首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
Small volumes of timber from Acacia and Eucalyptus woodlands of western Queensland, Australia, have achieved high prices in specialty timber markets, which has aroused the interest of landholders. A postal survey of 225 domestic and international specialty timber product manufacturers was undertaken to determine current utilisation of these lesser-known species, establish their suitability for various product markets, ascertain desirable timber dimensions and condition, and estimate potential future domestic and international demand. An overall response rate of 31% was achieved. Responses indicated that current utilisation of these timbers is probably not more than 200 m3/yr. Nevertheless, respondents generally indicated that western Queensland hardwoods are highly suited to the manufacture of specialty timber products, including small-scale furniture items, custom knife handles and musical instruments, and that they have high export potential. Some furniture and musical instrument manufacturers indicated they would be willing to pay up to $3,000/m3 and $30,000/m3 respectively, for small volumes of high-quality appropriately processed western hardwoods. Large, well-directed marketing campaigns will be necessary to expand specialty timber markets for western Queensland hardwoods.  相似文献   

2.
《Southern Forests》2013,75(4):195-200
At least 200 000 m3 of timber is harvested annually using semi-mechanised harvesting systems on the Viphya forest plantations in Malawi. Although these systems have long been used on the Viphya, no investigation on their productivity has so far been reported. Additionally, the absence of localised productivity analyses in Malawi has created a paucity of information on appropriate timber harvesting systems for production maximisation and cost minimisation. The objective of this study was to compare the production rates and operational costs of chainsaw/grapple skidder (semi-mechanised) and feller-buncher/grapple skidder (mechanised) harvesting systems in order to determine the economic feasibility of mechanised systems in the Viphya forest plantations. The study was conducted in Pinus kesiya compartments at the Kalungulu and Champhoyo forest stations of the Viphya forest plantations. A work study approach was followed to capture harvesting time and volume data for the semi-mechanised system. Secondary work study data were used to simulate productivity of the mechanised system on similar compartment conditions. A timber-harvesting costing model was used to analyse the results. The study showed that the simulated mechanised system was associated with lower operating costs and inventories with higher production rates than the semi-mechanised system. The cost marginal difference was US$0.89 m–3. It was therefore established that migration to mechanised systems could optimise timber harvesting productivity on the Viphya in future, if optimal volumes are available to ensure the efficient application of the mechanised harvesting system.  相似文献   

3.
Abstract

Growing markets for chopped firewood have created alternative uses for the by-products of sawmills. Based on empirical data and simulated results, the potential of birch (Betula pendula Roth, Betula pubescens Ehrh.) from commercial thinnings for combined industrial production of sawn timber and firewood billets was investigated. In the simulations, different sawing patterns were used for logs intended to combine production of sawn timber and billets for chopped firewood (‘sawlogs’), and for logs intended only to firewood production (‘firewood logs’). Finally, economical feasibility analysis was done concerning the differences between the sawmills’ traditional business concept and the novel concept combining sawn wood and firewood production. The bucking results for the volume yield of different timber assortments varied only slightly between the different bucking options, i.e. the combinations of timber assortments. The main differences in the volumes of timber assortments were due to the stand type where the birch trees were sampled (planted, naturally regenerated, mixed birch–spruce). In the sawing procedure, the output of sawn timber varied between 24% and 42% of the log volume in the sawlogs, depending on the log diameter class. As the volume yield of sawn timber and firewood billets was counted together in the case of sawlogs, the log consumption was c. 1.75 m3 of roundwood per 1 m3 of sawn timber and firewood billets. In the case of the firewood logs, the log consumption rate was considerably lower, only c. 1.35. The economic calculations showed that using the firewood approach in sawing may increase the net added value of products by €1.9–5.4 m?3 of logs, depending on their diameter class. As a conclusion, parallel production of sawn timber and firewood from logs from the first and second commercial thinning of birch-dominated stands is a concept that could work as an alliance between a sawmiller and a firewood entrepreneur. The concept could be competitive compared with both traditional sawmilling and production of chopped firewood.  相似文献   

