Search Results (8)

Researchers build growth models to predict the growth of forest stands and propose management measures to improve the overall quality of these stands. In this study, data collected from 91 sample plots from the eighth (2010) and ninth (2015) Chinese National Forest Inventories in Jiangxi Province were used to establish a transition-matrix growth model. Then, 12 potential equilibrium curves were set to guide forest management, and a transition-matrix growth model was used to predict stand growth in Jiangxi Province. In each 10-year management period, trees with diameters that exceeded the equilibrium curve were cut down. The results show that species diversity (H₁), size diversity (H₂), and basal area (B) have statistically significant influences on growth, mortality, and recruitment. Moreover, the high accuracy of the transition-matrix growth model is demonstrated. According to the simulation results, B = 35 m²/ha, the maximum diameter of retained trees D_max = 45 cm and the adjacent diameter ratio q = 1.7 constitute the optimal equilibrium curve to guide forest management. The diameter distribution guided by the equilibrium curve is reverse J-shaped and is associated with significant increases in the hardwood stock volume and current annual growth. Under the guidance of the equilibrium curve, the forests in Jiangxi Province can be reasonably managed, produce more high-economic-value timber, and achieve a more stable species composition. This study will help maximize the ecological and economic benefits of forests and provide a reference for the realization of the sustainable development of forestry. Furthermore, the results can be used to improve the facility and accuracy of natural forest harvesting. Full article

Teak (Tectona grandis) is a deciduous tree producing a popular, expensive, fancy timber with versatile utilization. The teak population and its habitats in the natural forest have been decreasing consistently; thus, the IUCN Red List classifies it as an endangered species. Teak tree logging from its native natural forest is banned, and commercial teak timber can only be harvested from the plantation. People plant teak on their private lands or in the community forest to meet the increasing demand. This study analyzed the annual tree rings of a teak disk taken from the community plantation and aimed to determine its biological rotation age. Tree ring interpretation provides the increment and growth that are mandatory fundamental components of knowledge in sustainable forest management. It may also decipher the tree’s biography, which contains information about past climate and future predictions responding to climate change. All of the disk’s annual tree rings were digitized, transformed, and then curve-fitted using an elliptical polar form of non-linear regression. The best-fitted curve estimation of every annual tree ring was employed to determine their age-related diameter and basal area, and then allometric equations estimated the above-ground biomass and clear-bole volume. The continuous and discrete formula fit the growth curve well, and this study determined that Chapman-Richards is the best fit among others. The growth curve, current annual increment (CAI), and mean annual increment (MAI) were graphed based on the clear-bole volume, above-ground biomass, and log timber price. The CAI and MAI intersections result in 28, 30, and 86 years of optimum harvesting periods when the growth calculation is based on volume, above-ground biomass, and log timber price, respectively. These results identified that the teak plantation is a sustainable and highly valuable asset to inherit with long-term positive benefits. The sociocultural provision of teak plants as an inheritance gift for the next generation has proven to be economically and ecologically beneficial. Full article

Growth and increment are extremely important in sustainable forest management, and in forest inventory they are periodically measured in a permanent sampling unit. The age of a tree is often unknown, especially in natural, community, and urban forests; therefore, determining growth and increment can be problematic. The aim of this study was to propose a solution for this problem by conducting annual tree-ring curve-fitting to determine a tree’s age-related dimension so that growth and increment can then be calculated smoothly. Sungkai (Peronema canescens), a luxurious commercial timber chosen as a case study, resulted in a satisfying growth curve following continuous models (Gompertz, Chapman–Richards, and von Bertalanffy) and discrete models (Bahtiar and Darwis exponential modification). The Chapman–Richards model gave the best-fit sigmoid growth curve. The first derivation (dN/dt) of the growth formula produces the current annual increment (CAI). CAI intersection with mean annual increment (MAI) at the peak of MAI resulted in the optimum biological rotation age and a cutting cycle period of 30 years for the Sungkai plantation commonly planted in urban forests. Full article

