共查询到20条相似文献，搜索用时 31 毫秒
1.
Fotini A. Koutroumpa Bruno Vincent Géraldine Roux-Morabito Carine Martin François Lieutier 《Annals of Forest Science》2008,65(7):707-707
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Guillermo Riesco Muñoz Andrés Remacha Gete Manuel Gasalla Regueiro 《Annals of Forest Science》2013,70(7):695-706
Context
The commercial feasibility of sawmilling depends on the expected volume and value of sawn planks. Models that predict the volume of sawn timber of a particular quality and produced from logs of known characteristics are therefore very useful.Aims
The objectives were to study variation in sawing yield and to obtain models that predict lumber volume and grade recovery on the basis of easy-to-measure predictor variables of saw logs.Methods
Forty-six oak trees growing in Galicia (NW Spain) were felled and cut into logs. The logs were visually graded and sawn mainly into quartersawn planks, which were dried, planed and visually graded for structural purposes.Results
The total volumetric sawing yield was 47.6 %. The sawing yield for planks of structural dimensions (cross-section, 70?×?120 or 70?×?170 mm) was 43.4 %, but decreased to 8.4 % for structural sized and quality grade beams because of wane and biotic damage in many pieces. Log grade did not significantly affect sawing yield in the sample analysed, despite the wide range of diameter over bark at the smallest end in the sampled logs (22–77 cm). The sawing pattern affected total sawing yield (F?=?4.913; p value?=?0.001) and the sawing yield for structural planks (F?=?6.142; p value?=?0.0002); radial sawing with one cut and live sawing of half logs provided the highest yields. Three models were proposed for estimating sawn volume in timber products, with the small-end log diameter over bark as the predictor variable and R adj 2 between 0.31 and 0.78 (p value?<?0.01).Conclusion
For the purpose of producing oak timber destined for structural use, the presence of bark and sapwood in planks must be reduced in the sawing process; this would decrease the total lumber recovery but increase the timber value yield. Air drying must be accelerated to reduce biotic damage in sawn planks. Geometric mean diameter over bark at the smallest end (d) outperforms other measures as a predictor variable for total or structural sawn timber volume. 相似文献4.
Phellinus tremulae is an important fungal decay agent common to aspen and a critical component to the cavity-nesting bird complex found in western aspen stands. Little information exists on the conditions that facilitate infection and spread of P. tremulae in aspen forests. I used Forest Inventory and Analysis (FIA) data to explore the relationships of several tree and stand characteristics to the presence and frequency of P. tremulae in aspen measured across several western states of the United States. Results suggest a strong relationship between tree age, tree diameter, and compacted crown ratio with infection frequency in trees while stand purity, canopy cover and stand age had a positive relationship with the occurrence of P. tremulae in forest stands containing aspen. Logistic regression modeling identified stand age as the only variable that increased the odds of predicting infection at the stand-level while all tree-level variables were included in the tree model. Data also show that infection rates in the study area were lower than in other parts of aspen's range, and that average size of infected trees was smaller in the study area than those reported elsewhere. These results have important implications to management of aspen for wildlife, especially for birds that use decayed aspen for nesting. 相似文献
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Prof. Dr. W. Stein 《Journal of pest science》1994,67(8):168-175
In laboratory experiments, the behavior of the granary weevil,Sitophilus granarius (L.), was investigated under the special aspect of dispersal of this species. The results, too, should demonstrate possible changes in the behavior during the life time of the adults and differences between single specimens of the same population. The most important results are:
- The running activity increases shortly after emergence but then it decreases again slowly till the end of life.
- The fitness of the weevils declines during the life time continuosly.
- A dispersal phase exists in the first days after emergence. If a dispersal is prevented artificially for 12 or 20 days, only a small number of weevils still leaves the substrate (wheat), thus demonstrating the end of a dispersal phase.
- The feeding activity is nearly similar during the whole life.
- A few days after emergence, unmated females begin to produce typical egg-laying holes in the wheat kernels. This behavior exists nearly unchanged during the whole life time.
