Forests

19 pages, 869 KiB

Open AccessArticle

Whole-Genome Identification and Expression Profiles of WRKY Genes Related to the Leaf Expansion Period in the Camphor tree

by Shilin Long, Jingyao Jiang and Hanyang Lin

Forests 2025, 16(2), 266; https://doi.org/10.3390/f16020266 - 2 Feb 2025

Abstract

The camphor tree (Cinnamomum camphora) is of great economic and ecological value, and the WRKY transcription factor (TF) family plays a crucial role in regulating plant growth and development as well as the responses toward environmental changes. However, the research on [...] Read more.

The camphor tree (Cinnamomum camphora) is of great economic and ecological value, and the WRKY transcription factor (TF) family plays a crucial role in regulating plant growth and development as well as the responses toward environmental changes. However, the research on WRKY TFs in C. camphora remains scarce, and their roles in the leaf expansion period are unknown. In this study, we identified WRKY TFs across the C. camphora genome, followed by a phylogenetic analysis. Then, we conducted RNA sequencing and qPCR experiments on leaves collected from three distinct stages during leaf expansion (S1, S2, and S3) to determine which WRKY genes showed significant up-regulation during these stages. Here, a total of 72 CcWRKY TFs were found in the C. camphora genome, and they were phylogenetically clustered with corresponding subfamilies of Arabidopsis thaliana. These CcWRKY proteins were divided into three major groups (I, II, and III), where group II consisted of five subgroups. We found that three genes (CcWRKY24, CcWRKY42, and CcWRKY70) were upregulated from both S1 to S2 and from S1 to S3. The expression level of CcWRKY24 increased gradually from S1 to S3, while CcWRKY42 and CcWRKY70 exhibited higher expression levels in S2 and S3 than in S1. These predicted gene expression profiles were further confirmed by qPCR experiments. In summary, this study analyzed WRKY TFs in C. camphora from a genome-wide perspective and paves the way for future research on the functions of CcWRKYs. Full article

(This article belongs to the Special Issue Genome-Wide Identification and Expression Analysis for the Genetic Improvement of Forest Plants)

11 pages, 3059 KiB

Open AccessArticle

Assessment of the Modulus of Rupture and Modulus of Elasticity in Static Bending of Yellow Pine Earlywood and Latewood

by Piotr Mańkowski, Zbigniew Karwat and Agnieszka Laskowska

Forests 2025, 16(2), 265; https://doi.org/10.3390/f16020265 - 2 Feb 2025

Abstract

The purpose of this research was to investigate the modulus of rupture (MOR) and modulus of elasticity (MOE) in the static bending of yellow pine (Pinus ponderosa Douglas ex C. Lawson) earlywood and latewood. The relationship between the properties of these wood [...] Read more.

The purpose of this research was to investigate the modulus of rupture (MOR) and modulus of elasticity (MOE) in the static bending of yellow pine (Pinus ponderosa Douglas ex C. Lawson) earlywood and latewood. The relationship between the properties of these wood zones and the MOR and MOE of yellow pine wood tested was determined with the methodology specified in the standards. An important element of the research was to verify the suitability of the developed method for testing the MOR and MOE of small wood samples obtained from the earlywood and latewood zone. The MOR of the earlywood was about 6% higher than the MOR of the pine wood determined using standard samples, and these differences were not statistically significant. However, the MOR of the latewood was approximately three times higher than the MOR of the pine wood determined using standard samples, and these differences were statistically significant. The MOR of the latewood was found to be 2.5 times higher than the MOR of the earlywood. The MOE of the latewood was found to be two times higher than the MOE of the earlywood. This was due to the density of particular wood zones and the dimensions of structural elements—tracheids. The maximum load (F_max) transferred by latewood zones was four times higher than the F_max transferred by earlywood zones. The deflection at the F_max of the earlywood zone was 20% smaller than the deflection at the F_max of the latewood zone. Full article

(This article belongs to the Section Wood Science and Forest Products)

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13 pages, 2616 KiB

Open AccessArticle

Ecological Traits of Three Species of Xiphydria Woodwasps from Japan: Host Tree Species and Eggs, Symbiotic Fungi, and Mucus in Their Bodies

by Ryu Takagi and Hisashi Kajimura

Forests 2025, 16(2), 264; https://doi.org/10.3390/f16020264 - 1 Feb 2025

Abstract

Woodwasps (Siricidae and Xiphydriidae) inhabit living, weakened, or freshly dead trees and their larvae feed on sapwood. Siricidae have been intensively researched for pest management. In contrast, the ecology of Xiphydriidae remains largely unknown. In the present study, we collected xiphydriid woodwasp adults [...] Read more.

