomass has received growing attention. In this study, an acorn-based wood adhesive was developed using Quercus fagaceae, offering a sustainable alternative that not only supports the multifunctional use [...] Read more.
With the concept of sustainable development gaining increasing traction, the high-value utilization of forest biomass has received growing attention. In this study, an acorn-based wood adhesive was developed using Quercus fagaceae, offering a sustainable alternative that not only supports the multifunctional use of acorn shell resources, but also reduces dependence on fossil-based materials in traditional wood adhesives, a development of significant importance to the wood industry. The effects of various crosslinking agents and phenolic resin (PF) additions on the performance of the acorn-based adhesive (AS) were investigated. Among the crosslinking agents tested, isocyanate (MDI), epoxy resin E51, and trimethylolpropane diglycidyl ether (TTE), PF demonstrated the best bonding performance. The modified AS adhesive with a 30% PF addition showed the highest bonding strength (0.93 MPa) and superior water resistance. These improvements are attributed to the formation of a stable, multi-dimensional crosslinked network structure resulting from the interaction between gelatinized starch molecules and PF resin. Moreover, the AS-PF adhesive exhibited a remarkably low formaldehyde emission of 0.14 mg/L, representing a 90.67% reduction compared to the national E1 standard. The incorporation of PF also enhanced the adhesive’s mildew resistance and toughness. These findings highlight the potential of acorn-based adhesives as a sustainable alternative for applications in the wood and bamboo industries. Full article
(This article belongs to the Special Issue Advances in the Cultivation, Protection and High-Value Utilization of Forest Resources)
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15 pages, 2607 KiB  
Article
The Offset of the Ecological Benefits of Decreasing Forest Disturbance Severity in Europe Caused by Climate Change
by Wei Zheng, Yundi Zhang and Xiuzhi Chen
Forests 2025, 16(5), 852; https://doi.org/10.3390/f16050852 - 20 May 2025
Viewed by 323
Abstract
Forest ecosystems critically regulate land surface temperature (LST) from local to regional scales. Over the last three decades (1986–2016), increasingly frequent and severe disturbances have substantially altered the European forest canopy structure and carbon storage. However, the biophysical interactions between forest disturbance severity [...] Read more.
Forest ecosystems critically regulate land surface temperature (LST) from local to regional scales. Over the last three decades (1986–2016), increasingly frequent and severe disturbances have substantially altered the European forest canopy structure and carbon storage. However, the biophysical interactions between forest disturbance severity (FDS) and LST, particularly their spatiotemporal dynamics, remain insufficiently quantified at regional-to-continental scales. This study integrated multi-source, high-resolution remote sensing data spanning 1986–2016 to systematically investigate European FDS and its biophysical control over LST. We find significant spatiotemporal heterogeneity in FDS, which decreased markedly from 5.92 ± 4.6 in 1986 to 0.35 ± 2.36 in 2016, stabilizing after a sharp decline pre-2000. Concurrently, the mean regional LST exhibited significant warming trends, increasing from −27.04 ± 10.15 K to 16.47 ± 10.67 K, and declining FDS indirectly contributed up to 65% of this temperature rise. Mechanistically, the reduced FDS enhanced the secondary forest leaf area index (LAI), decreasing surface albedo and increasing net radiation absorption, thereby inducing positive radiative feedback that drives surface warming. Our findings demonstrate that the carbon sequestration benefits accrued during forest recovery can be partially offset by associated biophysical warming effects. This evidence is crucial for optimizing European forest management strategies to balance carbon sink enhancement and climate regulation functions. Full article
(This article belongs to the Special Issue Forests as Nature-Based Solutions: Ecosystem Services, Multiple Benefits, and Trade-Offs)
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21 pages, 1368 KiB  
Review
Why Are Seed Dispersal Models Rarely Used? Limitations of Scalability and Improvement Measures
by Sle-gee Lee and Tae Kyung Yoon
Forests 2025, 16(5), 851; https://doi.org/10.3390/f16050851 - 20 May 2025
Viewed by 372
Abstract
Seed dispersal studies have primarily relied on prediction model methods, which limit clarity regarding how variables affect movement direction. Suggestions for improvement are limited to specific domains due to the lack of quantitative evaluation of the comprehensive scope of the basic steps, from [...] Read more.
