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Forests, Volume 15, Issue 6 (June 2024) – 165 articles

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14 pages, 2712 KiB  
Article
Characteristics and Driving Mechanisms of Understory Vegetation Diversity Patterns in Central and Southern China
by Yaqin Xiao, Yuxin Tian, Qingan Song and Nan Deng
Forests 2024, 15(6), 1056; https://doi.org/10.3390/f15061056 (registering DOI) - 18 Jun 2024
Abstract
Large-scale forest restoration projects significantly reduce the net rates of forest loss. However, as a key component of forest restoration, planted forests have failed to restore biodiversity. China has implemented a large-scale afforestation program, which includes pure planted forests in particular, leading to [...] Read more.
Large-scale forest restoration projects significantly reduce the net rates of forest loss. However, as a key component of forest restoration, planted forests have failed to restore biodiversity. China has implemented a large-scale afforestation program, which includes pure planted forests in particular, leading to various changes in ecosystem processes. Despite this, a comprehensive analysis of understory vegetation diversity patterns in these pure planted forests is still lacking. This study aimed to analyze the data on understory vegetation diversity from three typical pure and natural forest ecosystems of Hunan ecological forests to reveal their diversity patterns. The results revealed no significant difference in the understory diversity index between natural and pure forest types, although natural forests had a bigger species pool. The Zipf–Mandelbrot model was a better fit for species abundance distribution. The fitted results suggested that both environmental filtering and neutral processes affected the species abundance distribution and pure understory communities during restoration succession. Natural forests had the most stable understory diversity structure, whereas pure Phyllostachys heterocycla (Carr.) Mitford forests had the least stable structure. Multivariate regression tree analysis identified indicator species for each community. The gradient boosting model indicated that isothermality and slope direction were the most important factors affecting diversity. The β-diversity analysis showed that community establishment in the four forest types was affected via different mechanisms. The findings of this study have significant implications for understanding the impact of afforestation on the mechanisms for maintaining diversity. Full article
(This article belongs to the Section Forest Biodiversity)
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41 pages, 2790 KiB  
Review
Forest Aboveground Biomass Estimation and Inventory: Evaluating Remote Sensing-Based Approaches
by Muhammad Nouman Khan, Yumin Tan, Ahmad Ali Gul, Sawaid Abbas and Jiale Wang
Forests 2024, 15(6), 1055; https://doi.org/10.3390/f15061055 (registering DOI) - 18 Jun 2024
Viewed by 105
Abstract
Remote sensing datasets offer robust approaches for gaining reliable insights into forest ecosystems. Despite numerous studies reviewing forest aboveground biomass estimation using remote sensing approaches, a comprehensive synthesis of synergetic integration methods to map and estimate forest AGB is still needed. This article [...] Read more.
Remote sensing datasets offer robust approaches for gaining reliable insights into forest ecosystems. Despite numerous studies reviewing forest aboveground biomass estimation using remote sensing approaches, a comprehensive synthesis of synergetic integration methods to map and estimate forest AGB is still needed. This article reviews the integrated remote sensing approaches and discusses significant advances in estimating the AGB from space- and airborne sensors. This review covers the research articles published during 2015–2023 to ascertain recent developments. A total of 98 peer-reviewed journal articles were selected under the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Among the scrutinized studies, 54 were relevant to spaceborne, 22 to airborne, and 22 to space- and airborne datasets. Among the empirical models used, random forest regression model accounted for the most articles (32). The highest number of articles utilizing integrated dataset approaches originated from China (24), followed by the USA (15). Among the space- and airborne datasets, Sentinel-1 and 2, Landsat, GEDI, and Airborne LiDAR datasets were widely employed with parameters that encompassed tree height, canopy cover, and vegetation indices. The results of co-citation analysis were also determined to be relevant to the objectives of this review. This review focuses on dataset integration with empirical models and provides insights into the accuracy and reliability of studies on AGB estimation modeling. Full article
(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)
24 pages, 5631 KiB  
Article
Siberian Pine and Larch Response to Warming-Drying Climate in the Southern Boundary of Their Range
by Ilya A. Petrov, Viacheslav I. Kharuk, Alexey S. Golyukov, Sergei T. Im, Sergei O. Ondar and Alexander S. Shushpanov
Forests 2024, 15(6), 1054; https://doi.org/10.3390/f15061054 (registering DOI) - 18 Jun 2024
Viewed by 104
Abstract
Trees’ growth and areal responses to changing climate are primarily expected within the edges of the species range. Here, we compared the responses of Siberian pine (Pinus sibirica Du Tour), a moisture-sensitive species, and drought-resistant larch (Larix sibirica Ledeb.) at the [...] Read more.
Trees’ growth and areal responses to changing climate are primarily expected within the edges of the species range. Here, we compared the responses of Siberian pine (Pinus sibirica Du Tour), a moisture-sensitive species, and drought-resistant larch (Larix sibirica Ledeb.) at the southern part of their ranges in the Siberian Mountains (the Tannu-Ola Ridge). We study the species’ growth and proportion in the forests from forest-steppe to treeline ecotone along the elevation gradient. These studies are based on radial growth index (GI) analysis and GI dependence on the climate variables. We used satellite time series to detect the land cover changes (areas of larch and Siberian pine, as well as shrubs and birch). We compared trees’ GI before and after warming “restart” in the late 1990s. Generally, GI dependence on the air temperature was negative at elevations below c. 1600 m a.s.l., whereas GI dependence on the moisture variables (precipitation, vapor pressure deficit, and soil moisture) was positive for both species. Above 1600 m, increasing air temperatures stimulated species growth, whereas the influence of moisture variables was negative (for larch) or neutral (for Siberian pine). After the warming restart, the GI of both conifers increased in moisture-sufficient high elevations and treeline ecotone, whereas within low elevations (<1300 m), the GI was stagnant or suppressed. Both species’, especially Siberian pine, negative growth dependence on air temperature and positive dependence on the moisture variables strongly increased since the warming restart. We found a risen growth dependence of both species on the soil-stored water during the previous year (September–October), which smoothed moisture stress at the beginning of the growing season. Yet both species’ growth also suffered as a result of early spring warms. We found that larch is migrating in both uphill and downhill directions, while Siberian pine is migrating uphill only. Forests loss occurred at low elevations (<1300 m), whereas forest and shrub gain occurred at high (>2000 m) ones. The upper boundary of the forests and shrubs is migrating uphill at rates of about 0.8 and 0.3 m/y, respectively. We observed a decrease in Siberian pine proportion in the forests, whereas areas of larch and birch strongly increased (by 150% and 100%, respectively), which indicates the retreat of Siberian pine from its southern habitat. We suggested afforestation of the areas of Siberian pine mortality by the drought-tolerant larch species. Full article
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13 pages, 15265 KiB  
Article
Effects of Soil Microorganisms on Carbon Sequestration under Different Mixed Modification Models in Pinus massoniana L. Plantation
by Meng Chen, Congjun Yuan, Shuang He, Jin Chen, Jun Luo, Fangjun Ding and Guohua Yan
Forests 2024, 15(6), 1053; https://doi.org/10.3390/f15061053 (registering DOI) - 18 Jun 2024
Viewed by 109
Abstract
In forests, microbial populations in the soil can directly influence the decomposition of carbon from surface plants, promoting carbon storage and stability. However, in sustainable forest management, it is still unclear how soil microorganisms under different plantation types affect organic carbon sequestration and [...] Read more.