Woodwasps (Siricidae and Xiphydriidae) inhabit living, weakened, or freshly dead trees and their larvae feed on sapwood. Siricidae have been intensively researched for pest management. In contrast, the ecology of Xiphydriidae remains largely unknown. In the present study, we collected xiphydriid woodwasp adults and dissected female adults to elucidate the cornerstone ecology of this family and compared these findings with those of siricid woodwasps. The findings provide new host records for these species and indicate that their host ranges span multiple families. Notably, all Xiphydria species had female-biased sex ratios. All adult females had gourd-shaped eggs, similar to those found in gall wasps (Cynipidae), which contrast with the oval-shaped eggs of Siricidae. Slit-like mycangia were located at the base of the ovipositor, with pairs of fungal masses composed of hyphal fragments or spores directly positioned below the seventh sternum, differing structurally from the pouch-like mycangia in Siricidae. Mucus reservoirs and secretory glands were found in the terminal abdominal segments, similar to Siricidae. Mucus in X. annulitibia and X. ogasawarai was colorless and transparent, as reported in Siricidae, whereas X. eborata exhibited deep wine-red mucus, which is the world’s first discovery in all dissected species of Siricidae and Xiphydriidae. Full article

(This article belongs to the Special Issue Biodiversity and Ecology of Organisms Associated with Woody Plants)

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17 pages, 7841 KiB

Open AccessArticle

Fire Severity Outperforms Remote Sensing Indices in Exploring Post-Fire Vegetation Recovery Dynamics in Complex Plateau Mountainous Regions

by Pengfei Liu, Weiyu Zhuang, Weili Kou, Leiguang Wang, Qiuhua Wang and Zhongjian Deng

Forests 2025, 16(2), 263; https://doi.org/10.3390/f16020263 - 1 Feb 2025

Abstract

Understanding post-fire vegetation recovery dynamics is crucial for damage assessment and recovery planning, yet spatiotemporal patterns in complex plateau environments remain poorly understood. This study addresses this gap by focusing on Yunnan Province, a mountainous plateau region with high fire incidence. We developed [...] Read more.

Understanding post-fire vegetation recovery dynamics is crucial for damage assessment and recovery planning, yet spatiotemporal patterns in complex plateau environments remain poorly understood. This study addresses this gap by focusing on Yunnan Province, a mountainous plateau region with high fire incidence. We developed an innovative approach combining differenced Normalized Burn Ratio (dNBR) and visual interpretation on Google Earth Engine (GEE) to generate high-quality training samples from Landsat 5 TM/7 ETM+/8 OLI imagery. Four supervised machine learning algorithms were evaluated, with Random Forest (RF) demonstrating superior accuracy (OA = 0.90) for fire severity classification compared to Support Vector Machine (SVM) OA of 0.88, Classification and Regression Tree(CART) OA o f0.85, and Naive Bayes(NB) OA of 0.78. Using RF, we generated annual fire severity maps alongside the Land Surface Water Index (LSWI), Normalized Difference Vegetation Index (NDVI), and Normalized Burn Ratio (NBR) from 2005 to 2020. Key findings include the following: (1) fire severity classification outperformed traditional remote sensing indices in characterizing vegetation recovery; (2) distinct recovery trajectories emerged across severity levels, with moderate areas recovering in 7 years, severe areas transitioning within 2 years, and low severity areas peaking at 2 years post-fire; (3) southern mountainous regions exhibited 1–2 years faster recovery than northern areas. These insights advance understanding of post-fire ecosystem dynamics in complex terrains and support more effective recovery strategies. Full article

(This article belongs to the Special Issue Image Processing for Forest Characterization)

17 pages, 1462 KiB

Open AccessArticle

Extracting Individual Tree Positions in Closed-Canopy Stands Using a Multi-Source Local Maxima Method

by Guozhen Lai, Meng Cao, Chengchuan Zhou, Liting Liu, Xun Zhong, Zhiwen Guo and Xunzhi Ouyang

Forests 2025, 16(2), 262; https://doi.org/10.3390/f16020262 - 1 Feb 2025

Abstract

The accurate extraction of individual tree positions is key to forest structure quantification, and Unmanned Aerial Vehicle (UAV) visible light data have become the primary data source for extracting individual tree locations. Compared to deep learning methods, classical detection methods require lower computational [...] Read more.

The accurate extraction of individual tree positions is key to forest structure quantification, and Unmanned Aerial Vehicle (UAV) visible light data have become the primary data source for extracting individual tree locations. Compared to deep learning methods, classical detection methods require lower computational resources and have stronger interpretability and applicability. However, in closed-canopy forests, challenges such as crown overlap and uneven light distribution hinder extraction accuracy. To address this, the study improves the existing Revised Local Maxima (RLM) method and proposes a Multi-Source Local Maxima (MSLM) method, based on UAV visible light data, which integrates Canopy Height Models (CHMs) and Digital Orthophoto Mosaics (DOMs). Both the MSLM and RLM methods were used to extract individual tree positions from three different types of closed-canopy stands, and the extraction results of the two methods were compared. The results show that the MSLM method outperforms the RLM in terms of Accuracy Rate (85.59%), Overall Accuracy (99.09%), and F1 score (85.21%), with stable performance across different forest stand types. This demonstrates that the MSLM method can effectively overcome the challenges posed by closed-canopy stands, significantly improving extraction precision. These findings provide a cost-effective and efficient approach for forest resource monitoring and offer valuable insights for forest structure optimization and management. Full article

