Chemical changes of kenaf core binderless boards during hot pressing (I): influence of the pressing temperature condition

Self-bonding is the main factor of the performance expression of binderless boards, and therefore its clarification is considered to be an important issue. For this purpose, a series of chemical analyses were conducted on kenaf core binderless boards and their chemical changes during the hot-pressing process are discussed in this article. First of all, binderless boards were prepared from kenaf core powder at different pressing temperatures (without steam-explosion process) and were used for chemical analyses after they were reduced into powders and extracted with methanol. To investigate their chemical changes, lignin, holocellulose, and neutral sugar contents were determined, Fourier transform infrared (FTIR) spectra were recorded, and the nitrobenzene oxidation procedure was applied. As a result, it was found that parts of lignin and hemicelullose were decomposed during the hot-pressing process; however, the contribution of the resulting fractions to selfbonding was not observed. In addition, progress of condensation reactions in lignin and the formation of chemical bonds by low molecular weight conjugated carbonyl compounds in methanol extractives were observed. Thermal softening of lignin is also suggested to play an important role in the expression of board performance.     

Atmospheric lead and cadmium deposition within forests in the Kanto district, Japan

Atmospheric lead and cadmium deposition in bulk precipitation and throughfall was investigated at four forests in the Kanto district, Japan, to assess the impact of human activities on the environmental health of forests. Annual lead and cadmium depositions in bulk precipitation ranged from 8.9 to 25.7 g ha⁻¹ year⁻¹ and from 0.77 to 1.30 g ha⁻¹ year⁻¹, respectively. Lead and cadmium deposition increased in the summer at every forest due to large amounts of rainfall. At one of the forests, the depositions were also high in the winter due to heavy snowfall. These depositions were similar to recent depositions observed at other rural and urban sites in Japan and several forests in Europe and North America after 1990. These results indicate that although anthropogenic lead and cadmium are deposited at these rates over wide areas, depositions are still higher than in remote areas.     

沙地樟子松天然更新与降水因子的灰色关联度分析

沙地樟子松人工固沙林的天然更新在大部分引种地不能很好地进行，其天然更新存在着某些障碍因子。通过对辽宁省昌图县傅家林场樟子松天然更新情况的调查，采用灰色关联度分析的方法，对更新与降水因子的关系进行了分析。结果表明，更新产生的当年12月和翌年1，2月的降水量，即冬季降雪情况与天然更新关联最大。说明了冬季降雪是影响樟子松天然更新的一个关键因子。     

亚热带杉木、马尾松人工林水文功能的研究

1984-1990年,在江西省分宜县山下林场,对22年生杉木,马尾松人工林中的主要水文要素:降雨、林冠截留、树干茎流、土壤水分含量、径流及各种水的养分含量进行了测定,结果表明:人工林林冠的截留率为10.20-17.56％,茎流率为0.98-1.40％。土壤层较薄,含水率低,水文物理性质较差,土壤蓄渗性能较弱。林地径流量较小,且多为表层流。降雨输入林地的养分量大于径流的输出量。林内雨和树干茎流淋溶的养分量占养分还原总量的48-53％。其淋溶的K、Mg、N的养分量超过凋落物归还量。     

甘蔗渣苯甲基化改性研究

以NaOH作为润胀荆及催化剂，以氯化苄为醚化剂对甘蔗渣进行了苯甲基化改性，研究了氯化苄用量、反应温度、碱用量及反应时间对甘蔗渣苯甲基化反应的影响，并用红外光谱对苯甲基化甘蔗渣进行了初步表征。     

国外引种松树松脂化学组成的特征

Ｗ．Ｂ．Ｃｒｉｔｃｈｆｉｅｌｄ和Ｅ．Ｌ．Ｌｉｔｔｌｅ，Ｊｒ．将油松组松树分成６个亚组。本文采用ＧＣ、ＧＣ－ＭＳ方法对分属４个亚组的１６种国外引种松树松脂化学组成的特征进行研究，发现每一个亚组的松脂各有其特点。马尾松、黄山松等国内松树树种与黑松、琉球松、同属一个亚组，其松脂的化学特征比较相似；而与湿地松、火炬松等另一亚组松脂则有较大区别，说明亚组的划分有利于松树的化学分类。不同地理变种的加勒比松松脂     

温度和降水变化对太行山森林蓄积增长的影响

利用太行山区 77个气象台站和 72 1个人工林标准地的调查数据 ,借助回归分析方法 ,对温度、降水变化对森林生长的影响进行了探讨。结果表明 ,在太行山区 ,温度与纬度、海拔之间相关显著 ,温度与森林蓄积量显著相关 ;对于平均林龄为 2 3a左右的人工林 ,在西北坡 ,温度升高、降水变化 ,对森林蓄积量无显著影响 ;但在河北省即太行山东南坡 ,温度每升高 1℃ ,森林蓄积量下降 6 88～ 8 12m3 hm2 ,降水每增加 10 0mm ,森林蓄积量增加 2 1 1m3 hm2 。     

Rapid assessment of wood chemical properties and pulp yield of Eucalyptus camaldulensis in Thailand tree plantations by near infrared spectroscopy for improving wood selection for high quality pulp

Near-infrared (NIR) spectroscopy has been demonstrated as a means for rapid nondestructive determination of the chemical composition and final pulp yield of Eucalyptus camaldulensis in Thailand tree plantations. Multiple linear regression (MLR) analysis and partial least squares (PLS) analysis were introduced to develop statistical models in terms of calibration equations for total pulp yield, screened pulp yield, and contents of -cellulose, pentosans, and lignin in wood. In MLR analysis, a reasonably good calibration equation was found only for pentosans (standard error of prediction (SEP): 0.98%). The PLS analysis improved the accuracy of prediction for every criterion variable, especially for pentosans (SEP: 0.91%) and lignin (SEP: 0.52%). Also, in the case of screened pulp yield, we were able to use such a statistical result as an indicator of the characteristics of the pulp and paper. Thus, NIR spectroscopy could be satisfactorily used as an effective assessment technique for Eucalyptus camaldulensis plantation trees.     

Water absorption of boron-treated and heat-modified wood

Heat treatments change the chemical and physical properties of wood and dimensional stability and hygroscopicity are affected as a result of modifications of wood cell components. This study evaluated the water absorption of wood specimens treated with boron compounds followed by heat treatment. Sugi (Cryptomeria japonica D. Don) sapwood specimens treated with either boric acid (BA) or disodium octoborate tetrahydrate (DOT) solutions were heat-modified at either 180° or 220°C for 2 or 4 h. Carbohydrate composition and water absorption of the specimens were then measured and compared with those of untreated and unheated specimens. Wood carbohydrates were significantly degraded in the specimens after heat treatment. The heat treatment evidently decreased the water absorption and the heat-modified specimens absorbed less water than unheated specimens. The higher the treatment temperature and the longer the treatment time, the lower the amount of absorbed water. The boron-treated and heat-modified specimens, however, showed increased water absorption due to the hygroscopic properties of BA and DOT.     

小陇山林区主要林分对降水的再分配

选择锐齿栎、油松、华山松和落叶松林分为对象，系统同步观测了大气一次性降水过程中，不同郁闭度梯度林分群体的林冠透过降水、树干流量、林冠层截留量与大气降水历时、降水强度变化的基本数据。用数量级化理论(I)和线性方程，动态地描绘出各分量随大气降水变化而变化的趋势。揭示出林分对降水的再分配以及求算1年内不同时段林地补给水量的可靠方程。