Seed dispersal studies have primarily relied on prediction model methods, which limit clarity regarding how variables affect movement direction. Suggestions for improvement are limited to specific domains due to the lack of quantitative evaluation of the comprehensive scope of the basic steps, from explaining seed dispersal to its application in related fields. This study aimed to reconsider the classification of seed movement mechanisms, identify research trends from an integrated perspective, and discuss the current implications and improvement measures. The data included 240 studies related to seed dispersal across the observation, generalization, and application phases. By classifying the mechanisms based on the direction of movement, the main variables affecting movement due to gravity or wind can be clearly distinguished. Although seed dispersal models assume gravity as the core principle, only 12.91% of the studies addressed terminal velocity, and a mere 1.25% measured the diaspore area, both of which are essential for accurate prediction. In addition, attempts to utilize seed dispersal for natural regeneration were relatively frequent (14.58%), but they remained at the empirical model stage, relying on data collected in the field, and thus lacked connection with models developed in previous studies. The requirements for enhancing the field usability of seed dispersal based on the current review include (1) improving the data collection system for securing primary data, (2) collecting sufficient field data, and (3) developing a unified model that can be applied to various conditions and species. Full article
(This article belongs to the Special Issue Topicalities in Forest Ecology of Seeds, 2nd Edition)
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12 pages, 1746 KiB  
Article
Multi-Dimensional Patterns of Variation in First-Order Shoot Traits of Larix principis-rupprechtii in Northern China
by Yang Yu, Huayong Zhang, Zhongyu Wang and Zhao Liu
Forests 2025, 16(5), 850; https://doi.org/10.3390/f16050850 - 20 May 2025
Viewed by 271
Abstract
As the most active fundamental unit in the aboveground branching system of woody plants, it remains unclear the relative importance of acclimation at the level of allocation and morphology in shoots. Additionally, the main dimensions of trait variation in shoots and whether their [...] Read more.
As the most active fundamental unit in the aboveground branching system of woody plants, it remains unclear the relative importance of acclimation at the level of allocation and morphology in shoots. Additionally, the main dimensions of trait variation in shoots and whether their trait relationships conform to the common assumptions of the root economics spectrum (RES) have not yet been established. By collecting 1551 larch shoots, we measured and estimated five functional traits, including shoot diameter (SD), length (SL), dry matter content (SDM), specific stem length (SSL), and stem tissue density (STD). Furthermore, we assessed the relationships between bivariate and multivariate traits through a Pearson correlation analysis and principal component analysis (PCA), including standardized major axis (SMA) regression analysis. We found that SDM exhibited the greatest degree of variation. Meanwhile, SL and SDM were significantly and strongly positively correlated with SD. In contrast, SSL and STD were significantly negatively correlated with SD, and SSL and STD showed a weak positive correlation. In addition, these five functional traits were distributed across two nearly orthogonal (independent) principal component analysis (PCA) axes. These results revealed that shoots generally exhibit greater flexibility in altering their biomass allocation compared to their morphology. Meanwhile, the variation in shoot traits is associated with two main dimensions: a diameter-related dimension potentially integrating shoot construction, maintenance, and persistence, and the other dimension consisting of SSL and STD traits representing shoot plastic responses to the environment. And the relationship between SD and STD does not support the predictions of the root economics spectrum (RES). Our study may offer a promising pathway for better understanding the functions and ecological strategies of shoots. Full article
(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)
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16 pages, 4249 KiB  
Article
Toward Safer Resin Tapping: Assessing Alternative Chemical Stimulants for Pinus pinaster
by Faustino Rubio Pérez, Aida Rodríguez-García, Santiago Michavila, Ana Rodríguez, Luis Gil and Rosana López
Forests 2025, 16(5), 849; https://doi.org/10.3390/f16050849 - 19 May 2025
Viewed by 483
Abstract
The use of chemical stimulants in resin tapping is essential for prolonging the resin flow and enhancing production. Traditional stimulants, primarily composed of sulfuric acid, pose concerns related to workplace safety, environmental impact, and tree health. In this study, we compared alternative stimulant [...] Read more.
