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17 pages, 6535 KB

Open AccessArticle

Biomimetic Assessment of 3D-Printed T-Shape Joints Bio-Inspired by the Stem-Branch Junction in Common Ash (Fraxinus excelsior L.) Trees

by Rastislav Lagaňa, Roman Nôta, Zuzana Tončíková, Tomáš Holeček, Nadežda Langová and Jaroslav Ďurkovič

Biomimetics 2026, 11(1), 15; https://doi.org/10.3390/biomimetics11010015 - 28 Dec 2025

Viewed by 425

Abstract

The stem–branch junction in trees demonstrates exceptional structural design. This study examined two key features of the branch junction in common ash (Fraxinus excelsior L.) wood: the interlocked area (ILA) formed above a knot and the spatial arrangement of fibers in the [...] Read more.

The stem–branch junction in trees demonstrates exceptional structural design. This study examined two key features of the branch junction in common ash (Fraxinus excelsior L.) wood: the interlocked area (ILA) formed above a knot and the spatial arrangement of fibers in the junction. Bio-inspired by the microstructural features revealed by micro-computed tomography imaging, we developed 3D-printed models and compared their mechanical performance to standard symmetrical T-joints. We evaluated the models using mechanical tests and finite element modeling (FEM). Asymmetrical 3D-printed joints mimicking vessel and fiber distribution in the stem–branch junction were 2% stiffer in the elastic region than symmetrical joints and showed, on average, 10% lower deflection at failure. While the ILA had minimal effect on elastic stiffness, measured surface strain analysis indicated that it positively influenced the redistribution of shear strain in the junctions. Thanks to the bio-inspired design, the joints were stiffer and can be utilized in multiple design configurations while maintaining the same underlying principle. Full article

(This article belongs to the Section Biomimetics of Materials and Structures)

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20 pages, 4127 KB

Open AccessArticle

Comparative Analysis of Machine Learning and Deep Learning Models for Individual Tree Structure Segmentation Using Terrestrial LiDAR Point Cloud Data

by Sangjin Lee, Woodam Sim, Yongkyu Lee, Jeongmook Park, Jintaek Kang and Jungsoo Lee

Remote Sens. 2025, 17(13), 2245; https://doi.org/10.3390/rs17132245 - 30 Jun 2025

Viewed by 2702

Abstract

This study aims to segment individual tree structures (stem, crown, and ground) from terrestrial LiDAR-derived point cloud data (PCD) and to compare the segmentation accuracy between two models: XGBoost (machine learning) and PointNet++ (deep learning). A total of 17 input features were categorized [...] Read more.

This study aims to segment individual tree structures (stem, crown, and ground) from terrestrial LiDAR-derived point cloud data (PCD) and to compare the segmentation accuracy between two models: XGBoost (machine learning) and PointNet++ (deep learning). A total of 17 input features were categorized into spatial coordinates and normals, geometric structure features, and local distribution features. These were combined into four input configurations and evaluated under three downsampling conditions (2048, 4096, and 8192 points), resulting in 12 experimental setups. XGBoost achieved the highest stem segmentation F₁-score of 87.8% using all features with 8192 points, whereas Point-Net++ reached 92.1% using only spatial coordinates and normals with 4096 points. The analysis of missegmentation patterns showed that XGBoost frequently confused structures near stem-to-ground boundaries and around branch junctions, while PointNet++ occasionally missegmented complex regions between stems and crowns. Regarding processing time, XGBoost required 10 to 47 min across all conditions, whereas Point-Net++ required 49 min for the 2048-point condition and up to 168 min for 8192 points. Overall, XGBoost provided advantages in computational efficiency and in generating feature-importance scores, while PointNet++ outperformed XGBoost in segmentation accuracy and the recognition of structurally complex regions. Full article

(This article belongs to the Special Issue Remote Sensing for Digital Twins in Forestry: Applications and Future Perspectives)

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17 pages, 5174 KB

Open AccessArticle

Mechanical Properties and Optimization Strategies of Tree Fork Structures

by Yi-Sen Peng, Bai-You Cheng and Tung-Chi Liu

Plants 2025, 14(2), 167; https://doi.org/10.3390/plants14020167 - 9 Jan 2025

Cited by 2 | Viewed by 1929

Abstract

Trees are complex and dynamic living structures, where structural stability is essential for survival and for public safety in urban environments. Tree forks, as structural junctions, are key to tree integrity but are prone to failure under stress. The specific mechanical contributions of [...] Read more.