In forests, microbial populations in the soil can directly influence the decomposition of carbon from surface plants, promoting carbon storage and stability. However, in sustainable forest management, it is still unclear how soil microorganisms under different plantation types affect organic carbon sequestration and whether the mechanisms of influence are the same. In this research, we focused on four mixed forests and pure Pinus massoniana-planted forest in the state-owned forest farm of Dushan County. Three replicated plots were set up for each model, and soil samples were collected from different layers (0–20 cm, 20–40 cm, and 40–60 cm), totaling 45 samples. We elucidated the effects of soil microorganisms on carbon sequestration under five mixed modification models of P. massoniana and further explored the mechanisms by which microbial functional communities regulate soil carbon sequestration under different mixed models through molecular sequencing and collinear network analysis. Variance analysis indicated that the soil organic carbon (SOC) of the same soil layer varied significantly, and there were also significant differences in the composition of soil bacterial and fungal microbial communities. Moreover, the bacterial community was more sensitive to changes in the vegetation environment, while the fungal community structure was more resistant to changes in the soil environment. Correlation analysis indicated that the diversity and composition of the bacterial community had more positive effects on soil organic carbon than those of the fungal community. Linear fitting and redundancy analysis (RDA) showed that particulate organic carbon (POC) in soil had the strongest correlation with SOC content. Soil microorganisms affected the storage and stability of soil carbon mainly by regulating the conversion of litter (carbon sources) into POC. The soil environment of different mixed models had different effects on soil carbon accumulation. Both correlation and collinearity network analyses indicated that soil microbial functional groups could enhance carbon storage by regulating readily oxidizable carbon (EOC) and POC content in mixed forest plantations. The results of our study provide a sound basis for replanting a reasonable forest model structure to improve forest carbon storage. Full article
(This article belongs to the Section Forest Soil)
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18 pages, 2067 KiB  
Article
Evaluation of Different Modeling Approaches for Estimating Total Bole Volume of Hispaniolan Pine (Pinus occidentalis Swartz) in Different Ecological Zones
by Santiago W. Bueno-López, Luis R. Caraballo-Rojas and Juan G. Torres-Herrera
Forests 2024, 15(6), 1052; https://doi.org/10.3390/f15061052 - 18 Jun 2024
Viewed by 95
Abstract
Pinus occidentalis (Swartz) is the primary timber species in the Dominican Republic (DR). Despite its economic importance, studies conducted on this species are scarce, making it difficult to estimate current inventory levels. This study aims to enhance the accuracy of estimating the total [...] Read more.
Pinus occidentalis (Swartz) is the primary timber species in the Dominican Republic (DR). Despite its economic importance, studies conducted on this species are scarce, making it difficult to estimate current inventory levels. This study aims to enhance the accuracy of estimating the total bole volume of P. occidentalis in different ecological zones (EZs) within La Sierra, evaluating and comparing two established volume equations—combined variable (CV) and Schumacher and Hall (S&H) across nine modeling variants. An indicator variables analysis determined the necessity of distinct equations for two EZs. Fitting included both linear and nonlinear models. Our comprehensive statistical analysis included goodness-of-fit metrics to evaluate each model variant’s performance rigorously. The second modeling variant (SH02) for the SH equation was most effective in the Dry Ecological Zone, showing superior performance in both the fitting and validation phases. Similarly, the third modeling variant (SH03) for the SH equation emerged as the best fit for the Combined Intermediate and Humid Ecological Zones, achieving the lowest overall ranking sum among tested variants. SH02 and SH03 provide reliable and precise volume estimations, allowing for the optimization of forestry management practices for P. occidentalis trees. The SH models outperformed the CV model variants’ consistency in parameter estimation. This tailored approach ensures more accurate volume predictions, which is crucial for sustainable management and conservation efforts. Full article
(This article belongs to the Special Issue Forest Biometrics, Inventory, and Modelling of Growth and Yield)
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15 pages, 3579 KiB  
Article
Woody Plant Structural Diversity Changes across an Inverse Elevation-Dependent Warming Gradient in a Subtropical Mountain Forest
by Yuqiao Su, Xianhua Gan, Weiqiang Zhang, Guozhang Wu and Fangfang Huang
Forests 2024, 15(6), 1051; https://doi.org/10.3390/f15061051 - 18 Jun 2024
Viewed by 106
Abstract
Examining the changes in woody plant structural diversity along an inverse elevation-dependent warming gradient will enhance our mechanistic understanding of how warming affects forest communities because such an inverse elevational gradient reflects a warming trend in a mountain landscape. Here, we investigated the [...] Read more.
Examining the changes in woody plant structural diversity along an inverse elevation-dependent warming gradient will enhance our mechanistic understanding of how warming affects forest communities because such an inverse elevational gradient reflects a warming trend in a mountain landscape. Here, we investigated the effects of warming on the patterns of species composition and structural diversity in a subtropical broadleaved forest. We calculated a warming index based on elevational difference and modeled the aspect-related potential incident radiation (PDIR) using nonparametric multiplicative regression. We tested the changes in structural diversity of three communities for significant differences along the warming gradient. We associated both the warming index and PDIR with the principal components and tested their relationships for significant differences. We found that trees of different sizes varied in their response to the warming gradient. While a significant decreasing trend was exhibited in both species diversity and size diversity for trees of all sizes and for adult trees along the warming gradient, no significant changes in seedlings were found, and the average basal area value was the highest for the warmest community. Our findings demonstrated that a short-range elevational gradient was adequate to separate the communities in species composition and structural diversity. Patterns of structural diversity along the warming gradient varied in size classes. The community at a higher elevation had more indicator species that were unique in separating the community from others. Principal component analysis showed that the first two principal components were negatively correlated with the warming index, indicating that warming destabilized species composition and community structure. Our study suggests that warming is the major driver of changes in structural diversity and species composition of woody plant communities in a subtropical broadleaved forest and that warming may promote tree productivity at the community level but reduce structural diversity at the quadrat level. Full article
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16 pages, 7035 KiB  
Article
A Lightweight Pine Wilt Disease Detection Method Based on Vision Transformer-Enhanced YOLO
by Quanbo Yuan, Suhua Zou, Huijuan Wang, Wei Luo, Xiuling Zheng, Lantao Liu and Zhaopeng Meng
Forests 2024, 15(6), 1050; https://doi.org/10.3390/f15061050 - 18 Jun 2024
Viewed by 151
Abstract
Pine wilt disease (PWD) is a forest disease characterized by rapid spread and extremely high lethality, posing a serious threat to the ecological security of China’s forests and causing significant economic losses in forestry. Given the extensive forestry area, limited personnel for inspection [...] Read more.
Pine wilt disease (PWD) is a forest disease characterized by rapid spread and extremely high lethality, posing a serious threat to the ecological security of China’s forests and causing significant economic losses in forestry. Given the extensive forestry area, limited personnel for inspection and monitoring, and high costs, utilizing UAV-based remote sensing monitoring for diseased trees represents an effective approach for controlling the spread of PWD. However, due to the small target size and uneven scale of pine wilt disease, as well as the limitations of real-time detection by drones, traditional disease tree detection algorithms based on RGB remote sensing images do not achieve an optimal balance among accuracy, detection speed, and model complexity due to real-time detection limitations. Consequently, this paper proposes Light-ViTeYOLO, a lightweight pine wilt disease detection method based on Vision Transformer-enhanced YOLO (You Only Look Once). A novel lightweight multi-scale attention module is introduced to construct an EfficientViT feature extraction network for global receptive field and multi-scale learning. A novel neck network, CACSNet(Content-Aware Cross-Scale bidirectional fusion neck network), is designed to enhance the detection of diseased trees at single granularity, and the loss function is optimized to improve localization accuracy. The algorithm effectively reduces the number of parameters and giga floating-point operations per second (GFLOPs) of the detection model while enhancing overall detection performance. Experimental results demonstrate that compared with other baseline algorithms, Light-ViTeYOLO proposed in this paper has the least parameter and computational complexity among related algorithms, with 3.89 MFLOPs and 7.4 GFLOPs, respectively. The FPS rate is 57.9 (frames/s), which is better than the original YOLOv5. Meanwhile, its [email protected]:0.95 is the best among the baseline algorithms, and the recall and [email protected] slightly decrease. Our Light-ViTeYOLO is the first lightweight method specifically designed for detecting pine wilt disease. It not only meets the requirements for real-time detection of pine wilt disease outbreaks but also provides strong technical support for automated forestry work. Full article
(This article belongs to the Special Issue Applications of Artificial Intelligence in Forestry)
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13 pages, 4264 KiB  
Article
The Potential Distribution Prediction of the Forestry Pest Cyrtotrachelus buqueti (Guer) Based on the MaxEnt Model across China
by Chun Fu, Zhiling Wang, Yaqin Peng and Zhihang Zhuo
Forests 2024, 15(6), 1049; https://doi.org/10.3390/f15061049 - 18 Jun 2024
Viewed by 102
Abstract
Exploring the geographical distribution of forestry pests is crucial for formulating pest management strategies. Cyrtotrachelus buqueti (Guer) stands out as one of the primary pests among China’s forestry hazards. This study employs the MaxEnt model, along with 19 bioclimatic variables and habitat characteristics, [...] Read more.
