纤维性质对成纸性能的影响

对纤维的三个基本性质－长度、强度和粗度对纸性的影响进行了综述，着重讨论了对强度性质的影响。     

文心兰茎尖离体培养研究

文心兰茎尖培养的研究，试验结果表明：文心兰茎尖在MS BA2mg／L NAA0．5mg／L培养基上，离体培养1个月后产生原球茎．改良KC基本培养较适原球茎的增殖；用BAI．5mg／L NAA0．2mg／L的激素配比，原球茎月增殖宰可达332．5％；CW可以减少原球茎褐死现象和促进原球茎的增殖：壮苗阶段，以附加NAA0．5% 10％香蕉汁的效果较好．水苔是良好的移栽基质，成活率在85．3％．     

Genetic Relationships among Prunus mume var. pendula Using AFLP Markers

Genetic relationships among Prunus mume var. pendula were studied by using AFLP markers. 18 accessions representing 14 cultivars ofPrunus murne var. pendula were selected from the germplasm collection at the Research Center of China Mci Flower. Seven Mse I-EcoR I AFLP primer combinations revealed 450 legible bands, and 269 of which were polymorphic markers. A similarity matrix was prepared using the simple matching coefficient of similarity and Nei‘s (72) distance coefficient. A UPGMA dendrogram demonstrated the genetic relationships of the cultivars. The information given by AFLP markers was basically consistent with the morphological classification and the evolutionary history of the morphotypes, and roughly supported the new revised classification system for Chinese Mci Cultivars. But there were still several exceptions: 1) the ‘Guhong Chuizhi‘ inserted between the ‘Tiaoxue Chuizhi‘ and the ‘Danfen Chuizhi‘; 2) the ‘Wufu Chuizhi‘ kept off the Pink Pendant Form, and the ‘Moshan Chuizhi‘ was removed from Viridiflora Pendant Form; 3) the ‘Danbi Chuizhi‘ and the ‘Shuangbi Chuizhi‘ of Viridiflora Pendant Form got together well but fell within the Pink Pendant Form.     

Promoting old-growth characteristics and long-term wood production in Douglas-fir forests

Trade-offs among wood production, wood quality and ecological characteristics in the management of harvested forest stands are explored through model simulation of various silvicultural regimes. Long-term production of merchantable wood, production of various types of high-quality wood, and the level of certain quantitative ecological indicators are projected for coniferous forests of Pacific Northwestern USA. The set of ecological indicators used is based on the species composition and physical structure of old, unlogged forest stands. Simulations are performed with an ecological model of forest stand dynamics that tracks the fate of live and dead trees. Short rotations (<50 years) produce the least amount of high-quality wood over the multi-century simulation period. They also fail to generate ecological attributes resembling those of old forest stands. Production of high-quality wood is moderate to high under all rotations of 80 years or more; however, most ecological indicators require longer rotations unless alternatives to clearcutting are applied. Alternatives examined include retention of 15% cover of live tree canopy at each harvest in combination with artificial thinning between harvests. Thinning from below can expedite the development of large live and dead trees, and canopy height diversity without greatly diminishing wood quantity or quality. Proportional thinning retains understory stems, thereby expediting the recruitment of shade-tolerant trees. A possible drawback to thinning, particularly proportional thinning, is the diminished production of clean-bole wood at rotations of 150 and 260 years. It is concluded that most wood quantity, wood quality and ecological objectives can be met with long rotations (ca. 260 years). Certain objectives can be met with shorter rotations (80–150 years) when treatments of thinning and canopy tree retention are applied.     

海南岛柚木的木材性质

１１—１３龄柚木２０株，１７—１９龄７株，取自海南岛尖峰岭，用以研究木材比重及纤维长度的某些特性及测定标准物理力学性质。以胸高圆盘加权平均数为单元，比重０．４６６—０．５８８，平均０．５１６：纤维长度０．８７８—１．２３０ｍｍ，平均１．０６３ｍｍ。生长轮宽度与比重及纤维长度之间表现弱的负相关。第１轮和第９轮的材性存在显著的相关关系。材性在标地间的差异不显著，标地内株间的差异很显著。径向变异：髓心附近几轮的纤维长度和比重均增长很快，第８轮以后，前者增长缓慢，后者多起伏。轴向变异：１．心部系列（髓心向外６生长轮）第１轮纤维长度的轴向变异很小，其外几轮的纤维长度缓慢向上减轻或有起伏；基部各生长轮的比重很大，向上急剧减小至１．３ｍ高度，此后各生长轮的变化不一致。２．边部系列（树皮向内６生长轮）纤维长度和比重均很快向上减小。讨论了影响纤维长度轴向变异的主要因素。提出标准物理力学性质的试验结果。     

