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1.
以海南省的２种针叶树材及１５种阔叶树材为材料，进行了海口地区板材气干试验。试样厚度以２５ｍｍ为主，试验结果如下：①一年中，１、２、１１及１２月的干燥速率低，不适宜于木材气干；②树种与板材厚度对干燥率影响大；③以２５ｍｍ厚板的干燥率为１．０，１５ｍｍ板为２．２，５０ｍｍ板为０．３；④气干过程，木材含水率对干燥率的影响最大，相对湿度和温度次之，风速和大气压力的影响不显著；④板材种间的平均平衡含水率差异显著，厚度间差异不显著 相似文献
2.
高温炭化处理对木材平衡含水率的影响规律 总被引：1，自引：1，他引：0
本文在160~220℃范围内,对人工林马尾松木材进行了高温炭化处理,并研究了处理温度和处理时间对木材平衡含水率的影响规律。结果表明:随着炭化温度的提高,木材的平衡含水率降低,当炭化温度为160℃、180℃、200℃、220℃时,马尾松木材的平衡含水率分别为7.18%、6.84%、6.25%和4.88%,与对照材相比,其平衡含水率分别降低了16.81%、20.83%、27.60%和43.53%;随着炭化时间的延长,木材的平衡含水率逐渐降低,当炭化时间为1 h、2 h、3 h、4 h时,马尾松木材的平衡含水率分别为7.01%、6.83%、6.48%和6.25%,与未处理材相比,其平衡含水率分别降低了18.82%、20.89%、24.92%和27.60%。 相似文献
3.
在4个不同温度和时间水平下,对人工林杉木木材进行高温热处理,研究了处理温度和时间对木材吸湿性和尺寸稳定性的影响规律。结果表明:高温热处理可以显著降低木材平衡含水率、吸水率和体积膨胀率,提高尺寸稳定性;随着处理温度的增加和处理时间的延长,杉木平衡含水率、吸水率和体积膨胀率降低;与处理时间相比,处理温度对平衡含水率、吸水率和体积膨胀率的影响程度更大。在本研究范围,与对照材相比,通过高温热处理可以使杉木平衡含水率降低17.73%~66.74%,吸水率降低33.99%~64.00%,体积膨胀率减少36.7%~69.30%。 相似文献
4.
在木材加工技术中,木材干燥理论包括木材平衡含水率理论、木材传热理论、木材水分扩散理论以及木材干燥应力与应变理论。以上几大理论涉及到木材的干燥处理、加工、维护以及强度设计。木材干燥理论在木材加工中具有十分重大的意义。 相似文献
5.
采用人工神经网络BP型3层映射模式,对东北林业大学木材干燥实验室俄罗斯产落叶松进行木材含水率测定,干球温度平衡含水率和预热阶段干燥阶段的木材含水率以干燥机内部所测定为基准作为输入矩阵,以所测定的木材降温阶段和湿热阶段所测定的木材含水率作为输出矩阵从而确定3层形式,作出一段周期内落叶松控制系统降温和湿热阶段含水率预测,通过网络训练获得最佳权值,作为预测模拟参数,通过调整干球温度和其他参数使在半自动控制中木材含水率达到可控效果,从而在今后的干燥过程中可以通过含水率的预测得以实现对温度的调控。 相似文献
6.
防止马尾松木材蓝变的技术措施 总被引：4，自引：0，他引：4
防止马尾松木材蓝变的技术措施欧阳明八，何显进（中国林科院木材工业研究所北京１０００９１）（广西宁明木材厂宁明５３２５０１）马尾松边材色泽素白，纹理美观，强度适中，是我国南方主要用材树种，但马尾松木材在存放过程中易发生蓝变。刚采伐的松木，含水率达１００... 相似文献
7.
ＮＥＭ－２型电容数字式木材刨花含水率测定仪是为木材刨花板生产线而设计，采用ＭＣＳ－５１单片机应用系统，利用频率测量法测定木材刨花通过电容传感器时由于含水率不同引起的电容的变化，从而测定了木材刨花的含水率。 相似文献
8.
9.