(This article belongs to the Special Issue Forest Ecology and Resource Monitoring Based on Sensors, Signal and Image Processing)

19 pages, 3312 KiB

Open AccessArticle

Cool Temperatures and Post-Germination Adaptations Enhance Seedling Recruitment in the Subalpine Oak Quercus longispica (Fagaceae)

by Yu Tu, Luting Liu, Qiansheng Li, Hongying Chen and Min Deng

Forests 2025, 16(2), 261; https://doi.org/10.3390/f16020261 - 31 Jan 2025

Abstract

Quercus longispica is a dominant shrub in the Himalayan subalpine region, demonstrating high levels of persistence despite high seed predation and extreme climatic conditions. However, its seed germination ecology and adaptations for seedling recruitment remain poorly understood. This study investigated the effects of [...] Read more.

Quercus longispica is a dominant shrub in the Himalayan subalpine region, demonstrating high levels of persistence despite high seed predation and extreme climatic conditions. However, its seed germination ecology and adaptations for seedling recruitment remain poorly understood. This study investigated the effects of temperature, water potential, and insect damage on seed germination and seedling establishment. Pre-germination seed traits and seed-to-seedling ontogeny were systematically analyzed. Our results demonstrated that seed germination percentages decreased with increasing insect damage across all temperature and water potential treatments. Cool temperatures (5–10 °C) yielded the highest germination percentages, potentially due to the suppression of parasitoid activity and mildew growth. While drought conditions also suppressed parasitoid activity, they significantly increased seed mortality. Despite a decline in seedling performance with increasing seed damage, overall seedling establishment remained robust. Several adaptive traits enable Q. longispica to persist in its harsh environment. Multi-seeded, non-apical embryos combined with rapid germination help embryos evade or escape damage from parasitism and predation. The rapid elongation of cotyledonary petioles pushes the embryo axis into the soil, with rapid nutrient and water transfer from the cotyledon to the taproot, thereby avoiding the threats of predation, drought, cold, and wildfire. Additionally, temperature-regulated epicotyl dormancy at the post-germination stage prevents the emergence of cold-intolerant seedlings in winter. This study provides the first comprehensive description of seed-to-seedling ontogeny in this Himalayan subalpine oak, offering crucial insights into the adaptive mechanisms that facilitate successful seedling recruitment in the challenging subalpine habitats. Full article

(This article belongs to the Special Issue Adaptive Mechanisms of Tree Seedlings to Adapt to Stress—Second Edition)

18 pages, 3061 KiB

Open AccessArticle

Fostering Digitalization: How Local Policies Are Transforming Rural Areas in Italy

by Valerio Di Stefano, Alessandro Paletto, Raffaele Cortignani and Giorgia Di Domenico

Forests 2025, 16(2), 260; https://doi.org/10.3390/f16020260 - 31 Jan 2025

Abstract

In recent years, several policies and strategies have been developed by the European Union to promote innovation and digitalization in the agricultural and forestry sector, including the Common Agricultural Policy (CAP), which allocates just under EUR 150 billion for the period of 2023–2027. [...] Read more.

In recent years, several policies and strategies have been developed by the European Union to promote innovation and digitalization in the agricultural and forestry sector, including the Common Agricultural Policy (CAP), which allocates just under EUR 150 billion for the period of 2023–2027. In Italy, digitalization in the agricultural and forestry sector has grown significantly over the past decade, with 3.8% increasing to 15.8% of farms now being computerized. This growth has been fostered by the Italian strategy for digitalization in agriculture, part of the CAP Strategic Plan, implemented at the regional level through the Rural Development Complements (RDCs), adopted in 2023. This study analyzes the RDCs of Italian regions, comparing the strategies adopted in terms of digitalization and innovation from both technical and economic perspectives. This analysis focuses on the interventions of three regional support groups (SRGs)—SRG07, SRG08, SRG09—assessing whether they have been activated in all regions and delves into the political and technical reasons behind any lack of implementation. The study compares the funding allocated for each intervention, highlighting regional differences and underlying causes. The main strengths, weaknesses, opportunities, and threats of digitalization in the agricultural and forestry sector were prioritized through an A’WOT analysis. The major strengths include the provision of job security and sustainability, while the major weaknesses comprise the challenges of the digital divide and a lack of technical training. The opportunities identified include the potential for the development of precision agriculture and eco-sustainable practices, but these are hampered by critical issues such as spatial fragmentation and limited economic resources. This analytical framework offers a comprehensive view of regional dynamics in Italy, providing useful insights for the development of more effective policies that can promote equitable and innovative digitalization in the agricultural and forestry sector. Full article

