油松株内幼龄材与成熟材材性的比较研究

本文就中条山油松株内幼龄材与成熟材材性差异的比较研究,讨论对幼龄期划分的依据。根据木材解剖特征、物理力学性质的径向变异规律,确定其幼龄期为14年。随着树干高度的增加,油松木材幼龄期逐渐缩短、株内幼龄材范围及所占断面上的比例变小。株内幼龄材与成熟材材性差异显著。幼龄材管胞长度短、直径小,胞壁薄,微纤丝角度大,生长轮较宽,晚材率低,浸提物含量高,基本密度较大。幼龄材的力学强度远远小于成熟材。     

杨树微纤丝角的变异及其与木材性质的相关关系

微纤丝角为细胞次生壁S2层微纤丝排列方向与细胞主轴所形成的夹角,与木材的物理性质、力学性质和化学性质都有着直接的关系。应用x射线衍射法测定了7个杨树无性系(14株样木)胸径处各年轮的微纤丝角,并对应分析和测定了各年轮的木材基本密度、纤维长度、纤维宽度和纤维素含量。研究结果表明,杨树微纤丝角在年轮间存在显著差异,其径向变异规律为从髓心向外以微纤丝角逐渐降低,年轮间的平均微纤丝角在7.8旱?8褐洌荒静幕久芏取⑾宋ざ取⑾宋矶群拖宋睾吭谀曷旨湟泊嬖谙灾钜臁O喙胤治霰砻鳎⑾怂拷怯肽静幕久芏取⑾宋ざ取⑾宋矶群拖宋睾看嬖谙灾母合喙毓叵??0.01),相关系数分别为-0.450、-0.586、-0.516和-0.660。回归分析结果表明,多项式方程可较好地描述杨树微纤丝角与所测定的木材性质的关系,相关系数均在-0.45以上(n=125)。本文的研究结果认为,在今后针对杨树材性改良的育种计划中,微纤丝角是一个重要的选育和改良指标。图3表3参34。     

Competitive interactions between juvenile trembling aspen and lodgepole pine: A comparison of two interior British Columbia ecosystems

To facilitate ecosystem-specific management of juvenile mixtures of lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) and trembling aspen (Populus tremuloides Michx.) in south-central British Columbia, we compared the characteristics of pine–aspen competition between a moist sub-boreal spruce and a dry interior Douglas-fir ecosystem. A total of 252 lodgepole pine and their neighbourhoods were examined across four untreated stands, each of which was sampled three times between ages 12 and 24 years. Pine diameter and height decreased with increasing density of trembling aspen at least as tall as the target pine (tall aspen) in both ecosystems. Regression analysis was used to examine the ability of tall aspen density and four competition indices (CIs) to predict pine size. Tall aspen density, which is easily assessed in the field, accounted for 63% and 69% of the variation in pine diameter and height in 20–24 year-old stands, respectively. The most successful competition index, based on the basal diameter ratio (BDR) of trembling aspen to pine accounted for, respectively, 78% and 73% of the variation. In the same stands, R² values were 1–5% lower when tall aspen density and BDR at age 15–19 years were used to predict size of 20–24-year-old pine.     

Utilization of polar metabolite profiling in the comparison of juvenile wood and compression wood in loblolly pine (Pinus taeda)

Juvenile wood (JW) of conifers is often associated with compression wood (CW), with which it is sometimes believed to be identical. To determine whether JW and CW can be distinguished metabolically, we compared gas chromatographic profiles of 25 polar metabolites from rooted cuttings of a single loblolly pine (Pinus taeda L.) clone raised in controlled environment chambers and subject to three treatments: (1) grown erect with minimal wind sway (control); (2) swayed by wind from oscillating fans; and (3) with 30-cm growth increments successively bent at an angle of 45 degrees to the vertical. Profiles were compared by principal component analysis. Substantial increases in abundances of coniferin and p-glucocoumaryl alcohol separated immature JW-forming xylem tissues of the control trees from the CW-forming xylem of the bent and swayed trees.     

Clones of Armillaria ostoyae and the pattern of infected juvenile lodgepole pine in Alberta,Canada

Small patches of dead trees were common among 7- to 15-year-old Pinns contorta var. latifolia in Alberta, Canada. The sizes of clones of Armillaria ostoyae, determined by pairing diploid isolates, was larger than these patches. Pairing diploid isolates on strips of Betula papyrifera provided a clear indication of clonal relationships.     

