Diameter distribution of trees in natural stands managed on polycyclic cutting system

Diameter frequency distribution in a specific stand provides basic information for forest resources management.In this study,four probability models were applied to analyze diameter distribution of natural forests after selective cutting with different intensities (low intensity of 13.0% in volume,medium intensity of 29.1%,high intensity of 45.8%,and extra-high intensity of 67.1%).The results show that the skewness and kurtosis of the four models are positive except that of low intensity selective cutting,which suggest that the number of small-size trees dominate the stand.The more intensity of selective cutting,the wider range of diameter distributions.The diameter structure of selective cutting with low intensity met Weibull and Beta distributions;that of medium intensity met Weibull,negative exponential as well as Gamma distributions;that of high intensity cutting met Weibull and negative exponential distributions,but that of extra-high intensity could not meet any above model.Weibull distribution model fits better than others regarding the structure of diameter distribution in natural forests managed on polycyclic cutting system.The results will provide basic information for sustainable management for mixed natural stands managed on a polycyclic cutting system.     

Weibull and percentile models for lidar-based estimation of basal area distribution

Abstract

The aim of this study was to assess the accuracy of basal area distributions of sample plots in coniferous forest derived from small-footprint airborne laser scanner data, and to compare the accuracy of two methods for derivation of such distributions based on: (1) two percentiles of a two-parameter Weibull and parameter recovery, and (2) a system of 10 percentiles defined across the range of observed diameters. The 12 percentiles were derived from the empirical basal area distributions of 141 plots with size 300–400 m². Regression analysis was used to relate the percentiles to various canopy height and canopy density metrics derived from the laser data. On average, the distance between transmitted laser pulses was 0.9 m on the ground. The plots were divided into three strata according to age class and site quality. The stratum-specific regressions explained 7–91% of the variability. Total plot volume predicted from the estimated distributions was used to assess the accuracy of the regressions. Cross-validation of the regressions revealed a bias of ?1.2 to 2.1% between predicted and ground-truth values of plot volume. The standard deviations of the differences between predicted and ground-truth values of plot volume were 15.1–16.4%. Neither bias nor standard deviation differed significantly between the two validated methods.     

抚育间伐对栓皮栎人工林直径和树高分布的影响

[目的]以河南登封林场栓皮栎人工林为研究对象,研究抚育间伐对林分不同生长阶段林木株数、林木直径分布和树高分布的影响,为制定科学合理的抚育经营措施奠定理论和技术基础.[方法]在株数强度为31.55％的间伐林分和条件基本一致的未间伐林分内,分别设置1个1 hm2样地,间伐作业2 a后获取每木检尺数据,分别利用Normal分...     

林分模拟径阶株数法确定小班蓄积的试验

利用数学模拟方法对小班林木径阶株数分布和小班蓄积量进行了模拟试验，结果表明：模拟法与标准地实测法差异不显著，且模拟法具有实用性强、生产使用方便、能充分发挥计算机的优越性等特点，可以快速模拟出林分的直径分布，为林业调查提供了快捷有效的技术手段。     

Evaluation of moisture content distribution in wood by soft X-ray imaging

A technique for nondestructive evaluation of moisture content distribution in Japanese cedar (sugi) during drying using a newly developed soft X-ray digital microscope was investigated. Radial, tangential, and cross-sectional samples measuring 100 × 100 × 10 mm were cut from green sugi wood. Each sample was dried in several steps in an oven and upon completion of each step, the mass was recorded and a soft X-ray image was taken. The relationship between moisture content and the average grayscale value of the soft X-ray image at each step was linear. In addition, the linear regressions overlapped each other regardless of the sample sections. These results showed that soft X-ray images could accurately estimate the moisture content. Applying this relationship to a small section of each sample, the moisture content distribution was estimated from the image differential between the soft X-ray pictures obtained from the sample in question and the same sample in the oven-dried condition. Moisture content profi les for 10-mm-wide parts at the centers of the samples were also obtained. The shapes of the profiles supported the evaluation method used in this study. Part of this work was presented at the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, August 2007     