(This article belongs to the Special Issue The Role of Public Policies in Incentivizing Forest, Mountain and Rural Economy)

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17 pages, 2371 KiB

Open AccessArticle

Effects of Choosing Different Parameterization Data in Two-Phase Forest Inventories for Standing Stock Estimation

by Ambros Berger and Thomas Gschwantner

Forests 2025, 16(2), 259; https://doi.org/10.3390/f16020259 - 30 Jan 2025

Abstract

The demands on national forest inventories to provide detailed information for small geographical regions are rising. Two-phase estimators are often employed to obtain forest resource estimates, yet there is little information on optimal training data selection. This study evaluates the impact of different [...] Read more.

The demands on national forest inventories to provide detailed information for small geographical regions are rising. Two-phase estimators are often employed to obtain forest resource estimates, yet there is little information on optimal training data selection. This study evaluates the impact of different training data on two-phase estimators, with a focus on small area estimators for standing stock and aims to develop guidelines on selecting appropriate training datasets. Linear regression models were parameterized using multiple datasets and subsets based on ecological and administrative boundaries. The models were then applied on varying scales, and their estimates and their confidence intervals were compared to each other as well as to the single-phase, purely terrestrial forest inventory. Results suggest that the different two-phase models generally yield comparable estimates but differ notably from single-phase estimates. Specifically, differences increase in smaller areas and with correspondingly smaller training datasets, suggesting a minimum of 100 data points. To ensure robust estimates, we recommend adapting training sets to local conditions and exercising caution with small training datasets and areas because implausible results may occur. Pooling appropriate datasets is the preferable solution. Full article

(This article belongs to the Special Issue Modeling of Biomass Estimation and Stand Parameters in Forests)

13 pages, 4053 KiB

Open AccessArticle

Growth Rate, Tree Rings, and Wood Anatomy of a Tropical Cloud Forest Tree Invader

by Guadalupe Williams-Linera, Milton H. Díaz-Toribio and Guillermo Angeles

Forests 2025, 16(2), 258; https://doi.org/10.3390/f16020258 - 30 Jan 2025

Abstract

The presence of shade-tolerant tree invaders has been recently noted in tropical and temperate forest understories. Maximum growth rate is an important trait for exotic trees becoming invaders in a forest. This study aimed to determine the growth rate of Eriobotrya japonica in [...] Read more.

The presence of shade-tolerant tree invaders has been recently noted in tropical and temperate forest understories. Maximum growth rate is an important trait for exotic trees becoming invaders in a forest. This study aimed to determine the growth rate of Eriobotrya japonica in a secondary cloud forest in central Veracruz, Mexico. The objectives of this study were to determine wood density, tree ring boundaries and number, and their relationship to diameter at breast height (DBH) and climate data. Tree ring counts were obtained using Python-based software with subsequent visual validation. Growth rates were measured using diametric tape, dendrometric bands, and the pinning method. The number of rings increased with DBH, presenting values ranging from 14 to 27. Tree rings were delimited by fibers that were five times narrower in the ring limit zone than in the intra-ring zone. The growth ring delimitation zones were formed when vascular cambium activity stalled during the relatively dry-cold season (January–February). The growth rate of E. japonica was statistically similar (ca. 0.2 mm yr⁻¹) regardless of the method employed to measure it. Relative growth rate was low (0.02 cm cm⁻¹ yr⁻¹). Wood density (0.76 g cm⁻³) values lay within the upper values for mature forest trees. Eriobotrya japonica is a potential invader, with traits such as high wood density and a relatively low growth rate, which are characteristic of the shade-tolerant tree species. Full article

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

17 pages, 3007 KiB

Open AccessArticle

A Lightweight Stepwise SCMA Codebook Design Scheme for AWGN Channels

by Min Hua, Shuo Meng, Yue Juan, Borui Bian and Xiaoming Liu

Forests 2025, 16(2), 257; https://doi.org/10.3390/f16020257 - 30 Jan 2025

Abstract

Forests play a critical role in maintaining global ecological balance, regulating climate, and supporting biodiversity. Effective forest management and monitoring relies on the deployment of large-scale wireless sensor networks (WSNs) for real-time data collection, enabling the protection of ecosystems and the early detection [...] Read more.