Trees are complex and dynamic living structures, where structural stability is essential for survival and for public safety in urban environments. Tree forks, as structural junctions, are key to tree integrity but are prone to failure under stress. The specific mechanical contributions of their internal conical structures remain largely unexplored. This study explores how conical structures optimize stress distribution, filling key gaps in the understanding of tree fork mechanics and supporting safety assessments. This study focused on the following factors: (1) external shape, (2) internal conical reinforcement, (3) interface of the conical connection, and (4) material changes within the conical structure. By analyzing physical samples to extract structural and morphological features, simulating these features in controlled variable models, and performing finite element analysis, we explored mechanical behavior, stress distribution, and performance characteristics, revealing the factors and mechanisms that strengthen tree forks. Insights from this study may facilitate safety assessments and inform pruning strategies for urban tree management. Full article

(This article belongs to the Special Issue Development of Woody Plants)

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15 pages, 5903 KB

Open AccessArticle

Leaf Pruning End-Effector for Adaptive Positioning at the Branch–Stem Junction of Tomato Plants

by Yuhuan Sun, Wenqiao Lu, Qingchun Feng, Liang He, Hongda Diao, Yuhang Ma and Liping Chen

Agriculture 2024, 14(12), 2281; https://doi.org/10.3390/agriculture14122281 - 12 Dec 2024

Cited by 3 | Viewed by 2080

Abstract

To address the needs of mechanized tomato leaf pruning, this paper presents the design of an end-effector capable of adaptive positioning at the base of the branch. This design effectively prevents infection at the cut sites of a residual branch and protects the [...] Read more.

To address the needs of mechanized tomato leaf pruning, this paper presents the design of an end-effector capable of adaptive positioning at the base of the branch. This design effectively prevents infection at the cut sites of a residual branch and protects the rest of the plant from damage. The design objectives for the pruning actuator were established through the measurement of key parameters related to the morphology and mechanical properties of the lateral branch. Based on this foundation, we developed an innovative gripper featuring a spiral guide groove, enabling simultaneous axial traction and radial cutting of the branch. This design ensures that the branch–stem junction conforms to the cutting blade under shear stress, achieving the required adaptive positioning. By analyzing the mechanical properties of the lateral branch, we modeled the actuator’s traction and cutting forces to determine the key geometric parameters of the spiral fingers and the necessary driving torque. We validated the actuator’s operational effectiveness through discrete element simulation and practical application tests. The experimental results indicate that when removing the branch, a traction force of 32.5 N and a cutting force of 66.3 N are generated. Harvesting effectiveness tests conducted in the tomato field achieved a success rate of 85%. This research offers technical support for the development of handheld pruning devices and pruning robots. Full article

(This article belongs to the Section Agricultural Technology)

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16 pages, 4654 KB

Open AccessEditor’s ChoiceArticle

Fibrin-Based Hydrogels with Reactive Amphiphilic Copolymers for Mechanical Adjustments Allow for Capillary Formation in 2D and 3D Environments

by Svenja Wein, Carina Schemmer, Miriam Aischa Al Enezy-Ulbrich, Shannon Anna Jung, Stephan Rütten, Mark Kühnel, Danny Jonigk, Wilhelm Jahnen-Dechent, Andrij Pich and Sabine Neuss

Gels 2024, 10(3), 182; https://doi.org/10.3390/gels10030182 - 6 Mar 2024

Cited by 7 | Viewed by 5077

Abstract

This study focuses on enhancing controllable fibrin-based hydrogels for tissue engineering, addressing existing weaknesses. By integrating a novel copolymer, we improved the foundation for cell-based angiogenesis with adaptable structural features. Tissue engineering often faces challenges like waste disposal and nutrient supply beyond the [...] Read more.

