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1.
Reduction in the rotation ages of softwood saw-log plantations in South Africa is causing increased proportions of low stiffness sawn lumber at final harvest. It has been shown for some species that the microfibril angle (MFA) of the S2 layer of tracheids is strongly related to the modulus of elasticity (MOE) of wood, even more so than wood density, especially in wood formed during juvenile growth. The objectives of this study were to describe the variation in MFA in young Pinus patula trees and to determine the relationship between MFA and the dynamic MOE of sawn P. patula lumber. Thirty 16- to 20-year-old trees from six compartments from the Mpumalanga escarpment were processed into discs and lumber. The MFA, density and ring width were measured at two height levels using Silviscan 3. The average annual ring MFA varied between 7° and 29°; the pattern of variation depended mainly on height level and the ring number from the pith. The MFA in P. patula followed the same within-tree variation trends as in New Zealand-grown Pinus radiata but the average MFA was lower in absolute terms and differences between height levels were less pronounced. The MFA and density exhibited highly significant Pearson correlations of 0.73 and 0.70, respectively, with board dynamic MOE. A multiple regression model, which included MFA, density and ring width, explained 71% of the variation in the dynamic MOE of boards. A sensitivity analysis on the model showed that MFA and density had approximately similar influences on predicting the dynamic MOE of Pinus patula boards.  相似文献   

2.
The presence of quarantine pathogen Lecanosticta acicola, the causal agent of brown spot needle blight, was confirmed using molecular methods for the first time in northern part of Poland on the coastal area adjacent to the Baltic Sea. This area includes sandy beaches, where Pinus mugo and P. sylvestris were planted. Symptomatic needles were collected in 2017 from 20 P. mugo trees growing in one stand in Ustka. Typical symptoms of brown spot needle blight infection, including dead needle tips and central zones with yellow or reddish brown, circular spots in green tissue, were observed on all samples. Only, the asexual stage of L. acicola was obtained during this work. The pathogen species identity was confirmed using classical morphological methods (microscopic examination of the infected needles), real‐time and species‐specific priming (SSPP) PCR, and ITS sequencing. Analysis of mating‐type (MAT) genes showed the presence of both mating types in northern Poland.  相似文献   

3.
This study investigated whether the physiological condition of wood influenced patterns of colonization by mould and sapstain fungi. The extent of fungal defacement on sawn pine lumber Pinus nigra var. maritima that had been killed by gamma‐irradiation was compared with the defacement on untreated, still living timber that had been aged for up to 16 weeks prior to being sawn. All the sawn lumber was exposed to the natural inoculum of sapstain and mould fungi in a working sawmill environment over a 4‐week period. The results indicated that the pattern of fungal defacement differed markedly in dead or aged wood compared with untreated wood. Mould fungi were most prevalent on the dead irradiated wood, whereas sapstain fungi dominated the freshly sawn lumber which was still living. The differences appear to be independent of wood moisture content and may be related to the production of inhibitory compounds by living cells in wood as it becomes senescent and dies.  相似文献   

4.
Healthy lodgepole pine trees and trees at three stages (green, red and grey) of infestation by mountain pine beetles (MPB) were examined for moisture and blue-stain distribution in the radial and longitudinal directions. The sapwood moisture content of trees dropped about 100% from the healthy stage while the heartwood moisture dropped about 10%, regardless of green, red or grey attack stages. Moisture content variation with tree height was unique up to the time since beetle attack. The volume of blue stain increased with increasing time since beetle attack. Maximum discolouration in wood occurred at about 3 m above ground level and expanded rapidly upward. Lumber sawn and tracked from the MPB attacked logs showed a decrease in moisture content with increasing time since beetle attack, indicating the need for specific drying schedules employing lower energy levels. The economic implication of the effect of blue stain was evaluated by the percentage of Japanese grade (J-grade) lumber produced. The J-grade lumber yield decreased with increasing time since beetle attack. Early harvest and conversion of MPB infected trees will positively impact product value and recovery. Part of this research was funded by Forestry Innovation Investment Ltd., Government of British Columbia.  相似文献   