The use of chemical stimulants in resin tapping is essential for prolonging the resin flow and enhancing production. Traditional stimulants, primarily composed of sulfuric acid, pose concerns related to workplace safety, environmental impact, and tree health. In this study, we compared alternative stimulant pastes containing ethrel, salicylic acid, and citric acid with the traditional Spanish and Brazilian stimulant pastes with higher contents of sulfuric acid. We tapped Pinus pinaster seedlings with five different stimulants, using untreated and mechanically wounded plants as controls. The resin yield, tree growth, and physiological parameters were compared. The pines stimulated with citric acid released ca. 50% more resin, while ethrel and salicylic acid yielded similar amounts to the traditional paste, suggesting their potential as viable alternatives. Although all stimulants reduced the seedling growth, no significant differences were observed in the midday water potential or stomatal conductance. The internal resin accumulation and resin canal density were strongly correlated with the total resin production, and more-acidic pastes tended to cause xylem damage and resin retention. Our findings suggest that moderate acidity is sufficient to trigger resin biosynthesis and release, and that safer, less corrosive formulations, like citric acid, may provide viable, safer, and more sustainable alternatives to conventional stimulants. While the results from the seedlings provide a rapid and cost-effective screening tool, anatomical and physiological differences from mature trees should be considered when extrapolating findings to operational settings. Full article
(This article belongs to the Special Issue Advanced Technology for Extraction, Processing and Testing of Forest Products)
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14 pages, 1705 KiB  
Article
The Influence of Pruning on the Growth and Wood Properties of Populus deltoides “Nanlin 3804”
by Weiqi Leng, Pei Cao, Chao Chen and Luozhong Tang
Forests 2025, 16(5), 848; https://doi.org/10.3390/f16050848 - 19 May 2025
Viewed by 275
Abstract
During the natural growth of trees, a large number of branches are formed, with a negative impact on timber quality. Therefore, pruning is an essential measure in forest cultivation. In this work, the effect of pruning on poplar timber quality was evaluated. This [...] Read more.
During the natural growth of trees, a large number of branches are formed, with a negative impact on timber quality. Therefore, pruning is an essential measure in forest cultivation. In this work, the effect of pruning on poplar timber quality was evaluated. This study used an artificial forest of Populus deltoides “Nanlin 3804”, established in 2014, as the research object. Pruning was carried out in March 2018 and March 2020 with a pruning intensity of one-third, and a control group was also set up. In December 2023, the growth of 11-year-old poplars under different treatments was investigated and analyzed, and sample trees were cut down for a wood property analysis. The results showed that pruning did not have a significant effect on the growth of the diameter at breast height, the tree height, or the volume. However, pruning could significantly facilitate the forming of higher-quality timber with smaller knots. Compared to unpruned wood, the ring width decreased 1–2 years after pruning, while it turned out to be greater than that of the control 3 years after pruning. Moreover, pruning can reduce the degree of trunk tapering. The fiber aspect ratio two years after pruning was greater than that of the control. The distribution frequency of fiber lengths of between 1500 μm and 1900 μm and that of fiber widths of between 32 μm and 38 μm were higher than that of the control. However, pruning had little effect on their density and oven-dried shrinkage. In addition, compared to the control, the bending strength and the modulus of elasticity increased by approximately 11%–14%, the impact toughness decreased by approximately 5%, and the compressive strength increased by approximately 6%. Pruning proved to be a successful method to improve the timber quality. Full article
(This article belongs to the Special Issue Uses, Structure and Properties of Wood and Wood Products)
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17 pages, 3522 KiB  
Article
The Changes in Annual Precipitation in the Forest–Steppe Ecotone of North China Since 1540
by Xiaodong Wang, Jinfeng Ma, Long Fei, Xiaohui Liu and Xiaoqiang Li
Forests 2025, 16(5), 847; https://doi.org/10.3390/f16050847 - 19 May 2025
Viewed by 355
Abstract
Understanding precipitation changes over a long period of time can provide valuable insights into global climate change. Taking the forest–steppe ecotone of North China as the research area, based on the tree ring width index of Carya cathayensis Sarg (Carya cathayensis), [...] Read more.