- The negative phototaxis of the first days after emergence decreases during the next days while the positive phototaxis increases. In older weevils, however, the reaction is again reverse.
- Within a population, considerable differences exist between single specimens in respect to running activity, feeding activity, and phototaxis. This results in an occurrence of “pioneer specimens” which have special importance for the dispersal of the species and for a foundation of new populations.
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John M. Koch Andrew H. Grigg Ross K. Gordon Jonathan D. Majer 《Annals of Forest Science》2010,67(1):106-106
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《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
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Matthew G. Hamilton Brad M. Potts Bruce L. Greaves Greg W. Dutkowski 《Annals of Forest Science》2010,67(5):511-511
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??Context
In the construction sector, wood is facing competition with other materials such as concrete, steel or plastics. Therefore, there is a need for more efficiency in the forest–wood chain by improving silvicutural management and wood processing technologies.??Aims
The objective of the study is to analyse the influence of log diameter and quality to recovery rate, veneer quality and economic benefit.??Methods
The trees used in the study came from a 30-year-old Pinus taeda L. thinning trial in Southern Brazil. In total, 57 logs (20.7 to 67.0 cm) were peeled following the standard industrial processing methods of the plywood mill.??Results
Average recovery rate was 54 % ranging from 35 to 72.6 %, with a linear trend (R 2?=?0.48) of increasing recovery with an increment on the log small-end diameter. Results show that the gap between theoretically possible and real recovery was lower in the logs with bigger diameters, indicating their higher efficiency in industrial processing. Moreover, the economic analysis detected that the current prices for log assortments reflect only the industrial potential of low-quality pruned logs. An optimised pruning strategy would result in higher industrial efficiency, which would allow higher log prices.??Conclusion
The results indicate that the recovery rate of bigger logs is higher in terms of volume of peeled veneer. The quality and therefore the value obtained from each log were negatively influenced by inadequate pruning strategies. Management of pines for higher value utilisation requires optimized thinning and pruning strategies in order to meet high growth rates and proportionally bigger dimensions of clear wood. 相似文献12.
Ahmed Mohareb Peter Sirmah Lyne Desharnais Stéphane Dumarçay Mathieu Pétrissans Philippe Gérardin 《Annals of Forest Science》2010,67(5):504-504
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P. J. Baldwin H. T. L. Stewart P. R. Bird W. I. Hamer D. W. Flinn K. N. Cumming D. J. Connor 《Agroforestry Systems》1988,6(1-3):213-233
From 1983 to 1985, a network of agroforestry research trials was established at six localities throughout Victoria. This paper describes experimental designs and establishment procedures used at the trial sites. The overall aim of the research program is to provide definitive information on the costs and benefits of a wide range of agroforestry combinations. Accordingly, trials were established at the following locations to test a total of 93 tree species grown in combination with specific types of agriculture:
- Carngham (near Ballarat) — sheep grazing andPinus radiata D. Don (radiata pine);
- Hamilton (several sites) — sheep grazing and mixed tree species;
- Kyabram — irrigated pastures andEucalyptus grandis W. Hill ex Maiden (flooded gum);
- Rutherglen — cereal cropping and shelterbelts;
- Myrtleford — irrigatedMentha spp. (mint) and two clones ofPopulus spp. (poplar); and
- Neerim South (near Warragul) — cattle grazing and mixed tree species.
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Nestor Laurier Engone Obiang Alfred Ngomanda Lee J. T. White Kathryn J. Jeffery Éric Chézeaux Nicolas Picard 《Annals of Forest Science》2013,70(3):241-249
- Context Okoume (Aucoumea klaineana) is the most important timber species in Gabon, while being classified as vulnerable in the IUCN red list. Thousands of growth measurements for this species have been performed since the 1950s but, because of a lack of integrated analysis, did not bring a consistent view on its growth pattern.
- Aims This study aims at disentangling the effects of tree size and local competition on tree growth.
- Methods A growth model was fitted for okoume, using data from seven sites in Gabon and Congo. The growth model was designed to be useful for forest management, which means that it relied on variables that could be computed using forest inventory data.
