共查询到20条相似文献,搜索用时 46 毫秒
1.
Kinetic analysis of color changes in keyaki (Zelkova serrata) and sugi (Cryptomeria japonica) wood during heat treatment 总被引:1,自引:0,他引:1
The kinetics of color changes in keyaki (Zelkova serrata Makino) and sugi (Cryptomeria japonica D. Don) wood during heat treatment were examined. The color of wood specimens treated at 90, 120, 150, and 180 °C was measured by an imaging spectrophotometer and expressed using CIELAB color parameters. At any treatment temperature, values for L* and $ \Updelta E_{ab}^{*} $ decreased and increased in both wood species, respectively, with increased treatment time. Changes in a* and b* varied depending on wood species and treatment temperature. The color changes were successfully analyzed using the kinetic approach applying time–temperature superposition method. This approach elucidated and accurately predicted color changes during heat treatment. 相似文献
2.
3.
Michael Kohlpaintner Christian Huber Boris Matejek Axel G?ttlein 《Annals of Forest Science》2012,69(8):895-905
Context
In N-saturated forests nitrate concentrations in seepage water ( $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ ) regularly show high spatial variability even within homogeneous stands. Up to now the reasons of this variability are not fully understood.Aims
The main objective was to identify the crucial parameters that control spatial variability of $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ at the H?glwald site.Methods
We investigated a multitude of parameters (e.g. N turnover, root biomass, soil chemistry, soil physics, stand parameters) and related them to $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ , measured in 40?cm depth with suction cups.Results
A small number of biological parameters (net N mineralization, root distribution, and stand density) explained up to 93?% of the variability of $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ in linear regression models. Net N-mineralization rates in the humus layer and fine root biomass in the upper mineral soil influenced $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ positively. Fine root biomass in deeper soil layers (30?C40?cm depth) and stand density had a negative influence.Conclusion
The rate of net N mineralization in the organic layer is decisive for the nitrate production in the soil. Roots in the upper mineral soil increase $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ by intensive water uptake but excluding nitrate at the same time. The variation of these two parameters is responsible for most of the small-scale variability of $ {\text{N}}{{\text{O}}_3}{^{ - }_{\text{seepage}}} $ . 相似文献4.
Rempei Suwa 《Journal of Forest Research》2013,18(3):238-245
The wave attenuation function of a Japanese black pine forest was evaluated based on its growth at different initial planting densities (P ini) using the spatially explicit, individual-based, dynamic global vegetation model. The forest dynamics were simulated for 150 years utilizing datasets for tree density and stem diameter at different stand ages obtained in the field. To elucidate the ability of the forest to reduce the wave height $ \eta_{t} $ (m), a long linear wave that propagates on dry ground was assumed. The attenuation of $ \eta_{t} $ (m) was expressed as follows: $ \eta_{t} = \eta_{t0} \exp ( - k_{\text{i}} x) $ , where $ \eta_{t0} $ , x, and k i are the initial wave height (m), the distance (m), and the wave attenuation coefficient (m?1), respectively. The tree destruction caused by the waves was considered in order to estimate k i. The model suggested that there was a peak age that maximized k i and was dependent on $ \eta_{t} $ , and that the maximum k i attained decreased with increasing $ \eta_{t} $ . When P ini was varied widely from 0.5 to 4 m?2, the maximum k i for a relatively low wave height (≤3 m) changed dramatically. For example, when $ \eta_{t} = 2{\text{ m}},$ the maximum k i ranged from 0.008 to 0.031 m?1, depending on P ini. Thus, utilizing a relatively low P ini would be an efficient way of quickly creating a forest capable of sufficient wave attenuation in areas where a relatively high wave height (≥4 m) is expected. It was concluded that regular harvesting and planting would be required to realize the full potential of the coastal forests to attenuate waves, and that tailoring P ini is one of the management options that could be used to establish a wave prevention forest. 相似文献
5.