Characterization of juvenile wood to mature wood transition age in black spruce (Picea mariana (Mill.) B.S.P.) at different stand densities and sampling heights

The radial pattern of both maximum ring density and ring area of 36 black spruce trees were used to determine the transition age from juvenile wood to mature wood. The data were obtained by X-ray densitometry and both segmented linear and polynomial regressions were used to point out the age of the juvenile wood boundary. Three stand densities (1,790, 2,700 and 3,400 stems/ha) and three sampling heights (2.4, 5.1 and 7.8 m) were studied. Although maximum ring density and ring area presented similar radial patterns, they gave two significantly different results of transition ages. The maximum ring density over-estimated the transition age (17.6 years) in contrast to ring area (14 years). The results show that the transition from juvenile wood to mature wood occurred after 12 years at 7.8 m (versus 13.1 years at a height of 5.1 m, and 17.6 years at 2.4 m). Although transition age occurred later in the high stand density group (21 years), the difference was not significant between the three stand density groups. Nevertheless, transition age remains difficult to determine since no standard definition exists. The transition occurs over years, and most probably a transition wood exists between juvenile wood and mature wood. Estimation of the juvenile wood proportion in volume shows that it remains constant along the stem and it increases with stand density.     

Variation in the susceptibility of lodgepole pine provenances to Sirococcus shoot blight: results from artificial inoculations

Fourteen provenances of lodgepole pine artificially inoculated with a local isolate of Sirococcus strobilinus varied in their susceptibility to the pathogen. Provenances from the Dry Interior (31.9%) and the Sierra (14.3%) had significantly lower disease incidence than those from the Interior Wet Belt (51.9%), the Coast (62.5%) and the Cascade Range (58.6%). These results indicate the potential for selecting seed sources with low levels of susceptibility to Sirococcus shoot blight.     

Stem damage of lodgepole pine clonal cuttings in relation to wood and fiber traits,acoustic velocity,and spiral grain

Eight clones from a 16-year-old field trial of clonal cuttings of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) were analyzed for growth, growth pattern, and stem damage in the field. In addition, wood and fiber traits (acoustic velocity [AcVel] and spiral grain) were analyzed and wood density, microfibril angle, modulus of elasticity, and radial fiber diameter (FibDR) determined from SilviScan analyzes. Two clones with considerably more bent, broken, and leaning stems differed from the other clones in terms of microfibril angle and modulus of elasticity (MOE) in the outermost annual rings. FibDR and, to some extent, MOE in the outermost annual rings were negatively correlated with the frequency of bent, leaning, or broken stems, while microfibril angle (MFA) was positively correlated. AcVel was negatively correlated with both MFA and the frequency of bent, broken, and leaning stems. We conclude that AcVel could be used as an effective tool to predict severe stem damage and determine stem strength in the field instead of using costly lab-based SilviScan measurements of microfibril angle. If developed further, this approach could be used for large-scale screening of progeny tests when selecting for stem strength.     

Shear strength and perpendicular-to-grain tensile strength of defect-free Scots pine wood from mature stands in Finland and Sweden

Variations in parallel-to-grain static shear strength and perpendicular-to-grain tensile strength of Scots pine wood from mature stands in Finland and Sweden were studied by means of linear mixed model analyses. Approximately 35% of the total variation in shear strength could be described with readily available independent background variables; if the basic density was included, approximately two-thirds of the total variation could be controlled. In tensile strength perpendicular to grain, only approximately one-fourth of the total variation could be described with the respective background variables; the property was found to be independent on wood density, and the reasons for the absence of strength–density relationship are discussed.     

Fibril angle of loblolly pine wood as related to specific gravity,growth rate,and distance from pith

Summary Fibril angles were greater for earlywood (avg. 33.4°) than for latewood tracheids (avg. 26.9°). For earlywood, fibril angle did not differ between growth rates when the specific gravity was low (avg. 33.3°). When the specific gravity was high, wood of fast growth had a higher fibril angle (avg. 35.1°) than wood of slow growth (avg. 32.0°). No differences were detected between core, middle, and outer wood. In latewood tracheids, fibril angles were greater in corewood (avg. 28.0°) than in middle or outer wood (avg. 26.3°). For whole wood (a weighted average of earlywood and latewood), fibril angle averaged 30.7° and was greater in corewood (avg. 32.2°) than in middle or outer wood (avg. 29.9°).     