林木直径大小多样性量化测度指数的比较研究

[目的]为了客观恰当地量化表达林分水平上的林木直径大小多样性。[方法]采用6块定位样地数据,对比分析基于直径分布的Simpson(D_N)、Shannon(H_N)及单木断面积Gini系数(GC),基于直径大小分化度的Simpson(DT)、Shannon(HT)及其均值(T-)这6种林木直径大小多样性量化测度指数,筛选出符合逻辑排序且具有较好辨别能力的直径大小多样性量化测度指数。[结果]6块样地的林木直径大小多样性逻辑排序为吉林胡桃楸针阔混交林经营样地吉林胡桃楸针阔混交林对照样地甘肃锐齿栎阔叶混交林经营样地甘肃锐齿栎阔叶混交林对照样地北京油松落叶松人工混交林样地北京侧柏人工纯林;林木直径大小多样性为天然林高于人工林,更为成熟的吉林老龄林样地高于甘肃中龄林样地,经过至少5年结构化经营的样地高于对照样地,人工混交林样地高于人工纯林样地。基于直径分布的DN、HN和GC测度的6块样地林木直径大小多样性排序结果与逻辑排序不一致;基于直径大小分化度的D_T、H_T和珔T测度的各林分林木直径大小多样性排序与逻辑排序一致。[结论]基于直径分布的D_N、H_N和GC量化测度指数不能恰当地表达林木直径大小多样性。基于直径大小分化度的D_T、H_T和珔T量化测度指数能恰当表达林木直径大小多样性;相对D_T和H_T,珔T是一个连续型变量的测度指数,而且能从林分整体水平上量化林木间的大小分化程度,易于解释其生物学意义。因此,认为珔T是恰当表达及区分各林分林木直径大小多样性的最优量化测度指数。     

Feature Extraction of defects on wood surface

IntroductionAtpresent,usingthecomputerimageprocessil1gsys-temtofinishthefeatureextractiol1ofw0oddefectsisi11anexpIorat0rystage.ThismetI1odmaydecreasetI1ellmitati0noftl1eexperilnel1talcol1ditions,suChasIights,instrumentsandsomespccialmateriaIs.Itiscol1venic11ttousethiswayandthegoodresuItswilIbeacI1ieved.TherearethreetypicaIwo0dsurfacedefectst0bestudiedintheexperiment,whicI1arekn0t,boreI1oleal1ddecayofLarixandBeIlIlu.Tl1eworkist0separatetl1edefectsfromthewoodsurfaceimagesandprovideagoodba…     

竹木复合砧板基材对其硬度和甲醛释放量的影响

为探究竹木复合砧板基材对其硬度和甲醛释放量的影响,分别选择基材为木材、竹材和人造板的3类竹木复合砧板,测定并分析其硬度与甲醛释放量。结果表明：基材为木材和竹材的竹木复合砧板硬度大于基材为人造板的竹木复合砧板硬度;基材为人造板的竹木复合砧板甲醛释放量大于基材为竹材和木材的竹木复合砧板甲醛释放量。研究结果可为生活中选择竹木复合砧板提供参考。     

锦州市自来水硬度特点及净化对策研究

通过表征锦州自来水,阐述了锦州自来水的特点,主要是高硬度特性,同时为了得到精确数值,采用EDTA络合滴定的方法进行了测定 ,得到总硬度数值为368.4,并采用煮沸法得到了锦州城市自来水的暂时硬度和永久硬度 ,分别为61.2和307.2.通过对数据分析,永久硬度所占比重大,提出了为去除永久硬度,建议采用离子交换吸附法去除.     

Characterising the diameter distribution of Sal plantations by comparing normal,lognormal and Weibull distributions at Tilagarh Eco-park,Bangladesh

For many years foresters have been using statistical probability density functions to describe and characterise stand structure. Predicting the current and future yields of a stand is essential for successful stand and timber management. Implicit prediction of current yield is accomplished by using diameter distribution methods. All diameter distribution yield systems predict the number of trees per unit area by diameter class. In this study, the normal, lognormal and the three-parameter Weibull probability density function were compared to characterise the diameter distributions of Sal (Shorea robusta) plantations grown at Tilagarh Eco-park, Bangladesh. Data from 70 plots, established in three plantations, were used for this study. The Weibull parameters were estimated by the maximum likelihood and moments estimator methods. A one-sample Kolmogorov–Smirnov test was used for the goodness of fit for all models. The Kolmogorov–Smirnov test results showed that both lognormal and Weibull distributions were suitable to characterise the diameter distributions of Sal plantations in the study area and may be applicable for other Sal forests in Bangladesh.     