Understanding precipitation changes over a long period of time can provide valuable insights into global climate change. Taking the forest–steppe ecotone of North China as the research area, based on the tree ring width index of Carya cathayensis Sarg (Carya cathayensis), the relationship between tree growth and climate factors is analyzed, and the annual precipitation is reconstructed from data from the nearest five weather stations from AD 1540 to 2019. The results show that the growth of trees was affected by the changes in precipitation. The precipitation was divided into three dry periods and three wet periods over 480 years, based on wavelet analysis. There were 328 years of precipitation within the mean plus or minus one standard deviation (SD) (accounting for 68.3% of 480 years), indicating that relatively stable climate conditions exist in the study area, which has become one of the main agricultural areas in China. Each period lasted 2–7 years according to the multi-taper method, indicating that precipitation change was closely related to the El Niño–Southern Oscillation (ENSO) on a short time scale and affected by the Atlantic Multidecadal Oscillation (AMO) on a medium time scale during the period of 60–80 years based on wavelet analysis. Full article
(This article belongs to the Special Issue Changes of Climate and Ecology Recorded by Density and Stable Isotopes of Tree Rings)
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16 pages, 2043 KiB  
Article
Being Edgy: Ecotones of Ground Cover Vegetation in Managed Black Alder Habitats
by Agnese Anta Liepiņa, Didzis Elferts, Roberts Matisons, Āris Jansons and Diāna Jansone
Forests 2025, 16(5), 846; https://doi.org/10.3390/f16050846 - 19 May 2025
Viewed by 304
Abstract
Retention forestry creates anthropogenic ecotones that diversify forest landscapes in terms of age and biomass. Such diversification can have ambiguous ecological impacts, raising uncertainties, particularly for black alder swamp woodlands, which are considered sensitive and are prioritized in EU conservation policy. This study [...] Read more.
Retention forestry creates anthropogenic ecotones that diversify forest landscapes in terms of age and biomass. Such diversification can have ambiguous ecological impacts, raising uncertainties, particularly for black alder swamp woodlands, which are considered sensitive and are prioritized in EU conservation policy. This study aimed to examine the effects of adjacent clear-cutting on ground cover vegetation in 12 black alder stands in the hemiboreal zone in Latvia 11 to 120 years since the harvest. Ground cover vegetation was recorded by species along 40 m transects. The effects of the time since adjacent stand harvesting and exposure to the edge on species richness and Shannon diversity were assessed using linear mixed-effects models. A detrended correspondence analysis was used to explore the main environmental gradients. A total of 103 species were recorded: 15 in the tree and shrub layer, 66 in the herbaceous layer, and 22 in the moss and lichen layer. The exposure to the adjacent stand had a moderate positive effect on species diversity, while the effects of edge age were complex and varied by stand type. The scale of disturbance (the absolute length of the analyzed edge), rather than edge age or exposure, had the most pronounced effect on ground cover vegetation composition, suggesting persistent secondary edge effects that should be considered in forest management and conservation planning. Full article
(This article belongs to the Special Issue Forest Disturbance and Management)
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18 pages, 3922 KiB  
Article
Partitioning of Available P and K in Soils During Post-Agricultural Pine and Spruce Reforestation in Smolensk Lakeland National Park, Russia
by Polina R. Enchilik, Pavel D. Chechenkov, Guang-Hui Yu and Ivan N. Semenkov
Forests 2025, 16(5), 845; https://doi.org/10.3390/f16050845 - 19 May 2025
Viewed by 391
Abstract
Gradual reforestation and transformation of both vegetation and soils characterize post-agricultural landscapes, which form after the abandonment of arable land. The change in content and vertical distribution of available K and P was analysed by stages in sandy and loamy soils in the [...] Read more.
Gradual reforestation and transformation of both vegetation and soils characterize post-agricultural landscapes, which form after the abandonment of arable land. The change in content and vertical distribution of available K and P was analysed by stages in sandy and loamy soils in the north-west of the Smolensk region, forming two chronosequences of pine and spruce succession, mainly in triplicates. During natural succession, from the earliest to the later stages, the content of available P and K decreased in soils due to a reduction in the amount and diversity of plant remains and the downward movement of soluble substances. The loss of available P from the uppermost 0–5 cm topsoil layer was more pronounced than that of K because its leaching in the late successional stages was not compensated by plant uptake. The distribution of nutrients was found to be significantly influenced by forest type, successional stage, and soil proxies. The distribution of available K showed greater stability across successional stages and was influenced by forest type and pH. Available P showed greater variation with forest type and succession stages. Full article
(This article belongs to the Section Forest Soil)
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20 pages, 3939 KiB  
Article
Experimental and Numerical Modeling of Bending Characteristics of Fir and Black Pine Wood from Different Forest Regions in Türkiye
by Fatih Kurul, Hızır Volkan Görgün, Sedanur Şeker, Tülay Yılmaz, Türker Dündar and Nadir Ayrilmis
Forests 2025, 16(5), 844; https://doi.org/10.3390/f16050844 - 19 May 2025
Viewed by 299
Abstract
The bending test is a good indicator of wood characterization, including compression, tension, and shear stresses. Therefore, many studies have been published on bending tests for wood. Its heterogeneous structure, anisotropic behavior during the physical and mechanical tests, and anatomical and chemical differences [...] Read more.
