Forests

24 pages, 3814 KiB

Open AccessArticle

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 (registering DOI) - 20 May 2025

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)

23 pages, 605 KiB

Open AccessArticle

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 (registering DOI) - 20 May 2025

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)

11 pages, 939 KiB

Open AccessArticle

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 (registering DOI) - 20 May 2025

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)

20 pages, 1416 KiB

Open AccessReview

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

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)

21 pages, 7181 KiB

Open AccessArticle

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

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)

14 pages, 6773 KiB

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessReview

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

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

Open AccessArticle

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

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, 4248 KiB

Open AccessArticle

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

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

Open AccessArticle

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 (registering DOI) - 19 May 2025

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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, 2100 KiB

Open AccessArticle

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

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)

26 pages, 12162 KiB

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

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

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

Open AccessArticle

Stem Profile Estimation of Pinus densiflora in Korea Using Machine Learning Models: Towards Precision Forestry

by Chiung Ko, Jintack Kang, Hyunkyu Won, Yeonok Seo and Minwoo Lee

Forests 2025, 16(5), 840; https://doi.org/10.3390/f16050840 - 19 May 2025

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

Open AccessArticle

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 67

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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21 pages, 15277 KiB

Open AccessArticle

A Concise Approach to Characterizing the Distribution of Canopy Leaf Mass per Area in Broad-Leaf Species Based on Crown Three-Dimensional Position and Vegetation Index

by Depeng Zhang, Yueqi Wang, Xiguang Yang, Shengtao Yang, Yuanyuan Liu, Zijuan Yu and Xingcai Zhao

Forests 2025, 16(5), 838; https://doi.org/10.3390/f16050838 - 18 May 2025

Viewed by 81

Abstract

Leaf mass per area (LMA) represents the allocation of carbon resources per unit leaf area, which is closely related to the photosynthetic capacity of tree leaves. Clarifying the distribution features of LMA is very useful in understanding nutrient and energy transmission and photosynthetic [...] Read more.

Leaf mass per area (LMA) represents the allocation of carbon resources per unit leaf area, which is closely related to the photosynthetic capacity of tree leaves. Clarifying the distribution features of LMA is very useful in understanding nutrient and energy transmission and photosynthetic capacity in the canopy. To this aim, the leaf samples of varied forest types were collected, and LMA and related spectral data were measured. The Partial Least Squares (PLS), Linear Mixed Models (LMM), Support Vector Machine Regression (SVM), and Random Forest (RF) methods were used to establish a new model of three-dimension LMA prediction by using vegetation index, DBH, and the vertical and horizontal position of leaves in this study. The results found that the LMA varies significantly with the change in the spatial position of the leaves and horizontal distance to the tree trunk. Statistically speaking, changes in LMA were not significantly related to the direction where the leaves were located. The best model of 3D LMA estimation was RF with a 10-fold R² value of 0.939. Compared to the RF model, the maximum and minimum of R² of 10-fold testing of other models increased by 23.75% and 55.87%. The results indicated that RF has a strong generalization ability and can predict the LMA distribution in 3D with a high accuracy. This study showed a reference for LMA 3D feature distribution and is helpful in clarifying the photosynthetic capacity of the canopy. Full article

(This article belongs to the Special Issue Advances in Remote Sensing for Forestry: Theory, Methods, Applications, and Validation)

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13 pages, 4379 KiB

Open AccessArticle

Biochar Applications Did Not Increase Summer Soil Respiration in a European Beech Forest

by Andrea Vannini, Debora Tarasconi, Filippo Grillo, T’ai Gladys Whittingham Forte, Michele Carbognani and Alessandro Petraglia

Forests 2025, 16(5), 837; https://doi.org/10.3390/f16050837 - 18 May 2025

Viewed by 143

Abstract

This study aimed to assess the impact of different biochar (BCH) applications (0%, 10%, 20%, and 50%, v/v) on soil respiration in a European beech (Fagus sylvatica L.) forest located in the Tuscan-Emilian Apennines. The experiment was conducted over four [...] Read more.