Exploring the geographical distribution of forestry pests is crucial for formulating pest management strategies. Cyrtotrachelus buqueti (Guer) stands out as one of the primary pests among China’s forestry hazards. This study employs the MaxEnt model, along with 19 bioclimatic variables and habitat characteristics, to predict the current and future distribution of C. buqueti under three typical emission scenarios for 2050 and 2070 (2.6 W/m2 (SSP1-2.6), 7.0 W/m2 (SSP3-7.0), and 8.5 W/m2 (SSP5-8.5)). Among the 19 bioclimatic variables, BIO 14 (precipitation of the driest month), BIO 8 (mean temperature of the wettest quarter), Elev, slope, and aspect were identified as significant contributors. These five variables are critical environmental factors affecting the suitability of habitats for C. buqueti and are representative of its potential habitat. The results indicate that C. buqueti predominantly inhabits southern regions such as Chongqing, Guizhou, Yunnan, Sichuan, Guangxi, Shaanxi, Hubei, Hainan, and Taiwan. Among them, Chongqing, Guizhou, and Yunnan are the primary distribution areas of high suitability. In the future, the centroid’s movement direction will generally shift southward, with an expansion trend observed in the distribution areas of each province. This study enhances researchers’ understanding of forestry pest dynamics and promotes proactive management strategies to mitigate their impact on forest ecosystems and agricultural productivity. Full article
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11 pages, 4768 KiB  
Article
The Culprit behind the Mass Death of Mangroves: Egrets or Rats (Rattus losea)?
by Yunhong Xue, Wenai Liu, Lianghao Pan, Yancheng Tao, Xin Liao, Qiuxia Liang, Huiying Wu and Weiguo Jiang
Forests 2024, 15(6), 1048; https://doi.org/10.3390/f15061048 (registering DOI) - 18 Jun 2024
Viewed by 130
Abstract
Mangroves play a crucial role in maintaining coastal ecological balance. This study focused on the impact of branch-breaking behavior on the mortality of Rhizophora stylosa in the Guangxi Shankou Mangrove Reserve. However, we found mangrove mortality in areas devoid of egret habitation, prompting [...] Read more.
Mangroves play a crucial role in maintaining coastal ecological balance. This study focused on the impact of branch-breaking behavior on the mortality of Rhizophora stylosa in the Guangxi Shankou Mangrove Reserve. However, we found mangrove mortality in areas devoid of egret habitation, prompting a reevaluation of our research hypothesis. Further investigation suggested that nesting behavior was the primary cause of mangrove mortality. A comparison of the data from areas with egrets (Egretta garzetta, Ardea intermedia) and lesser rice-field rats (Rattus losea) activity indicated significant mechanical damage caused by rats to mangroves as the main cause of mortality. Additionally, we found that the biological characteristics of R. stylosa, particularly its stunted growth and recovery abilities after branch breaking, were key factors affecting its survival. These findings imply that rat-induced mortality may not occur in other less susceptible mangrove species. The results contradict assumptions regarding the impact of egret behavior and highlight the importance of the biological characteristics of R. stylosa. This offers fresh insights into mangrove conservation and management, emphasizing the need for ongoing observation and hypotheses verification. Future studies should explore the influence of lesser rice-field rats’ activity and the intrinsic characteristics of R. stylosa on the ecosystem’s long-term stability. Full article
(This article belongs to the Section Forest Health)
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18 pages, 2174 KiB  
Article
Analyzing the Eucalyptus Timber Value Chain in Thailand: Profit Distribution and Opportunities for Improvement
by Aerwadee Premashthira, Kitipong Tangkit, Warayost Lamaisri, Nopparat Kaakkurivaara, Chakrit Na Takuathung, Trairat Neimsuwan, Narinthorn Jumwong, Ponthep Meunpong and Tomi Kaakkurivaara
Forests 2024, 15(6), 1047; https://doi.org/10.3390/f15061047 - 18 Jun 2024
Viewed by 244
Abstract
The Thai forestry sector relies greatly on Eucalyptus as a raw material. The rapid expansion of plantations during the last few decades and the high demand for Eucalyptus for several purposes has led to numerous supply chain practices. A comprehensive understanding of the [...] Read more.
The Thai forestry sector relies greatly on Eucalyptus as a raw material. The rapid expansion of plantations during the last few decades and the high demand for Eucalyptus for several purposes has led to numerous supply chain practices. A comprehensive understanding of the Eucalyptus value chain is lacking in Thailand, which has consequences for optimization, sustainability, and profitability aspects. This study analyzed actors and their activities along the value chain and estimated added value and profit margin benefit distributions. The study method involved a value chain analysis approach, whereby input data were collected from the following groups: seedling suppliers and developers, farmers and tree growers, timber traders and collectors, intermediaries, processors, wholesalers, and consumers via key informant interviews, in-depth interviews, and group discussions. The results revealed the vertical integration of Eucalyptus timber businesses, where sapling breeders were the major input suppliers with a significant role in the value chain based on the role of controlling the majority of seedling production, promoting cultivation, and ensuring the raw material supply for the pulp industry through a full-cycle membership program. Total gross marketing margin was highest (90.6%) in the path of the pulp mill industry and lowest in the path of the biomass power plant (73.4%). The profit share of growers varied between 9.9% and 26.6% depending on the path and chain. The overall benefit distribution analysis demonstrated a positive gross profit margin but minor distribution to the growers. Our study determined that decision-makers should create supportive programs, funding opportunities, and infrastructural support for research and development, capacity building, and regulation to ensure suitable benefits for all actors in the Eucalyptus timber value chain in Thailand. Full article
(This article belongs to the Section Forest Economics, Policy, and Social Science)
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24 pages, 13312 KiB  
Article
A Multi-Criterion Evaluation Process for Determining Cost-Effective Harvesting Systems in Fragmented Boreal Forests
by Léo Painchaud and Luc LeBel
Forests 2024, 15(6), 1046; https://doi.org/10.3390/f15061046 - 17 Jun 2024
Viewed by 191
Abstract
Nordic forests, like those found in Canada, used to consist of large and relatively homogeneous mature stands. Such a spatial pattern allows for harvest operations to be highly concentrated, minimizing procurement costs. However, the growing fragmentation of these forests makes planning difficult and [...] Read more.
Nordic forests, like those found in Canada, used to consist of large and relatively homogeneous mature stands. Such a spatial pattern allows for harvest operations to be highly concentrated, minimizing procurement costs. However, the growing fragmentation of these forests makes planning difficult and increases the costs of road building and machinery relocation. While operational solutions have been developed in regions with small harvest areas, their transferability to different settings is unknown. Finding the most suitable combination of equipment for a given context is challenging considering the multitude of possibilities. The objective of this study is to identify, from all possible options, a subset of harvest systems expected to perform well in fragmented boreal forests. The results from this research are two-fold. First, a comprehensive review of forest machines and harvest systems is provided. Second, a multi-criteria decision analysis (MCDA) methodology is proposed to evaluate the alternatives. In a boreal forest context, the conventional harvester-forwarder system (CTL) was ranked among the best solutions, along with mild adaptations of the usual configurations. Several whole-tree (WT) system configurations were also highly ranked. While the results are specific to the case studied, the review and selection methodology can serve in different operational contexts. Full article
(This article belongs to the Special Issue Sustainable Forest Operations Planning and Management)
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13 pages, 12826 KiB  
Article
Virulence and Pathological Characteristics of a New Metarhizium anisopliae Strain against Asian Long-Horn Beetle Anoplophora glabripennis Larvae
by Ji-Yang Zheng, Chun-Cheng Jian and Dun Wang
Forests 2024, 15(6), 1045; https://doi.org/10.3390/f15061045 - 17 Jun 2024
Viewed by 182
Abstract
The Asian long-horn beetle (ALB) is a serious wood-boring insect. Continuous isolation of different fungal strains is vital for using fungi for the control of ALB. The virulence and pathological characteristics of a new Metarhizium anisopliae strain DES3 isolated from the desert afforestation [...] Read more.