短周期工业材干缩率和干燥应变规律的研究 总被引：1，自引：0，他引：1
研究了短周期工业材在干燥过程中木材表层和内部各层干缩率及弹性和塑性应变的变化规律。结果表明,基准硬度水平对应变值的大小和最大变就值的到达时间有显著影响。干燥前期,木材表层伸张弹性应变最大值随着温度和平衡含水率的增加而减少,木材表层塑性应变则随平衡含水率的增加而增加。正确调节基准初期阶段的平衡含水率水平,能有效地控制干燥前期应变最大值,从而达到控制干燥质量的目的。 相似文献
10.
广州地区木材平衡含水率及吸湿滞后的研究 总被引：3，自引：1，他引：3
根据1972-1974年在广州测定的数据,通过电子计算机进行运算,得出 W_6=-2.657557-0.01391679t+0.2315497φ线性回归方程式。并用北京、哈尔滨、十堰、厦门等地的平衡含水率实测值与线式计算值、现行教科书中的曲线回归方程式进行比较。这些材料说明,在表示木材平衡含水率与周围大气温湿度之间变化规律时,线性回归方程优于曲线回归方程。另外,还对木材吸湿和解吸进行具体地论述。 相似文献
11.
海口市古树名木现状及其保护对策 总被引：4，自引：0，他引：4
根据海口市(2005~2006年)古树名木普查结果,讨论分析了海口市古树名木的数量、种类、树龄组成及分布情况,结合保护现状及存在问题提出了相应的保护对策。
相似文献
12.
本文利用在安徽省安庆市大观区海口镇南埂长江滩地不同时期所做的杨树解析木资料,较为系统地研究了滩地杨树人工林的生物量及生长量,并建立了其材积生长方程和生物量方程。结果表明：长江滩地杨树林分具有较高的生长量和森林生产力,并且能够维持较长时间的快生长,这有利于长期维持滩地森林生态系统的稳定性,持续有效地发挥“抑螺防病林”的功能,同时也具有较高的经济效益;长江滩地杨树的数量成熟迟于一般杨树林分,约在22年左右;长江滩地杨树树干生物量的分配比例在60％以上,树枝17％左右,树叶3％左右,树根大致在13％-19％之间,树干生物量分配比例随年龄增加而增加,枝叶则略有下降,而树根下降较多。 相似文献
13.
基于异速生长和理论生长方程的广东省木荷生物量动态预测 总被引：1，自引：0，他引：1
【目的】将异速生长方程与理论生长方程相结合,预测广东省木荷生物量动态,为广东省木荷林碳汇计量提供模型和方法,为其他树种碳汇计量提供可借鉴的方法学支持。【方法】基于实测样木生物量调查数据,包括40株树干解析资料,构建由胸径和年龄的理论生长方程以及地上生物量和胸径的异速生长方程组成的模型系,利用非线性度量误差联立方程组,在胸径生长速度分级情况下拟合模型参数;基于3期森林资源连续清查固定样地样木数据,对广东省木荷生物量动态进行预测。采用决定系数( R 2)和均方根误差(RMSE)评价模型拟合效果,通过生物量存量估计误差和增量估计误差判断模型预测效果。【结果】在胸径生长速度分级情况下,理论生长方程中年龄对胸径的解释率达0.95以上,比不分级提高0.166 3,均方根误差下降到1.97 cm,降低2.16 cm以上,预测胸径对地上生物量的解释率提高到近0.82;接近独立异速生物量模型中实测胸径对地上生物量的解释率达0.88以上,比不分级提高近0.30,均方根误差下降到51 kg左右,下降30 kg以上。在胸径生长速度不分级情况下,各期生物量存量估计误差变动幅度在-46.31%~77.45%之间,而分级情况下下降到-16.13%~7.06%;在尺度上,分级与不分级均呈相同规律,即单木误差小于林分误差、林分误差小于区域误差。不分级时,单木水平和区域尺度间的误差不大于10%,而分级时小于8%。不同间隔期生物量增量估计误差,不分级时估计值普遍偏大,在32.57%~115.45%之间,而分级时下降到-6.57%~15.77%之间,在单木尺度上不超过±10%;随着尺度增大,增量估计误差不断增加,不分级时单木水平和区域尺度间的误差介于10%~15%之间,分级时稳定在8%左右。【结论】对于理论生长方程和异速生长方程组成的模型系,分级可极大提高模型精度,减小预测估计误差;生长速度不分级时,仅利用胸径或年龄数据,分级时,则可利用2期胸径数据或1期胸径和年龄数据,就可预测未来生物量动态,简单方便,在森林资源连续清查和碳汇造林的碳汇量计量中具有极大应用价值,区域尺度上的估计误差也可基本满足精度要求。 相似文献
14.