5.
The occurrence of pitch pockets in a stand of Picea abies [L.] Karst, was studied, focusing on variations in amount, number and size of pitch pockets within trees and between trees from the centre and the border part of a stand. Pitch pockets were more abundant in the border part, which had a lower site index and was also more exposed to the wind. The highest frequency of pitch pockets was noted for sawn faces near the pith of the tree from around the half tree height. The size of pitch pockets on sawn faces is described by two exponential functions. In both parts of the stand there was a similar increase of pitch pocket length with increasing distance from the pith, but generally trees in the border part had longer pitch pockets. In order to determine the relative amount of pitch pockets accurately at different distances from the pith and to explain the variation within and between trees, further analyses are necessary.  相似文献   

6.
The frequency of needles and the proportion of needle segments infected by Lophodermium piceae were compared in symptomless and Chrysomyxa abietis‐infected, 1‐year‐old needles of Picea abies. In late spring, symptomless needles from both rust‐infected and healthy saplings were sampled. In addition, rust‐infected, totally chlorotic needles and needles with chlorosis along about half their length from the diseased trees were examined. In all three stands, the proportion of segments infected by L. piceae was larger in the rust‐infected half of the needle than in the symptomless half; but the difference was statistically significant in only one of the stands. The proportion of L. piceae‐infected segments among the nonrust‐infected needles was the same as that found for the uninfected half of rust‐infected needles (after correction for size differences). No differences in the proportion of L. piceae‐infected segments were found between the totally chlorotic, rust‐infected needles and the green needles of diseased or healthy trees.  相似文献   

7.
杉木生材含水率分布及其对气干的影响   总被引：2，自引：0，他引：2  
以人工林杉木为研究对象,研究生材状态下不同厚度锯材含水率的差异,比较含髓心、钝棱与其他类型等3类锯材的含水率差异,建立生长轮宽度与锯材含水率的关系,分析生材状态含水率对锯材气干周期的影响。研究结果显示,25mm和40 mm的锯材含水率差异极显著;含髓心锯材含水率最低,其次是其他类的,最大是含钝棱锯材;随着生长轮宽度减少,锯材含水率增大;生长轮宽度为4 mm时,是生材含水率分界线,即当生长轮平均宽度小于和不小于4.0 mm时,锯材含水率差异极显著;25 mm和40 mm厚不同含水率锯材各2组气干至含水率25%,低含水率锯材较高含水率的气干周期分别缩短57%和66%。  相似文献   

8.
《Southern Forests》2013,75(3-4):137-147
The objectives of this study were to determine the bending strength and stiffness properties of young Pinus elliottii x P. caribaea var. hondurensis timber from the Southern Cape, South Africa, and to evaluate the predictability of these properties from acoustic measurements on standing trees, logs and their sawn boards. The timber has good bending strength (MOR) properties but the mean stiffness (MOEstat) was significantly lower than that required for structural-grade timber. The mean MOEstat was also about 30% lower than a P. radiata control sample. The MOEstat of sawn boards could be predicted from acoustic stress wave measurements on standing trees with a correlation (r) of 0.48 and from acoustic resonance frequency measurements on sawn boards with a correlation of 0.85. The MOR of sawn boards was not significantly correlated with acoustic stress wave measurements on standing trees and only moderately correlated with acoustic resonance frequency measurements on sawn boards (r = 0.45).  相似文献   