This study focuses on enhancing controllable fibrin-based hydrogels for tissue engineering, addressing existing weaknesses. By integrating a novel copolymer, we improved the foundation for cell-based angiogenesis with adaptable structural features. Tissue engineering often faces challenges like waste disposal and nutrient supply beyond the 200 µm diffusion limit. Angiogenesis breaks through this limitation, allowing the construction of larger constructs. Our innovative scaffold combination significantly boosts angiogenesis, resulting in longer branches and more capillary network junctions. The copolymer attached to fibrin fibers enables precise adjustment of hydrogel mechanical dynamic properties for specific applications. Our material proves effective for angiogenesis, even under suppression factors like suramin. In our study, we prepared fibrin-based hydrogels with and without the copolymer PVP12400-co-GMA10mol%. Using a co-culture system of human umbilical vein endothelial cells (HUVEC) and mesenchymal stem cells (MSC), we analyzed angiogenetic behavior on and within the modified hydrogels. Capillary-like structures were reproducibly formed on different surfaces, demonstrating the general feasibility of three-dimensional endothelial cell networks in fibrin-based hydrogels. This highlights the biomaterial’s suitability for in vitro pre-vascularization of biohybrid implants. Full article

(This article belongs to the Special Issue Biopolymer-Based Gels for Drug Delivery and Tissue Engineering)

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14 pages, 6682 KB

Open AccessArticle

Physiological and Physical Strategies to Minimize Damage at the Branch–Stem Junction of Trees: Using the Finite Element Method to Analyze Stress in Four Branch–Stem Features

by Tung-Chi Liu, Yi-Sen Peng and Bai-You Cheng

Plants 2023, 12(23), 4060; https://doi.org/10.3390/plants12234060 - 3 Dec 2023

Cited by 2 | Viewed by 3094

Abstract

This study analyzed the mechanical and physiological strategies associated with four features in the branch–stem junction of a tree, namely the U-shaped branch attachment, the branch collar, the branch bark ridge, and the roughened lower stem. Models were established for each stage of [...] Read more.

This study analyzed the mechanical and physiological strategies associated with four features in the branch–stem junction of a tree, namely the U-shaped branch attachment, the branch collar, the branch bark ridge, and the roughened lower stem. Models were established for each stage of tree growth by adding these four features sequentially to a base model, and the finite element method (FEM) was employed to create three-dimensional models of an Acer tree’s branch–stem structure for static force analysis. According to the results, the development of the branch collar shifted the point of breakage to the outer part of the collar and, thus, constituted a physiological strategy that prevented decay in the stem. Additionally, the concentration of stress in the branch bark ridge limited the area of tear in the bark following breakage. Finally, the U-shaped branch attachment reduced stress and shifted the point of peak stress toward the branch, while the thickening of the lower stem reduced the overall stress. The development of these features, including the spatial positioning of the branch bark ridge and branch collar, resulted in two breakage points constituting a physical and a physiological strategy that limited damage to the tree and protected the xylem structure. This is the part that has been challenging to decipher in previous discussions of tree-related self-protection mechanisms. Full article

(This article belongs to the Special Issue In Vitro Morphogenesis of Plants)

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25 pages, 10495 KB

Open AccessArticle

Conjoining Trees for the Provision of Living Architecture in Future Cities: A Long-Term Inosculation Study

by Max D. Mylo, Ferdinand Ludwig, Mohammad A. Rahman, Qiguan Shu, Christoph Fleckenstein, Thomas Speck and Olga Speck

Plants 2023, 12(6), 1385; https://doi.org/10.3390/plants12061385 - 20 Mar 2023

Cited by 8 | Viewed by 6282

Abstract

Faced with the environmental challenges posed by climate change, architects are creating nature-based solutions for urban areas, such as transforming living trees into artificial architectural structures. In this study, we have analyzed stem pairs of five tree species conjoined for more than eight [...] Read more.

Faced with the environmental challenges posed by climate change, architects are creating nature-based solutions for urban areas, such as transforming living trees into artificial architectural structures. In this study, we have analyzed stem pairs of five tree species conjoined for more than eight years by measuring the stem diameters below and above the resulting inosculation and by calculating the respective diameter ratio. Our statistical analyses reveal that Platanus × hispanica and Salix alba stems do not differ significantly in diameter below inosculation. However, in contrast to P. × hispanica, the diameters of the conjoined stems above inosculation differ significantly in S. alba. We provide a binary decision tree based on diameter comparisons above and below inosculation as a straightforward tool for identifying the likelihood of full inosculation with water exchange. Moreover, we have compared branch junctions and inosculations by means of anatomical analyses, micro-computed tomography, and 3D reconstructions showing similarities in the formation of common annual rings that increase the capacity for water exchange. Due to the highly irregular cell arrangement in the center of the inosculations, cells cannot be assigned clearly to either of the stems. In contrast, cells in the center of branch junctions can always be attributed to one of the branches. Full article