林分未来直径分布预估精度的研究

为了给森林资源经营、管理提供指导,利用3块编号固定标准地调查资料,对常用的均匀分布、Meyer修正数据、累积分布曲线法等几种未来直径分布预估法进行了分析。结果表明,各种方法适应性都很强,其中以累积分布曲线法的精度最高,其精度是82.7%。     

木材加工企业供配电系统节能增效技术研究

通过对木材加工企业供配电系统中造成电能损耗的主要原因分析 ,进而提出节能增效的技术对策     

Diversity,structure and standing stock of wood in the homegardens of Kerala in peninsular India

A survey was conducted in 17 selectedthaluks (revenue sub-divisions) of Kerala state to elucidate the floristic structure, composition and the extent of similarities and diversities in the composition of homegardens of Kerala, with particular reference to small (below 0.4 ha), medium (0.5 to 2 ha) and large (>2.0 ha) holding size categories. Besides attempts wer also made to characterize the potential of homegardens to supply commercial timber and fuelwood. Two hundred and fifty two farmers were selected through a stratified random process. In addition to gathering general information on crop and livestock production enterprises, all scattered trees and shrubs (15 cm girth at breast height) on the homestead and border trees except palms and rubber were enumerated.There was tremendous variability both in the number of trees and shrubs present and species diversity of the selected homesteads in different provinces. The small, medium and large sized holdings also exhibited profound variability in the number of woody taxa and individuals present. In total, 127 woody species (Girth at Breast Height (GBH) 15 cm) were encountered. The mean number of woody taxa found in the homegardens ranged from 11 for Pathanapuram to 39 in Perinthalmanna. Floristic diversity was higher in the smaller homesteads. It decreased with increasing the size of holdings. Mean Simpson's diversity index for the homesteads ranged from 0.251 (Kochi) to 0.739 (Kottarakkara) suggesting that floristic diversity of homegardens was moderate to low compared to a value over 0.90 for the species-rich evergreen forests of the Western Ghats. The Sorensen's similarity indexes suggested a moderately high degree of similarity for the different tree species encountered in the homesteads of Kerala.No clear cut planting pattern was discernible in the homegardens of Kerala. The homegarden trees and shrubs were either scattered throughout the homestead or on farm boundaries. Farmers tend to prefer timber trees such as ailanthus (highest frequency) and teak besides fruit trees such as mango, jack, cashew and the like. Major homegarden species were represented in all diameter classes. The diameter structure, however, exhibited a slightly skewed (+) distribution pattern, having the highest frequency in the 20–30 cm classes ensuring adequate regeneration status and in that process making homegardens a sustainable as well as dynamic land use system.Standing stock of timber and firewood in the homestead of differentthaluks are presented. Average commercial standing stock of homesteads ranged from 6.6 to 50.8 m³ ha^–1 and fuel wood volume was of the order of 23 to 86 m³ ha^–1. Implicit in the high commercial timber volume and fuel wood volume is that a substantial proportion of the society's wood demands are met from the homesteads. Palms, however, constituted the dominant component of standing commercial timber and fuel wood volumes accounting as much as 63% and 72%, respectively, of the total wood in these categories.     

基于高斯-马尔可夫随机场的木材表面纹理分类

阐述了高斯-马尔可夫随机场模型的基本原理,建立了木材表面纹理的2-5阶高斯-马尔可夫随机场(Gauss-MRF)模型,用最小二乘法估计了300个木材样本表面纹理的2-5阶Gauss-MRF参数。数据分析表明,各不同纹理特征参数之间具有明显的分布性;Gauss-MRF参数值最大的参数所表示的纹理集聚方向为纹理的主方向;对于纹理主方向相同的样本,纹理越细致,其相应参数越大,而其他参数越小;Gauss-MRF阶数越高,纹理描述越细致;在2阶Gauss-MRF模型情况下,弦切纹理的B1参数大于径切纹理的B1;弦切纹理的B2、B3、B4分别小于径切纹理的B2、B3、B4。根据分离判据的值,确定以5阶Gauss-MRF参数为特征向量进行初步聚类,总体正确率为88%。     

木质材料激光表面处理研究进展

激光以其能量密度高、运行轨迹自如、方向性好等优点,被广泛用于木质材料切削加工以及表面处理等领域.其中,木质材料激光表面处理,即利用激光热/光电子效应促进材料发生物理、化学变化,以实现改性的目的.笔者对木质材料激光表面处理原理、激光类型与用途以及激光表面处理技术特点与应用领域等内容的研究现状进行了综述与分析.现有研究表明...     