The beam stability factor (C_L) is applied in construction practices to adjust the reference bending design value (F_b) of sawn lumber to consider the lateral-torsional buckling. Bending tests were carried out on 272 specimens of four wood species, namely, red meranti (Shorea sp.), mahogany (Swietenia sp.), pine (Pinus sp.), and agathis (Agathis sp.), to analyze a simply supported beam subjected to concentrated loads at several points. The empirical C_L value is a ratio of the modulus of rupture (S_R) of a specimen to the average S_R of the standard-size specimens. The non-linear regression estimated the Euler buckling coefficient for sawn lumber beam (K_bE) in this study as 0.413, with 5% lower and 5% upper values of 0.338 and 0.488. Applying the 2.74 factor, which represents an approximately 5% lower exclusion value on the pure bending modulus of elasticity (E_min) and a factor of safety, the adjusted Euler buckling coefficient (K_bE′) value for a timber beam was 1.13 (0.92–1.34), which is within the range approved by the NDS (K_bE′ = 1.20). This study harmonizes the NDS design practices of C_L computation with the empirical results. Because agathis has the lowest ductility (μ), most natural defects (smallest strength ratio, S), and highest E/S_R ratio, the agathis beam did not twist during the bending test; instead, it failed before twisting could occur, indicating inelastic material failure. Meanwhile the other specimens (pinus, mahogany, and red meranti), which have smaller E/S_R ratio, higher ductility, and less natural defects, tended to fail because of lesser beam stability. This phenomenon resulted in the C_L curve of agathis being the highest among the others. The C_L value is mathematically related to the beam slenderness ratio (R_B) and the E/S_R ratio. Because the strength ratio (S) and ductility ratio (μ) have significant inverse correlations with the E/S_R ratio, they are correlated with the C_L value. Applying the C_L value to adjust the characteristic bending strength is safe and reliable, as less than 5% of the specimens’ S_R data points lie below the curve of the adjusted characteristics values. Full article

The burgeoning human population exhibited a rapid amplification in demand for timber and fuelwood and as a result, the natural population of the native tree Tecomella undulata reduced rapidly due to its high economic and medicinal significance. The recognition of appropriate regions for threatened plants in the climate change scenario is a fundamental step for the restoration and conservation of biodiversity. The current study predicts the potentially suitable areas in Pakistan for T. undulata restoration. This research identifies the highly appropriate regions for vulnerable T. undulata through the maximum entropy model from MaxEnt software. The model’s Area Under Curve 0.968 suggested its accuracy. The mean temperature of the wettest quarter, precipitation of the warmest quarter, and mean temperature in the driest quarter significantly shaped the T. undulata distribution. Future suitable areas for T. undulata were made by using RCP (4.5 and 8.5) for the years 2050 and 2070 through 19 bioclimatic variables and 66 occurrence points. The current highly suitable area for T. undulata is approximately 135,749 km² (15.4%) while the unsuitable area identified is approximately 404,917 km² (45.91%). The highly suitable area for T. undulata increases by 3.6–7% under climate change regimes (RCP 4.5 and RCP 8.5). The Central Punjab (District Faisalabad, Nankana sahib, Jhang, Kasur, and Okara), Salt Range, Western Khayber Pakhtunkhwa (KPK), FATA area, Eastern Balochistan, and Thar and Tharparker in Sindh are the current appropriate habitats for T. undulata. Under all future climatic circumstances, the extremely appropriate area for T. undulata was anticipated to expand, whereas the unsuitable zones would all shrink. The research would be significant for the further development of T. undulata management and conservation techniques. Full article