This study aimed to assess the impact of different biochar (BCH) applications (0%, 10%, 20%, and 50%, v/v) on soil respiration in a European beech (Fagus sylvatica L.) forest located in the Tuscan-Emilian Apennines. The experiment was conducted over four months during summer 2023. Results revealed that BCH applications did not significantly affect overall soil respiration. On the other hand, soil respiration was positively influenced by soil temperature and soil moisture, the latter only for the 10% and 20% BCH amendments. At higher BCH concentrations (50%), soil respiration was not enhanced by moisture, probably due to soil water saturation and reduced oxygen availability. In conclusion, it appears that BCH does not directly stimulate soil respiration in field conditions, although specific concentrations may improve soil carbon sequestration. These findings highlight the potential for BCH amendments to be employed as a climate-smart forestry strategy in support of carbon sequestration and ecosystem stability in temperate forest ecosystems. Full article

(This article belongs to the Special Issue Functions of Biochar in Carbon Emission and Carbon Sequestration in Forest Ecosystems, 2nd Edition)

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27 pages, 4807 KiB

Open AccessArticle

Utilizing LightGBM to Explore the Characterization of PM_2.5 Emission Patterns from Broadleaf Tree Combustion in Northeastern China

by Bingbing Lu, Hui Huang, Zhiyuan Wu, Tianbao Zhang, Yu Gu, Feng Wang and Zhan Shu

Forests 2025, 16(5), 836; https://doi.org/10.3390/f16050836 - 18 May 2025

Viewed by 48

Abstract

PM_2.5 emissions significantly impact atmospheric environments and human health in the context of forest fires. However, research on PM_2.5 emissions from forest fires remains insufficient. This study systematically investigated PM_2.5 emission characteristics from broadleaf tree combustion through controlled experiments examining [...] Read more.

PM_2.5 emissions significantly impact atmospheric environments and human health in the context of forest fires. However, research on PM_2.5 emissions from forest fires remains insufficient. This study systematically investigated PM_2.5 emission characteristics from broadleaf tree combustion through controlled experiments examining three key factors: species variation (Acer tegmentosum [AT], Acer ukurunduense [AU], Acer pictum [AP], Tilia amurensis [TA], Phellodendron amurense [PA], Ulmus davidiana [UD], Ulmus laciniata [UL], Prunus padus [PP], Prunus maackii [PM]), moisture content (0%–20%), and phenological stages (budding [A], growing [B], defoliation [C]). The results demonstrated: (1) Significant interspecies differences, with UL showing the lowest, and PM the highest emissions; (2) A unimodal moisture—emission relationship peaking at 15% moisture content across most species, while AT, UL and PM exhibited unique linear responses; (3) Distinct phenological patterns, including triphasic fluctuations during the growing and defoliation phases. The LightGBM model effectively predicted emissions (R² = 0.97), identifying species (36.2% importance) and moisture content (21.6%) as dominant factors. These findings provide critical data for wildfire emission modeling and highlight the need for species-specific parameters in air quality forecasts. Full article

(This article belongs to the Section Forest Ecology and Management)

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8 pages, 956 KiB

Open AccessArticle

Addressing Sustainability Challenges in the Global Aquarium Wood Market

by Alan Crivellaro, Paolo Galli, Francesco Negro and Flavio Ruffinatto

Forests 2025, 16(5), 835; https://doi.org/10.3390/f16050835 - 18 May 2025

Viewed by 154

Abstract

The aquarium trade includes a niche but significant market for ornamental wood, yet its sustainability remains largely unexamined. This study combines traditional wood anatomical methods with conservation assessments to investigate the sustainability of this overlooked sector. We investigated the botanical identity of aquarium [...] Read more.

The aquarium trade includes a niche but significant market for ornamental wood, yet its sustainability remains largely unexamined. This study combines traditional wood anatomical methods with conservation assessments to investigate the sustainability of this overlooked sector. We investigated the botanical identity of aquarium wood products to assess mislabelling, conservation concerns, and potential environmental risks. Using macroscopic and microscopic wood anatomy techniques, we analysed wood samples from the aquarium trade to determine taxonomic identity. We also examined the origin, conservation status, and possible ecological implications of the identified taxa. We identified woods from diverse families, including Myrtaceae, Ericaceae, Fabaceae, and Ebenaceae, with some species listed as threatened. Widespread mislabelling obscures conservation status, enabling unsustainable trade. Moreover, several samples were identified as roots, raising concerns about soil disruption and habitat degradation. By linking wood anatomy and ecosystem impacts, we show that the aquarium wood trade lacks transparency, posing risks to biodiversity conservation and ecosystem stability. Our findings underscore the pressing need for effective regulatory oversight, accurate labelling, and sustainable sourcing to mitigate environmental impacts and promote responsible trade practices. Full article

