用热扩散式茎流计测定园林树木蒸腾耗水量

采用热扩散式边材液流探针和环境自动监测系统对北京3种园林树木的树干液流及主要环境因子进行了一个生长季的同步观测.结果表明,3树种树干液流的日变化呈明显的单峰曲线,晴天的液流速率大于多云天和阴天,紫叶李和悬铃木的日耗水量明显大于元宝枫;对不同天气3树种每h的液流速率与相应的环境因子进行逐步回归分析.结果显示,影响3树种液流速率的主要环境因子是空气温度、空气相对湿度、辐射强度和5 cm土层温度,在不同天气里起主导作用的因子不同,环境因子与树干液流之间的数量关系能较好地预测树木的蒸腾耗水量.     

An “electronic nose” as a potential device for fire detection of forest product fire loads in enclosures

Abstract

Saving lives and properties are of primary importance in fire disasters. Unfortunately, current fire detectors are not fast enough to allow the detection of many fires, especially, at the smouldering stages. Some preliminary studies on laevoglucosan (LG), as an important product from cellulose degradation, have shown interesting properties and could be detected by devices classified as “electronic noses” (e-noses). In the present work, the mechanisms of pyrolysis of some ligno-cellulosic materials were investigated using thermo-gravimetric analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy and by a tube furnace with a view to determining the major degradation products from wood, white paper and cardboard samples. Additionally, an odour sensor, made of tin oxide semiconductor thin film, was employed to evaluate its sensitivity in detecting LG. It was found that LG can be readily found among the thermal degradation products of cellulosic materials in question, and that the metal oxide sensor employed was sufficiently sensitive in detecting its presence. Therefore, the work opens up the potential of using such a sensor as an “e-nose” for the early detection of fires stemming from forest product fire loads in storage places and in other enclosures.     

应用回归分析法测定白杨无性系生长的稳定性

本文报道了3个白杨杂种无性系在河北省5个县6a的造林试验结果。应用回归分析方法测定了无性系生长的稳定性,预测了它们的适生范围。结果表明,3个无性系平均树高和平均胸径均优于对照种易县毛白杨。741树高生长在有利环境条件下优势明显,胸径生长稳定性强,适合在各种生产水平下栽种。303树高生长在较差环境下表现出较大优势,胸径生长在各生产水平下栽种均表现较好。106稳定性较差,选用时应慎重。     

Improvements in dimensional stability and lightfastness of wood by butyrylation using microwave heating

Microwave heating was used as the heat source for butyrylation of wood with the aim of reducing the reaction time. The photostability and dimensional stability of butyrylated wood were also investigated in this study. Chemical changes of wood were confirmed by cross polarization/magic angle spin ¹³C-nuclear magnetic resonance and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) after butyrylation by microwave heating. Results from DRIFT with the Si-Carb sampling technique revealed that, using microwave heating, a higher degree of butyrylation of maple wood occurred in the middle of the specimen than on the outer surface. The increase in yellowness index of butyrylated wood treated with microwave heating was much less than that of untreated wood after the lightfastness test, indicating that photoyellowing of wood is effectively inhibited by butyrylation using microwave heating. The dimensional stability of wood was also improved after modification.     

内应力释放对刨花板尺寸稳定性的影响分析

研究了热压过程中内应力的形成机理和板材内部应力状态,探讨了内应力释放对刨花板尺寸稳定性的影响,提出了减小内应力和提高尺寸稳定性的工艺措施.刨花板会发生变形,即尺寸不稳定,源于以下两个基本原因:(1)构成刨花板主体单元的木材有吸湿性;(2)刨花板在热压过程中产生了内应力即残余应力.刨花板内应力释放时,人们可以实实在在地感觉到,例如:刨花板热压结束后,卸板时板坯内会传出嘣、嘣、嘣的声音,或者是规整而无变形的刨花板在开料后会发现有翘曲变形出现.这就是残存在刨花板内部的应力在释放.本文根据木材传热传质的理论、应力松驰理论、相平衡理论对刨花板内应力形成机理和应力状态及内应力释放对刨花板尺寸稳定性的影响进行分析和研究,为生产提供理论指导.     