A new composite k-tree estimator of stem density 总被引:1,自引:1,他引:0
Steen Magnussen 《European Journal of Forest Research》2012,131(5):1513-1527
This study presents a generally applicable and robust k-tree composite estimator of density. We propose to estimate stem density by a weighted average $ \left( {\hat{\lambda }_{\text{aic}} } \right) $ of 16 individual density estimators. The weights given to individual estimators are inversely proportional to the relative fit (Akaike’s corrected information criterion) of each estimator to the assumed distribution of observed k-tree distances. The performance of the proposed estimator is evaluated in simulated simple random sampling with k?=?3 and 6 in 58 forest stands (54 actual and 4 simulated) and 600 replications. Sample sizes were 15 and 30 locations per stand. Eleven estimators were novel, including three designed for regular spatial patterns. Absolute stand-level bias with k?=?6 varied from 0.1 to 8.1% (mean 1.8%), and a bias larger than 6% was limited to 3 stands with either pronounced density gradients or a strong clustering of stem locations. Root mean squared errors were approximately 16% (k?=?6 and n?=?15) versus 12% for sampling with comparable fixed-area plots. Coverage of computed 95% confidence intervals ranged from 0.72 to 0.99 (median?=?0.98 with n?=?15 and 0.95 with n?=?30), with 98% of all intervals achieving a coverage of 0.85 or better. In seven stands used in an assessment of a novel spatial point pattern reconstruction k-tree density estimator (RDE) by Nothdurft et al. (Can J For Res 40:953–967, 2010), the average absolute bias of $ \hat{\lambda }_{\text{aic}} $ with k?=?6 was 1.5 versus 0.7% for $ \hat{\lambda }_{\text{RDE}} $ . 相似文献
6.
Blaise Ratcliffe Foster J. Hart Jaroslav Klápště Barry Jaquish Shawn D. Mansfield Yousry A. El-Kassaby 《Annals of Forest Science》2014,71(3):415-424
Context
Wood quality traits are important to balance the negative decline of wood quality associated with selection for growth attributes in gymnosperm breeding programs. Obtaining wood quality estimates quickly is crucial for successful incorporation in breeding programs.Aims
The aims of this paper are to: (1) Estimate genetic and phenotypic correlations between growth and wood quality attributes, (2) Estimate heritability of the studied traits, and (3) Assess the accuracy of in situ non-destructive tools as a representative of actual wood density.Methods
Wood density (X-ray densitometry), tree height, diameter, volume, resistance drilling, acoustic velocity, and dynamic modulus of elasticity were estimated, along with their genetic parameters, for 1,200, 20-year-old trees from 25 open-pollinated families.Results
Individual tree level heritabilities for non-destructive evaluation attributes were moderate ( $ {\widehat{h}}_i^2=0.37-0.42 $ ), wood density and growth traits were lower ( $ {\widehat{h}}_i^2=0.23-0.35 $ ). Favorable genetic and phenotypic correlations between growth traits, wood density, and non-destructive evaluation traits were observed. A perfect genetic correlation was found between resistance drilling and wood density (r G ?=?1.00?±?0.07), while acoustic velocity and dynamic modulus of elasticity showed weaker genetic correlations with wood density (r G ?=?0.25?±?0.24;?0.46?±?0.21, respectively).Conclusion
This study confirmed that resistance drilling is a reliable predictor of wood density in western larch, while the weak genetic correlations displayed by acoustic velocity and dynamic modulus of elasticity suggest limited dependability for their use as fast in situ wood density assessment methods in this species. 相似文献7.