The bending test is a good indicator of wood characterization, including compression, tension, and shear stresses. Therefore, many studies have been published on bending tests for wood. Its heterogeneous structure, anisotropic behavior during the physical and mechanical tests, and anatomical and chemical differences due to species and growing area make the characterization difficult. Accordingly, research has focused on mathematical models and simulation programs for predicting material characteristics. More data on using many wood species in such models or programs still need to be collected. This study aimed to eliminate these deficiencies for two softwood species grown in Türkiye. In this context, three- and four-point bending tests were performed on 5656 samples from fir (Abies spp.) and black pine (Pinus nigra) species that were collected from 13 regions. A nonlinear material model was generated from the load-deformation data for both species, and the results were found in agreement regarding the bending features of both softwood species. The results show that nonlinear numerical modeling could predict the bending results with significant rates (min. 94%). Additionally, bending characteristics such as limits of proportionality (LOP), and elastic potential were found and compared between and within the species, regions, and test methods. Load-deformation curves showed that the LOP ranged between 40% and 60% of the maximum load, which was higher than the theoretical approach in the standards. Full article
(This article belongs to the Section Wood Science and Forest Products)
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26 pages, 12162 KiB  
Article
Deciphering Spatiotemporal Dynamics of Vegetation Drought Resilience in China
by Leyi Li, Yuan Yuan and Xiangrong Wang
Forests 2025, 16(5), 843; https://doi.org/10.3390/f16050843 - 19 May 2025
Viewed by 375
Abstract
Under accelerated global warming, frequent droughts pose mounting threats to vegetation productivity, yet the spatiotemporal patterns and primary controls of drought resilience (DR) in China remain insufficiently quantified. This study aimed to characterize DR trends across Köppen–Geiger climate zones in China from 2001 [...] Read more.
Under accelerated global warming, frequent droughts pose mounting threats to vegetation productivity, yet the spatiotemporal patterns and primary controls of drought resilience (DR) in China remain insufficiently quantified. This study aimed to characterize DR trends across Köppen–Geiger climate zones in China from 2001 to 2020 and to identify the dominant drivers and their interactions. We constructed a hazard–exposure–adaptability framework, combining multi-source satellite observations and the station data. A Bayesian-optimized Light Gradient Boosting Machine (LightGBM, version 4.3.0) model was trained under five-fold cross-validation. Shapley Additive exPlanations (SHAP) analysis decomposed each driver’s main and interaction effects on DR. The results indicated that DR was better in tropical regions, whereas arid and polar regions require more attention. From 2001 to 2020, 45.3% of China’s land area saw DR increases, while 36.4% declined. The key drivers influencing DR were temperature, sunlight hours, potential evapotranspiration, and precipitation. Notably, an increase in sunlight hours was often accompanied by a decrease in precipitation, resulting in suboptimal DR in China. When the normalized precipitation fell within the range of 0.12 to 0.65, elevated temperature exhibited an inhibitory effect on DR. Overall, this study established a DR assessment framework, elucidated its spatiotemporal dynamics, and revealed key driver interactions, offering timely insights for ecosystem research and management in the face of climate change. Full article
(This article belongs to the Section Forest Ecology and Management)
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13 pages, 1580 KiB  
Article
Effects of Mixed Addition of Fraxinus mandshurica Rupr. and Larix gmelinii (Rupr.) Kuzen. Litter on Nitrogen Mineralization in Dark Brown Soil of Northeast China
by Shixing Han, Xuesong Miao, Yandong Zhang and Hailong Sun
Forests 2025, 16(5), 842; https://doi.org/10.3390/f16050842 - 19 May 2025
Viewed by 310
Abstract
The changes in soil nitrogen mineralization rate induced by litter input can determine the availability of nitrogen for plant growth in the soil. In forest ecosystems, the mixing of different species of litter can alter the chemical properties of the litter, ultimately affecting [...] Read more.