A comparison of lodgepole pine responses to varying levels of trembling aspen removal in two dry south-central British Columbia ecosystems

We used manual cutting to manipulate trembling aspen (Populus tremuloides Michx.) density and spatial arrangement in relation to crop lodgepole pine (Pinus contorta Dougl. Ex Loud. var. latifolia Engelm.) on two sites in contrasting dry, cool to cold ecosystems of south-central British Columbia. In the dry, cool interior Douglas-fir ecosystem (IDFdk3), we reduced the density of tall aspen (aspen at least as tall as target pine) to 0 (broadcast removal), 1000, 2500, or 4000 stems/ha when the planted lodgepole pine was 6 years old. Eight years later, pine height/diameter ratio (HDR) was significantly lower in the broadcast removal and 1000 stem/ha treatments than in the control. There were no other significant growth responses and pine survival and vigour were good regardless of treatment. In contrast, in a dry, cold sub-boreal pine spruce ecosystem (SBPSxc) where treatments were applied at a stand age of 11 years, naturally regenerated lodgepole pine stem diameter increased significantly in the broadcast removal treatment relative to the untreated control within 2 years. After 4 years, HDR had declined significantly relative to the control where tall aspen density was ≤1000 stems/ha. There were no significant pine responses where 2500 tall aspen stems/ha were retained or where tall aspen were removed only within a 1-m radius around pine. The greater difference in height (height differential) between aspen and pine at the SBPSxc than the IDFdk3 site may partly explain the differing response of lodgepole pine to treatment. Trends of decreasing sucker density with increasing aspen retention were evident at both sites, but differences were significant (p ≤ 0.05) only at the SBPSxc site.     

Changes in physiological attributes of ponderosa pine from seedling to mature tree

Plant physiological models are generally parameterized from many different sources of data, including chamber experiments and plantations, from seedlings to mature trees. We obtained a comprehensive data set for a natural stand of ponderosa pine (Pinus ponderosa Laws.) and used these data to parameterize the physiologically based model, TREGRO. Representative trees of each of five tree age classes were selected based on population means of morphological, physiological, and nearest neighbor attributes. Differences in key physiological attributes (gas exchange, needle chemistry, elongation growth, needle retention) among the tree age classes were tested. Whole-tree biomass and allocation were determined for seedlings, saplings, and pole-sized trees. Seasonal maxima and minima of gas exchange were similar across all tree age classes. Seasonal minima and a shift to more efficient water use were reached one month earlier in seedlings than in older trees because of decreased soil water availability in the rooting zone of the seedlings. However, carbon isotopic discrimination of needle cellulose indicated increased water-use efficiency with increasing tree age. Seedlings had the lowest needle and branch elongation biomass growth. The amount of needle elongation growth was highest for mature trees and amount of branch elongation growth was highest for saplings. Seedlings had the highest biomass allocation to roots, saplings had the highest allocation to foliage, and pole-sized trees had the highest allocation to woody tissues. Seedlings differed significantly from pole-sized and older trees in most of the physiological traits tested. Predicted changes in biomass with tree age, simulated with the model TREGRO, closely matched those of trees in a natural stand to 30 years of age.     

Genetic variation and relationships to growth traits for microfibril angle,wood density and modulus of elasticity in a Picea abies clonal trial in southern Sweden

Abstract

Genetic variation in wood density, microfibril angle (MFA), wood stiffness (MOE), height, diameter and volume was investigated in a 26-year-old Norway spruce [(Picea abies (L.) Karst.] clonal trial in southern Sweden. Wood quality measurements were performed on 10 mm increment cores using SilviScan. For MFA, mean values of annual rings showed the highest value (30°) at ring 2 counting from the pith, followed by a steep decrease and a gradual stabilization around ring 12 at approximately 14°. MOE showed a monotonic increase from 5 GPa to 14 GPa when moving from pith to bark. High broad-sense heritability values were found for wood density (0.48), MFA (0.41) and MOE (0.50). All growth traits displayed heritability values of similar magnitudes as reported in earlier studies. The generally high age–age correlations between different sections of the wood cores suggested that early selection for wood quality traits would be successful. Owing to unfavorable genetic correlations between volume and MOE, the correlated response indicated that selection for volume only at age 10 would result in a 0.27% decrease in weighted MOE at age 26 for every 1% increase in volume.     

Multivariate modeling of acoustomechanical response of 14-year-old suppressed loblolly pine (<Emphasis Type="Italic">Pinus taeda</Emphasis>) to variation in wood chemistry,microfibril angle and density

The polymeric angle and concentration within the S₂ layer of the softwood fiber cell wall are very critical for molecular and microscopic properties that influence strength, stiffness and acoustic velocity of wood at the macroscopic level. The main objective of this study was to elucidate the effect of cellulose, hemicellulose, lignin, microfibril angle and density on acoustic velocity and material mechanical properties of 14-year-old suppressed loblolly pine. Cellulose, hemicellulose and density are consistently the most important drivers of strength, stiffness and velocity. Cellulose and lignin are the highest and lowest contributor to velocity, respectively, with lignin acting as a sound wave dispersant, while cellulose is the most important conductor of sound wave at the molecular level, while hemicellulose acts as a special coupling agent between these components. The polymeric constituents are thus important drivers of sound wave propagation at the molecular level, while density played a subsequent role at the macroscale.     