The Asian long-horn beetle (ALB) is a serious wood-boring insect. Continuous isolation of different fungal strains is vital for using fungi for the control of ALB. The virulence and pathological characteristics of a new Metarhizium anisopliae strain DES3 isolated from the desert afforestation stands against the larvae of ALB were assessed in this study. The corrected mortality reached 100% at the conidial concentration of 109 and 108 conidia/mL, and 91.11 ± 4.44% at 107 conidia/mL. Similarly, the LC/LT showed high virulence as well. Meanwhile, the virulence of a commercial M. anisopliae strain against the ALB larvae was evaluated. The corrected mortality was only 33.33% at 109 conidia/mL, and less than 10% at 108 conidia/mL. The pathological characteristics after infection by the M. anisopliae strain DES3 were evident, mainly embodied in the rupture of the adipose tissue, muscle tissue, and midgut. But there was no obvious change after infection by the commercial M. anisopliae strain. In conclusion, these results establish that the M. anisopliae strain DES3 has high virulence in a dosage-dependent manner against ALB larvae, indicating the potential of fungal strain DES3 to be developed as biopesticide for biocontrol of A. glabripennis. Full article
(This article belongs to the Section Forest Health)
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11 pages, 4330 KiB  
Article
Involvement of the Transporter CgTrk1 in Potassium Uptake, Invasive Growth, and Full Virulence in Colletotrichum gloeosporioides
by Zhi Wang, Jiyun Yang, Meiling Sun, Yuting Pan and Lin Huang
Forests 2024, 15(6), 1044; https://doi.org/10.3390/f15061044 - 17 Jun 2024
Viewed by 225
Abstract
Colletotrichum gloeosporioides is one of the more economically important pathogen causing anthracnose on crops and trees worldwide. As an essential mineral nutrient, potassium play a vital role for fundamental cellular processes in organisms. In this study, a high-affinity potassium transporter CgTrk1 was identified [...] Read more.
Colletotrichum gloeosporioides is one of the more economically important pathogen causing anthracnose on crops and trees worldwide. As an essential mineral nutrient, potassium play a vital role for fundamental cellular processes in organisms. In this study, a high-affinity potassium transporter CgTrk1 was identified in C. gloeosporioides. Cytological examinations revealed that CgTrk1 was localized in the plasma membrane. The gene deletion mutant of CgTRK1 significantly depressed the potassium uptake. CgTrk1 is also required for vegetative growth, appressorium development, invasive growth, and full virulence. The data also indicate that CgTrk1 plays dominant roles in potassium uptake and pathogenicity rather than its homologous protein CgTrk2. These results imply that the potassium transporter CgTrk1 is involved in invasive growth and full virulence in C. gloeosporioides. Full article
(This article belongs to the Special Issue Diversity, Taxonomy and Functions of Forest Microorganisms)
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21 pages, 4299 KiB  
Article
A Hybrid Method for Individual Tree Detection in Broadleaf Forests Based on UAV-LiDAR Data and Multistage 3D Structure Analysis
by Susu Deng, Sishuo Jing and Huanxin Zhao
Forests 2024, 15(6), 1043; https://doi.org/10.3390/f15061043 - 17 Jun 2024
Viewed by 232
Abstract
Individual tree detection and segmentation in broadleaf forests have always been great challenges due to the overlapping crowns, irregular crown shapes, and multiple peaks in large crowns. Unmanned aerial vehicle (UAV)-borne light detection and ranging (LiDAR) is a powerful tool for acquiring high-density [...] Read more.
Individual tree detection and segmentation in broadleaf forests have always been great challenges due to the overlapping crowns, irregular crown shapes, and multiple peaks in large crowns. Unmanned aerial vehicle (UAV)-borne light detection and ranging (LiDAR) is a powerful tool for acquiring high-density point clouds that can be used for both trunk detection and crown segmentation. A hybrid method that combines trunk detection and crown segmentation is proposed to detect individual trees in broadleaf forests based on UAV-LiDAR data. A trunk point distribution indicator-based approach is first applied to detect potential trunk positions. The treetops extracted from a canopy height model (CHM) and the crown segments obtained by applying a marker-controlled watershed segmentation to the CHM are used to identify potentially false trunk positions. Finally, the three-dimensional structures of trunks and branches are analyzed at each potentially false trunk position to distinguish between true and false trunk positions. The method was evaluated on three plots in subtropical urban broadleaf forests with varying proportions of evergreen trees. The F-score in three plots ranged from 0.723 to 0.829, which are higher values than the F-scores derived by a treetop detection method (0.518–0.588) and a point cloud-based individual tree segmentation method (0.479–0.514). The influences of the CHM resolution (0.25 and 0.1 m) and the data acquisition season (leaf-off and leaf-on) on the final individual tree detection result were also evaluated. The results indicated that using the CHM with a 0.25 m resolution resulted in under-segmentation of crowns and higher F-scores. The data acquisition season had a small influence on the individual tree detection result when using the hybrid method. The proposed hybrid method needs to specify parameters based on prior knowledge of the forest. In addition, the hybrid method was evaluated in small-scale urban broadleaf forests. Further research should evaluate the hybrid method in natural forests over large areas, which differ in forest structures compared to urban forests. Full article
(This article belongs to the Topic Individual Tree Detection (ITD) and Its Applications)
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15 pages, 3497 KiB  
Article
Understorey Plant Functional Traits of Platycladus orientalis Depends on Crown Closure and Soil Properties in the Loess Plateau, China
by Gaohui Duan, Lifeng Liu, Zhongming Wen, Yu Tang and Boheng Wang
Forests 2024, 15(6), 1042; https://doi.org/10.3390/f15061042 - 16 Jun 2024
Viewed by 271
Abstract
The crown closure of Platycladus orientalis forests has a wide-ranging impact on vegetation and soil, thereby affecting the overall functioning of the ecosystem. There is limited research on the effects of the Platycladus orientalis forest crown closure on changes in community plant functional [...] Read more.
The crown closure of Platycladus orientalis forests has a wide-ranging impact on vegetation and soil, thereby affecting the overall functioning of the ecosystem. There is limited research on the effects of the Platycladus orientalis forest crown closure on changes in community plant functional traits, and their interactions are not yet clear. Therefore, we investigated 50 plots of different types of Platycladus orientalis crown closure, and we measured the functional traits of nine shrub species and 68 herb species in 50 plots under five different densities of Platycladus orientalis forests in the Loess Plateau. The consequence of Pearson’s correlation analysis showed significant positive correlations between LC and LTD, LN and LP, LN and LNP, LN and LV, LN and H, LP and LV, LP and H, and SLA and LV (p < 0.05). LC was significantly negatively correlated with LP, LC with SLA, LC with LV, LN with LTD, LP with LNP, LP with LTD, and LTD with H (p < 0.05). Only the soil phosphorus content (SP) and soil water content (SWC) showed a significant positive correlation with multiple plant functional traits. The crown closure of Platycladus orientalis forests increased significantly, as did the plant functional features. Changes in the Platycladus orientalis forest crown closure significantly increased the LC, LV, LN, LP, and SLA in plant functional traits. An increase in Platycladus orientalis forest crown closure significantly increased the soil organic carbon (SC), soil phosphorus content (SP), soil nitrogen content (SN), soil water content (SWC), field capacity (FC), and soil porosity (PO). Based on a structural equation model, we found that, while changes in the Platycladus orientalis forest crown closure did not directly affect plant functional traits, they could indirectly influence these traits through soil factors, primarily the soil water content (SWC) and soil phosphorus content (SP) (p < 0.05). Additionally, the mechanisms of the Platycladus orientalis forest crown closure’s impact on different functional traits vary. The research results provide scientific elements for the ecological restoration of Platycladus orientalis forests on the Loess Plateau. Full article
(This article belongs to the Special Issue Forest Disturbance and Management)
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18 pages, 9383 KiB  
Article
Impact of Root Cutting on Acer platanoides and Tilia cordata Tree Stability in Urban Parks: A Case Study in Quebec City, Canada
by Clément Pallafray, Sivajanani Sivarajah and Jean-Claude Ruel
Forests 2024, 15(6), 1041; https://doi.org/10.3390/f15061041 - 16 Jun 2024
Viewed by 402
Abstract
Trees growing in urban environments are often impacted by maintenance or construction work involving the cutting of roots. Tree protection zones have been proposed to avoid critical damage to the tree. However, despite incorporating quantitative information, they heavily rely on expert judgement that [...] Read more.