(This article belongs to the Special Issue From Harvest to Market: Assessing Sustainability in Wood Industry Management and Operations)

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17 pages, 11437 KiB

Open AccessArticle

A Comprehensive Evaluation of Simulating Thermal Conductivity in Oak Wood Using XCT Imaging

by Jingyao Zhao, Bonan Chen, Jiajun Lv, Jiancong Yi, Liying Yuan, Yuanchu Liu, Yingchun Cai and Xiang Chi

Forests 2025, 16(5), 834; https://doi.org/10.3390/f16050834 - 17 May 2025

Viewed by 89

Abstract

Wood drying is the most critical and energy-intensive process in the wood industry. However, the complex pore structure of wood significantly affects its thermal performance. Therefore, it is essential to study the relationship between the pore structure and the thermal properties of wood. [...] Read more.

Wood drying is the most critical and energy-intensive process in the wood industry. However, the complex pore structure of wood significantly affects its thermal performance. Therefore, it is essential to study the relationship between the pore structure and the thermal properties of wood. In this study, X-ray-computed tomography (XCT) technology, combined with digital image processing (DIP) techniques, was used to visualize and characterize the three-dimensional structure of oak samples. Parameters such as porosity, pore size and distribution, and fractal dimensions were obtained to investigate their relationship with thermal conductivity. Subsequently, the thermal conductivities of the oak samples in the tangential, radial, and axial directions were simulated based on their three-dimensional structure. The simulation results were validated using the transient plane source method (TPS). The results showed that there were significant differences in porosity and pore size between earlywood and latewood, which in turn affect the correlation between fractal dimension and thermal conductivity. The higher the self-similarity of the wood structure is, the stronger the correlation between porosity and fractal dimension will be. Due to the limitations of CT resolution and threshold segmentation methods, there may be some axial deviations in the heat transfer simulation based on XCT. However, overall, this method provides a relatively accurate estimate of the effective thermal conductivity of oak wood. In addition, the pit structure and the research on heat conduction of wood-based multi-scale pore structures are of crucial importance to the study of heat conduction in wood. Full article

(This article belongs to the Special Issue Wood Processing, Modification and Performance)

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20 pages, 5647 KiB

Open AccessArticle

Trends and Influencing Factors of Summer Air Quality Changes in Four Forest Types

by Zichen Jia, Ruyi Zhou, Jiejie Jiao, Chunyu Pan, Zhihao Chen, Yichen Huang, Yufeng Zhou and Guomo Zhou

Forests 2025, 16(5), 833; https://doi.org/10.3390/f16050833 - 17 May 2025

Viewed by 144

Abstract

Forest ecosystems are crucial in mitigating air pollution and improving air quality. Therefore, investigating the relationships between air quality, forest structure, and environmental factors in different forest types is of significant importance. This study conducted three months of continuous monitoring (June–September 2023) of [...] Read more.

Forest ecosystems are crucial in mitigating air pollution and improving air quality. Therefore, investigating the relationships between air quality, forest structure, and environmental factors in different forest types is of significant importance. This study conducted three months of continuous monitoring (June–September 2023) of air quality factors (particulate matter (PM_2.5 and PM₁₀), ozone (O₃), and negative air ions (NAI)) and environmental factors (air temperature (TA), relative humidity (RH), light intensity (LI), and wind speed (WS)) in four subtropical forest types, along with vegetation characteristic surveys. The effects of forest structure and environmental factors on air quality were determined by correlation and multiple regression analysis. The results showed that the forest air quality is at its best in July during the summer season. Concentrations of particulate matter (PM) and ozone (O₃) in mixed coniferous and broadleaf forests (MCB), as well as deciduous broadleaf forests (DB), are lower than those in moso bamboo forests (MB) and evergreen broadleaf forests (EB). The troughs of PM concentrations occur in the early morning (4:00–6:00), while the troughs of O₃ concentrations occur in the early morning (4:00–6:00) and in the evening (18:00). NAI concentrations were highest in DB (1287 ions/cm³), followed by MCB (1187 ions/cm³), MB (896 ions/cm³), and EB (584 ions/cm³), with NAI concentrations peaking between 14:00 and 16:00. PM concentrations in forest air were primarily influenced by stand density (SD) and the Shannon–Wiener index of herbaceous layer (SWH) (p < 0.05); ozone concentrations were significantly affected by tree height (TH) and canopy density (CD) (p < 0.05); and NAI concentrations were primarily related to TH and diameter at breast height (DBH). Air particulate matter concentrations were negatively affected by TA and RH (p < 0.01), and ozone concentrations were negatively influenced by RH and WS and were positively influenced by TA. TA has a direct and significant positive effect on the NAI concentration (p < 0.01), and RH indirectly influences the changes in NAI concentration through its interaction with TA. This study provides new insights for vegetation optimization in forest parks and planning forest health-promoting activities for sub-healthy populations. Full article