This study investigated near-infrared spectroscopy (NIRS) to rapidly estimate physical and mechanical properties of No. 2 2 × 4 southern pine lumber. A total of 718 lumber samples were acquired from six mills across the Southeast and destructively tested in bending. From each piece of lumber, a 25-mm-length block was cut and diffuse reflectance NIR spectra were collected from the transverse face using a FOSS 5000 scanning spectrometer. Calibrations were created using partial least squares (PLS) regression and their performance checked with a prediction set. Overall moderate predictive ability was found between NIRS and the properties for the calibration and prediction sets: block specific gravity (SG) (R 2 = 0.66 and R p 2 = 0.63), lumber SG (0.54 and 0.53), modulus of elasticity (MOE) (0.54 and 0.58), and modulus of rupture (MOR) (0.5 and 0.4). Model performance for MOE (R p 2 = 0.70) and MOR (R p 2 = 0.50) improved when performing PLS regression on a matrix containing lumber SG and NIR spectra. Overall NIRS predicted MOE better than linear models using lumber SG (R 2 = 0.46), whereas lumber SG (R 2 = 0.51) predicted MOR better than NIRS. Overall NIRS has reasonably good predictive ability considering the small volume of wood that is scanned with the instrument. 相似文献
8.
Bamboo is a kind of biological composite reinforced by unidirectional long fibers. The cleavage strength along grain of bamboo internode is low; however, the existence of bamboo node can hinder the propagation of interlaminar crack to make up for the defect of weak opening mode fracture toughness along interlamination. In this article, the double cantilever beam method was applied to test the Mode I interlaminar fracture toughness of Moso bamboo internode specimens and specimens with node to study the difference of the Mode I interlaminar fracture toughness between Moso bamboo internode specimens and specimens with node. The results are shown as follows: the Mode I interlaminar fracture toughness of Moso bamboo internode specimens was \( G_{{{\text{I}}C}}^{\text{Internode}} \) = 498 J/m2 (SD = 65 J/m2); the Mode I interlaminar fracture toughness of Moso bamboo specimens with node was \( G_{{{\text{I}}C}}^{\text{Node}}\) = 1,431 J/m2 (SD = 198 J/m2). It can be seen that the Mode I interlaminar fracture toughness of bamboo specimens with node was higher than that of bamboo internode specimens, and the toughness contribution of node to bamboo Mode I interlaminar fracture toughness was 1.87 times. The conclusion was drawn that bamboo node can contribute a lot to hinder the interlaminar fracture of bamboo. 相似文献
9.
Within-tree variations in the surface free energy of wood assessed by contact angle analysis 总被引:1,自引:0,他引:1
Davide Rossi Sergio Rossi Hubert Morin Antonio Bettero 《Wood Science and Technology》2012,46(1-3):287-298
Although the heterogeneity of wood could preclude assessment of the performances of adhesion, the within-tree variations in its thermodynamic properties still remain unexplored. This study analyzed the surface free energy of wood (γ W ) calculated by the geometric mean approach along the radius and at different sampling heights in black spruce and balsam fir with a statistical model, employing apparent contact angles of three testing liquids. Sampling height and species affected the apparent contact angles, and consequently the polar ( $ \gamma_{W}^{P} $ ) and dispersed ( $ \gamma_{W}^{D} $ ) components of γ W , but no significant difference was observed along the radius. On average, γ W was 43.77?mJ?m?2 at the stem base and gradually decreased, attaining 27.19?mJ?m?2 at 14?m of height. $ \gamma_{W}^{P} $ was markedly higher than $ \gamma_{W}^{D} $ with an opposite pattern along the tree height. These findings demonstrated the huge variability in γ W along the stem, which could be related to the structural or chemical features of wood. 相似文献
10.
Makrem Afif Chokri Messaoud Abdennacer Boulila Hnia Chograni Afef Bejaoui Mohamed Nejib Rejeb Mohamed Boussaid 《Annals of Forest Science》2008,65(7):710-710
11.