Trees growing in urban environments are often impacted by maintenance or construction work involving the cutting of roots. Tree protection zones have been proposed to avoid critical damage to the tree. However, despite incorporating quantitative information, they heavily rely on expert judgement that remains to be validated. In a study conducted across six parks in Quebec City, Canada, two commonly found tree species, Acer platanoides L. and Tilia cordata Mill., presumed to be different in terms of vulnerability to root damage, were subjected to a range of trenching treatments. The trees were between 23 and 40 cm diameter at breast height (DBH). A safety factor was calculated relating the turning moment the tree can withstand to the turning moment imposed by high winds likely to occur. The safety factor against uprooting was assessed for each tree before and after root trenching using a non-destructive pulling approach. The effects of tree species, distance to the trench, and their combined interaction were tested on tree stability. The relationship between tree stability and soil texture, tree characteristics, and the number of damaged roots were also tested. Safety factors were initially variable, ranging from 0.5 to 4.5. T. cordata safety factors were lower than those of A. platanoides and influenced by soil texture. Trenching treatments had no effect on the safety factor, even when two perpendicular trenches were dug at 1 m from the stem. No index of the amount of root damaged was significantly related to the safety factor. Root trenching treatments that encroached closer to the tree trunk than the recommended tree protection zones did not affect the stability of both species. Nevertheless, it is essential to recognize that other ecophysiological processes might still be influenced, and long-term monitoring is crucial. Both should be taken into account when determining these zones. Full article
(This article belongs to the Special Issue Urban Forestry and Sustainable Cities)
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17 pages, 2783 KiB  
Article
Enzyme Activity Stoichiometry Suggests That Fertilization, Especially Nitrogen Fertilization, Alleviates Nutrient Limitation of Soil Microorganisms in Moso Bamboo Forests
by Haoyu Chu, Wenhui Su, Yaqi Zhou, Ziye Wang, Yongmei Long, Yutong Sun and Shaohui Fan
Forests 2024, 15(6), 1040; https://doi.org/10.3390/f15061040 - 16 Jun 2024
Viewed by 335
Abstract
Rational application of N fertilizer is essential for maintaining the long-term productivity of Moso bamboo forests. Microbial activity is a crucial indicator of soil quality. Changes in soil nutrient resources due to N addition can lead to microbial nutrient limitations, thereby impeding the [...] Read more.
Rational application of N fertilizer is essential for maintaining the long-term productivity of Moso bamboo forests. Microbial activity is a crucial indicator of soil quality. Changes in soil nutrient resources due to N addition can lead to microbial nutrient limitations, thereby impeding the maintenance of soil quality. Currently, there is limited research on the effects of N application on microbial nutrient limitations in Moso bamboo forest soils. To examine the changes in extracellular enzyme activity and microbial nutrient limitations in Moso bamboo forest soils following N application, we conducted an N application experiment in northern Guizhou. The findings revealed that the N3 treatment (726 kg·N·hm−2·yr−1) significantly reduced β-glucosidase (BG) activity by 27.61% compared to the control group (no fertilization). The N1 (242 kg·N·hm−2·yr−1), N2 (484 kg·N·hm−2·yr−1), and N3 treatments notably increased the activities of leucine aminopeptidase (LAP) and N-acetyl-β-D-glucosidase (NAG) by 11.45% to 15.79%. Acid phosphatase (ACP) activity remained unaffected by fertilization. N application treatments significantly decreased the C:Ne and C:Pe ratios, while the N:Pe ratio was less influenced by N fertilizer application. Scatter plots and vector characteristics of enzyme activity stoichiometry suggested that microorganisms in the study area were limited by C and N, and N fertilizer application reduced the vector length and increased the vector angle, indicating that N application alleviated the C and N limitation of microorganisms in Moso bamboo forests. Redundancy Analysis (RDA) demonstrated that microbial biomass phosphorus (MBP) was the most critical factor affecting extracellular enzyme activity and stoichiometry. Furthermore, Random Forest Regression analysis identified MBP and the N:Pm ratio as the most significant factors influencing microbial C and N limitation, respectively. The study demonstrated that N application modulates the microbial nutrient acquisition strategy by altering soil nutrient resources in Moso bamboo forests. Formulating fertilizer application strategies based on microbial nutrient requirements is more beneficial for maintaining soil quality and sustainably managing Moso bamboo forests. Additionally, our study offers a theoretical reference for understanding carbon cycling in bamboo forest ecosystems in the context of substantial N inputs. Full article
(This article belongs to the Special Issue How Does Forest Management Affect Soil Dynamics?)
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21 pages, 14996 KiB  
Article
Predicting Soil Erosion Using RUSLE and GeoSOS-FLUS Models: A Case Study in Kunming, China
by Jinlin Lai, Jiashun Li and Li Liu
Forests 2024, 15(6), 1039; https://doi.org/10.3390/f15061039 - 16 Jun 2024
Viewed by 211
Abstract
Abstract: Revealing the relationship between land use changes and soil erosion provides a reference for formulating future land use strategies. This study simulated historical and future soil erosion changes based on the RULSE and GeoSOS-FLUS models and used a random forest model to [...] Read more.
Abstract: Revealing the relationship between land use changes and soil erosion provides a reference for formulating future land use strategies. This study simulated historical and future soil erosion changes based on the RULSE and GeoSOS-FLUS models and used a random forest model to explain the relative importance of natural and anthropogenic factors on soil erosion. The main conclusions are as follows: (1) From 1990 to 2020, significant changes in land use occurred in Kunming, with a continuous reduction in woodland, grassland, and cropland, being converted into construction land, which grew by 195.18% compared with 1990. (2) During this period, the soil erosion modulus decreased from 133.85 t/(km²·a) in 1990 to 130.32 t/(km²·a) in 2020, with a reduction in soil loss by 74,485.46 t/a, mainly due to the conversion of cropland to construction and ecological lands (woodland, grassland). (3) The expansion of construction land will continue, and it is expected that by 2050, the soil erosion modulus will decrease by 3.77 t/(km²·a), 4.27 t/(km²·a), and 3.27 t/(km²·a) under natural development, rapid development, and ecological protection scenarios, respectively. However, under the cropland protection scenario, the soil erosion modulus increased by 0.26 t/(km²·a) compared with 2020. (4) The spatial pattern of soil erosion is influenced by both natural and anthropogenic factors, and as human activities intensify in the future, the influence of anthropogenic factors will further increase. Traditionally, the expansion of construction land is thought to increase soil loss. Our study may offer a new perspective and provide a reference for future land use planning and soil loss management in Kunming. Full article
(This article belongs to the Section Forest Soil)
16 pages, 6138 KiB  
Article
Effects of Dowel Rotation Welding Conditions on Connection Performance for Chinese Fir Dimension Lumbers
by Xiao Zhong, De Li, Xiaoxue Xu, Quan Li, Danyun Yu, Zhigang Wu, Jiankun Liang, Jun Peng, Wen Gu, Xin Zhao, Shuang Yin, Guifen Yang and Feiyan Gong
Forests 2024, 15(6), 1038; https://doi.org/10.3390/f15061038 - 15 Jun 2024
Viewed by 199
Abstract
In this study, the rotating welding process of Chinese fir (Keteleeriafortunei) in Guizhou, China, was systematically analyzed. The effects of rotating welding conditions, including the dowel-to-guide hole diameter ratio, welding time, depth, base surface, angle, and dowel type, on the performance [...] Read more.
