共查询到20条相似文献,搜索用时 31 毫秒
1.
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
2.
Makrem Afif Chokri Messaoud Abdennacer Boulila Hnia Chograni Afef Bejaoui Mohamed Nejib Rejeb Mohamed Boussaid 《Annals of Forest Science》2008,65(7):710-710
3.
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
4.
5.
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6.
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
7.
Luciana Cavalcante Pereira-Rollo Demóstenes Ferreira da Silva Filho Mario Tomazello Filho Sergio de Oliveira Moraes Hilton Thadeu Zarate do Couto 《Wood Science and Technology》2014,48(4):689-701
Tomography is a wave-based technique used to depicture tree cross-sections; specifically, impulse tomography uses data given by the passage of impulse waves, which were primarily influenced by density, modulus of elasticity, and moisture content of wood. The influence of wood characteristics on various kinds of waves has been extensively studied, allowing the establishment of statistical correlations between wave behavior and wood properties. In this context, the relationship between impulse speed from cross-section tomography and conditioned density that was obtained on diametrical sample by X-ray densitometry was analyzed using logs of three tree species with different densities that were air dried to 12 % moisture content. For each species, means from 5 mm length intervals of conditioned density profile graph (ρ 12%) and impulse speed distribution graph (S 12%) on the same diametrical sample are used to fit models. Joining data from all species, the exponential model \( \ln \rho_{12\% } = - 4.32822 + 1.67894 *\ln S_{12\% } \) was obtained with correlation coefficient of 0.85 and highly significant parameters. The results indicate that conditioned density could be explained by impulse speed on the cross-section, but research is necessary to make a useful tool out of it. 相似文献
8.
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
9.
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
10.
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11.
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
12.
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13.
Jinghui Jiang Jianxiong Lu Yongdong Zhou Rongfeng Huang Youke Zhao Jiali Jiang 《Wood Science and Technology》2014,48(2):253-267
The properties of oak heat treated at temperatures of 160–220 °C, oxygen concentrations of 2–10 %, steam pressures of 0.1–0.4 MPa and treatment time of 2–4 h were investigated. Although modulus of elasticity (MOE), modulus of rupture (MOR) and equilibrium moisture content (EMC) of the heat-treated wood (HTW) were reduced, the value of $ \Updelta E^{*} $ was increased, and the dimensional stability [anti-swelling efficiency in radial (ASE-R), anti-humidity efficiency (AHE)] was improved considerably. Six regression equations (temperature, oxygen concentration, steam pressure and time as functions of MOE, MOR, ASE-R, AHE, EMC and $ \Updelta E^{*} $ ) were developed for the estimation and a nonlinear programming model was derived with operation research theory to obtain the most desirable HTW properties under some production constraints. 相似文献
14.
A digital image correlation (DIC) method was utilized to measure strain distributed within approximately 0.5 mm of the cutting edge during slow-speed orthogonal cutting of air-dried hinoki (Chamaecyparis obtusa), to clarify the relationships of the strain distribution and cutting conditions, including cutting angle (\(\theta\)) and depth of cut (\(d\)). The strain was measured in 0.04 mm steps, and the measurable minimum strain was approximately 0.08%. Tensile strain of 3% or larger normal to the cutting direction, \({\varepsilon _y}\), tended to extend 0.2 mm or further ahead of the tool when \(\theta \leq 60^\circ\) and \(d \geq 0.1{\text{ mm}}\). This tensile \({\varepsilon _y}\) corresponded to the occurrence of the fore-split in Chip Type I. The tensile \({\varepsilon _y}\) detected along the path of the cutting edge decreased as \(\theta\) and/or \(d\) decreased. Positive shear strain, \({\gamma _{xy}}\), tended to be detected ahead of the tool in Type I. Negative \({\gamma _{xy}}\) tended to be detected ahead of the tool in Type II and III \(\left( {\theta \geq 70^\circ ,\,\,d \geq 0.05{\text{ mm}}} \right)\). These \({\gamma _{xy}}\) values were considered to be related to the elongation and shrinkage of the chip. The study confirmed the usability of the DIC method for the evaluation of cutting conditions and also to classify chip formation into chip types. 相似文献
15.
We investigated genetic parameters for juvenile to mature growth and stem forking in black spruce [Picea mariana (Mill.) B.S.P.] in order to obtain reliable estimates for supporting eastern Canadian tree breeding strategies. The study was based on data collected from two series of progeny tests of black spruce in New Brunswick (NB) including 285 open-pollinated families and more than 57,000 individual trees. Height (HT), diameter at breast height (DBH), and stem forking (SF) were periodically measured between ages 5 and 35 years. Results showed that tree volume (V), HT and DBH were highly genetically controlled, with average individual narrow-sense heritability (\(h_{i}^{2}\)) estimates of 0.29, 0.29 and 0.21, and family mean heritability (\(h_{F}^{2}\)) estimates of 0.82, 0.85 and 0.77, respectively. SF had low \(h_{i}^{2}\) (= 0.06 on average) but had moderate \(h_{F}^{2}\) (= 0.56), indicating family selection might effectively reduce SF. Both \(h_{i}^{2}\) and \(h_{F}^{2}\) increased with age and then stabilized or declined, being the highest around ages 15–20 years for all traits. The type-B genetic correlation (\(r_{B}\)) estimates were moderate to high for all the traits, suggesting negligible genotype × environment interactions. Strong age–age genetic correlation estimates were found for growth traits, implying the potential for practicing early selection. Age–age genetic correlation estimates were moderate for SF (= 0.72). Trait–trait genetic correlation estimates were strong and positive among growth traits, but between growth traits and SF they were mostly negligible albeit positive. Overall, results suggest that genetic selection will be effective for growth traits but much less so for reducing stem forking in New Brunswick’s black spruce. 相似文献
16.