A microwave applicator for on line wood drying: Temperature and moisture distribution in wood

Summary An especially designed open microwave applicator was analysed using wood as the material to be heated and dried. The idea was to develop an on line microwave construction consisting of several small open applicators, each fed by a small standard magnetron (for example 1.4 kW main power). The process was analysed by measuring the wood temperature during heating using an IR-camera and detecting the moisture distribution during drying by CT-scanning. Pine and birch wood samples were used in the experiments, mainly 40 mm in thickness. The experiments show that the power distribution differs between dry wood and moist wood. The analysis of the temperature fields captured by the IR-camera during the first minutes allows a rather accurate determination of the MW power. Consequently, the drying proceeds unevenly in the wood specimens, especially in the longitudinal direction. The dimensions of the applicator and its relation to the wood dimension are very important. However, the wood was not destroyed, the temperature and moisture gradients did not affect the wood in terms of checks or deformations. The drying rate in different positions of the specimen varied between 0.30 and 0.80 percentage moisture content/min. The uneven energy, meaning temperature and field distribution, is to be compensated in the future by a moving wood load and by alternating the position of each applicator in a larger scale microwave pilot plant. Received 25 February 1997     

黄土高原刺槐根系垂直分布特征研究

在中国西北黄土高原地区，水分是树木生长发育的主要限制因子。根系分布特征由于反映了树木对环境条件的利用程度而具有更加特殊的生态意义。本研究选择阳坡和阴坡不同立地上年龄一致的刺槐林调查了根系分布特征。根系垂直分布特征的调查结果表明，在所有立地上，根系生物量随着深度的增加而降低，其中细根的分布深度大于粗根的分布深度。方差分析结果表明：不同立地上不同径级根系的分布特征也有明显的差别，粗根是差异存在的主要原因，阴坡立地上的根系生物量，特别是细根生物量大于阳坡立地上的。对根系消弱系数的分析结果表明，阴坡立地上的根系消弱系数大于0．982，而阳坡立地上的根系消弱系数小于0．982，说明阴坡市地上刺槐根系的生物量在深层土壤中的分布相对量更大一些。其中细根的根系消弱系数大于粗根的，这种根系分布特征有利于根系对深层土壤水分养分的吸收利用，进而促进树木地上部分的生长发育。图3表3参15。     

云南松易燃可燃物径级分布规律研究

利用云南松树冠部分的易燃可燃物调查取得的资料,将树冠分为3个层次,每个层次按照标准分为1时滞(<1 cm)、10时滞(1~2.5 cm)、100时滞(≥2.5 cm)3类,分别分析不同层次与不同时滞的枝、针叶之间的关系。结果表明:云南松树冠各层的易燃可燃物的重量均随着径级的增大而增大;云南松树冠叶量的多少与火灾的发生有着很密切的联系,但是叶量多少并不能完全决定火灾发生的程度。     

纳米Al_2O_3改性水性木器漆耐磨性和硬度的研究

为提高水性聚丙烯酸酯木器漆的耐磨性和硬度,进行纳米Al2O3浆料的制备及其对水性木器漆改性的研究,探讨分析不同制备方法和Al2O3添加量对漆膜耐磨性和硬度的影响。结果表明:以聚丙烯酰胺为分散剂、聚乙二醇和辛基酚聚氧乙烯醚为润湿剂、聚乙烯吡咯烷酮为稳定保护胶,在高速搅拌下制成的纳米Al2O3浆料,在透射电镜下观察发现纳米Al2O3颗粒分布均匀,具有良好的分散性;在不影响漆膜透明度的情况下,漆膜耐磨性和硬度随Al2O3添加量增加得到提高,添加量在1.5%时漆膜具有较好的耐磨性和硬度;纳米杂合工艺法的漆膜耐磨性和硬度优于后添加法制备的水性木器漆涂膜。     

现实异龄林分最佳直径分布模型的探讨

根据在林业中已应用的直径分布模型的统计特征,选择适宜于异龄林分直径分布模拟的指数分布、韦布尔分布、贝塔分布模拟现实异龄林分直径分布。结果表明,对于现实经营林分,由于直径分布不连续、左偏等原因,韦布尔分布模拟效果最好,贝塔分布次之,指数分布最差,这表明现实林分距理想林分还有较大差距。