In this study, the rotating welding process of Chinese fir (Keteleeriafortunei) in Guizhou, China, was systematically analyzed. The effects of rotating welding conditions, including the dowel-to-guide hole diameter ratio, welding time, depth, base surface, angle, and dowel type, on the performance of welded Chinese fir were explored. Moreover, the physical and chemical changes oftheChinese fir interface during welding were revealed by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results indicated the following: (1) The rotating welding technology can quickly achieve a strong connection between wood through friction heat without chemical adhesives and compared with traditional wood connection technology such as gluing or mechanical fixing;it has the advantages of simple operation, high production efficiency; and environmental friendliness. (2) Aftertherotating welding, the wood underwent significant pyrolysis, especially the degradation of hemicellulose. The heat generated in the welding process caused good melting and mechanical interlocking between the dowel and the wall of the guide hole, but it was also accompanied by afriction loss of the dowel and the substrate. (3) The welding parameters affected the wood’s connection strength and stability by altering heat production, distribution, transfer, and frictional losses. The impact of the dowel-to-guide hole diameter ratio had a great influence on the connection strength. When the diameter ratio was 1:0.7, the tensile strength was the highest, reaching 2.27 MPa. (4) The analyses of XPS, FTIR, XRD, and SEM proved thatthechemical composition changes at the interface, leading to a more structured crystalline bond and enhanced connection strength due to fiber entanglement and interlocking. This research providesatheoretical and experimental basis forthefurther innovation and development of wood processing technology and provides a new technical path forthegreen manufacturing of wood structure buildings. Full article
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18 pages, 3421 KiB  
Review
A Bibliometric Analysis of the Mechanisms Underlying Drought-Induced Tree Mortality
by Yaqian Gao, Zetao Chen, Jiaxian Chen, Ling Yang, Jiyue Li, Qian He, Quan Qiu and Yan Su
Forests 2024, 15(6), 1037; https://doi.org/10.3390/f15061037 - 14 Jun 2024
Viewed by 195
Abstract
Drought intensity and frequency have increased in recent years, which poses significant threats to forest ecosystems, especially in the context of global climate change. This paper is aimed at summarizing the current state of research and global development trends regarding drought-induced tree mortality [...] Read more.
Drought intensity and frequency have increased in recent years, which poses significant threats to forest ecosystems, especially in the context of global climate change. This paper is aimed at summarizing the current state of research and global development trends regarding drought-induced tree mortality mechanisms in tree physiology. Developing a robust literature foundation will facilitate in-depth research and foster the exchange of knowledge related to this subject. A literature review was conducted using tools such as VOSviewer, CiteSpace, and the Bibliometrix R-package to review the literature from the Web of Science’s core database from 1985 to 2023. We intend to determine the current state and evolution of global research on drought-induced tree mortality mechanisms. The results reveal that research on drought-induced tree mortality mechanisms gained momentum predominantly in the last two decades, with a marked surge post-2012. The United States is the epicenter of research, leading the global scientific community with its preeminence in publication volume, citation rates, and the scope of collaborative networks, with China in close pursuit. Tree Physiology stands out as the leading journal in this domain, boasting 129 articles. McDowell NG emerges as the most prolific author, with an H-index of 41, underscoring his influence in the field. There is a clear upward trend in collaborations spanning authors, journals, research institutions, and countries. The analysis of frequently cited keywords and topic evolution suggests that drought and tree mortality will likely remain key research areas for the foreseeable future. The future of research on drought-induced tree mortality mechanisms in physiology is promising, as it emphasizes multidisciplinary approaches and global collaborations. Full article
(This article belongs to the Special Issue Abiotic Stress in Tree Species)
17 pages, 3527 KiB  
Article
Soybean Meal–Oxidized Lignin as Bio-Hybridized Wood Panel Adhesives with Increased Water Resistance
by Wenbin Zhang, Chengyuan Liu, Zhiyuan Du, Hui Wang, Guanben Du, Hisham Essawy, Hong Lei, Xuedong Xi, Xiaojian Zhou and Ming Cao
Forests 2024, 15(6), 1036; https://doi.org/10.3390/f15061036 - 14 Jun 2024
Viewed by 159
Abstract
Soybean meal (SM) adhesive is widely acknowledged as a viable substitute for traditional formaldehyde-based adhesives, given its ability to be easily modified, the utilization of renewable sources, and its eco-friendly characteristics. However, the application of SM adhesive in manufacturing has been impeded due [...] Read more.
Soybean meal (SM) adhesive is widely acknowledged as a viable substitute for traditional formaldehyde-based adhesives, given its ability to be easily modified, the utilization of renewable sources, and its eco-friendly characteristics. However, the application of SM adhesive in manufacturing has been impeded due to its restricted bonding capacity and inadequate water resistance. Researchers in the wood industry have recognized the significance of creating an SM-based adhesive, which possesses remarkable adhesive strength and resistance to water. This study endeavors to tackle the issue of inadequate water resistance in SM adhesives. Sodium lignosulfonate (L) was oxidized using hydrogen peroxide (HP) to oxidized lignin (OL) with a quinone structure. OL was then used as a modifier, being blended with SM to prepare SM-based biomass (OLS) adhesives with good water resistance, which was found practically through its utilization in the production of plywood. The influence of the HP dosage and OL addition on plywood properties was examined. The changes in the lignin structure before and after oxidation were confirmed using gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The curing behavior and thermal stability of OLS adhesives were analyzed using dynamic mechanical analysis (DMA) and thermogravimetric (TG) analysis. The reaction mechanism was also investigated using FT-IR and XPS. The outcomes indicated a decrease in the molecular weight of L after oxidation using HP, and, at the same time, quinone and aldehyde functionalized structures were produced. As a result of the reaction between the quinone and aldehyde groups in OL with the amino groups in SM, a dense network structure formed, enhancing the water resistance of the adhesive significantly. The adhesive displayed exceptional resistance to water when the HP dosage was set at 10% of L and the OL addition was 10% based on the mass of SM. These specific conditions led to a notable enhancement in the wet bonding strength (63 °C, 3 h) of the plywood prepared using the adhesive, reaching 0.88 ± 0.14 MPa. This value represents a remarkable 125.6% increase when compared to the pure SM adhesive (0.39 ± 0.02 MPa). The findings from this study introduce a novel approach for developing adhesives that exhibit exceptional water resistance. Full article
28 pages, 1557 KiB  
Article
The Impact of the Governance Fragmentation of Forestry Communities on the Economic Performance of State-Owned Forest Enterprises in Northeast China: An Empirical Analysis Based on the Transaction Cost Perspective
by Yuan Ji, Shenwei Wan and Shuifa Ke
Forests 2024, 15(6), 1035; https://doi.org/10.3390/f15061035 - 14 Jun 2024
Viewed by 181
Abstract
The 2015 reform of state-owned forest regions (SOFRs) in Northeast China required state-owned forest enterprises (SOFEs) to transfer their governmental and social roles to local authorities. This transition, however, created fragmented governance within forestry communities due to the absence of cooperative mechanisms between [...] Read more.
The 2015 reform of state-owned forest regions (SOFRs) in Northeast China required state-owned forest enterprises (SOFEs) to transfer their governmental and social roles to local authorities. This transition, however, created fragmented governance within forestry communities due to the absence of cooperative mechanisms between SOFEs and local governments. This study examines the economic effects of this governance fragmentation on SOFEs and explores the underlying mechanisms. The research combines new institutional economics and transaction cost theory to develop hypotheses and employs empirical analysis using fixed-effects models on data from 39 SOFEs, belonging to two forest industry groups from 2015 to 2022, collected through surveys and field investigations. The findings indicate that governance fragmentation has a significant negative impact on the economic performance of SOFEs. The high transaction costs incurred by SOFEs in achieving community co-governance with local governments are identified as a key mediating mechanism. These costs lead to resource dispersion and diminished trust between SOFEs and local governments. The economic impact of this governance fragmentation varies based on the economic conditions of the SOFEs, their operational scales, and the clarity of geographical management boundaries with local governments. To mitigate the adverse effects of governance fragmentation, the study suggests proactive institutional designs to reduce transaction costs. These findings offer new insights into the corporate social responsibilities of Chinese SOFEs and suggest improvements in the governance structures of forestry communities in SOFRs in Northeast China. Additionally, the study expands the application of transaction cost theory in public affairs governance and enhances quantitative research on the economic impact on enterprises. Full article
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14 pages, 1337 KiB  
Article
The Added Value of Urban Trees (Tilia tomentosa Moench, Fraxinus excelsior L. and Pinus nigra J.F. Arnold) in Terms of Air Pollutant Removal
by Slaveya Petrova
Forests 2024, 15(6), 1034; https://doi.org/10.3390/f15061034 - 14 Jun 2024
Viewed by 195
Abstract
The serious densification of human settlements necessitates an increase in the role and importance of green infrastructures in the overall functioning of urban ecosystems. Accordingly, the aim of the present study was to (1) assess the efficiency of air pollutant removal (potentially toxic [...] Read more.