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
17.
To improve wood quality for pulpwood industries, it is important to examine not only wood density but also its components, especially tracheid characteristics. We studied genetic variations in the following tracheid traits by earlywood (EW) and latewood (LW): tracheid length (TL), double wall thickness (WT), radial lumen diameter (R_D1), tangential lumen diameter (T_D1), radial central diameter (R_D2), and tangential central diameter (T_D2). We also studied the relationship with the following growth traits: diameter at breast height (DBH), height (H), crown breadth south-north axis (NSC), crown breadth east–west axis (EWC), ring width (RW), latewood percentage (LWP), and wood density (WD). All sample materials were collected from a 33-year old clonal seed orchard of Pinus tabuliformis Carr. Genetic variation among clones was moderate for all tracheid traits, 9.49–26.03%. Clones significantly affected WT, R_D1, R_D2, T_D1, T_D2, and the two ratios WT/R_D1 and TL/T_D2 in EW but had no effects in LW. Clones significantly affected TL in LW but had no effects in EW. \( H\frac{2}{C} \) was higher in LW (0.50) than in EW (0.20) for TL, while \( H\frac{2}{C} \) was higher in EW (0.27–0.46) for other tracheid traits and the two ratios (TL/T_D2 and WT/R_D1) than in EW (0.06–0.22). WD and TL were significantly positively correlated, but WT and TL were negatively correlated both at individual and clone levels; all tracheid diameters and the four ratio values (EW_WT/R_D1, LW_WT/R_D1, EW_TL/T_D2 and LW_TL/T_D2), were strongly positively correlated with DBH, H, NSC, WEC and RW, and strongly negatively correlated with WD both at individual and clone levels. The most important variables for predicting WD were LW_TL, EW_WT and R_D1 in both EW and LW (r2 = 0.22). Selecting the top 10% of the clones by DBH would improve DBH growth by 12.19% (wood density was reduced by 0.14%) and produced similar responses between EW and LW for all tracheid traits: a reduction of 0.94 and 3.69% in tracheid length and increases in tracheid diameters (from 0.36 to 5.24%) and double wall thickness (0.07 and 0.87%). The two ratios WT/R_D1 and TL/T_D2 across tissues (EW and LW) declined 0.59 and 4.56%, respectively. The decreased tracheid length and the ratio between tracheid length and diameter is disadvantageous for pulp production. The unfavorable relationship of tracheid traits with wood density indicate that multiple trait selection using optimal economic weights and optimal breeding strategies are recommended for the current long-term breeding program for P. tabuliformis. 相似文献
18.
Modeling height–diameter relationships is an important component in estimating and predicting forest development under different forest management scenarios. In this paper, ten widely used candidate height–diameter models were fitted to tree height and diameter at breast height(DBH)data for Populus euphratica Oliv. within a 100 ha permanent plots at Arghan Village in the lower reaches of the Tarim River, Xinjiang Uyghur Autonomous Region of China. Data from 4781 trees were used and split randomly into two sets:75 % of the data were used to estimate model parameters(model calibration), and the remaining data(25 %) were reserved for model validation. All model performances were evaluated and compared by means of multiple model performance criteria such as asymptotic t-statistics of model parameters, standardized residuals against predicted height,root mean square error(RMSE), Akaike’s informationcriterion(AIC), mean prediction error(ME) and mean absolute error(MAE). The estimated parameter a for model(6) was not statistically significant at a level of a = 0.05. RMSE and AIC test result for all models showed that exponential models(1),(2),(3) and(4) performed significantly better than others. All ten models had very small MEs and MAEs. Nearly all models underestimated tree heights except for model(6). Comparing the MEs and MAEs of models, model(1) produced smaller MEs(0.0059) and MAEs(1.3754) than other models. To assess the predictive performance of models, we also calculated MEs by dividing the model validation data set into 10-cm DBH classes. This suggested that all models were likely to create higher mean prediction errors for tree DBH classes[20 cm. However, no clear trend was found among models.Model(6) generated significantly smaller mean prediction errors across all tree DBH classes. Considering all the aforementioned criteria, model(1): TH ? 1:3 t a= e1 t b?eàc?DBHT and model(6): TH ? 1:3 t DBH2= ea t b?DBH t c ? DBH2T are recommended as suitable models for describing the height–diameter relationship of P. euphratica. The limitations of other models showing poor performance in predicting tree height are discussed. We provide explanations for these shortcomings. 相似文献
19.
Liesbeth De Vetter Griet Depraetere Colin Janssen Marc Stevens Joris Van Acker 《Annals of Forest Science》2008,65(5):504-504
20.