Forests play a critical role in maintaining global ecological balance, regulating climate, and supporting biodiversity. Effective forest management and monitoring relies on the deployment of large-scale wireless sensor networks (WSNs) for real-time data collection, enabling the protection of ecosystems and the early detection of environmental changes. However, such massive deployments pose serious challenges with increasingly scarce radio resources. Sparse code multiple access (SCMA), a non-orthogonal multiple access (NOMA) technique, has been identified as a promising solution for facilitating wireless communications among numerous distributed sensors in large-scale WSNs with improved spectral efficiency. This is essential for application scenarios involving a substantial number of terminal devices, including forest monitoring and management. Codebook design is a critical issue for SCMA systems. It is closely related to the detection performance at the receiver, which in turn has a direct effect on the communication coverage or quality of service (QoS) for the terminal devices. This paper investigates the symbol error rate (SER) performance of SCMA systems over AWGN channels and derives its theoretical upper bound. The optimization objectives for each stage of codebook design are mathematically analyzed for a single resource element (RE), a single device, and multi-device, multi-RE scenarios. On this basis, a lightweight stepwise codebook design scheme is proposed in this paper. Simulation results demonstrate that the proposed codebooks can maintain fairness among devices while guaranteeing detection performance. Full article

(This article belongs to the Special Issue Climate-Smart Forestry: Forest Monitoring in a Multi-Sensor Approach)

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21 pages, 631 KiB

Open AccessArticle

25 Years of EU Forest Policy—An Analysis

by Evgenia Gordeeva, Bernhard Wolfslehner and Norbert Weber

Forests 2025, 16(2), 256; https://doi.org/10.3390/f16020256 - 30 Jan 2025

Abstract

A comparison between the most relevant forest-focused and forest-related EU policies from the time periods of the three EU forest(ry) strategies of 1998, 2013 and 2021 has revealed an overall rise in the number of forest-related policies that is mainly rooted in the [...] Read more.

A comparison between the most relevant forest-focused and forest-related EU policies from the time periods of the three EU forest(ry) strategies of 1998, 2013 and 2021 has revealed an overall rise in the number of forest-related policies that is mainly rooted in the environmental policy sector. Next to the increasing number of policies, a growing preference for regulations over directives as policy instruments was identified. New policy fields that have gained increasing importance over the last 25 years, most prominently climate, energy and bioeconomy policy, create and define additional demands on forests through their cross-cutting relations with other policy sectors. At the same time, multi-issue strategies that have recently been employed by the European Commission might turn out to be unable to solve the trade-offs that are produced by opposing policy goals. Full article

(This article belongs to the Section Forest Economics, Policy, and Social Science)

14 pages, 2561 KiB

Open AccessArticle

Wood Species Differentiation: A Comparative Study of Direct Analysis in Real-Time and Chromatography Mass Spectrometry

by Ilena Isak, Harriet Laura Newson and Tripti Singh

Forests 2025, 16(2), 255; https://doi.org/10.3390/f16020255 - 30 Jan 2025

Abstract

This study reports for the first time the fingerprinting extractives analysis of the indigenous wood species of Podocarpus totara from New Zealand, Eucalyptus saligna from Australia and Pinus radiata imported from California, USA and grown in New Zealand. We evaluated the use of [...] Read more.

This study reports for the first time the fingerprinting extractives analysis of the indigenous wood species of Podocarpus totara from New Zealand, Eucalyptus saligna from Australia and Pinus radiata imported from California, USA and grown in New Zealand. We evaluated the use of analytical techniques for wood species discrimination. We compared the chemical fingerprinting of extractive compounds obtained using traditional chromatographic techniques with direct analysis in real-time–time of flight-mass spectrometry (DART-TOF-MS) with the auxiliary of chemometrics and principal component analysis. The traditional wet chemistry analysis of wood extracts provided a comprehensive characterisation of all extractive components. However, the more eco-friendly, sustainable and faster DART-TOF-MS technique effectively distinguished between wood species when heartwood and sapwood samples were combined. Notably, neither wet chemistry nor DART-TOF-MS could clearly differentiate between heartwood and sapwood within the same wood species. DART-TOF-MS analysis demonstrates potential as a reliable quality control tool for identifying wood species necessary in commercial and timber trading markets as well as for detecting the illicit trade of counterfeit wood products. Full article

(This article belongs to the Section Wood Science and Forest Products)

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18 pages, 1297 KiB

Open AccessArticle

A Study on the Prediction of Long-Term Carbon Absorption by Applying the Renewal Scenario of Forest in Korea

by Soongil Kwon, Yoon-Seong Chang, Junbeum Kim, Yong Woo Hwang and Jean-Christophe Lata

Forests 2025, 16(2), 254; https://doi.org/10.3390/f16020254 - 29 Jan 2025

Abstract

As global warming has emerged as an essential global solution, the role of carbon neutrality is required to respond to rapidly changing environmental policies. Forests are an important means for achieving carbon neutrality as they act as a key carbon sink, and, among [...] Read more.

