One of the alternative sustainable and green construction materials to concrete is timber. Timber is of numerous varieties, and this acts as a barrier to the extent of its usage, especially in structural application. ...One of the alternative sustainable and green construction materials to concrete is timber. Timber is of numerous varieties, and this acts as a barrier to the extent of its usage, especially in structural application. Despite many researches on wood’s mechanical and physical properties, only a few are geared toward the structural application of wood. The present work investigated the mechanical properties of five timber species;Gmelina arborea, Tectona grandis (Teak), Terminalia superba (Afara), Ayin (Anogeissus leiocarpus), and Acacia (Robinia pseudoacacia), to determine their suitability for constructing long-span roof trusses. These are available in the South Western part of Nigeria. Their mechanical properties;bending strength, compressive strength, shear strength, tensile strength, Modulus of Elasticity (MOE), Modulus of Rupture (MOR), and density, were determined in the laboratory. The results obtained showed that all the timber types, except Terminalia superba (Afara), have higher values of mechanical properties than the values that are obtainable for classes of strength D30 to class D70 in the British Code of Practice. It means these species are of higher quality than the stipulated strength classes in the British code. The results also show that the order of relevance of the species for structural design (or work) is Acacia (Robinia pseudoacacia), Ayin (Anogeissus leiocarpus), Gmelina Arborea, and Tectona grandis (Teak). Terminalia superba (Afara) is not recommended for structural works.展开更多
As forests in neotropical regions,particularly in developing countries,are devastated,interventions to restore biodiversity and its ecological functions are needed.Rural producers have thus been encouraged to grow tre...As forests in neotropical regions,particularly in developing countries,are devastated,interventions to restore biodiversity and its ecological functions are needed.Rural producers have thus been encouraged to grow trees for wood production as an economic activity.The objective of this study was to quantify the increment of wood density of four forest species from different successional classes of a mixed system of restoration in a neotropical forest in Brazil.Tree discs were sampled at breast height and analyzed radially by X-ray densitometry to obtain apparent density and basic density.Three trees each of a species from the pioneer,early and late secondary successional stages and of the dominant species in the climax community.The radial profiles indicated increasing density from the pith to bark of trunks,except for some variations due to wood defects and growth.Average density was 0.576 g cm^(-3),0.655 g cm^(-3),0.706 g cm^(-3)and 0.775 g cm^(-3),respectively,for Peltophorum dubium,Schinus terebinthifolius,Cariniana estrellensis and Hymenaea courbaril.Radial profiles indicated higher amplitudes in the apparent densities for slow-growing species.X-ray densitometry generated parameters such as minimum,average and maximum densities,and radial density variations.These parameters are important for understanding the ecological functional role of successional classes of the Atlantic Forest from the Neotropical region.展开更多
Assessment of forest recovery following disturbance is enhanced by the use of biological indicators. One such indicator, the abundance of understory species, was examined in coast redwood (Sequoia sempervirens) forest...Assessment of forest recovery following disturbance is enhanced by the use of biological indicators. One such indicator, the abundance of understory species, was examined in coast redwood (Sequoia sempervirens) forests using non-metric multiple dimensional scaling (NMDS) and indicator species analysis (ISA). Randomly distributed 10 m diameter circular plots were employed to record the abundance of all understory species across three treatments: actively managed (0 - 45 years since harvest);mature second-growth (~80 - 120 years since harvest);and unharvested old-growth stands. NMDS with perMANOVA analysis signified separation between treatments with the shade tolerant herbaceous species Trillium ovatum, Viola sempervirens, and Oxalis oregana positively correlated with mature second-growth and old-growth treatments. ISA supported the inclusion of T. ovatum, with the addition of Prosartes hookerii, as indicators of mature second-growth and old-growth. Both NMDS and ISA specified associations for Ceanothus thyrsiflorus and Stachys bullata with actively-managed stands. Occurrence of non-natives was low across treatments, though significantly higher on actively managed stands, with the shade intolerant invasive plants, Cortaderia sp. and Myosotis latifolia, occurring exclusively in actively-managed sites.展开更多
Gmelina arborea Roxb. (Melina), also known as white teak, is a tropical tree of great importance with multiple benefits. It is a timber species with renewal capacity and accelerated growth, highly durable and high qua...Gmelina arborea Roxb. (Melina), also known as white teak, is a tropical tree of great importance with multiple benefits. It is a timber species with renewal capacity and accelerated growth, highly durable and high quantity and quality pulp production, widely used in commercial programs of reforestation. In view of a possible increase of Melina areas in the state of Tabasco Mexico, information was needed in relation with the physical environment and natural factors in order to locate the most suitable areas under rainfed conditions. In this way, decision makers will be provided with a basic tool to direct and promote commercial plantations in the best suitable areas. The software Arc/View version 3.3 was used to process and analyze the information. The optimum agroclimatic requirements of Melina were identified and each variable factor was matched with those found at ground level. A cartographic mapping was carried out to regionalize and locate the optimal and suboptimal zones. It was determined that there are 191,532 ha of high potential and 542,573 ha of medium potential production areas of Melina in Tabasco, Mexico under rainfed conditions.展开更多