Inverse gas chromatography (IGC) was used to determine the surface properties of a series of polyurethane adhesives, A 1, A 2, A 3 and A 4 cured with water. The weight percentages of isocyanate group (NCO) in polyurethane adhesives were 5.3, 7.0, 13.0 and 19.6%, respectively. Four n-alkanes, C6, C7, C8 and C9 were chosen as non-polar probes to characterize the dispersive component of surface free energy, $ \gamma_{s}^{d} . $ Acetone, tetrahydrofuran and ethyl acetate were chosen as polar probes to detect the Lewis acid–base parameters, K a and K b. The trend of $ \gamma_{s}^{d} $ and K a and K b of the series of cured adhesives was also shown in this paper. The cured adhesives were all amphoteric, but predominantly Lewis basic. The adhesion strength of the poplar plywood bonded with polyurethane adhesives was tested. The results showed that the adhesion strength of plywood increased with increasing the NCO content of the adhesives and K b/K a of the cured adhesives. 相似文献
12.
Mesele Negash Mike Starr Markku Kanninen Leakemaraiam Berhe 《Agroforestry Systems》2013,87(4):953-966
Coffee, Coffea arabica L., which is native to Ethiopia, is the world’s most widely traded tropical agricultural commodity. While much is known about the productivity and management of coffee for coffee beans little attention has been given to the plants overall biomass production and carbon sequestration. The objective of this study was to develop and evaluate allometric equations for estimating the aboveground biomass of C. arabica plants growing in indigenous agroforestry system in the Rift Valley escarpment of south-eastern Ethiopia. Coffee plays an important role in providing income and in sustaining these productive systems. Biomass harvesting of 31 plants with 54 stems was carried out in a 40 km2 area varying in elevation from 1,500 to 1,900 m. The stem accounted for most (56 %) of plant biomass, followed by branches (39 %) and twigs plus foliage (5 %). Plant mean biomass was 22.9 ± 15.8 kg. Power equations using stem diameter measured at either 40 cm (d 40) or at breast height (d, 1.3 m) with and without stem height (h) were evaluated. The square power equation, $ Y \; = \; b_{ 1} d_{ 40}^{ 2} $ , was found to be the best (highest ranked using goodness-of-fit statistics) for predicting total and component biomass. The reliability of the prediction decreased in the order: stem > branches > twigs plus foliage. A cross-validation procedure showed that equation parameterization was stable and coefficients reliable. Our parameterized square power equation for total aboveground biomass was also found to be better than the equations parameterized by Hairiah et al. (Carbon stocks of tropical land use systems as part of the global C balance: effects of forest conversion and options for clean development activities, International Centre for Research in Agroforestry, Bogor, 2001) and Segura et al. (Agroforest Syst 68:143–150, 2006) for C. arabica grown in agroforestry systems, confirming the importance of parameterization of allometric equations with site specific data when possible. 相似文献
13.
A simple theory to link bole surface area,stem density and average tree dimensions in a forest stand 总被引:1,自引:0,他引:1
Vladimir L. Gavrikov 《European Journal of Forest Research》2014,133(6):1087-1094
A geometrical model of a forest stand has been analyzed. A forest stand has been modeled as a population of cones which was described by the change of total bole surface area with density \(\hat{S}(N)\) , relation between density and a horizontal dimension (radius r) r(N), and the relation between vertical dimension (generatrix l) and radius l(r). It has been shown that there are close relationships between \(\hat{S}(N)\) , l(r) and r(N). In case of \(\hat{S}(N) = const\) , power exponent of l(r) can be predicted from the power exponent of r(N) and vice versa. A comparison of the model analysis with the data available on Scots pine (Pinus sylvestris L.) stands has been performed. In spite of the model simplicity, its inferences proved to be workable in many cases where the data can be interpreted as a dynamics of an even-aged forest stand. In particular, if the estimation of total bole surface area is constant, the power exponent in the relation of diameter and stand density DBH(SD) can be calculated on the basis of the power exponent in the relation of height and diameter H(DBH) and vice versa. Possible limitations and the meaning of the analysis are discussed. 相似文献
14.
15.