9.
Faster growth and reduced harvesting ages are causing a reduction in the stiffness of lumber from South African grown pine plantations. The objective of this study was to determine whether increased planting densities of Pinus elliottii would result in improved stiffness of its sawn lumber and whether it would affect other relevant lumber properties. Four planting density treatments (403, 1 097, 1 808, and 2 981 stems ha?1) of a 12-year-old experimental spacing trial were processed into lumber. The static modulus of elasticity (MOEstat), modulus of rupture (MOR), warp, knot properties and density of the lumber were measured for 172 boards. Results showed that the planting density had a significant effect on the MOEstat of the lumber. The higher mean MOEstat (up to 27% increases) of lumber from densely planted trees seems to be the result of the higher slenderness and the slower diameter growth of these trees. Planting density also had a significant effect on the twist, knot area ratio and the number of knots per board. The magnitude of the effect on each of these properties, however, was relatively low.  相似文献   

10.
South Africa is a timber-scarce country that will most probably experience a shortage of structural softwood lumber in the near future. In this study the concept of using young, green finger-jointed Eucalyptus grandis lumber was evaluated for possible application in roof truss structures while the timber is still in the green, unseasoned state. Drying will occur naturally while the lumber is fixed within the roof truss structure. The objectives of this study were (1) to investigate the strength and stiffness variation of the finger-jointed E. grandis product in both the green and dry state for different age and dimension lumber, (2) to investigate the variation in density, warp and checking in the lumber when dried in a simulated roof-space environment and (3) to evaluate the potential of this finger-jointed product as a component in roof truss structures. Green finger-jointed E. grandis lumber of ages 5, 11 and 18 years and dimensions 48×73?mm and 36×111?mm from Limpopo province were evaluated. The study showed that the young finger-jointed E. grandis timber had very good flexural, tensile parallel to grain, and shear properties in both the green and dry state. The mean and characteristic modulus of elasticity and modulus of rupture values of the finger-jointed E. grandis product were higher and the variation lower in comparison to currently used South African pine sources. The tensile perpendicular to grain and compression perpendicular to grain strength did not conform to SANS requirements for the lowest structural grade (S5). Both tree age and product dimension were sources for variation in the physical and strength properties. Based on the results from this study the concept of producing roof trusses from green, finger-jointed young E. grandis timber has potential.  相似文献   

11.
Summary This study investigated the effect of Atropellis canker,Atropellis piniphila (Weir) Lohman and Cash, and stalactiform blister rust,Cronartium coleosporioides Arth., on the bending strength and stiffness of lumber from lodgepole pine,Pinus contorta Dougl. var.latifolia Engelm. The modulus of rupture, was unaffected by either disease. However, the modulus of elasticity (MOE) of lumber from infected trees, as determined by the Cook Bolinders and static bending tests, was significantly reduced from those of healthy trees. This impact should affect the use of lumber from infected trees when serviceability criteria govern the design of a structure. Should MOE-based, machine stress-rating of lumber become standard in the future, there may be an adverse, stress-related impact of these diseases on lumber value.We thank Mr. D. Hutcheson, B.C. Forest Service, Kamloops Region for advice and assistance, Messers, T. Jeanes, B. Geiselmann and D. Crabtree, Balco Forest Products Ltd., for advice, assistance, and particularly for harvesting and manufacture of the test material; Mr. L. Olsen, Forintek Canada Ltd. for assistance, and Dr. A. Harestad, Simon Fraser University for critical review. The research was supported in part by the Natural Sciences and Engineering Research Council, Canada, Operating Grant No. A3881  相似文献   

12.
In this research, we examined decay patterns occurring in Quercus castaneifolia wood under natural conditions compared with controlled decay in vivo. Pleurotus ostreatus‐infected oak wood was obtained from the Sari forests in the north of Iran. The species causing decay was verified as P. ostreatus using rDNA‐ITS sequencing of pure cultures from infected sapwood. In addition to P. ostreatus, two wood‐inhabiting Ascomycota, Trichoderma harzianum and T. lixii, were present. Mass loss in oak sapwood samples exposed to P. ostreatus for 60 days was around 10 per cent. Samples were prepared from both naturally decayed wood and wood decayed under controlled conditions and examined using microscopy. P. ostreatus was found to produce a simultaneous white‐rot decay pattern in both conditions.  相似文献   