The changes in soil nitrogen mineralization rate induced by litter input can determine the availability of nitrogen for plant growth in the soil. In forest ecosystems, the mixing of different species of litter can alter the chemical properties of the litter, ultimately affecting the rates of soil nitrogen transformation and cycling. In this study, litters with Fraxinus mandshurica Rupr. and Larix gmelinii (Rupr.) Kuzen. and mixed litter with Fraxinus mandshurica and Larix gmelinii were added to dark brown soil and incubated in the lab for 175 days at 25 °C. NH4+-N and NO3−-N contents and nitrogen mineralization rates were periodically measured to explore the effect of mixed litter addition on soil nitrogen mineralization. The results showed that compared to Larix gmelinii litter, Fraxinus mandshurica litter demonstrates higher carbon, nitrogen, and phosphorus contents while exhibiting lower lignin and cellulose contents and lower C/N and lignin/N ratios. Soil inorganic nitrogen content showed a trend of initial decrease followed by an increase. At the end of the incubation, soil NH4+-N and NO3−-N and the total inorganic nitrogen contents were 4.6–7.8 times, 2.2–3.4 times, and 2.9–4.3 times higher than the initial value, respectively. The soil nitrogen mineralization rate exhibited an initial rapid increase followed by stabilization. During days 7–28 of incubation, the nitrogen mineralization rates in litter addition treatments were lower than that in the control, while they were higher than that in the control during days 42–175. The soil nitrogen mineralization rate in the treatments with Fraxinus mandshurica litter and mixed litter were higher than those in the treatment with Larix gmelinii litter. The cumulative net nitrogen mineralization amounts in the Fraxinus mandshurica litter and mixed litter treatments were higher than those in the Larix gmelinii litter treatment, being 1.5 and 1.2 times those of the Larix gmelinii litter treatment, respectively. MBC and MBN presented a trend of first increasing and then decreasing, peaking on days 7 and 14 of incubation, respectively. Correlation analysis revealed that soil inorganic nitrogen content and nitrogen mineralization rate were positively correlated with the litter total nitrogen and soil microbial carbon and nitrogen and negatively correlated with litter C/N and lignin/N. The changes in soil inorganic nitrogen and nitrogen mineralization are primarily associated with soil microbial immobilization. Initially, in the treatments with litter addition, an increase in microbial biomass enhanced the immobilization of soil inorganic nitrogen. Subsequently, as litter mineralization progressed, the amount of litter decreased, leading to reduced microbial biomass and weakened immobilization. This study indicates that the interaction between litter types and soil microorganisms is the key factor affecting soil nitrogen mineralization process and soil mineral nitrogen content. These findings provide a scientific basis for soil fertility management in the forest ecosystems of Northeast China. Full article
(This article belongs to the Special Issue Forest Soil Microbiology and Biogeochemistry)
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23 pages, 3881 KiB  
Article
Enhanced Accuracy in Urban Tree Biomass Estimation: Developing Allometric Equations with Land Use Classifications
by Jeong-Min Lee, Hyung-Sub Kim, Byeonggil Choi, Jun-Young Jung, Seungmin Lee, Heejae Jo, Gaeun Kim, Sanggeun Kwon, Sang-Jin Lee, Tae Kyung Yoon, Choonsig Kim, Kye-Han Lee, Woo-Kyun Lee and Yowhan Son
Forests 2025, 16(5), 841; https://doi.org/10.3390/f16050841 - 19 May 2025
Viewed by 489
Abstract
Urban trees grow in diverse environments where site conditions and human management may influence their growth patterns. However, few allometric equations (AEs) have been developed for urban trees, and the effects of environmental variations across urban land use categories on tree biomass remain [...] Read more.