杉木采伐对集水区土壤热状况的影响

土壤作为森林生态系统的子体系 ,是林木扎根并赖以生存的基础 ,也是土壤微生物一切生命活动的场所。因此 ,有关土壤养分、水分及其土壤物理结构特征等方面的研究报告颇多 (王政权等 ,2 0 0 0 ;张合平等 ,1 997)。但是有关森林土壤的热状况 ,以及林木采伐后对土壤热状况影响的研究报导很少 (康文星等 ,1 989;刘煊景等 ,1 993)。本文在获得采伐前连续 3年和采伐后连续 3年的观测数据的基础上 ,就杉木人工林生态系统土壤的热状况各因子之间 ,土壤各组成成分对热状况的单一或组合效应 ,以及皆伐这种人为强烈干扰对土壤热状况的影响进行了剖析。…     

Thermal diffusion in Masson pine wood

In order to analyze the effects of the temperature gradient on moisture movement during the highly intensive microwave-vacuum drying, thermal diffusion of Masson pine wood was studied. Internal distribution of temperature and moisture in Masson pine samples sealed by epoxy resin and aluminum foil was measured, the magnitude of thermal diffusion was calculated and the influencing factors of thermal diffusion were discussed. Results showed that with the transfer of moisture toward the low temperature in wood, opposite temperature and moisture gradient occurred. The initial moisture content （MC）, temperature and time are important factors affecting this process; the thermal diffusion is in proportion to wood temperature, its initial moisture and time. The temperature and distance from hot surface is strongly linearly correlated, and the relationship between MCs at different locations and distance from the hot end surface changes from logarithmically form to exponentially form with the increase in experimental time.     

Plant antifreeze proteins and their expression regulatory mechanism

Low temperature is one of the major limiting environmental factors which constitutes the growth, development,productivity and distribution of plants. Over the past several years, the proteins and genes associated with freezing resistance of plants have been widely studied. The recent progress of domestic and foreign research on plant antifreeze proteins and the identification and characterization of plant antifreeze protein genes, especially on expression regulatory mechanism of plant antifreeze proteins are reviewed in this paper. Finally, some unsolved problems and the trend of research in physiological functions and gene expression regulatory mechanism of plant antifreeze proteins are discussed.     

流溪河国家森林公园森林景观稳定性评价

在ARC/INFO支持下,将广州市流溪河森林公园划分为16个景观类型,选取12个景观稳定性指标,建立森林景观稳定性评价指标体系,利用FRAG STATS软件定量计算景观指标值,建立景观指标标准化矩阵,构造森林景观稳定性综合评价模型.结果表明:流溪河森林景观类型的稳定性差异较大,其稳定性大小依次为硬阔叶林—阔叶混交林—竹林—软阔叶林—非林地—针阔混交林—杉木—木荷—相思—茶叶—马尾松—荔枝—湿地松—龙眼—木本果树—未成林造林地.     

ＦＲ—１、ＦＲ—２及ＰＦ树脂对木材阻燃、防腐、尺寸稳定等效果的研究

功能性改良药剂ＦＲ－１、ＦＲ－２及ＰＦ树脂处理马尾松、毛白杨后对木材阻燃、防腐、尺寸稳定及ＭＯＥ／ＭＯＲ的研究结果表明，ＦＲ－１处理的马尾松吸药量为３４．５kg/m^3时，氧指数可达６１％。ＦＲ－１处理的马尾松、毛白杨达到阻燃标准时，其用药理根据板材的厚度进行了初步确定，剂量范围为３０－９０kg/m^3。ＦＲ－１及ＦＲ－２在达到阻燃用药量的同时，处理后的马尾松、毛白杨耐腐试验的重量损失率小于或按拉１０％。ＦＲ－１处理的马尾松、毛白杨、吸药量分别为７５．６及９３．５kg/m^3时，吸水至饱和时，木材抗湿胀率（antiswelling ef-ficacy,ASE)分别为３０％、４６％；ＰＦ树脂处理的马尾松、毛白杨 、吸药量分别为７９．０％、６３．８kg/m^3时，ＡＳＥ分别为４６．２％、４１．４％。各处理对抗弯弹性模具（ＭＯＥ）影响为，ＦＲ－１处理的马尾松，ＭＯＥ差异不明显，ＦＲ－１处理的毛白杨，ＭＯＥ增加幅度为６．１％，ＰＦ树脂处理的马尾松，毛白杨、ＭＯＥ增加幅度分别为１０．６％及１７．９％。ＦＲ－１处理的马尾松、毛白杨对抗弯强度（ＭＯＲ）影响不明显。