尾巨桉家系木材的解剖结构及纤维形态研究

对8个尾巨桉家系木材的解剖结构及纤维形态学参数进行了研究。结果表明：尾巨桉木材属阔叶散孔材，生长轮界限不易区分，木射线异形单列。尾巨桉家系木材纤维长度值主要集中在800—1100μm之间，且在个体水平上分布范围广。从纤维长度、长宽比及壁腔比三方面来评价，尾巨桉木材纤维能满足纤维工业原料的要求，是制浆造纸和纤维板生产的良好原料。     

巨尾桉叶中原花色素提取工艺比较及不同溶剂萃取物生物活性的研究

通过正交试验探讨了巨尾桉叶中原花色素的3种提取方法的最佳提取工艺条件,并进行了对比。结果显示,传统溶剂提取法的最优工艺为:60%乙醇、80 ℃、100 min、料液比1:14(g:mL,下同),原花色素得率5.95%;微波辅助提取法的最优工艺为:50%乙醇、微波功率200 W、微波时间4 min、料液比为1:20,得率5.48%;超声波辅助提取法的最优工艺为:60%乙醇、60 ℃、超声波时间25 min、料液比为1:14,得率为6.07%。超声波辅助提取法效果最好,时间短,得率高。实验对超声波提取物的不同溶剂萃取物体外抗氧化性和抗肿瘤活性进行了研究,结果表明,乙酸乙酯萃取物抗氧化作用较强,当质量浓度为1.2 g/L时,对DPPH自由基清除率达到96.33%;乙酸乙酯萃取物质量浓度为2 g/L时,对于人肝癌细胞Bel-7404具有很强的抗肿瘤活性,抑制率为56.37%。     

柠檬桉、尾叶桉、柳桉制浆性能研究

对柠檬桉、尾叶桉、柳桉3种速生桉木原料硫酸盐浆的制浆和漂白性能进行了研究，研究结果表明，3种桉木原料均具有优良的制浆和漂白性能。其较佳的蒸煮工艺条件为：用碱量(Na2O计)：柠檬桉14％～16％，尾叶桉14％，柳桉12％，硫化度25％，最高蒸煮温度165～170℃，液比1：5，保温时间90～120min。采用DEpP短程序漂白，3种原料漂白浆的白度可达到85％ISO以上，且漂白浆的物理性能较好。     

高卡伯值尾叶桉硫酸盐浆的蒸煮及其性能研究

本文研究了不同条件下尾叶桉硫酸盐法蒸煮的纸浆卡伯值和H因子,纸浆得率、HexA含量和黏度及基于总固形物的残碱含量与卡伯值的关系.结果表明,尾叶桉高卡伯值硫酸盐法蒸煮的特征卡伯值为40,其对应的H因子和较优的活性碱用量分别约为297和19%～20%,此时的细浆得率为52%.当纸浆卡伯值随蒸煮条件的加剧低于该特征值而又大于16时,继续蒸煮不但会导致纸浆得率和黏度的下降以及有效碱消耗的增加,同时纸浆中HexA含量也逐渐增大.     

Antioxidant activity of Egyptian Eucalyptus camaldulensisvar. brevirostrisleaf extracts

Leaves from Eucalyptus camaldulensis var. brevirostris trees, planted in the Nile delta in Egypt, were examined for the antioxidant activity of their nonvolatile compounds. The extracts obtained by ethanol digestion and by supercritical fluid extraction (SFE; CO₂ with 15% ethanol) showed the most promising antioxidative activities. In order to identify the most active compounds, both extracts were subjected to a semipreparative reversed‐phase HPLC separation, the main fractions were collected, tested for antioxidative activity and analysed by different chromatographical and spectroscopical methods for identification of the most relevant compounds. Gallic and ellagic acid were found to be the prevailing antioxidants in the ethanolic extract. The main two compounds of the SFE extract with antioxidative activity revealed to be flavones. To a high degree of probability they were identified as 5‐hydroxy‐7,4′‐dimethoxy flavone and 5‐hydroxy‐7,4′‐dimethoxy‐8‐methyl flavone, respectively. The extracts obtained by ethanol digestion were dried and administered to rats for toxicity evaluation (up to 3 g/kg body weight). No mortality was observed which indicates a very low lethality of the tested extract.     