4.
A field-based study was carried out to broaden our knowledge of fully mechanized cut-to-length harvesting productivity in naturally grown forests in the northern European part of Russia (NEPR). The recorded data comprised 38 midsized single-grip harvesters (JD 1270D) in clear-cutting operations in the Karelia, Komi, Vologda, Leningrad, Tver, and Kirov regions in NEPR, 4.3 million felled trees, and 1.4 million m3 u.b. (under bark) of processed timber. Harvesting operations were conducted in forest stands composed of spruce (48% on average), pine (19%), birch (22%), and aspen (11%), with an average stem volume 0.31 m3 u.b. The cut-to-length harvesters produced from 4.3 to 14.9 m3 u.b./productive machine hour (PMH) and 16.0–49.5 m3 u.b./stem processing machine hour (S proc MH). A machine evaluation analysis and a regression analysis were used to formulate models for predicting cutting productivity of modern single-grip harvester. The regression models were developed to estimate the productivity of the harvesters in the regions taking into account two significant factors influencing the productivity: the stem volume and tree species of the felled trees. Productivity/cubic meter u.b. of processed timber/PMH was calculated according to stem volume and tree species distributions in most forest-covered NEPR regions. Further research is suggested to improve the developed productivity models and to allow prediction of system performance over a broad range of stand and site conditions.  相似文献   

5.
A silvopastoral model that combines the production of pasture herbage with valuable native timber species has potential to simultaneously address the multiple goals of reforestation, conservation of native species and enterprise intensification. The objective of this study was to design, establish and monitor early growth of a silvopastoral experiment on a dairy farm in the north Atlantic zone of Costa Rica. Two indigenous timber species, Vochysia guatemalensis and Hyeronima alchorneoides were planted with and without the tropical pasture legume, Arachis pintoi in a split plot design, (2 × 2) factorial arrangement of treatments with four replications. After the first two years, V. guatemalensis was significantly taller (3.1 m) than H. alchorneoides (2.5 m). The mean root collar diameter for V. guatemalensis was significantly larger (6.5 cm) than H. alchorneoides (4.5 cm). Two-year establishment was acceptable for the tree component (83 to 85% survival) but poor for A. pintoi (2 to 8% of the sward). The most important pest affecting the establishment of the timber species was the leaf cutter ant, Atta cephalotes. An insect larvae, Cosmopterix sp., severely damaged 39% of the V. guatemalensis trees by repeatedly attacking their apical meristems. The two-year establishment data was insufficient to accurately predict future wood volume. A hypothetical economic analysis concluded that the silvopastoral system must average at least 1.2 m3 wood volume/paddock/year (20 m3/ha/year) throughout the first ten years of growth to assure a positive economic return from timber. The experiment is planned for a ten year period, which corresponds to the estimated rotation length for harvesting the timber species. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   

6.
Queensland, Australia, has a proud pastoral history; however, the private and social benefits of continued woodland clearing for pasture development are unlikely to be as pronounced as they had been in the past. The environmental benefits of tree retention in arid regions of the State are now better appreciated and market opportunities have arisen for the unique timbers of western Queensland. A financial model is developed to facilitate a comparison of the private profitability of small-scale timber production from remnant Acacia woodlands against clearing for pasture development in the Mulga Lands and Desert Uplands bioregions of western Queensland. Four small-scale timber production scenarios, which differ in target markets and the extent of processing (value-adding), are explored within the model. Each scenario is examined for the cases where property rights to the timber are vested with the timber processor, and where royalties are payable. For both cases of resource ownership, at least one scenario generates positive returns from timber production, and exceeds the net farm income per hectare for an average grazing property in the study regions over the period 1989–1990 to 2000–2001. The net present value per hectare of selectively harvesting and processing high-value clearwood from remnant western Queensland woodlands is found to be greater than clearing for grazing.  相似文献   

7.