Estimating leaf area index in different types of mature forest stands in Switzerland: a comparison of methods

Leaf area index (LAI) was estimated at 15 sites in the Swiss Long-Term Forest Ecosystem Research Programme (LWF) in 2004–2005 using two indirect techniques: the LAI-2000 plant canopy analyzer (Licor Inc.) and digital hemispherical photography, applying several exposure settings. Hemispherical photographs of the canopy were analysed using Hemisfer, a software package that offers several new features, which were tested here: (1) automatic thresholding taking the gamma value of the picture into account; (2) implementation of several equations to solve the gap-fraction inversion model from which LAI estimates are derived; (3) correction for ground slope effects, and (4) correction for clumped canopies. In seven broadleaved stands in our sample set, LAI was also estimated semi-directly from litterfall. The various equations used to solve the gap-fraction inversion model generated significantly different estimates for the LAI-2000 measurements. In contrast, the same equations applied in Hemisfer did not produce significantly different estimates. The best relationship between the LAI-2000 and the Hemisfer estimates was obtained when the hemispherical photographs were overexposed by one to two stops compared with the exposure setting derived from the reading of a spotmeter in a canopy gap. There was no clear general relationship between the litterfall and the LAI-2000 or the hemispherical photographs estimates. This was probably due to the heterogeneity of the canopy, or to biased litterfall collection at sites on steep slopes or sites subject to strong winds. This study introduces new arguments into the comparison of the advantages and drawbacks of the LAI-2000 and hemispherical photography in terms of applicability and accuracy.     

Photosynthesis of a Scots pine shoot: a comparison of two models of shoot photosynthesis in direct and diffuse radiation fields

Two models of shoot photosynthesis, the needle surface element model (SEM) and needle volume element model (VEM), were tested against empirical data obtained from measurements of the photosynthetic response of twelve Scots pine (Pinus sylvestris L.) shoots in direct and diffuse radiation. The models assume that shoot photosynthesis is obtained as the integrated response of either all needle surface area elements (SEM) or all needle volume elements (VEM) of the shoot. The models differ in that needles are treated as optically black in SEM, whereas in VEM radiation penetrates into the needle. The photosynthetic response of a surface/volume element was described as a Blackman-type curve and the distributions of irradiance on the elements were derived by computer simulation, based on a model of shoot geometry. The parameters (initial slope and maximum rate) of the Blackman-curve of an element were estimated iteratively by the method of least squares, i.e., by minimizing the residual sum of squares of simulated and measured rates of shoot photosynthesis. The parameter estimation was done separately for direct and diffuse radiation, and the models were evaluated based on the notion that, for the "ideal" model, the estimated parameter values should be the same in direct and diffuse radiation. Both models produced shoot photosynthesis curves that agreed well with measurements, but there was a discrepancy in the estimated parameter values, indicating that differences in the photosynthetic response of shoots in direct and diffuse radiation could not be explained solely on the basis of the simulated irradiance distributions. The agreement was, however, much better for the volume element model, which accounts for penetration of radiation into the needles.     

Effect of selected operational variables on the susceptibility of NaOH-pretreated pine wood to enzymatic hydrolysis: a mathematical approach

Summary Pinus pinaster wood samples were treated with NaOH solutions in order to improve their susceptibility to enzymatic hydrolysis. The variations caused by pretreatments on the chemical composition of treated samples and on the extent of enzymatic saccharification were correlated with the experimental variables studied (temperature, liquor/wood ratio and alkali concentration). Empirical models were used to assess the extraction and the hydrolysis steps. The reliability of the mathematical models was confirmed by further experimentation. Additional aspects affecting the studied process (such as selectivity of extraction and kinetics of enzymatic hydrolysis) are discussed.The authors are grateful to Xunta de Galicia for its financial support of this work (Proj. XUGA38302A91)     

Climatic signal in cellulose microfibril angle and tracheid radial diameter of Picea crassifolia at different altitudes of the Tibetan plateau,northwest China

Wood Science and Technology - Little attention was given to the climatic signals in wood properties, such as microfibril angle (MFA) and tracheid radial diameter (TRD). In this article,...