(This article belongs to the Section Forest Meteorology and Climate Change)

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16 pages, 5589 KiB

Open AccessArticle

Exploring the Root–Soil Anchoring Dynamics of Bambusa pachinensis (Pachi Bamboo) Root System

by Chia-Cheng Fan, Chung-Hao Chen and Chunhsiung Chen

Forests 2025, 16(5), 832; https://doi.org/10.3390/f16050832 - 16 May 2025

Viewed by 51

Abstract

Bamboo is widely distributed throughout the world, particularly in tropical and subtropical regions. This study aims to investigate the biomechanical properties of the root system of Bambusa pachinensis (Pachi bamboo). The root system of Pachi bamboo grows densely in clusters, with most roots [...] Read more.

Bamboo is widely distributed throughout the world, particularly in tropical and subtropical regions. This study aims to investigate the biomechanical properties of the root system of Bambusa pachinensis (Pachi bamboo). The root system of Pachi bamboo grows densely in clusters, with most roots growing vertically and potentially penetrating more than one meter into the soil after growing for several years. Owing to these characteristics, Pachi bamboo is considered a promising plant species for soil reinforcement. However, research on its root reinforcement capabilities remains limited. In situ shear and pullout tests were conducted to assess the root reinforcement of the fibrous root system. The root diameters of Pachi bamboo are typically less than 4 mm, and its tensile strength is notably lower than that of tree roots. This study establishes a method for estimating the root reinforcement of Pachi bamboo based on the number and cross-sectional area of the culms in a single bamboo cluster. The relationship between the maximum tensile force (F_ult) and root diameter (D) is F_ult = (3.65)D^2.59, where F_ult is in Newtons (N), and D is in millimeters (mm). The relationship between the pullout resistance (P_ult) and the shear resistance (S_ult) with the number of culms (SN) is P_ult = 46.5(SN) and S_ult = 0.53(SN) + 5, where P_ult is in Newtons (N), and S_ult is in kilopascals (kPa). These results suggest a positive contribution of the number of culms to mechanical resistance. Full article

(This article belongs to the Special Issue How Does Forest Management Affect Soil Dynamics?)

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23 pages, 4503 KiB

Open AccessArticle

Monitoring and Assessing Ecological Environmental Quality in Qianping Reservoir, Central China: A Remote Sensing Ecological Index (RSEI) Approach

by Enkai Xu, Guohang Zhang, Hua Wang, Mei Yang, Hao Tian, Ming Zhao, Nalin Dong, Congshi Li, Yongge Hu, Guohang Tian, Yakai Lei, Qian Chen and Dianwei Wei

Forests 2025, 16(5), 831; https://doi.org/10.3390/f16050831 - 16 May 2025

Viewed by 63

Abstract

The ecological impacts of dam and reservoir construction necessitate systematic environmental quality evaluation (EEQ) to reconcile ecological protection with sustainable development. To address this need, we integrated the Remote Sensing Ecological Index (RSEI)—a comprehensive metric synthesizing greenness, humidity, heat, and dryness—with a Land [...] Read more.

The ecological impacts of dam and reservoir construction necessitate systematic environmental quality evaluation (EEQ) to reconcile ecological protection with sustainable development. To address this need, we integrated the Remote Sensing Ecological Index (RSEI)—a comprehensive metric synthesizing greenness, humidity, heat, and dryness—with a Land Use Change Ecological Response (LUCER) model to quantify the long-term EEQ dynamics in reservoir-affected regions. This study utilized Landsat and Sentinel-2 remote sensing imagery with a 10 m resolution from the years 2000, 2005, 2010, 2015, and 2020 to compute the RSEI for the Qianping Reservoir area in Henan Province, investigating the spatiotemporal variations in EEQ. Key findings reveal: (1) Temporal trend: EEQ showed fluctuating improvement, with RSEI projected to rise gradually until 2030. (2) Spatial pattern: A lower ecological quality in central reservoir zones contrasts with higher quality in surrounding mountainous areas. (3) Mechanism: The Land Use Change Ecological Response (LUCER) model reveals that the conversion of cultivated land to forestland and grassland drives significant EEQ improvements, counterbalancing the negative impacts of hydrological fragmentation caused by reservoir construction and urbanization. This study advances RSEI applications in reservoir ecology by establishing a coupled monitoring–prediction framework, providing actionable insights for dam-related ecological restoration and governance. 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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17 pages, 4402 KiB