13.
Abstract

This research work presents a study on the properties of finger jointing green oak wood (Quercus conferta L.) using a one-component polyurethane adhesive. The effect of finger-joint orientation (vertical or horizontal fingers) was also examined. In general, the results from the measurements of modulus of rupture and modulus of elasticity of green-glued finger-jointed specimens indicated that the green gluing of a high-density species such as oak wood is feasible.  相似文献   

14.
Arceuthobium sichuanense is a hemiparasitic angiosperm that infects Qinghai spruce (Picea crassifolia Kom.) in Qinghai province, China, and causes severe damage to spruce forests in Qinghai‐Tibet Plateau. In this study, the impact of A. sichuanense infection on mature and young trees of Qinghai spruce was evaluated by examining needle and current‐year shoot morphology, needle water and nitrogen‐use efficiency (NUE) and needle nitrogen concentration. The most apparent effect of A. sichuanense infection was a significant reduction in both needle size distal to infection and current‐year shoot length in the infected branches (p < 0.001). Per cent reductions in needle and current‐year shoot length were similar between mature and young trees (58.9 vs. 56.3%; 59.7 vs. 62.9%). There was a high degree of correlation in foliar δ15N values between the dwarf mistletoe and its host trees (R2 = 0.9017, p < 0.001), while the foliar δ13C values of A. sichuanense were similar to those of infected mature and young spruce trees. The dwarf mistletoe infection also resulted in a significant decrease in host needle N concentration and δ13C values (p < 0.001). The per cent reduction in needle N concentration in young trees was nearly twice as much as that in mature trees (20.49 vs. 11.54%), while the per cent reduction in needle δ13C values was similar between young and mature trees (?0.98 vs.?1.1‰). The NUE in mature trees was not affected by A. sichuanense infection, but the NUE in young trees was increased by the infection.  相似文献   

15.
The needles of pine trees are indicative of the overall health of the tree, and their length is affected by many factors. This study describes the effect of high levels of pathogen infection on lengths of both needles and shoots. Dothistroma septosporum is an important foliar pathogen of pines causing necrosis and premature defoliation with successive years of high infection leading to growth reduction and in extreme cases tree death. Corsican pine trees with all foliage infected by D. septosporum had needles of primary, secondary and tertiary shoots reduced by 31.8%, 44.0% and 64.2%, respectively, compared to non‐infected trees. Needle lengths were reduced both in the upper and lower portions of the canopy, with a greater reduction lower in the canopy. Trees with high levels of infection had shorter shoots in the upper canopy with fewer, shorter needles on these shoots compared to trees with low levels of infection. The results demonstrate the substantial negative effect on needle and shoot lengths of trees with high levels of D. septosporum infection, comparable to factors such as water and nutrient availability known to have a strong influence on these parameters. The reductions in length reduce the photosynthetic capacity of the tree and compound the immediate reductions caused by necrosis and premature defoliation. These effects on needle and shoot lengths contribute to the reductions in volume growth of affected trees and, moreover, are longer lasting than the immediate effects of necrosis and premature defoliation.  相似文献   

16.
This study investigated the effects of various thinning and pruning methods on the knots (number and size) and lumber recovery from Taiwania (Taiwania cryptomerioides Hay.) plantation trees. The results showed that heavy thinning caused more knots and larger-diameter knots than medium or no thinning; moreover, pruning caused fewer numbers of knots and smaller-diameter knots than no pruning. Better-quality Taiwania trees occurred with the no-thinning/no-pruning treatments, as shown by analyzing the knots, although the results also showed that the healing process seemed to have produced not completely clear wood during the 9 years after the pruning treatment. The thinning intensity slightly enhanced the lumber recovery of logs. Pruning did not affect lumber recovery from taiwania trees and logs. Thinning increased the lumber recovery per tree due to an increase in the diameter at breast height.  相似文献   