The serious densification of human settlements necessitates an increase in the role and importance of green infrastructures in the overall functioning of urban ecosystems. Accordingly, the aim of the present study was to (1) assess the efficiency of air pollutant removal (potentially toxic elements) of three common ornamental trees (Tilia tomentosa Moench, Fraxinus excelsior L. and Pinus nigra J.F. Arnold) and (2) model the air quality regulatory services (removal of PM10, PM2.5 and NO2). Three different approaches were applied—enrichment factor (EF) and metal accumulation factor (MAI) per tree species, as well as simulation modeling for the whole urban forest. The MAI values of the three studied species were found to be very similar, in the range of 22.35 to 23.08, which suggests that these species could be a good choice for planting in urban areas with worsened air quality. The highest EF values were observed for U (3–18), followed by As (1.6–2.56) and Sr (0.87–2.46). The potential of urban forests in countering air pollution was highlighted by three simulated scenarios for PM10, PM2.5 and NO2 removal. The highest removal efficiency was calculated for evergreen species, followed by the mixed composition of deciduous (90%) and evergreen trees (10%), and the scenario with wholly deciduous trees had the lowest one. The contribution of nature-based solutions in meeting air quality standards and enhancing resilience in urban areas was clearly demonstrated. The functional complementarity of the different functional tree groups (coniferous, evergreen and deciduous broad-leaved species) was proven to be crucial for the support of both functional stabilities of the phytocenosis under diverse climatic conditions and during the change of seasonal cycles in the vegetation. Full article
15 pages, 1133 KiB  
Article
Predicting the Potential Distribution of Quercus oxyphylla in China under Climate Change Scenarios
by Shuhan Chen, Chengming You, Zheng Zhang and Zhenfeng Xu
Forests 2024, 15(6), 1033; https://doi.org/10.3390/f15061033 - 14 Jun 2024
Viewed by 184
Abstract
Global climate changes are expected to profoundly shape species distribution. Quercus oxyphylla, a valuable evergreen broad-leaved tree species, is rigorously conserved and managed in China owing to its substantial scientific, economic, and ecological value. However, the impact of projected climate change on [...] Read more.
Global climate changes are expected to profoundly shape species distribution. Quercus oxyphylla, a valuable evergreen broad-leaved tree species, is rigorously conserved and managed in China owing to its substantial scientific, economic, and ecological value. However, the impact of projected climate change on its future distribution and potential climatic drivers remains unclear. Here, a maximum entropy model (MaxEnt) was used to explore the distribution of Q. oxyphylla in China under current conditions and three future scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) for the 2050s and 2070s. We optimized the model using the ‘ENMeval’ package to obtain the best parameter combination (RM = 1, FC = LQHPT), and multiple evaluation metrics (AUC ≥ 0.9; TSS ≥ 0.6; Kappa ≥ 0.75) verified the high accuracy of the model and the reliability of the prediction results. We found the following: (1) The potential distribution of Q. oxyphylla spans across 28 provinces in China under current climatic conditions, predominantly in southern regions, with Sichuan exhibiting the largest suitable area for survival. The total suitable habitat covers 244.98 × 104 km2, comprising highly, moderately, and poorly suitable habitats of 51.66 × 104 km2, 65.98 × 104 km2, and 127.34 × 104 km2, respectively. (2) Under future climate conditions, the overall geographical boundaries of Q. oxyphylla are predicted to remain similar to the present one, with an increase of 10.29% in the 2050s and 11.31% in the 2070s. In the 2050s, the total suitable habitats for Q. oxyphylla under the three scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) might increase by 8.83%, 9.62%, and 12.42%, while in the 2070s they might increase by 10.39%, 17.21%, and 6.33%, respectively. (3) Moreover, the centroid of the suitable area is expected to migrate southwestward under the three scenarios in the future. (4) Annual precipitation, isothermality, and temperature annual range emerged as the main factors influencing the distribution of Q. oxyphylla, with contributions of 55.9%, 25.7%, and 13.5%, respectively. Our findings refined the spatial arrangement of Q. oxyphylla growth and revealed its climate resilience. This suggested that under climate change, Sichuan and Shaanxi are the optimal regions for cultivation and management, while appropriate conservation strategies should be formulated in Tibet and Hubei. Full article
(This article belongs to the Section Forest Meteorology and Climate Change)
16 pages, 7810 KiB  
Article
Topographic Variation in Ecosystem Multifunctionality in an Old-Growth Subtropical Forest
by Jiaming Wang, Han Xu, Qingsong Yang, Yuying Li, Mingfei Ji, Yepu Li, Zhongbing Chang, Yangyi Qin, Qiushi Yu and Xihua Wang
Forests 2024, 15(6), 1032; https://doi.org/10.3390/f15061032 - 14 Jun 2024
Viewed by 212
Abstract
Exploring the relationship between topography and forest multifunctionality enhances understanding of the mechanisms maintaining forest multifunctionality and proves beneficial for managing overall forest functions across different landscapes. Leveraging census data from a 20 ha subtropical forest plot, we investigated the topographic variations in [...] Read more.
Exploring the relationship between topography and forest multifunctionality enhances understanding of the mechanisms maintaining forest multifunctionality and proves beneficial for managing overall forest functions across different landscapes. Leveraging census data from a 20 ha subtropical forest plot, we investigated the topographic variations in individual functions, multifunctionality, and their interrelationships. Our results revealed that relative to lower elevations, higher elevations had higher woody productivity, sapling growth, and recruitment that drove higher average forest multifunctionality (FMA). However, forest multifunctionality at the 50% threshold level (FMt50) had no significant difference between high and low elevations. Compared with the valley and slope, higher woody productivity, higher sapling recruitment, and higher soil organic carbon stock drove higher forest multifunctionality (FMA and FMt50) in the ridge. These results indicate the ridge serves as a forest multifunctionality “hotspot” within the Tiantong 20 hm2 plot. Additionally, relative to the low elevation, the degree of synergy among functions at the high elevation was significantly lower, indicating difficulties in attaining high forest multifunctionality at the high elevation. Our work underscores the importance of topography in regulating subtropical forest multifunctionality and relationships between forest functions at a local scale, suggesting that future forest management strategies (such as regulating synergistic or trade-off relationships between functions) should give particular attention to topographic conditions. Full article
(This article belongs to the Special Issue Modeling and Remote Sensing of Forests Ecosystem)
17 pages, 13656 KiB  
Article
A Reliable DBH Estimation Method Using Terrestrial LiDAR Points through Polar Coordinate Transformation and Progressive Outlier Removal
by Zhenyang Hui, Lei Lin, Shuanggen Jin, Yuanping Xia and Yao Yevenyo Ziggah
Forests 2024, 15(6), 1031; https://doi.org/10.3390/f15061031 - 13 Jun 2024
Viewed by 334
Abstract
Diameter at breast height (DBH) is a crucial parameter for forest inventory. However, accurately estimating DBH remains challenging due to the noisy and incomplete cross-sectional points. To address this, this paper proposed a reliable DBH estimation method using terrestrial LiDAR points through polar [...] Read more.