Performances of Pinus taxa were studied to 10 years of age in two trials in each of Misiones and Entre Ríos provinces across the Mesopotamia region of Argentina. Taxa comprised 22 populations from sources in Argentina, Australia, Brazil and Zimbabwe including Pinus elliottii var. elliottii (Pee), Pinus caribaea var. hondurensis (Pch), their four, inter-specific hybrids (F1, F2 and backcrosses from F1 to Pch and to Pee—all as broadly based bulks); other Pee and Pinus taeda (Pt) comprised narrower or unspecified bulks. Variable numbers of taxa were missing at each site. Mean survival across sites at age 10 years ranged 53.2–91.3% averaging 74.2%. Analysis of variance of plot means indicated population effect was statistically significant (p < 0.05) for all or most growth and quality traits at all sites. However, significant differences from the nominated check seedlot at the Entre Ríos sites (Pee, Australia) were extremely rare, while quite common at the northern, Misiones sites (check seedlot a Pt population). In the Misiones trials, F1, F2 and both backcross hybrids showed better stem straightness than Pee and Pt from Argentina, generally with statistically significant differences (p < 0.05). Pt showed lowest forking scores (desirable). Taxon × environment interaction was statistically significant (p < 0.01) for growth traits only (p > 0.05). However, this interaction contributed an average of only 34.1% of the taxon variance suggesting a lack of practical importance. Taxa most suitable for deployment in the Mesopotamia region, Argentina are suggested. 相似文献
16.
Guillaume Roblot Damien Coudegnat Laurent Bleron Robert Collet 《Annals of Forest Science》2008,65(8):812-812
17.
Within-stem variations in the mechanical properties of 17–19-year-old Melia azedarach planted in two sites in northern Vietnam were examined by destructive and nondestructive methods. Wood samples were collected from 10, 50, and 90% of the radial length from pith on both sides (North and South) at 0.3, 1.3, 3.3, 5.3, and 7.3 m heights above the ground. The mean values in whole trees of wood density (WD), modulus of rupture (MOR), modulus of elasticity (MOE), and dynamic modulus of elasticity (Ed) at 12% moisture content were 0.51 g/cm3, 78.58 MPa, 9.26 GPa, and 10.93 GPa, respectively. Within the stem, the radial position was a highly (p?<?0.001) significant source of variation in mechanical properties. MOR, MOE, and Ed increased from pith to bark. WD had a strong positive linear relationship with both MOR (r?=?0.85, p?<?0.001) and MOE (r?=?0.73, p?<?0.001). This suggests that it is potentially possible to improve mechanical properties through controlling WD. MOR had also a strong linear relationship with Ed (r?=?0.84, p?<?0.001). This indicates that Ed is a good indicator to predicting the strength of wood if the density of measured element is known. Besides, the stress wave method used in this study provides relatively accurate information for determining the stiffness of Melia azedarach planted in northern Vietnam. 相似文献
18.
Eduardo P. Cappa Alvin D. Yanchuk Charlie V. Cartwright 《Annals of Forest Science》2012,69(5):627-640
Context
The gain in accuracy of breeding values with the use of single trial spatial analysis is well known in forestry. However, spatial analyses methodology for single forest genetic trials must be adapted for use with combined analyses of forest genetic trials across sites.Aims
This paper extends a methodology for spatial analysis of single forest genetic trial to a multi-environment trial (MET) setting.Methods
A two-stage spatial MET approach using an individual-tree model with additive and full-sib family genetic effects was developed. Dispersion parameters were estimated using Bayesian techniques via Gibbs sampling. The procedure is illustrated using height growth data at age 10 from eight large Tsuga heterophylla (Raf.) Sarg. second-generation full-sib progeny trials from two series established across seven sites in British Columbia (Canada) and on one in Washington (USA).Results
The proposed multi-environment spatial mixed model displayed a consistent reduction of the posterior mean and an increase in the precision of error variances $ \left( {\sigma _{e}^{2}} \right) $ than the model with ??sets in replicates?? or incomplete block alpha designs. Also, the multi-environment spatial model provided an average increase in the posterior means of the narrow- and broad-sense individual-tree heritabilities (h N 2 and h B 2 , respectively). No consistent changes were observed in the posterior means of additive genetic correlations (r Ajj??).Conclusion
Although computationally demanding, all dispersion parameters were successfully estimated from the proposed multi-environment spatial individual-tree model using Bayesian techniques via Gibbs sampling. The proposed two-stage spatial MET approach produced better results than the commonly used nonspatial MET analysis. 相似文献19.