I. Ezenwa L. Reynolds M. E. Aken'ova A. N. Atta-Krah J. Cobbina 《Agroforestry Systems》1995,29(1):9-20
A study was conducted at Fasola (7°45 N and 3°5 E) in southwest Nigeria to determine the best tree cutting scheme for forage production and the effects of hedge configurations on tree, grass and total forage productivity of 6–8-year-old leucaena (Leucaena leucocephala Lam. de Wit) and gliricidia (Gliricidia sepium Walp.)-Guinea grass (Panicum maximum Jacq. cv. Ntchisi) mixture. After a uniform cut at the end of January 1990 (mid-dry season), the trees were cut according to the following cutting regimes: one cut after a 12-month regrowth (12M); two cuts after three- and nine-month regrowth (3–9M); two cuts every six months (6-6M); two cuts after nine- and three-month regrowth (9-3M); three cuts, two cuts every three months and the third cut after a six-month regrowth (3-3-6M), and four cuts every three months (3-3-3-3M). Grass was cut every six weeks between April and October followed by a cut in January. The hedge configuration was either one or three hedgerows of mixed stands of leucaena and gliricidia. There were twice as many trees and one-third less grass in the triple than in the single hedgerow hedge configuration.The 3-3-3-3M, 9-3M and 3-3-6M cutting regimes produced the highest total forage (tree foliage + grass) dry matter yields (DM) of 6.54, 5.80 and 5.77 t DM ha–1 annum–1, respectively. The magnitude of the difference between the tree forage yields of the triple and single hedgerow plots (16%) did not reflect the theoretical difference in the number of trees (33%) in the two arrangements. 相似文献
15.
Aboveground respiration of five 8-year-old trees of field-grown hinoki cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) was nondestructively measured at monthly intervals over 1 year with an enclosed standing tree method. The relationship between monthly specific respiration rate and monthly mean relative growth rate at the individual tree level was described by a linear equation. During the dormant season, respiration was used mainly for maintenance purposes, whereas during the growing season, more than 40% of the respiration was used for growth purposes, i.e., 60 to 70% in May. We conclude that annual maintenance and growth respiration of a tree are directly proportional to the aboveground phytomass and its annual increment, respectively. The maintenance coefficient was estimated to be 0.504 +/- 0.039 (SE) kg kg(-1) year(-1), indicating that the amount respired for maintaining already existing phytomass was equivalent to about half of the existing phytomass. The growth coefficient was estimated to be 0.772 +/- 0.043 (SE) kg kg(-1), indicating that the amount respired for constructing new phytomass was equivalent to about three-fourths of the annual phytomass increment. The annual stand maintenance and growth respiration were, respectively, 8.8 Mg ha(-1) year(-1) for an aboveground biomass of 17.4 Mg ha(-1) and 5.0 Mg ha(-1) year(-1) for an annual stand aboveground biomass increment of 6.5 Mg ha(-1) year(-1). About two-thirds of the total respiration was used to maintain already existing biomass, and about one-third was used to construct new biomass. 相似文献
16.
We evaluated annual productivity and carbon fluxes over the Fontainebleau forest, a large heterogeneous forest region of 17,000 ha, in terms of species composition, canopy structure, stand age, soil type and water and mineral resources. The model is a physiological process-based forest ecosystem model coupled with an allocation model and a soil model. The simulations were done stand by stand, i.e., 2992 forest management units of simulation. Some input parameters that are spatially variable and to which the model is sensitive were calculated for each stand from forest inventory attributes, a network of 8800 soil pits, satellite data and field measurements. These parameters are: (1) vegetation attributes: species, age, height, maximal leaf area index of the year, aboveground biomass and foliar nitrogen content; and (2) soil attributes: available soil water capacity, soil depth and soil carbon content. Main outputs of the simulations are wood production and carbon fluxes on a daily to yearly basis. Results showed that the forest is a carbon sink, with a net ecosystem exchange of 371 g C m(-2) year(-1). Net primary productivity is estimated at 630 g C m(-2) year(-1) over the entire forest. Reasonably good agreement was found between simulated trunk relative growth rate (2.74%) and regional production estimated from the National Forest Inventory (IFN) (2.52%), as well as between simulated and measured annual wood production at the forest scale (about 71,000 and 68,000 m(3) year(-1), respectively). Results are discussed species by species. 相似文献
17.