Diameter at breast height (DBH) is a crucial parameter for forest inventory. However, accurately estimating DBH remains challenging due to the noisy and incomplete cross-sectional points. To address this, this paper proposed a reliable DBH estimation method using terrestrial LiDAR points through polar coordinate transformation and progressive outlier removal. In this paper, the initial center was initially detected by rasterizing the convex hull, and then the Cartesian coordinates were transformed into polar coordinates. In the polar coordinate system, the outliers were classified as low and high outliers according to the distribution of polar radius difference. Both types of outliers were then removed using adaptive thresholds and the moving least squares algorithm. Finally, DBH was estimated by calculating the definite integral of arc length in the polar coordinate system. Twenty publicly available individual trees were adopted for the test. Experimental results indicated that the proposed method performs better than the other four classical DBH estimation methods. Furthermore, several extreme cases scanned using terrestrial LiDAR in practice, such as cross-sectional points with lots of outliers or larger data gaps, were also tested. Experimental results demonstrate that the proposed method accurately calculates DBH even in these challenging cases. Full article
(This article belongs to the Special Issue LiDAR Remote Sensing for Forestry)
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18 pages, 7131 KiB  
Article
Forest Fire Image Deblurring Based on Spatial–Frequency Domain Fusion
by Xueyi Kong, Yunfei Liu, Ruipeng Han, Shuang Li and Han Liu
Forests 2024, 15(6), 1030; https://doi.org/10.3390/f15061030 - 13 Jun 2024
Viewed by 243
Abstract
UAVs are commonly used in forest fire detection, but the captured fire images often suffer from blurring due to the rapid motion between the airborne camera and the fire target. In this study, a multi-input, multi-output U-Net architecture that combines spatial domain and [...] Read more.
UAVs are commonly used in forest fire detection, but the captured fire images often suffer from blurring due to the rapid motion between the airborne camera and the fire target. In this study, a multi-input, multi-output U-Net architecture that combines spatial domain and frequency domain information is proposed for image deblurring. The architecture includes a multi-branch dilated convolution attention residual module in the encoder to enhance receptive fields and address local features and texture detail limitations. A feature-fusion module integrating spatial frequency domains is also included in the skip connection structure to reduce feature loss and enhance deblurring performance. Additionally, a multi-channel convolution attention residual module in the decoders improves the reconstruction of local and contextual information. A weighted loss function is utilized to enhance network stability and generalization. Experimental results demonstrate that the proposed model outperforms popular models in terms of subjective perception and quantitative evaluation, achieving a PSNR of 32.26 dB, SSIM of 0.955, LGF of 10.93, and SMD of 34.31 on the self-built forest fire datasets and reaching 86% of the optimal PSNR and 87% of the optimal SSIM. In experiments without reference images, the model performs well in terms of LGF and SMD. The results obtained by this model are superior to the currently popular SRN and MPRNet models. Full article
(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)
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15 pages, 1065 KiB  
Article
Converting Low-Productivity Pasture to Well-Managed Pasture and Silvopastoral System Cause Relevant Changes in Soil Chemical and Microbiological Characteristics
by Libério Junio da Silva, Igor Costa de Freitas, Luiz Henrique Gomes de Abreu, Dener Márcio da Silva Oliveira, Demerson Luiz de Almeida Barbosa, Cléber Cunha Figueredo, Vagner Luis Camilotti, Marcus Vinícius Teixeira and Leidivan Almeida Frazão
Forests 2024, 15(6), 1029; https://doi.org/10.3390/f15061029 - 13 Jun 2024
Viewed by 212
Abstract
This study evaluated the chemical and microbiological soil attributes in a silvopastoral system compared to well-managed pasture, degraded pasture, and Cerrado vegetation in Brazil. A randomized design with four replications was employed to collect soil samples at seven depths. These samples were analyzed [...] Read more.
This study evaluated the chemical and microbiological soil attributes in a silvopastoral system compared to well-managed pasture, degraded pasture, and Cerrado vegetation in Brazil. A randomized design with four replications was employed to collect soil samples at seven depths. These samples were analyzed for carbon (C), nitrogen (N), pH, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and cation exchange capacity (CEC). Soil microbial attributes were also evaluated at three depths during the dry and wet seasons. Carbon stocks in the evaluated systems varied (0–100 cm), with the highest stocks found in well-managed pasture (MP) (129.5 Mg C ha−1), followed by the silvopastoral system (SPS) (106.6 Mg C ha−1), and the lowest values in native vegetation (NV) (84.8 Mg C ha−1) and degraded pasture (DP) (63.4 Mg C ha−1). Higher pH and base sum were observed in MP. Soil microbial biomass (Cmic) did not differ between treatments during the wet season but was generally higher in MP and lower in DP during the dry season. MP effectively regulated the chemical and biological quality of the soil. The SPS demonstrated that it is possible to combine the cultivation of trees and pastures in the same area, contributing to the improvement of the chemical and biological attributes of the soil in the Brazilian Cerrado. Full article
21 pages, 2833 KiB  
Article
Optimizing Hardwood Lignin Precipitation from Kraft Black Liquor: A Study of Temperature and pH Effects
by Richard Nadányi, Grigory Zinovyev, Matúš Majerčiak, Martin Štosel, Michal Jablonský and Aleš Ház
Forests 2024, 15(6), 1028; https://doi.org/10.3390/f15061028 - 13 Jun 2024
Viewed by 273
Abstract
Lignin, a complex and heterogeneous biopolymer derived from wood, holds immense potential as a sustainable feedstock for various industrial applications. Kraft pulping, a widely employed process in the paper industry, generates black liquor containing lignin along with other organic and inorganic compounds. The [...] Read more.
Lignin, a complex and heterogeneous biopolymer derived from wood, holds immense potential as a sustainable feedstock for various industrial applications. Kraft pulping, a widely employed process in the paper industry, generates black liquor containing lignin along with other organic and inorganic compounds. The precipitation of lignin from black liquor offers an opportunity for valorization, contributing to the circular economy and reducing the environmental impact. Although the precipitation process of softwood lignin is extensively documented and outlined in the existing literature, the identical process originating from hardwood-derived black liquor poses challenges attributed to the distinct composition of hardwood. This study systematically investigates the individual and combined influences of temperature and pH on the precipitation of hardwood lignin from kraft black liquor, utilizing a factorial design to evaluate lignin functional characteristics. The characterization of the precipitated lignin was performed using various analytical techniques, mainly NIR, elemental composition, UV-VIS, and calorimetry. The results reveal remarkable interactions between temperature and pH, indicating their synergistic effects on lignin precipitation. The optimal conditions for hardwood lignin precipitation were identified and successfully upscaled during piloting experiments conducted under industrial conditions. This research provides valuable insights into the fundamental factors governing hardwood lignin precipitation from kraft black liquor and offers a basis for the development of efficient and sustainable lignin recovery processes in the pulp and paper industry. Full article
(This article belongs to the Section Wood Science and Forest Products)
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15 pages, 7917 KiB  
Article
Influence of Early-Season Drought on the Peak of Growing Season in China Varies by Drought Timing and Biomes
by Zexing Tao, Junhu Dai, Xiaoyue Wang and Yuan Wang
Forests 2024, 15(6), 1027; https://doi.org/10.3390/f15061027 - 13 Jun 2024
Viewed by 295
Abstract
The peak of growing season (POG) represents the timing of the maximum capacity of vegetation photosynthesis and acts as a crucial phenological indicator for the carbon cycle in terrestrial ecosystems. However, little is known about how POG responds to extreme climate events such [...] Read more.
The peak of growing season (POG) represents the timing of the maximum capacity of vegetation photosynthesis and acts as a crucial phenological indicator for the carbon cycle in terrestrial ecosystems. However, little is known about how POG responds to extreme climate events such as drought across different biomes. Based on two drought indices, we analyzed the temporal–spatial pattern of drought and POG in China and then investigated how drought influenced the POG in different periods of the early season through correlation analysis. In general, a trend towards increased aridity and earlier POG was found in most areas. The impact of drought on POG differed among periods. On the one hand, an earlier POG enabled plants to reduce evapotranspiration and mitigate the risk of severe summer drought. On the other hand, the drought that occurred in spring impeded plant growth and caused a delay in spring phenology, thereby postponing POG. Summer drought led to an earlier POG in relatively dry biomes but inversely led to a later peak in photosynthetic activity in wetter biomes. We also observed a 1-month/2-month lagged effect of drought on POG in almost half of the areas and a 2-month/ 3-month cumulative effect of drought in the north of 50° N. These findings enhance our understanding of carbon uptake in terrestrial ecosystems by clarifying the mechanisms by which climate change impacts vegetation growth and photosynthetic activity. Full article
(This article belongs to the Special Issue Woody Plant Phenology in a Changing Climate)
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