高效培育麻竹笋用林技术研究

通过对麻竹笋用林立竹密度、施肥量、截梢、灌溉等技术的试验研究,结果表明4种措施对竹笋产量有显著影响,前三者与竹笋产量呈抛物线型关系,竹笋产量随立竹密度、施肥量、截梢增加呈现先上升后下降的趋势;竹笋产量与灌溉次数呈直线相关,竹笋产量随灌水间隔时间增长而减少。4种因素的影响程度大小依次为：施肥量、立竹密度、灌溉、截梢。提出高效培育麻竹笋用林的优化模式为：施肥量为1800kg／hm^2,立竹密度为3600株／hm^2,灌溉为发笋期连晴10d浇水1次,截梢是保留竹秆高4m为宜。     

Seasonal response of soil enzyme activity to thinning intensity of aerial seeded Pinus tabulaeformis stands

Aerial seeding is one of the most important vegetation restoration patterns in remote hilly areas, and studies concerning soil quality and its management have practical value. In 2000, a study of the effect of thinning intensities at five different treatments levels, 0 (CK), 30% (slight thinning), 48.75% (medium thinning), 53.75% (intense thinning) and 65.6% (super intense thinning) on soil enzyme activity was carried out on 9-year-old aerial seeded Chinese pine (Pinus tabulaeformis Carr.) stands with an initial density of 8000 trees/hm², in the Wang-jiapu Aerail Seeding Center, Yanqing County, Beijing. Five years later, the activities of five kinds of soil enzymes, soil urease, alkaline phosphatase, inertase, catalase and polyphenol oxidase in the first 20 cm of soil layer were compared during four seasons. Relationships among soil enzymes and soil physiochemical properties were also analyzed to examine the possibility of using soil enzymes to evaluate thinning intensities. The results showed that the maximum enzyme activities of catalase and polyphenol oxidase occurred in June, those of soil urease and alkaline phosphatase occurred in October, and soil invetase had its maximum in April. In addition, the five soil enzymes were affected differently by thinning intensities. Soil catalase, urease and invertase showed the highest response to a slight thinning, followed by medium thinning, which is the opposite experienced with polyphenol oxidase and alkaline phosphatase. There are statistically significant and positive relationships between soil enzymes and organic matter and available K. It should be noted that soil water was a limiting factor to soil enzyme activity. Compared with soil physicochemical characteristics, soil enzymes were more sensitive to levels of thinning intensities. Among the enzymes, soil alkaline phosphatase and catalase could be regarded as indicators to assess soil quality. It is concluded that a suitable thinning intensity benefits the development of undergrowth and soil enzymes. Generally, when the stand with initial density of 8000 trees/hm² grows up to nine years old, the most suitable thinning intensity should be about 50%. __________ Translated from Journal of Beijing Forestry University, 2008, 30(2): 82–88 [译自: 北京林业大学学报]     

采伐方式对马尾松林下植被和土壤肥力的影响

采伐作业是森林经营中重要环节,不同采伐方式对森林植被和土壤肥力产生不同的影响。文章对32年生马尾松林开展不同采伐方式试验研究,结果表明,随着采伐强度增大,林下植被得到恢复和发展,但皆伐方式导致植被严重破坏;土壤孔隙度、持水量等物理性质及全氮、水解氮、速效磷、速效钾等化学性质均随采伐强度增大不断下降,土壤容重增加;皆伐使土壤理化性质恶化。     

樟子松热处理材耐久性能的评价

对樟子松热处理材进行室内防霉、防蚁蛀及野外埋地检测,综合评价其耐久性能。结果表明:樟子松热处理材对霉菌、变色菌均无防治效力,不抗白蚁蛀蚀;樟子松热处理材的耐久年限约为3年。     

人工林班克松木材材质径向变异规律研究

以人工林班克松的木材解剖性质为研究对象,分析研究其株内木材材质径向变异模式,对其幼龄材和成熟材进行初步界定。结果表明：早材管胞径弦向直径和晚材胞壁率的变化符合PashinⅠ模型,早材胞壁率的变化符合PanshinⅢ模型;回归分析中早材拟合度较晚材好;幼龄材和成熟材的初步界定年限为9-11a。     

干旱、半干旱地区异砧红松嫁接技术研究

试验分析了砧木选择、嫁接时间、嫁接方法等因子对干旱、半干旱地区异砧红松嫁接成活率和生长的影响。结果表明:樟子松、油松、赤松均可作为砧木嫁接红松。采用单芽接穗好于多芽接穗;适时早接有利于接穗木质化程度的提高;正交试验结果显示最佳处理组合为A1B1C1,即砧木为樟子松、4月中旬嫁接、芽端楔接法的组合,成活率达到90%以上。     

某碟形弹簧疲劳失效分析

以某振动机构中碟形弹簧为研究对象,对其进行了瞬态分析。分析结果表明,该碟形弹簧在结构设计上存在缺陷,无法满足其使用寿命,通过理论分析为后续结构改进提供相关依据。     

深圳地铁信号专业道岔设备维护模式及故障处理流程探讨

根据深圳轨道交通二期蛇口线信号联锁系统和ZDJ(9)转辙机设备的特点,主要探讨信号专业道岔设备维护模式和故障处理流程,以提高设备检修质量和故障处理效率,减少设备故障,降低对运营带来的影响。     

云南金沙江流域华山松人工林水土保持效益研究

以裸地为对照 ,对云南金沙江流域的华山松人工林林地的土壤物理性状及营养成分、林分涵养水源的能力、林冠层降雨截流功能、土壤水分动态变化、土壤渗透能力、林地地表径流及泥沙量以及地表生物量和根系分布状况进行了定点、定量观测研究。结果表明 :华山松林对改良土壤、增加肥力具有明显的作用 ,与裸地相比 ,其林地有机质、土壤月均含水率、渗透性能分别是裸地的 2 74、 1 14、 4 6 1倍 ,土壤最大蓄水量比裸地高5 6 74 % ;华山松林分年降雨截流量为 6 3 7mm ,截流率为 2 0 2 % ,径流率为 5 7%。径流削减率为 91 3% ,泥沙削减率为 95 6 % ;土层 2 0cm之上根系占总量的 83% ,对地面固土保水起着重要的作用     

钢结构建筑的应用及发展

本文通过对钢结构体系的简要介绍，简述了钢结构在国内外建筑的应用概况和发展前景。