As global warming has emerged as an essential global solution, the role of carbon neutrality is required to respond to rapidly changing environmental policies. Forests are an important means for achieving carbon neutrality as they act as a key carbon sink, and, among them, forest management called afforestation is emerging as a decisive factor. However, although various studies are being conducted to enhance carbon absorption capacity, there are not many long-term research cases on afforestation. In this study, the cumulative carbon absorption for a total of 90 years from 1 January 2020 to 31 December 2100 was set as the baseline. Various changes were made according to the cyclical trend of the species and age classes planted nationwide, and various results were derived through the regeneration scenario. As a result of the study, the difference between the maximum value and the baseline CO₂ absorption was approximately 130 million t CO₂ when compared with the 90-year cumulative value. When converted into an annual unit, it increased by more than 14 million t CO₂. Based on the highest figures, compared with statistics from the Ministry of Environment’s Greenhouse Gas Information Center, it was confirmed that the forest absorption source, which was offset by 6.26 percent in 2019, could be changed by up to 8.74 percent. When analyzing the maximum figures from this study, depending on the method of afforestation, the greenhouse gases emitted by approximately 9.32 million passenger cars per year could be offset. In conclusion, among the carbon neutrality tasks that must be addressed at the national level, it is very important to establish long-term direction decisions and detailed plans for the forest sector, which is the core of carbon sinks, and a strategic approach is essential. Based on this study, it is expected that a more systematic direction can be presented for planning and implementing future afforestation. Full article

(This article belongs to the Special Issue Forest Management: Planning, Decision Making and Implementation)

23 pages, 6130 KiB

Open AccessArticle

Prediction of Color Change in Heat-Treated Wood Based on Improved Zebra Algorithm Optimized Deep Hybrid Kernel Extreme Learning Machine Model (IZOA-DHKELM)

by Jingjie Liang, Wei Wang, Zening Qu, Ying Cao and Jingxiang Gong

Forests 2025, 16(2), 253; https://doi.org/10.3390/f16020253 - 29 Jan 2025

Abstract

In this study, an Improved Zebra Optimization Algorithm (ZOA) is proposed based on the search mechanism of the Sparrow Optimization Algorithm (SSA), the perturbation mechanism of the Particle Swarm Algorithm (PSO), and the adaptive function. Then, Improved Zebra Optimization Algorithm (IZOA) was used [...] Read more.

In this study, an Improved Zebra Optimization Algorithm (ZOA) is proposed based on the search mechanism of the Sparrow Optimization Algorithm (SSA), the perturbation mechanism of the Particle Swarm Algorithm (PSO), and the adaptive function. Then, Improved Zebra Optimization Algorithm (IZOA) was used to optimize the Deep Hybrid Kernel Extreme Learning Machine Model (DHKELM), and the IZOA-DHKELM was obtained. The model has been used to predict the color of heat-treated wood for different species, temperatures, times, media, and profile types. In this article, the original DHKELM and the ZOA-DHKELM were compared to verify the validity and accuracy of the model. The results indicated that the IZOA-DHKELM decreased the mean absolute error (MAE), root mean square error (RMSE), and mean absolute percentage error (MAPE) by 56.2%, 67.4%, and 34.2%, respectively, while enhancing the coefficient of determination,

R^{2}

, to 0.9952 compared to the ZOA-DHKELM. This demonstrated that the model was significantly optimized, with improved generalization ability and prediction accuracy. It can better meet the actual engineering needs. Full article

(This article belongs to the Special Issue Advanced Technologies in Physical and Mechanical Wood Modification: 2nd Edition)

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19 pages, 4158 KiB

Open AccessArticle

Phenotypic Variation in Cone Scales and Seeds as Drivers of Seedling Germination Dynamics of Co-Occurring Cedar and Fir Species

by María Trujillo-Ríos, Antonio Gazol, José Ignacio Seco and Juan Carlos Linares

Forests 2025, 16(2), 252; https://doi.org/10.3390/f16020252 - 29 Jan 2025

Abstract

The intraspecific trait variations in the reproductive structures and early growth of seedlings may be critical in determining further regeneration. However, modularly built organisms, such as trees, challenge our notion of the phenotype concept, as the arrays of nonidentical homologous organs, such as [...] Read more.

The intraspecific trait variations in the reproductive structures and early growth of seedlings may be critical in determining further regeneration. However, modularly built organisms, such as trees, challenge our notion of the phenotype concept, as the arrays of nonidentical homologous organs, such as seed-bearing cone scales and seeds, depending on the individual capacity to produce phenotypically variable arrangements, but they also reflect abiotic selective effects. We investigated the variability in cone scale morphology, seed traits, and germination dynamics in coexisting fir (Abies marocana) and cedar (Cedrus atlantica) trees from northern Morocco. We quantified the degree of trait overlap in two co-occurring populations of both species, as a measure of population/species functional similarity. Cone scale size and seedling growth rate were species-dependent traits, as 70%–80% of the variance was explained by the species, while only 0%–2% was explained by the population. Conversely, seed weight was a tree-dependent trait, as 70% of the variation was observed among trees, while the species only explained 20% of the variation, and the contribution of the population was negligible. Species and populations showed the same characteristics in the correlations between variables, supporting different magnitudes but a constant relationship. Substantial variations in seed weight and early seedling growth occur concurrently among cones of a single tree, independently of the tree species or population. Further studies should consider both phenotype selection and inheritance of traits’ variance on the establishment, survival, and growth of seedlings in A. marocana and C. atlantica in nurseries and reforestation sites to improve adaptive capacity to changing environmental conditions. Full article