17.
Near-infrared (NIR) spectroscopy coupled with multivariate analysis was applied to estimate multiple traits of sawn lumber. The effects of the lumber conveying speed (LCS) and measurement resolution of spectra (MRS) on the calibrations were examined. NIR spectra ranging from 1300 to 2300 nm were acquired at LCSs of 10, 20, and 30 m/min and at MRSs of 2, 4, and 16 nm. Prediction models of bending strength (F b), modulus of elasticity in bending tests (E b), dynamic modulus of elasticity (E fr), and wood density (DEN) were developed using partial least-squares (PLS) analysis. LCS and MRS did not significantly influence the calibration performance for any wood property. The regression coefficients also showed no clear differences for any of the conditions. This indicates that the important explanatory variables included in the models are not greatly influenced by these measurement conditions. PLS2 analysis results, when presented graphically, allowed easy interpretation of the relationships between wood mechanical properties and chemical components, e.g., bending strength and stiffness were mainly related to polysaccharides cellulose and hemicellulose. NIR spectroscopy has considerable potential for online grading of sawn lumber, despite the harsh measurement conditions.  相似文献   

18.
The purpose of this study was to develop models for estimating yields of lumber grades and by-products of individual Scots pine (Pinus sylvestris L.) trees using stem and crown dimensions as explanatory variables. Two separate data sets were used: (1) one simulated by the process-based growth model, PipeQual, which provides information about stem form and branch properties. The model was used to predict the 3D structure of Scots pine stems from thinning regimes of varying intensity and rotation periods and (2) an empirical data set with detailed 3D measurements of stem structure. The stems were sawn using the WoodCim sawing simulator and the yields and grades of the individual sawn pieces, as well as by-products, were recorded. The sawn timber was classified on A, B, C and D-grades for side and centre boards separately (Nordic Timber grading). By-products were pulpwood, sawmill chips, sawdust and bark.  相似文献   

19.
Accurate estimates of lumber volume become an important indicator of production and monetary value for a sawmill. However, such estimates are only obtained directly after logging, and no accurate predictions are made for the Amazonian commercial species. In this sense, the objective was to generate equations of lumber volume for commercial species in Amapá (a state in northern Brazil) by adjusting and selecting regression models. The data of 50 logs processed from 10 commercial species were collected, as well as the quantity and volume of sawn products. Sixteen (16) statistical models were adjusted and statistical weights were performed to evaluate the quality of the estimates and to select the best equation by species. In summary, precise estimates of lumber volume can be obtained by the nº16 model for Carapa guianensis, while the models nº13 and nº15 are the most recommended for Dinizia excelsa and Hymenolobium petraeum, respectively. Model 7 presented the best adjustments for Hymenaea courbaril and Vochysia guianensis. Equations using only the log diameter variable suggest less precise estimates. Also, the log volume should be considered as an important predictor variable to obtain the serrated/lumber volume for the different Amazonian commercial species.  相似文献   

20.
The effect of eight fungicides and 15 endophytes isolated from twigs of healthy Pinus halepensis trees on the growth rate of four Spanish isolates of the pathogen Gremmeniella abietina was evaluated in vitro. In the fungicide experiments, four doses of each fungicide tested were added to the growth medium. In the endophyte experiments, dual cultures endophyte‐pathogen were paired in Petri dishes. Furthermore, growth of three G. abietina isolates was evaluated on malt agar with pine needle extract amended with filtrates from cultures of endophyte E14, which produced a brownish compound apparently inhibiting G. abietina growth. The results obtained suggested that chlorothalonil and daconil were the most suitable fungicides at low doses to reduce growth of G. abietina isolates from Spain. Four of the endophytes tested in vitro showed strong antagonistic activity against G. abietina and deserve further testing in vivo. The endophyte E14 produced in vitro a brownish compound which almost completely inhibited mycelial growth of G. abietina isolates from Spain.  相似文献   

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