Timber use in central Europe is expected to increase in the future, in line with forest policy goals to strengthen local wood supply for CO2-neutral energy production, construction and other uses. Growing stocks in low-elevation forests in Switzerland are currently high as exemplified by the Swiss canton of Aargau, for which an average volume of 346 ± 16 m3 ha−1 was measured in the 3rd Swiss National forest inventory (NFI) in 2004–2006. While this may justify a reduction of growing stocks through increased timber harvesting, we asked whether such a strategy may conflict with the sustainability of timber production and conservation goals. We evaluated a range of operationally relevant forest management scenarios that varied with respect to rotation length, growing stock targets and the promotion of conifers in the regeneration. The scenarios aimed at increased production of softwood, energy wood, the retention of potential habitat trees (PHTs) and the conversion to a continuous cover management system. They were used to drive the inventory-based forest simulator MASSIMO for 100 years starting in 2007 using the NFI sampling plots in Aargau. We analyzed model outputs with respect to projected future growing stock, growth, timber and energy yield and harvesting costs. We found growing stock to drop to 192 m3 ha−1 in 2106 if business-as-usual (BAU as observed between the 2nd and 3rd NFI) timber volumes were set as harvesting targets for the whole simulation period. The promotion of conifers and a reduction of rotation lengths in a softwood scenario yielded 25% more timber over the whole simulation period than BAU. An energy wood scenario that reduced growing stock to 200 m3 ha−1 by 2056 and promoted the natural broadleaved regeneration yielded 9% more timber than BAU before 2056 and 30% less thereafter due to decreasing increments. The softwood scenario resulted in higher energy yield than the energy wood scenario despite the lower energy content of softwood. Retaining PHT resulted in a reduction of timber harvest (0.055 m3 ha−1 yr−1 per habitat tree) and higher harvesting costs. Continuous cover management yielded moderate timber amounts throughout the simulation period, yet sustainably. Considering climate change, we discuss the risks associated with favoring drought- and disturbance-susceptible conifers at low elevations and emphasize that continuous cover management must allow for the regeneration of drought-adapted tree species. In conclusion, our simulations show potential for short-term increases in timber mobilization but also that such increases need to be carefully balanced with future forest productivity and other forest ecosystem services.

  相似文献   

8.
《Southern Forests》2013,75(3):169-173
Spotted gum (Corymbia citriodora subsp. variegata) is a popular tree species for hardwood saw timber plantations in Southeast Queensland (SEQ), Australia. In many parts of the world, logs up to 10cm top diameter are considered to be merchantable logs and acceptable at sawmills. However, due to the higher handling costs of smaller-sized logs, sawmills in SEQ are only buying logs with a top diameter of 25cm and larger. This necessitates the determination of the volume of logs with top diameters between 10 and 25cm. This paper compares the taper rates of different sizes of spotted gum logs and estimates the stem volume of spotted gum logs between 10 and 24.94cm diameter. Analysis showed that there is a statistically significant difference between the mean taper rates of bottom (30.5–64.2cm diameter) and top parts of stems (10–24.94cm diameter) at harvesting age. Using only the average taper rate of large diameter logs would underestimate the log volume of smaller-diameter logs. The average length of spotted gum logs between 10 and 24.94cm was found to be 19.27 m. Therefore, by the sawmill declining to use 10–24.94cm diameter logs, approximately 0.55m3 of log volume per tree at harvesting age would be lost.  相似文献   

9.
Private native forests in Australia perform a dual production and conservation role, providing an important source of timber, and complementing formal conservation reserves. A comparison of policies for private native forests in New South Wales, Queensland, Victoria and Tasmania illustrates the scope for timber harvesting, the provision for environmental values, and initiatives for responsible and sustainable forest management. The sustainable management of Australia’s forests requires initiatives by both government and landowners to accommodate changes in community attitudes, new management strategies, integrated catchment management principles and both commercial and non-commercial opportunities for forest use. Of all of the Australian states, New South Wales has the most restrictive laws in terms of forest management and harvesting. Queensland and Victorian legislation have a more commercial focus, while Tasmania has a balance of both environmental and commercial objectives. The duty of care for private native forests is a responsibility that falls to the landholder, and while this should be enforced by legislation, the private provision of community benefits requires both recognition and reward. The presence or absence of incentives potentially determines the effectiveness of forest codes of practice.  相似文献   