(This article belongs to the Special Issue Production in Forest Nurseries, Field Performance of Seedlings and Natural Regeneration in the Context of Climate Change)

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12 pages, 2614 KiB

Open AccessArticle

The Effect of Tree Spacing on the Growth and Biomass of Wattle Trees in Northwestern Ethiopia

by Saifu Amanuel, Qijing Liu, Andualem Genetu and Anteneh Yenesew

Forests 2025, 16(2), 251; https://doi.org/10.3390/f16020251 - 29 Jan 2025

Abstract

The wattle tree (Acacia mearnsii) is gaining importance as an exotic species in northwestern Ethiopia, providing ecological, environmental, and economic benefits, especially for fuelwood and charcoal production. This study aimed to investigate the effect of tree spacing on the growth and [...] Read more.

The wattle tree (Acacia mearnsii) is gaining importance as an exotic species in northwestern Ethiopia, providing ecological, environmental, and economic benefits, especially for fuelwood and charcoal production. This study aimed to investigate the effect of tree spacing on the growth and biomass of wattle trees. The study employed a randomized complete block design with three replications across three spacing treatments (0.5 m × 0.5 m, 1 m × 1 m, and 1.5 m × 1.5 m) in the Fagita district. Tree height and diameter measurements were taken at 12, 18, and 30 months post-planting from stands established in 2021. The results showed significant differences in tree height among the spacing treatments at 18 and 30 months. The closest spacing (0.5 m × 0.5 m) yielded the highest average tree heights of 32.12 cm, 84.86 cm, and 302.98 cm at 12, 18, and 30 months, respectively. At 18 months, the largest average diameter (1.22 cm) was found in the narrowest spacing (0.5 m × 0.5 m), whereas at 30 months, the widest spacing (1.5 m × 1.5 m) recorded the largest diameter (1.51 cm). Throughout the study, height, diameter, and average aboveground biomass exhibited an inverse relationship with spacing, with this effect diminishing as trees aged. Tree spacing significantly impacted average aboveground biomass at 18 months, with the densest spacing (0.5 m × 0.5 m) yielding the highest average aboveground biomass (1.97 kg at 18 months and 2.41 kg at 30 months). Average aboveground biomass increased as the trees matured. These findings suggest that closer spacing of A. mearnsii can enhance biomass production, positioning it as a promising candidate for energy generation. Leveraging these insights can optimize resource utilization while supporting global energy demands and reforestation initiatives aimed at carbon sequestration. Full article

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

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17 pages, 2711 KiB

Open AccessArticle

Study on the Natural Regeneration Characteristics and Influencing Factors of Typical Quercus Forests in Northern China

by Xuefan Hu, Guangshuang Duan, Yingshan Jin, Yuxin Cheng, Fang Liang, Zhenghua Lian, Fang Li, Yuerong Wang and Hongfei Chen

Forests 2025, 16(2), 250; https://doi.org/10.3390/f16020250 - 28 Jan 2025

Abstract

This study aims to analyze the natural regeneration characteristics and the key factors of Quercus forests, providing a theoretical foundation for maintaining the ecological stability of Quercus forests in northern China. In June and July 2023, 17 square plots of five Quercus species [...] Read more.

This study aims to analyze the natural regeneration characteristics and the key factors of Quercus forests, providing a theoretical foundation for maintaining the ecological stability of Quercus forests in northern China. In June and July 2023, 17 square plots of five Quercus species in Beijing were surveyed, and seedling regeneration and environmental factors (site, stand and soil factors) were measured. Pearson correlation and random forest algorithms were used to identify the relevant and key environmental factors affecting seedling regeneration density (Seedling 1, Seedling 2, Seedling 3). The natural regeneration capabilities of the five Quercus species in the Beijing area vary, with Quercus aliena and Quercus variabilis being stronger, while Quercus mongolica, Quercus acutissima and Quercus dentata are relatively weaker. Correlation analysis showed that Seedling 1 has no significant correlation with environmental factors; Seedling 2 is significantly negatively correlated with Pielou’s evenness (J) and exchangeable calcium (ECa) (p < 0.05); Seedling 3 is significantly positively correlated with species richness (S), Shannon–Wiener index (H), stand volume (M), and litter layer thickness (LT) (p < 0.05), and significantly negatively correlated with Pielou’s evenness (J) (p < 0.01). The random forest algorithm indicated that the regeneration of Seedling 1 is mainly affected by stand factors, while the regeneration of Seedling 2 and Seedling 3 is more influenced by soil and site factors. The Quercus forests in the Beijing region exhibit a rich species composition and demonstrate a certain capacity for natural regeneration. However, seedling growth is more constrained by soil and site factors in the later stages. Therefore, in the management of Quercus forests, environmental factors can be regulated during the seedling growth stage to create more suitable conditions for regeneration. Full article