Tapani Hirvonen Joni Orava Niko Penttinen Katri Luostarinen Markku Hauta-Kasari Mika Sorjonen Kai-Erik Peiponen 《Wood Science and Technology》2014,48(5):995-1003
In this study, a comprehensive spectral image database of Nordic sawn timbers for public use was measured. Economically significant Finnish wood species birch (Betula sp.), Norway spruce (Picea abies) and Scots pine (Pinus sylvestris) were chosen for inclusion in the database. The total of samples was 107 containing heartwood, sapwood, decayed wood, blue stain, mold, resin, early wood, late wood, knots, cracks, pith, reaction wood and bark. Board and crosscut samples were measured in frozen, melted and room-dried conditions. The reflectance of samples was measured over a 300- to 2,500-nm wavelength range. Additionally, the photoluminescence of samples excited by an ultraviolet B light source was measured. The spot size used was 250 μm with an 80 mm \(\times \) 200 mm imaging area, and produced all in all 44 million spectra. In this paper, examples of the possibilities of this spectral image database as a means of detection of the spatial distribution of aromatic lignin and the moisture content (MC) of nonfrozen timber were introduced and provided. From the results, it was found that it was possible to detect the lignin distribution from spectral images, and simple and robust methods for wood MC estimations were also introduced. 相似文献
20.
Cristina Prades Isabel Gómez-Sánchez Juan García-Olmo Florentino González-Hernández José Ramón González-Adrados 《Wood Science and Technology》2014,48(4):811-830
The aim of this study was to evaluate the potential of visible and near infrared spectroscopy (Vis/NIRS) in predicting the chemical, physical and mechanical behavior of single-piece natural corks stoppers used for sealing wine bottles. Two training sets of 90 and 150 cork stoppers were used to obtain four spectra per sample in different positions: two of the stopper bases (transversal section) and two of the stopper sides (tangential section and radial section). The samples were scanned in the range of 400–2,500 nm using a Foss-NIRSystems 6500 SY II spectrophotometer equipped with a remote reflectance fiber-optic probe. On each training set, two-thirds of the samples were used to develop modified partial least square (MPLS) calibration equations, and the remaining one-third of the sample for the external validation of these MPLS equations. The best equations were obtained for the transversal section, which is the recommended one when applying Vis/NIRS technology to cork. The best results for the chemical composition were obtained for waxes and total polyphenols, showing coefficient of determination of the cross validation (r cv 2 ) values of 0.64 and 0.56 and coefficient of determination of the external validation (r EV 2 ) values of 0.53 and 0.55, respectively. The best equation for the physical and mechanical parameters was obtained for moisture content (r cv 2 = 0.86 and r EV 2 = 0.85), with somewhat lower results for density, compression force and extraction force (r cv 2 = 0.66, 0.72, 0.52 and r EV 2 = 0.52, 0.49, 0.51, respectively). The SECV (standard error of cross validation) and SEP (standard error of external validation) were similar for all the physical and mechanical parameters, thus confirming the robustness of the equations. MPLS model for moisture content fulfills the requirements for screening (RPD >2.5), but MPLS models obtained for waxes, total polyphenols, density, compression force and extraction force are not good enough for routine analysis or quality control. The results obtained from the MPLS models based on Vis/NIRS technology would permit the continuous quality control of humidity in the production line as well as obtaining information about certain chemical components (extractives contents) and some physical and mechanical parameters (density, extraction force and compression force). 相似文献