10.
A computer model was developed for the economic analysis of the damage caused to cocoa plants (Theobroma cacao) due to the harvest of timber shade trees (Cordia alliodora), based on field estimations from cocoa farms in the indigenous region of Talamanca, in the south east of Costa Rica. An economic cost-benefit analysis was carried out considering cocoa planting densities, yields, timber volumes and both cocoa and timber prices. Damage to cocoa plants was quantified in terms of severity levels and then translated into yield losses and their corresponding economic values. From the 49 harvested timber trees observed, 196 cocoa plants were affected, of which 4% required replanting and 38% coppicing. Tree trunks were involved in 55% of the damage cases (109) and tree crowns in 45% (89). Nevertheless, the revenue obtained from timber sales easily offset the costs of damage to the cocoa crop. The economic analysis showed that on average, the net gain derived from timber harvesting was around US316 per tree. For all considered scenarios, the timber market price that would balance discounted costs and benefits to zero ranged between US316 per tree. For all considered scenarios, the timber market price that would balance discounted costs and benefits to zero ranged between US22 and US$66 m−3 (current market price for C. alliodora is US$66 m−3 (current market price for C. alliodora is US128 m−3). There would be lower margins due to higher costs of cocoa damage in high yielding, high price cocoa scenarios. However, the study shows that damage due to tree felling should not be a major objection of farmers to the use of timber shade trees in cocoa farms even in these scenarios.  相似文献   

11.
We developed a model to estimate supply potentials and available amounts of timber and forest biomass resources from profitable sub-compartments of thinning and final felling operations. Economic balances were estimated while considering not only harvesting expenses but also reforestation expenses after final felling, which should be considered for sustainable forest management. Harvesting expenses were estimated based on two types of timber harvesting systems and three types of forest biomass harvesting systems in each sub-compartment. Then, the model was applied to Nasushiobara city of Tochigi prefecture, Japan. Reforestation expenses had large negative impacts on the financial balances of final felling operations. Few sub-compartments were profitable after considering reforestation expenses. Most profitable sub-compartments were those with mechanized operation systems and landing sales. These accounted for 17.19% of all sub-compartments, while only 5.75% of the sub-compartments were profitable based on their current operation systems and landing sales. Although the overall supply potentials of timber and forest biomass resources were 380,000 m3 and 210,000 Mg, respectively, and 15 times the planned harvest of coniferous tree volume of 25,000 m3year-1 and 50 times the annual demand for the woody gasification power generation of 4,000 Mg year-1 in Nasushiobara, available amounts of timber and forest biomass resources were only49,429 m3 and 33,333 Mg, which were 13.0% and 15.7% of supply potentials for landing sales with mechanized operation systems.  相似文献   

12.
Both model and field estimations were made of the damage inflicted to coffee plants due to the harvest of timber shade trees (Cordia alliodora) in coffee plantations. Economic analyses were made for different coffee planting densities, yields, and both coffee and timber prices.Damage due to tree felling and log skidding should not be a major limitation to the use of timber shade trees in coffee plantations. The timber price that would balance all discounted losses and benefits to zero, for scenarios with and without trees ranged between 8–20 US $/m3 (current overbark log volume at the saw mill yard is US$ 66/m3). There will be lower margins for coffee damage in high yielding plantations, specially in years of good coffee prices. Nevertheless, the use of timber shade trees is recommended even in these scenarios.  相似文献   

13.
A model was developed to estimate the stable timber output from shade stands of Cordia alliodora in coffee farms. The model predicts, for stand densities between 120–290 trees/ ha, timber yields of 9–24 and 6–15 m3/ha/yr of total and commercial overbark volumes, respectively. Current harvest rates in four sample farms are below these figures.The model is used to describe the transient trajectory (in terms of timber output over time) of Cordia alliodora stands with different initial DBH distributions. Practical recommendations are derived as to how farmers should manage their trees to achieve stable timber outputs in the shortest time possible.  相似文献   