(This article belongs to the Special Issue Estimation and Monitoring of Forest Biomass and Fuel Load Components)

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27 pages, 5861 KiB

Open AccessArticle

Priority Effect of Endophyte Community in Newly Fallen Leaves of Quercus acutissima Carruth. on Litter Decomposition and Saprotrophic Microbial Community

by Dongmei Yang, Yonghui Lin, Zaihua He, Xingbing He and Xiangshi Kong

Forests 2025, 16(2), 249; https://doi.org/10.3390/f16020249 - 28 Jan 2025

Abstract

This study examines the role of endophytic microbial colonization on the decomposition of oak leaf litter, a high-quality substrate in forest ecosystems. Over a one-year incubation, we observed a significant reduction in mass loss in colonized litter (46%) compared to non-colonized litter (80%), [...] Read more.

This study examines the role of endophytic microbial colonization on the decomposition of oak leaf litter, a high-quality substrate in forest ecosystems. Over a one-year incubation, we observed a significant reduction in mass loss in colonized litter (46%) compared to non-colonized litter (80%), indicating an inhibitory effect of endophytes on decomposition. Structural equation modeling revealed a bimodal impact of endophytic microbes, with an initial enhancement followed by a pronounced inhibition as decomposition progressed. Extracellular enzyme stoichiometry showed phosphorus limitation became significant, particularly with endophytic colonization, contributing to reduced decomposition rates. Microbial diversity analyses exposed the variable impacts of endophytic colonization on fungal and bacterial communities, with taxa such as Helotiales (order) and Burkholderia–Caballeronia–Paraburkholderia (genus) significantly affected. The identification of 16 keystone species, mostly endophytic bacteria, underscored their pivotal influence on decomposition processes. Despite initial endophytic impacts, abundant carbon resources promoted stochastic colonization, potentially surpassing the effects of early endophytic establishment. This study provides insights into the priority effects of endophytic colonization and niche differentiation, offering a foundation for further research into the mechanisms underlying these processes and their ecological consequences in various ecosystems. Full article

(This article belongs to the Special Issue Carbon, Nitrogen, and Phosphorus Storage and Cycling in Forest Soil)

27 pages, 17678 KiB

Open AccessArticle

From Crown Detection to Boundary Segmentation: Advancing Forest Analytics with Enhanced YOLO Model and Airborne LiDAR Point Clouds

by Yanan Liu, Ai Zhang and Peng Gao

Forests 2025, 16(2), 248; https://doi.org/10.3390/f16020248 - 28 Jan 2025

Abstract

Individual tree segmentation is crucial to extract forest structural parameters, which is vital for forest resource management and ecological monitoring. Airborne LiDAR (ALS), with its ability to rapidly and accurately acquire three-dimensional forest structural information, has become an essential tool for large-scale forest [...] Read more.

Individual tree segmentation is crucial to extract forest structural parameters, which is vital for forest resource management and ecological monitoring. Airborne LiDAR (ALS), with its ability to rapidly and accurately acquire three-dimensional forest structural information, has become an essential tool for large-scale forest monitoring. However, accurately locating individual trees and mapping canopy boundaries continues to be hindered by the overlapping nature of the tree canopies, especially in dense forests. To address these issues, this study introduces CCD-YOLO, a novel deep learning-based network for individual tree segmentation from the ALS point cloud. The proposed approach introduces key architectural enhancements to the YOLO framework, including (1) the integration of cross residual transformer network extended (CReToNeXt) backbone for feature extraction and multi-scale feature fusion, (2) the application of the convolutional block attention module (CBAM) to emphasize tree crown features while suppressing noise, and (3) a dynamic head for adaptive multi-layer feature fusion, enhancing boundary delineation accuracy. The proposed network was trained using a newly generated individual tree segmentation (ITS) dataset collected from a dense forest. A comprehensive evaluation of the experimental results was conducted across varying forest densities, encompassing a variety of both internal and external consistency assessments. The model outperforms the commonly used watershed algorithm and commercial LiDAR 360 software, achieving the highest indices (precision, F1, and recall) in both tree crown detection and boundary segmentation stages. This study highlights the potential of CCD-YOLO as an efficient and scalable solution for addressing the critical challenges of accuracy segmentation in complex forests. In the future, we will focus on enhancing the model’s performance and application. Full article

(This article belongs to the Special Issue Emerging Advances in Digital Forest Monitoring, Analysis, and Modeling)

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