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18 pages, 3376 KB

Open AccessArticle

Classification of Handheld Laser Scanning Tree Point Cloud Based on Different KNN Algorithms and Random Forest Algorithm

by Wenshu Lin, Weiwei Fan, Haoran Liu, Yongsheng Xu and Jinzhuo Wu

Forests 2021, 12(3), 292; https://doi.org/10.3390/f12030292 - 3 Mar 2021

Cited by 33 | Viewed by 3687

Abstract

Handheld mobile laser scanning (HMLS) can quickly acquire point cloud data, and has the potential to conduct forest inventory at the plot scale. Considering the problems associated with HMLS data such as large discreteness and difficulty in classification, different classification models were compared [...] Read more.

Handheld mobile laser scanning (HMLS) can quickly acquire point cloud data, and has the potential to conduct forest inventory at the plot scale. Considering the problems associated with HMLS data such as large discreteness and difficulty in classification, different classification models were compared in order to realize efficient separation of stem, branch and leaf points from HMLS data. First, the HMLS point cloud was normalized and ground points were removed, then the neighboring points were identified according to three KNN algorithms and eight geometric features were constructed. On this basis, the random forest classifier was used to calculate feature importance and perform dataset training. Finally, the classification accuracy of different KNN algorithms-based models was evaluated. Results showed that the training sample classification accuracy based on the adaptive radius KNN algorithm was the highest (0.9659) among the three KNN algorithms, but its feature calculation time was also longer; The validation accuracy of two test sets was 0.9596 and 0.9201, respectively, which is acceptable, and the misclassification mainly occurred in the branch junction of the canopy. Therefore, the optimal classification model can effectively achieve the classification of stem, branch and leaf points from HMLS point cloud under the premise of comprehensive training. Full article

(This article belongs to the Section Forest Inventory, Modeling and Remote Sensing)

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13 pages, 2335 KB

Open AccessArticle

Long-Lasting Insecticide Netting for Protecting Tree Stems from Attack by Ambrosia Beetles (Coleoptera: Curculionidae: Scolytinae)

by Christopher M. Ranger, Christopher T. Werle, Peter B. Schultz, Karla M. Addesso, Jason B. Oliver and Michael E. Reding

Insects 2020, 11(1), 8; https://doi.org/10.3390/insects11010008 - 20 Dec 2019

Cited by 15 | Viewed by 3565

Abstract

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are destructive wood-boring insects of horticultural trees. We evaluated long-lasting insecticide netting for protecting stems against ambrosia beetles. Container-grown eastern redbud, Cercis canadensis, trees were flood-stressed to induce ambrosia beetle attacks, and deltamethrin-treated netting was wrapped from [...] Read more.

Ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are destructive wood-boring insects of horticultural trees. We evaluated long-lasting insecticide netting for protecting stems against ambrosia beetles. Container-grown eastern redbud, Cercis canadensis, trees were flood-stressed to induce ambrosia beetle attacks, and deltamethrin-treated netting was wrapped from the base of the stem vertically to the branch junction. Trees were deployed under field conditions in Ohio, Virginia, Tennessee, and Mississippi with the following treatments: (1) flooded tree; (2) flooded tree with untreated netting; (3) flooded tree with treated ‘standard mesh’ netting of 24 holes/cm²; (4) flooded tree with treated ‘fine mesh’ netting of 28 holes/cm²; and/or (5) non-flooded tree. Treated netting reduced attacks compared to untreated netting and/or unprotected trees in Mississippi in 2017, Ohio and Tennessee in 2018, and Virginia in 2017–2018. Inconsistent effects occurred in Mississippi in 2018. Fewer Anisandrus maiche, Xylosandrus germanus, and Xyleborinus saxesenii were dissected from trees deployed in Ohio protected with treated netting compared to untreated netting; trees deployed in other locations were not dissected. These results indicate long-lasting insecticide netting can provide some protection of trees from ambrosia beetle attacks. Full article

(This article belongs to the Collection Integrated Pest Management Strategies for Horticultural Crops)

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