- Results A lognormal growth model with a negative response to stand basal area was selected. A significant residual site effect on growth was found, with a slower growth in the sites near the border of the natural range of okoume than in the sites far from it.
- Conclusion Growth strongly responded to local stand attributes such as tree density and basal area. Growth decrease with stand age in monodominant okoume stands was correctly predicted, although tree age was not incorporated into the model.
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Jianzhong Luo Roger Arnold Shiqi Ren Ying Jiang Wanhong Lu Yan Peng Yaojian Xie 《Annals of Forest Science》2013,70(4):417-428
Context
Processing young, small eucalypt logs into veneer is a burgeoning industry across southern China. However, plantations supplying these logs were mostly established for pulpwood; little information is available on variation and selection among commercial eucalypt clones/varieties in regards to suitability for veneer production.Methods
Tree growth and log form were assessed on 11 eucalypt clones from a 5-year-old trial in southern China. Logs from these were rotary peeled for veneer; recovery percentages plus a range of quality and value traits were assessed on the outturn.Results
Tree volumes, green veneer recovery ratios (%), veneer quality grades, log value, and value m?3 varied significantly among both clones and log positions up the stem. The clone with the best veneer recovery ratio (50.5 %) provided nearly twice that of the poorest clone (28.4 %). Average veneer value log?1 by clone ranged from RMB 6.7 (US$1) up to RMB 15.1 (US$2) and average value m?3 by clone ranged from 589 RMB?m?3 (US$88) up to 925 RMB?m?3 (US$139). Overall, sweep was the key factor influencing veneer recovery ratio and value. Knots, especially dead knots, holes and splitting were major factors influencing veneer quality grade. Middle and upper logs had significantly higher veneer recoveries, grades, and values m?3 than the lower logs.Conclusions
Excellent potential exists for selecting among eucalypt clones, and even among log positions within trees, for optimizing veneer production. 相似文献16.
Fernando Silla Ana González-Gil Ma Esther González-Molina Sonia Mediavilla Alfonso Escudero 《Annals of Forest Science》2010,67(1):108-108
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《Forest Policy and Economics》2008,10(6):400-407
The FIA BioSum model was used to simulate three fire-hazard-reduction policies in an area comprising northern California, southwestern Oregon, and the east slopes of the Cascade Mountains in Oregon. The policy scenarios, all subject to a stand-scale fire-hazard-reduction effectiveness constraint, included maximize torching index improvement (Max TI), maximize net revenue recovery (Max NR), and minimize merchantable timber removal (Min Merch). Differences in the area treated under each scenario were considerable, ranging from 15 to 96% of the area for which effective treatments are technically feasible. For each scenario, weight, species, and source tree size of both dirty chips (hogfuel or biomass) and saw logs were estimated. The mix of species and sizes removed under each scenario was surprisingly similar, although the Min Merch scenario did remove more noncommercial species such as hardwoods and more saw logs in the midsize classes (10 to 16in. diameter at breast height (dbh); 25.4 to 40.6cm) than the other two scenarios. Saw logs accounted for 67 to 79% of the weight removed. Under all scenarios, the Douglas-fir (Pseudotsuga menziesii)/larch (Larix) and white woods (Picea spp., Tsuga spp, and Abies spp.) species groups accounted for nearly all of the saw logs removed. Tops and limbs of commercial species and noncommercial species accounted for most of the dirty chips. Stems of low value commercial conifers (7 to 16in; 17.8 to 40.6cm) were also an important source of dirty chips. Trees smaller than 7in. (17.8cm) dbh were a relatively minor component of the dirty chip mix. 相似文献
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Felipe Crecente-Campo Alberto Rojo Alboreca Ulises Diéguez-Aranda 《Annals of Forest Science》2009,66(8):808-808
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Sylvie La Spina Jean-Claude Gregoire Patrick Mertens Charles De-Canniere 《Annals of Forest Science》2010,67(2):209-209
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Gerhard Wieser Walter Oberhuber Lisa Walder Daniela Spieler Andreas Gruber 《Annals of Forest Science》2010,67(2):201-201