Timber forests contribute to the sustainable development of the biomes in tropical regions.The aim of this study was to evaluate the biological and chemical properties of the soil as a consequence of the cover with na...Timber forests contribute to the sustainable development of the biomes in tropical regions.The aim of this study was to evaluate the biological and chemical properties of the soil as a consequence of the cover with native and non-native species in the Acarau basin,a transition area from the coast to the Brazilian semi-arid region.Areas planted with four native species(Anadenanthera colubrina,Astronium fraxinifolium,Handroanthus impetiginosus,Colubrina glandulosa)and three exotic species(Acacia mangium,Casuarina equisetifolia,Eucalyptus urophylla)plus a non-forested agricultural area were evaluated for organic carbon contents,and microbial and chemical soil properties.The levels of soil organic carbon were highest in A.colubrina and C.equisetifolia plantations.Low basal soil respiration was observed but the microbial biomass was particularly low in the non-forested area.In the C.equisetifolia,E.urophylla,and H.impetiginosus plantations,elevated soil metabolic quotients were found.The A.colubrina and H.impetiginosus plantations had the highest levels of easily extracted-glomalin related soil protein.Tree species affect concentrations of essential nutrients and the biological quality of the soil in different ways.They can also improve the biological and chemical properties of the soil in the coastal plains of tropical regions.展开更多
A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east ...A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east Cameroon, was conducted between the months of July and September, 2007 to evaluate their suitability for the site. Twenty-two percent sampling intensity was conducted within annual allowable cuts and diameter readings taken on standing trees with the aid of a wide band Relascope. A non linear regression equation model was employed to compute volume equations and the student＇s t-test for the analysis of the existing models. Based on individual tree volumes within stands, new equations for the three species were constructed. A comparison was made between the new equations and those that were being used at the site. Results indicated a total standing volume of 0.007 m3/ha obtained for the three species （Sapelli 0.003 m3/ha, Tali 0.002 m3/ha and Assamela 0.002 m3/ha）. Two new volume equation models [B] and [C] were retained for their goodness-of-fit with [B] for Assamela and [C] for Sapelli and Tali. Results also showed that a total volume of 0.005 m3/ha was underestimated for the three species （Sapelli 0.002 m3/ha, Tali 0.001 m3/ha and Assamela 0.002 m3/ha） when existing volume equations were applied. It is imperative to construct new volume equations that are compatible with the ecological characteristics of the site using representative samples. Setting-up appropriate methods for their validation shall also serve as checks to future management errors.展开更多
文摘One of the alternative sustainable and green construction materials to concrete is timber. Timber is of numerous varieties, and this acts as a barrier to the extent of its usage, especially in structural application. Despite many researches on wood’s mechanical and physical properties, only a few are geared toward the structural application of wood. The present work investigated the mechanical properties of five timber species;Gmelina arborea, Tectona grandis (Teak), Terminalia superba (Afara), Ayin (Anogeissus leiocarpus), and Acacia (Robinia pseudoacacia), to determine their suitability for constructing long-span roof trusses. These are available in the South Western part of Nigeria. Their mechanical properties;bending strength, compressive strength, shear strength, tensile strength, Modulus of Elasticity (MOE), Modulus of Rupture (MOR), and density, were determined in the laboratory. The results obtained showed that all the timber types, except Terminalia superba (Afara), have higher values of mechanical properties than the values that are obtainable for classes of strength D30 to class D70 in the British Code of Practice. It means these species are of higher quality than the stipulated strength classes in the British code. The results also show that the order of relevance of the species for structural design (or work) is Acacia (Robinia pseudoacacia), Ayin (Anogeissus leiocarpus), Gmelina Arborea, and Tectona grandis (Teak). Terminalia superba (Afara) is not recommended for structural works.
基金This study is funded by the Coordination for the Improvement of Higher Education Personnel(CAPES).
文摘As forests in neotropical regions,particularly in developing countries,are devastated,interventions to restore biodiversity and its ecological functions are needed.Rural producers have thus been encouraged to grow trees for wood production as an economic activity.The objective of this study was to quantify the increment of wood density of four forest species from different successional classes of a mixed system of restoration in a neotropical forest in Brazil.Tree discs were sampled at breast height and analyzed radially by X-ray densitometry to obtain apparent density and basic density.Three trees each of a species from the pioneer,early and late secondary successional stages and of the dominant species in the climax community.The radial profiles indicated increasing density from the pith to bark of trunks,except for some variations due to wood defects and growth.Average density was 0.576 g cm^(-3),0.655 g cm^(-3),0.706 g cm^(-3)and 0.775 g cm^(-3),respectively,for Peltophorum dubium,Schinus terebinthifolius,Cariniana estrellensis and Hymenaea courbaril.Radial profiles indicated higher amplitudes in the apparent densities for slow-growing species.X-ray densitometry generated parameters such as minimum,average and maximum densities,and radial density variations.These parameters are important for understanding the ecological functional role of successional classes of the Atlantic Forest from the Neotropical region.