14.
Waste wood was studied in an economic enterprise by logging, function, tree species and log size in four Caspian hardwood sites. Damaged logs were recorded with additional information obtained for the location, dimensions and type of damage. The data were analyzed statistically to determine significant differences of damage during logging process. The results indicated that animal harvesting systems cause more volume (40.5% of log volume) and value loss (89.5 $·m?3) to logs than mechanized harvesting systems (13.9% and 6.0 $·m?3), also bucking resulted in significantly more volume (9.9% of log volume) and value loss (5.5 $·m?3) when compared to skidding (0.2% of log volume and 0.2 $·m?3), decking (0.4% of log volume and 0.2 $·m?3) and loading (0.2% of log’s volume and 0.3 $·m?3) operations. Study showed that the processes of skidding, decking and loading of logs have very little impact on damage levels. Volume and value losses of damaged logs are not sensitive to tree species and log size. The information from the field study is important in creating new guidelines or training to help minimize hardwood log damage during the timber harvesting process.  相似文献   

15.
Spotted gum (Corymbia citriodora subspecies Variegata) has the potential to be the major hardwood species for large-scale plantations in Southeast Queensland, Australia, but production research is limited due to the lack of age of research plots. Optimal spacing is a major subject of concern. Based on time series data from a spotted gum experiment site, growth performance was analyzed for five spacing levels: 11.3 m?×?11.3 m (78 stems ha?1), 7.4 m?×?7.4 m (182 stems ha?1), 5.4 m?×?5.4 m (343 stems ha?1), 3.6 m?×?3.6 m (771 stems ha?1), and 2.9 m?×?2.9 m (1189 stems ha?1). The major objective was assumed to be to maximize total merchantable log volume. A growth model was produced, and the mean diameter at breast height (DBH) and total merchantable log volume for each spacing level at a range of harvesting ages were estimated. From the analysis, the spacing level of 5.4 m?×?5.4 m was found to be optimal for maximizing merchantable log volume to a 10-cm small-end diameter. Further analysis of mean DBH, height, and volume of the largest 200 and 250 trees from this spacing level indicates that merchantable log volume could be maximized by retaining the 250 largest trees ha?1. The total financial revenue from the best spacing level in 25 and 30 yr are predicted to be Australian dollars (A$) 13,637 and A$17,779 ha?1, respectively. If full rotation data could be obtained, more reliable models could be produced, and a more accurate financial estimate could be made.  相似文献   

16.
This paper reports findings of surveys into small-scale sawmilling and timber processing in Phu Tho Province and the Tam Dao National Park buffer zone in northern Vietnam. The objective of these surveys was to examine the extent to which small sawmills and timber processors utilise farm-grown timber, so as to explore the prospects for expansion of farm-grown timber markets. The operational scope, supply chain and value chain of the industry are reported. Resource availability and current and future perspectives are discussed. Timber prices were found to vary greatly between species and study areas. Species most in demand by enterprises are Artocarpus heterophyllus, Melia azedarach, Manglietia conifera, Acacia spp., Chukrasia tabularis and Erythrophloeum fordii. Small-scale sawmilling and timber processing activities fit well with rural communities in Vietnam and have potential for further development if current constraints can be overcome. Further tree planting is needed to meet the presently unsatisfied timber demand and to create income and employment. Information from sawmillers and timber processors suggests the types of species that farmers should be considering for their plantings.  相似文献   

17.
Most timber harvesting operations in the southern Mediterranean area of Italy can be considered to be in an early stage of mechanization. It is mainly based on agricultural tractors that are sometimes equipped with specific forest-related accessories such as winches, hydraulic cranes, or log grapples. In recent years, there has been an increase of specialized forestry machines working in Calabria, southern Italy, including forwarders, skidders and cable yarders. This study assesses the efficiency and costs of extraction using forwarders, as a mechanized alternative to agricultural tractors and horse logging. Time studies were conducted to quantify the productivity and operational cost of log forwarding for two John Deere forwarders in two different coniferous stands: (A) Calabrian pine and (B) silver fir. The empirical time study included 100 forwarding cycles (i.e., 50 for each site) that were broken down into four different work phase elements. Models for cycle time, total productivity and individual work phases were calculated. The average load per cycle was 11.8 m3 in stand A and 9.97 m3 in stand B and the average one-way forwarding distance was 306 m in A and 597 m in B. The average productivity per scheduled machine hour (SMH) was 14.4 m3 in A and 15.7 m3 in B, while the costs, calculated to be 3.60 €/m3 in A and 4.90 €/m3 in B, were considered lower respect traditional methods.  相似文献   