循环解吸-吸湿处理对人工林桉木胀缩性影响的研究

旨在寻找降低木材胀缩性的新途径，探索木材胀缩性在循环处理中的变化规律，采用人工模拟大气湿度变化规律，对尾巨桉木材进行循环解吸-吸湿处理，并实时测定木材的弦向胀缩性．结果表明：在解吸过程中，初含水率对尾巨桉木材弦向干缩率影响显著，解吸-吸湿循环次数对尾巨桉木材弦向干缩率影响不显著；在吸湿过程中，初含水率对含水率差影响不显著，循环次数对尾巨桉木材弦向湿胀率影响显著．循环处理可以使尾巨桉木材弦向胀缩率达到稳定的时间减少，有利于其木材尺寸稳定．     

Impact of Eucalyptus camaldulensis plantation on an alluvial soil in south eastern Botswana

This paper examines the impact of a 33‐year plantation of Eucalyptus camaldulensis on an alluvial soil in Gaborone, south eastern Botswana, by comparing the soil under the plantation with similar soil under an adjoining native savanna woodland dominated by Acacia karoo. Soil clay content was significantly higher in the plantation soil in both the 0–10 cm and 10–20 cm layers. There were no significant differences between soil under the two ecosystems with respect to the levels of organic matter, exchangeable potassium and available phosphorus. Despite the higher clay contents of the plantation soil, exchangeable calcium and magnesium and pH were higher in soil under the native woodland. This suggests that E. camaldulensis immobilizes soil nutrients faster and that plantation nutrient cycles are less efficient than in the native Acacia woodland. Consequently, soil nutrient deficiency will limit plantation productivity after the first few rotations. It is important to adopt tree harvesting techniques that reduce drain on soil nutrients at the end of a plantation rotation.     

三种磺化化学机械浆纤维分析

通过对不同原料的磺化化学机械浆(SCMP)纤维特性变化的研究,发现慈竹SCMP纤维平均长度与马尾松SCMP相当,接近于尾叶桉SCMP的两倍,而细小纤维含量是马尾松SCMP的两倍。磨浆过程会使纤维平均长、宽度有不同程度的下降,细小纤维含量升高。对慈竹磺化过程中的用碱量变化对纤维特性影响的研究表明,用碱量增加到4%时,纤维平均长度有所增加,细小纤维含量升高,纤维平均宽度则出现下降。碱用量大于4%后,变化趋势不明显。     

DISCONNECTING THE FLOODPLAIN: EARTHWORKS AND THEIR ECOLOGICAL EFFECT ON A DRYLAND FLOODPLAIN IN THE MURRAY–DARLING BASIN,AUSTRALIA

Globally, dams and water extractions are well‐recognised disruptors of flow regimes in floodplain wetlands, but little is known of the hydrological and ecological impacts of floodplain earthworks constructed for irrigation, flood mitigation and erosion control. We mapped the distribution of earthworks with high‐resolution SPOT (Système Probatoire d'Observation de la Terre) imagery in an internationally recognised Ramsar wetland, the Macquarie Marshes of the Murray–Darling Basin, Australia. There were 339 km levees, 1648 km channels, 54 off‐river storages and 664 tanks (0.5–5 m high), detected within the 4793 km² floodplain study area. Earthworks reduced localised flooding compared with undeveloped sites. The most pronounced disconnection of the original floodplain (73.0%) occurred where earthworks were most concentrated compared with areas with few earthworks (53.2%). We investigated relationships between hydrological connectivity and mortality of the perennial flood‐dependent river red gum Eucalyptus camaldulensis at 55 floodplain sites (225 × 150 m). Over half of the river red gums were dead at 21.8% of the sites. Earthworks blocked surface flows to flood‐dependent vegetation and drowned vegetation in artificially inundated off‐river storages. Mortality was due to impacts of earthworks and potentially exacerbated by effects of river regulation, water extraction and climate. River red gums were healthiest in narrow river corridors where earthworks confined flows and flows could recede freely. Rehabilitation of flood‐dependent ecosystems should focus on reinstating lateral connectivity and protecting environmental flows. Copyright © 2011 John Wiley & Sons, Ltd.     

Simulating the impact of kraft pulping and bleaching parameters on Eucalyptus camaldulensis pulp properties using MATLAB

In this work, Eucalyptus camaldulensis was evaluated as the raw material for chemical pulp under different pulping and bleaching conditions. The pulping was carried out at different H‐factors, and at different effective alkalis. The resulting pulps were then oxygen delignified and bleached using various dosages of bleaching chemicals in a D₀EpD₁ sequence. The effect of independent variables (pulping or bleaching variables) on dependent variables (pulp properties) was analysed based on the multivariable least square method via MATLAB software. An agreement was found between the results predicted from the models and the experimental data. To obtain a kappa number of 15, the optimum pulping conditions were a temperature of 155°C, a time of 225 min, and an EA of 23%. Also, the hexenuronic acid (HexA) content of cooked pulp was significantly decreased in the chlorine dioxide bleaching stages, and was only marginally related to the final HexA content of bleached pulps.