长白落叶松人工林树冠形状的模拟

以长白山地区 2 6a生长白落叶松人工林为研究对象 ,采用枝解析的方法 ,测定了 2 5株林木 (直径 10 5～2 4 9cm)的树冠变量 ,并建立了预测树冠外侧形状的冠形模型。基于枝条着枝深度 (DINC)和林木变量所建立的树冠形状模型包括 :基径、枝长、着枝角度和弦长等预估模型。对于大小相同树木的主要枝条来讲 ,这些树冠变量是随着DINC的增加而增大 ;而林木的胸径 (DBH)和树高 (HT)变量很好地反映了不同大小树木的冠形变化。冠形预测模型预测效果良好 ,充分体现了树冠结构的变化趋势 :树冠形状在树冠的中上部呈抛物线体 ,而在树冠的下部则为近圆柱体。文中所建模型 ,可以合理地描述长白落叶松人工林的树冠形状及其变化规律。     

Effect of tool angles on the chips generated during milling of wood by straight router-bits

 The effect of tool angles on the shapes of chips generated by parallel-to-grain and end-grain milling was explored for China fir and maple under fixed spindle and feed speeds and cutting depth. The milling path was up-milling by straight router-bits with a diameter of 12 mm. The chip shapes could be distinguished as five types: spiral, splinter, flow, thin, and granules or powder. The flow and thin chips were generated most often (on a weight percentage basis) for all tool angles investigated for parallel-to-grain and end-grain milling of China fir and maple. More granule chips were produced with parallel-to-grain milling than with end-grain milling for both woods. The measured chip thickness (t′) was thicker than the calculated thickness (t _max). Thicker and longer maple chips were produced by end-grain milling than by parallel-to-grain milling. The tool geometries of 40°/15° (sharpness of the angle–rake angle), 50°/15°, and 60°/15° for China fir and 40°/25°, 50°/5°, and 60°/5° for maple produced relatively more flow chips with parallel-to-grain milling. Furthermore, the tool geometries of 40°/5°, 50°/15° and 60°/25° produced more flow chips (weight percentage) by end-grain milling of China fir and maple. Received: May 23, 2001 / Accepted: June 28, 2002 Acknowledgment This study was supported by a grant from the National Council of Science, Taiwan (NSC89-2313-B-415-011).     

Morphological plasticity of cotton roots in response to interspecific competition with pecan in an alleycropping system in the southern United States

A study was conducted in northwest Florida, USA, to investigate root development and morphology of cotton (Gossypium hirsutum L.) under pecan (Carya illinoensis K. Koch) trees in an alleycropping experiment. Root:shoot ratio, root biomass, total root length and root length density were examined under three treatments: (1) barrier (separating belowground interspecific competition by trenching to a depth of 120 cm and installing polyethylene barrier), (2) non-barrier (root systems were free to interact), and (3) monoculture of cotton (without above and belowground interspecific competition with trees). Results indicated that plants in the barrier and non-barrier treatments had lower root:shoot ratios compared to the monoculture treatment. Belowground competition for resources between pecan and cotton in the non-barrier treatment resulted in 25 and 33% reduction of total root length (359 cm) when compared to that of the barrier (477 cm) and monoculture (539 cm) treatments, respectively. The non-barrier plants also exhibited the lowest root length density. Specific root length was highest for the monoculture (179 cm g⁻¹) and lowest for the non-barrier treatment (146 cm g⁻¹) with the barrier treatment being intermediate (165 cm g⁻¹). Interspecific competition with pecan significantly altered root development and morphology of cotton plants. Research in agroforestry should take into account the developmental differences in root systems of the associated crop species so that better models incorporating nutrient and water uptake can be developed.