Open AccessArticle

Impact of Soil Preparation Method and Stock Type on Root Architecture of Scots Pine, Norway Spruce, Silver Birch and Black Alder

by Kārlis Dūmiņš, Sindija Žīgure, Santa Celma, Toms Artūrs Štāls, Viktorija Vendiņa, Austra Zuševica and Dagnija Lazdiņa

Forests 2025, 16(5), 830; https://doi.org/10.3390/f16050830 - 16 May 2025

Viewed by 19

Abstract

This study examines the spatial root development patterns of bareroot, containerized, and plug plus (plug+) saplings in hemiboreal forests of Latvia, focusing on the effects of two common soil preparation methods: mounding and disc trenching. In northern Europe, forest regeneration after clearcutting often [...] Read more.

This study examines the spatial root development patterns of bareroot, containerized, and plug plus (plug+) saplings in hemiboreal forests of Latvia, focusing on the effects of two common soil preparation methods: mounding and disc trenching. In northern Europe, forest regeneration after clearcutting often involves planting, with soil preparation aimed at enhancing sapling survival and productivity. This study included four tree species: Pinus sylvestris, Picea abies, Betula pendula, and Alnus glutinosa. The results reveal that saplings planted in mounded sites developed more radially symmetrical root systems, while roots in trenched sites predominantly grew parallel to the furrow. This spatial root distribution was consistent across all forest types and did not show significant variation between stock types (containerized, bareroot, or plug+) or treatments (control or fertilized). Additionally, the number of main roots did not differ significantly between the soil preparation methods. These findings align with previous research and raise important questions regarding the impact of early root architecture on stand resilience at a mature stage, particularly in relation to windthrow, heavy snowfall, drought, and flooding resistance. The study underscores the need to consider root system development as a key factor in forest management practices aimed at ensuring long-term forest stability. Full article

(This article belongs to the Section Forest Ecology and Management)

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20 pages, 5350 KiB

Open AccessArticle

Nutrient Attraction and Secondary Metabolites Induce Eogystia hippophaecola (Lepidoptera: Cossidae) Larvae Transfer from Sea Buckthorn Trunks to Roots

by Yurong Li, Yuying Shao, Jing Tao, Sanhe Liu, Xiangbo Lin and Shixiang Zong

Forests 2025, 16(5), 829; https://doi.org/10.3390/f16050829 - 16 May 2025

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Abstract

Eogystia hippophaecola (Hua, Chou, Fang & Chen, 1990) is a major borer pest of sea buckthorn (Hippophae rhamnoides L.), and during its four-year growth period, its feeding site shifts progressively from the trunks to the roots, establishing a complex mutualistic relationship with [...] Read more.

Eogystia hippophaecola (Hua, Chou, Fang & Chen, 1990) is a major borer pest of sea buckthorn (Hippophae rhamnoides L.), and during its four-year growth period, its feeding site shifts progressively from the trunks to the roots, establishing a complex mutualistic relationship with the host. The factors driving the host-shifting behavior of E. hippophaecola larvae remain unclear. In this study, we compared the nutrient composition of the roots and trunks, measured the activity of metabolizing enzymes in E. hippophaecola, and analyzed secondary metabolites in both the roots and trunks following infestation using LC-MS. Sugars, proteins, fats, and free amino acids were more abundant in the roots, and larvae feeding on this part exhibited a stronger resistance. Non-targeted metabolomics identified 8493 metabolites in total. The trunks exhibited 394 DEMs compared to the roots (223 up-regulated and 171 down-regulated). Lipids and lipid-like molecules represented more than two-thirds of the total, primarily involved in steroid biosynthesis, linoleic acid metabolism, and glycerophospholipid metabolism. The significant down-regulation of key compounds, such as lecithin and linoleate, suggests that resistance metabolism is less pronounced in the trunks compared to the roots. In summary, the host-shifting behavior of E. hippophaecola larvae is primarily driven by a combination of the host’s nutritional conditions and defense mechanisms. Full article

(This article belongs to the Section Forest Ecophysiology and Biology)

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