文摘Assessment of forest recovery following disturbance is enhanced by the use of biological indicators. One such indicator, the abundance of understory species, was examined in coast redwood (Sequoia sempervirens) forests using non-metric multiple dimensional scaling (NMDS) and indicator species analysis (ISA). Randomly distributed 10 m diameter circular plots were employed to record the abundance of all understory species across three treatments: actively managed (0 - 45 years since harvest);mature second-growth (~80 - 120 years since harvest);and unharvested old-growth stands. NMDS with perMANOVA analysis signified separation between treatments with the shade tolerant herbaceous species Trillium ovatum, Viola sempervirens, and Oxalis oregana positively correlated with mature second-growth and old-growth treatments. ISA supported the inclusion of T. ovatum, with the addition of Prosartes hookerii, as indicators of mature second-growth and old-growth. Both NMDS and ISA specified associations for Ceanothus thyrsiflorus and Stachys bullata with actively-managed stands. Occurrence of non-natives was low across treatments, though significantly higher on actively managed stands, with the shade intolerant invasive plants, Cortaderia sp. and Myosotis latifolia, occurring exclusively in actively-managed sites.
文摘Gmelina arborea Roxb. (Melina), also known as white teak, is a tropical tree of great importance with multiple benefits. It is a timber species with renewal capacity and accelerated growth, highly durable and high quantity and quality pulp production, widely used in commercial programs of reforestation. In view of a possible increase of Melina areas in the state of Tabasco Mexico, information was needed in relation with the physical environment and natural factors in order to locate the most suitable areas under rainfed conditions. In this way, decision makers will be provided with a basic tool to direct and promote commercial plantations in the best suitable areas. The software Arc/View version 3.3 was used to process and analyze the information. The optimum agroclimatic requirements of Melina were identified and each variable factor was matched with those found at ground level. A cartographic mapping was carried out to regionalize and locate the optimal and suboptimal zones. It was determined that there are 191,532 ha of high potential and 542,573 ha of medium potential production areas of Melina in Tabasco, Mexico under rainfed conditions.
基金Selection of species and definition of technical parameters for plantations of forest species in the State of Ceará,Brazil(Embrapa)。
文摘Timber forests contribute to the sustainable development of the biomes in tropical regions.The aim of this study was to evaluate the biological and chemical properties of the soil as a consequence of the cover with native and non-native species in the Acarau basin,a transition area from the coast to the Brazilian semi-arid region.Areas planted with four native species(Anadenanthera colubrina,Astronium fraxinifolium,Handroanthus impetiginosus,Colubrina glandulosa)and three exotic species(Acacia mangium,Casuarina equisetifolia,Eucalyptus urophylla)plus a non-forested agricultural area were evaluated for organic carbon contents,and microbial and chemical soil properties.The levels of soil organic carbon were highest in A.colubrina and C.equisetifolia plantations.Low basal soil respiration was observed but the microbial biomass was particularly low in the non-forested area.In the C.equisetifolia,E.urophylla,and H.impetiginosus plantations,elevated soil metabolic quotients were found.The A.colubrina and H.impetiginosus plantations had the highest levels of easily extracted-glomalin related soil protein.Tree species affect concentrations of essential nutrients and the biological quality of the soil in different ways.They can also improve the biological and chemical properties of the soil in the coastal plains of tropical regions.
文摘A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east Cameroon, was conducted between the months of July and September, 2007 to evaluate their suitability for the site. Twenty-two percent sampling intensity was conducted within annual allowable cuts and diameter readings taken on standing trees with the aid of a wide band Relascope. A non linear regression equation model was employed to compute volume equations and the student＇s t-test for the analysis of the existing models. Based on individual tree volumes within stands, new equations for the three species were constructed. A comparison was made between the new equations and those that were being used at the site. Results indicated a total standing volume of 0.007 m3/ha obtained for the three species （Sapelli 0.003 m3/ha, Tali 0.002 m3/ha and Assamela 0.002 m3/ha）. Two new volume equation models [B] and [C] were retained for their goodness-of-fit with [B] for Assamela and [C] for Sapelli and Tali. Results also showed that a total volume of 0.005 m3/ha was underestimated for the three species （Sapelli 0.002 m3/ha, Tali 0.001 m3/ha and Assamela 0.002 m3/ha） when existing volume equations were applied. It is imperative to construct new volume equations that are compatible with the ecological characteristics of the site using representative samples. Setting-up appropriate methods for their validation shall also serve as checks to future management errors.