This article presents the results of experimental research on the mechanical properties of pine wood (Pinus L. Sp. Pl. 1000. 1753). In the course of the research process, stress-strain curves were determined for cases of tensile, compression and shear of standardized shapes samples. The collected data set was used to determine several material constants such as: modulus of elasticity, shear modulus or yield point. The aim of the research was to determine the material properties necessary to develop the model used in the finite element analysis (FEM), which demonstrates the symmetrical nature of the stress distribution in the sample. This model will be used to analyze the process of grinding wood base materials in terms of the peak cutting force estimation and the tool geometry influence determination. The main purpose of the developed model will be to determine the maximum stress value necessary to estimate the destructive force for the tested wood sample. The tests were carried out for timber of around 8.74% and 19.9% moisture content (MC). Significant differences were found between the mechanical properties of wood depending on moisture content and the direction of the applied force depending on the arrangement of wood fibers. Unlike other studies in the literature, this one relates to all three stress states (tensile, compression and shear) in all significant directions (anatomical). To verify the usability of the determined mechanical parameters of wood, all three strength tests (tensile, compression and shear) were mapped in the FEM analysis. The accuracy of the model in determining the maximum destructive force of the material is equal to the average 8% (for tensile testing 14%, compression 2.5%, shear 6.5%), while the average coverage of the FEM characteristic with the results of the strength test in the field of elastic-plastic deformations with the adopted ±15% error overlap on average by about 77%. The analyses were performed in the ABAQUS/Standard 2020 program in the field of elastic-plastic deformations. Research with the use of numerical models after extension with a damage model will enable the design of energy-saving and durable grinding machines. Full article

Bamboo is emerging as a lightweight, versatile and renewable material that is projected to realise new methods of construction. There is a growing demand for using bamboo in different regions across the world. However, there are no specific design standards or guidelines that capitalise on the unique circular hollow cross section and internal nodal support of bamboo. Furthermore, there has been no strict analysis into how the curvature of bamboo members can help to better distribute stress through a structure. Bamboo is known as a more environmentally sustainable material than standard timber; however, due to the naturally occurring diaphragm nodal structure, it is less orthotropic in mechanical behaviour, with more out of plane stiffness than timber. To address this issue, this paper presents finite element analysis of three varying bamboo structures, each featuring a varying member curvature and lateral support system. In this paper, a preliminary set of design guidelines have been proposed for bamboo members, maximising the performance of its inherent mechanical properties. These guidelines propose the use of thick, low diameter bamboo members in axial loading and thin, high diameter members in flexural situations. Where available, the preliminary guidelines introduce the importance of curved bamboo members to uniformly distribute forces and crossing arched members to eliminate the need for lateral support systems, thereby reducing the total material required for construction. Finally, this report presents some novel consideration of the out-of-plane buckling of curved bamboo members–although for this purpose it does not consider the effect of the diaphragm components of bamboo, a source of future research and more comprehensive design guidelines. Full article

Various types of curved wooden have always been used in traditional Korean architecture. One component is a curvaceous column with varying thicknesses, and the others are curved beams or girders that are needed to support the roof and present diverse curvature. By examining the historical alteration of the parts and shapes of these curved members, it is possible to identify the sustainable aspects of Korean traditional architecture and infer the influence of the historical background on forming the sustainability of the architecture. To be specific, while the Goryeo Dynasty (10–14 C) showed an aesthetic summit of temple architecture in terms of extravagant curved wooden members precisely calculated and designed under the influence of Buddhism and aristocracy, the early Joseon Dynasty (15–16 C) presented restrained curve forms of wooden members with fewer materials and a faster process due to Neo-Confucianism, which emphasized austerity. After tremendous social crisis and two wars, the mid-Joseon Dynasty (17–18 C) showed creative indigenous houses with naturally curved timbers, minimizing the manufacturing process and maximizing the pragmatic functionality of the space under the influence of the wars and Silhak (the Realist School of Confucianism). In addition, the late Joseon Dynasty (19–20 C) presented office buildings with strengthened dynamic shapes of the naturally curved timbers as symbolic expression, which is an expanded concept beyond the functionality. In Korean traditional architecture, curved wood members have been used without interruption—although in varying degrees depending on social and economic situations—and have continued to be one of the characteristics of Korean architecture. Full article