红松苗龄型对苗木质量和造林效果的影响 总被引：5，自引：0，他引：5
以春季播种、2年生红松苗(S2-0),春季播种、2年后移栽、再培育1年的3年生红松苗(S2-1),春季播种、2年后移栽、再培育2年的4年生红松苗(S2-2)、秋季播种、2年生红松苗(F2-0)为对象,研究不同苗龄间苗木质量和造林效果的差异。结果表明:与S2-0相比,S2-1苗高、地径、FOLR、单株生物量分别增加100%,108.2%,100%和398.4%,单株氮、磷、钾含量分别增加368.6%,646.2%和349.3%;S2-0造林成活率仅为67.5%,S2-1比S2-0造林成活率提高20.6%。S2-0移栽2年后,苗木质量提升幅度较移栽1年小;S2-2与S2-1造林成活率、地径生长量无显著差异。F2-0的苗高较S2-0大35.4%,造林成活率提高5.6%,秋季播种红松可促进苗木质量的提高。S2-2,S2-1,S2-0,F2-0的FOLR分别为18,14,7和7,FOLR与造林成活率、苗高、地径均显著相关,FOLR是评价红松苗木质量的简易、可靠指标。 相似文献
18.
Changes in use of both stored and newly synthesized sources of carbon (C) and nitrogen (N) were investigated during rooting of leafy cuttings of Larix x eurolepis A. Henry. We used dual (13)C and (15)N long-term labeling of reserves of stock plants and followed isotope dilution of the labels in the cuttings to determine the respective proportions of C and N derived from stock plant reserves (Q(C,old), Q(N,old)) and from newly synthesized sources (Q(C,new), Q(N,new)). We also assessed their partitioning into the growing needles and roots. Because rooting development occurred over several months, destructive harvests were made during three periods (t(0): April 9; t(1): May 15 to June 5; t(2): June 12 to June 26). Total C content (Q(C)) of cuttings did not change with time, whereas total N content (Q(N)) decreased significantly between t(0) and t(2). In rooted cuttings, unlike unrooted cuttings, total N concentration decreased less markedly in needles and in the lower stem component between t(1) and t(2) than between t(0) and t(2). The lower stem of rooted cuttings contained more Q(N,old) than that of unrooted cuttings and showed lower C:N and (13)C:(15)N ratios. The increase in Q(N,new) in the lower stem was positively correlated with rooting status. At t(1), new roots appeared and grew mainly at the expense of Q(C,new) and Q(N,old). By t(2), root growth was mainly dependent on new assimilates. We conclude that in leafy cuttings the initial amount of N reserves, rather than C reserves, may constitute a limiting factor for rooting. 相似文献
19.
The equilibrium moisture content (EMC) of six wood species under desorption conditions of 20°C and 100% 0% relative humidity (RH), and the rate of adsorption at various depths of three wood species blocks under 98% RH at 22.5°C were studied. There were no significant differences among the EMC values for these six wood species over the RH range 40% 0%, but there were highly significant differences over the RH range 100% 50% at constant 20°C. The amount of moisture absorbed in the wood decreased curvilinearly with the increase of depth in the specimens as sorption time increased, and their relation could be represented by a semilogarithmic equation. Time-dependent adsorption behavior at various depths of the wood specimens could be represented by an exponential equation as a function of the product of the difference between moisture contents at equilibrium and initial conditions and the term (1 – e–t/). The value of of various wood species was found to increase linearly with the increased depth of the specimen and showed the following trend: hard maple (Acer sp.) > China fir (Cunninghamia lanceolata) > Japanese cedar (Cryptomeria japonica D. Don).Part of this report was presented at the 47th annual meeting of the Japan Wood Research Society, Kochi, April 1997. 相似文献