18.
Wood is graded according to strength in various applications. The ultimate strength can only be determined by breaking the specimen, and thus other characteristics like density and modulus of elasticity (MOE) are used for estimation of the strength. In this study, the properties of normally dried and thermally modified Scots pine were studied using electrical impedance and air-coupled ultrasound (ACU) methods. Density, hardness, MOE and strength were analysed and compared with the electrical and ultrasonic responses. The measurements were conducted in stable laboratory conditions with well equilibrated samples and the moisture content was not determined. Both the ultrasonic and electrical parameters correlated with the density and mechanical properties. Using multivariate analysis, density could be estimated with accuracy of 21 kg/m3 (SD) for normally dried timber and 13 kg/m3 (SD) for thermally modified timber (TMT; N = 15). MOE could be estimated with accuracy of 0.7 kN/mm2 (SD) for normally dried timber and 1 kN/mm2 (SD) for TMT (N = 14). According to the study, electrical impedance spectroscopy combined with ACU measured across the grain is a potential non-destructive technique for the strength estimation of wood.  相似文献   

19.
Sustained yield policies designed to ensure an even annual flow of timber harvests remain the most common approach to forest management on public lands in Canada. Such policies have been criticized on the environmental grounds that timber production is emphasized at the expense of other values, and on the economic grounds that policy-makers try to maximize the harvests level without regard for economic optimality (measured by whether or not revenues cover variable costs of production). In a case study from Northern Ontario, we used a spatially explicit harvest scheduling model to evaluate financial outputs for various scenarios, introducing different timber flow constraints, as well as varying utilization policies. We show that current policies do contribute to firms harvesting at uneconomic levels. More specifically, our results show that reducing harvest levels could increase firm profitability (measured in an increase in net revenues associated with harvesting operations). We estimate that to meet the annual allowable cut (AAC) of approximately 375,000 cubic metres (m3), the firm loses $500,000 annually (measured by the amount by which total harvesting costs exceed log values delivered at the mill). Reducing the target AAC to just under 300,000 m3 leads to a reversed situation, harvesting revenues now exceeding costs by $1.2 million annually. Dropping the even flow constraint leads to even higher annual profitability of $3.5 million, with the drawback that harvesting levels show significant variation over the 100-year planning period. Our results also show that the largest factor influencing the level of profitability is attributed to access costs (principally roading costs). In this case, other harvesting policies, such as utilization standards, may not be significant factors affecting costs in this region of Northern Ontario.  相似文献   

20.
The paper focuses on the determination of fuel consumption (CO2 emission) and exhaust emissions such as CO, HC, NOx, and PM in the process of timber extraction and transport. A complex assessment of fuel consumption and exhaust emissions was performed for the entire, fully mechanized supply chain including, tree felling, delimbing, and bucking with a harvester, timber extraction with a forwarder and transport with a truck. The performed investigations determined unit exhaust emissions (referred to 1 m3 of timber) for the entire technological process and its individual stages. The investigations of the exhaust emissions and fuel consumption were performed under actual conditions of typical forest operations and transport. State-of-the-art portable emissions measurement system equipment was used for the measurements. The fuel consumption was determined through the carbon balance method. The investigations were performed for the process of extraction and transport of pulpwood. The measurements were performed on location in the town of B?bnik?t near Poznań, in a pinewood forest, typical of this part of Europe. The analysis includes the transport of timber to the lumberyard on a distance of 31.4 km. The total fuel consumption for the entire mechanized supply chain was 2.10 dm3/m3. The total exhaust emissions, however, amounted to: CO—8.91 g/m3, HC—1.19 g/m3, NOx—45.32 g/m3, PM—4.04 g/m3.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号