Urban trees grow in diverse environments where site conditions and human management may influence their growth patterns. However, few allometric equations (AEs) have been developed for urban trees, and the effects of environmental variations across urban land use categories on tree biomass remain largely unexplored. Therefore, this study developed urban land-use-specific AEs for major urban tree species in South Korea. We selected eight major urban tree species groups (at genus level), harvested 201 trees, and non-destructively measured the stem volumes of 1995 trees using a laser dendrometer. Species-specific and generalized AEs to estimate stem volume were developed under three urban land use categories: street trees, urban parks, and others. The results indicated that differences in stem volume across urban land use categories varied by species, with street trees generally showing smaller stem volumes. Furthermore, due to the high variation in stem volume within species, sampling designs that encompass diverse size distributions are necessary when developing AEs for urban trees. Our findings indicate that various factors in urban environments influence tree volume and considering these differences is essential for improving biomass estimation accuracy. Full article
(This article belongs to the Section Urban Forestry)
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15 pages, 2817 KiB  
Article
Stem Profile Estimation of Pinus densiflora in Korea Using Machine Learning Models: Towards Precision Forestry
by Chiung Ko, Jintaek Kang, Hyunkyu Won, Yeonok Seo and Minwoo Lee
Forests 2025, 16(5), 840; https://doi.org/10.3390/f16050840 - 19 May 2025
Viewed by 415
Abstract
The stem taper function is essential in predicting diameter outside bark (DOB) variations along the tree height, contributing to volume estimation, harvest planning, and precision forestry. Traditional taper models, such as the Kozak function, offer interpretability but often fail to capture nonlinear growth [...] Read more.
The stem taper function is essential in predicting diameter outside bark (DOB) variations along the tree height, contributing to volume estimation, harvest planning, and precision forestry. Traditional taper models, such as the Kozak function, offer interpretability but often fail to capture nonlinear growth dynamics and regional variability, particularly in the upper stem segments. This study aimed to evaluate and compare the prediction accuracy of conventional and machine learning-based taper models using Pinus densiflora, a representative conifer species in Korea. Field data from two ecologically distinct regions (Gangwon and Central Korea) were used to build and test four models: the Kozak taper function, random forest, extreme gradient boosting, and an artificial neural network (ANN). Model performance was assessed using the RMSE, R2, and MAE, along with stem profile visualizations for representative trees. The results showed that the ANN consistently achieved the highest prediction accuracy across both regions, particularly at an upper crown zone relative height (RH) > 0.8, while maintaining smooth and stable taper curves. In contrast, the Kozak model tended to underestimate the diameter of the upper stem. This study demonstrates that machine learning models, particularly ANNs, can effectively enhance the taper prediction precision and serve as practical tools for data-driven forest management and the implementation of precision forestry in Korea. Full article
(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)
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15 pages, 2940 KiB  
Article
Changes in Plant Nitrogen Uptake Strategies Following Vegetation Recovery in Karst Regions
by Lin Yang, Lijun Liu, Hui Yang, Shuting Yang, Tongbin Zhu, Lei Meng and Dongni Wen
Forests 2025, 16(5), 839; https://doi.org/10.3390/f16050839 - 18 May 2025
Viewed by 281
Abstract
Understanding plant nitrogen (N) uptake strategies during vegetation recovery is essential for restoring and rehabilitating degraded ecosystems. However, there are few studies on plant N uptake strategies in karst regions. In this study, space-for-time substitution was used to investigate the dynamic changes in [...] Read more.
Understanding plant nitrogen (N) uptake strategies during vegetation recovery is essential for restoring and rehabilitating degraded ecosystems. However, there are few studies on plant N uptake strategies in karst regions. In this study, space-for-time substitution was used to investigate the dynamic changes in plant N uptake strategies during vegetation restoration. Grassland, shrub–grassland, shrubland, and woodland naturally recovering in karst ecosystems were chosen as the research objects. The dominant species at each stage were investigated. Dominant plant N uptake rates were measured using the 15N labeling technique, and plant root functional traits and available soil N were determined. Our results showed that soil inorganic N content and composition varied significantly with vegetation recovery. In early vegetation recovery stages, the soil inorganic N content was low and dominated by ammonium (NH4+), while in the late stages, soil inorganic N content increased, and nitrate (NO3−) became the dominant form. In early vegetation recovery stages, dominant plants preferentially absorbed NH4+, contributing to 90.3%–98.5% of the total N uptake. With vegetation recovery, plants increased the NO3− uptake ratio from 1.48%–9.42% to 30.1%–42.6%. Additionally, the root functional traits of dominant plants changed significantly during vegetation recovery. With vegetation recovery, specific root lengths and specific root areas decreased, while root N content and plant N uptake rates increased. In summary, plants developed N uptake strategies coordinated with soil N supply by modifying root functional traits following vegetation recovery in karst regions. Full article
(This article belongs to the Section Forest Ecology and Management)
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