上海外环绿带植物群落特征研究

选择上海环城绿带的典型群落进行调查,分析了环城绿带复层植物种类与群落组成,探讨了群落区系特征。结果表明:外环绿带植物种类丰富,调查的植物群落共有维管束植物53科83属97种,其中裸子植物4科4属4种,被子植物49科79属93种。整个绿带呈现草本层和灌木层物种丰富度高、乔木优势度大的多样性格局,不仅增加了群落稳定性及物种多样性,更提高了生态景观效果。绿带普遍采用乔-灌-草自然混交林式与模纹式相结合的配置结构,不仅丰富了生态景观,也提高了群落稳定性,降低了养护成本。     

作物残茬与生物篱组合对减轻土壤风蚀的作用

为了探究中国北方农牧交错带冬春风蚀季节生物篱与作物残茬组合对间作裸露秋翻地的防护作用,采用风蚀圈和野外移动式风洞试验的方法对研究区土壤风蚀情况进行监测,利用PC-3型自动气象站进行风速测定。结果表明,油葵秆生物篱减小了间作裸地近地面风速,提高了地表粗糙度;从防风蚀效果看草谷子茬优于油葵秆生物篱;在距油葵秆生物篱或草谷子茬下风向裸地不同位置处,土壤风蚀量基本呈先增加后减小的单峰曲线变化趋势,在4 m左右土壤风蚀量最大,在篱和茬的双重保护下,距茬5 m处发生了风积现象;土壤风蚀量降低率基本呈“V”字型分布;土壤风蚀模数随风速增大而增加,在生物篱的保护下5～15 m/s风速时土壤风蚀降低率为5.03%～20.53%。因此,油葵秆生物篱具有防风蚀作用,而且与草谷子残茬组合对间作裸地会起到更好的固土防蚀作用。     

混流式水轮机座环过渡段的结构分析

通过对混流式水轮机座环过渡段进行分析,获得了过渡段的最优结构。分析结果用C语言编写了程序,应用此程序可以提高设计精度,优化结构,缩短设计周期。     

Analysis of a steel tubular column filled with equidistant fiber reinforced polymer ring stiffening concrete

Based on theory of cylinders subjected to uniform internal pressure, the mechanical performance of a steel tubular column filled with equidistant fiber reinforced polymer (FRP) ring stiffening concrete is investigated. The solutions for the stress and displacement are regarded as the superposition of elementary and improved solutions. The elementary solutions are found by using two dimensional elastic theory. The improved solutions are found by using the Love displacement function method. Considering the conditions of the displacement continuum of the FRP ring and the steel tube exterior, a more accurate solution for an equidistantly FRP ring stiffened cylinder subjected to a uniform internal pressure is obtained. Several numerical calculations are also carried out. The results indicate the solutions possess good convergence.     

Tangential and radial shrinkage variation within trees in sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) cultivars

The transverse shrinkage variation within trees was examined for five sugi cultivars. The within-tree trends of tangential shrinkage (α _T) were different by cultivar, whereas radial shrinkage (α _R) increased from pith to bark in most cultivars. The tangential/radial shrinkage ratio (α _T/α _R) decreased from pith to bark in most cultivars, because the radial variation of α _R was larger than that of α _T. The cultivars showed significant differences among cultivars in α _T, α _R, and α _T/α _R, but the difference among cultivars for α _T/α _R was smaller. The relationships between transverse shrinkage and microfi bril angle (MFA), basic density (BD), tree ring parameters, and modulus of elasticity were examined. The α _T and α _R showed positive relationships with BD, latewood percentage, latewood density, and modulus of elasticity, and negative relationships with MFA and ring width. The relationships with earlywood density were weak. Sugi exhibited variation in transverse shrinkage within stem and among cultivars, with the variation affected by MFA, density, and tree ring parameters. Part of this article was presented at the 56th Annual Meeting of the Japan Wood Research Society, Akita, Japan, August 2006, and the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007     

保定市环城林带生态效益分析

通过调查将保定环城林带分成不同郁闭度、林带宽度、群落结构。并定点定时测定绿地中心和对照点的湿度、温度、噪音、粉尘、空气中细菌数。结果表明,林带绿地郁闭度、宽度增加,其降温增湿、滞尘、降噪功能越明显,而抑菌能力却下降;群落结构类型对林带生态效益的影响依次是乔灌草〉乔灌〉乔草〉灌草。     

六盘山地区气候因子对树木年轮生长的影响

为研究干旱半干旱地区气候因子对树木生长的影响,以六盘山地区4个主要树种(落叶松、白桦、椴树、辽东栎)为研究对象,在树干解析的基础上,依据年轮指数,采用相关函数和响应面函数分析了树木生长与气候因子的关系.结果表明:六盘山地区不同树木的生长趋势存在差异,对环境因子的敏感度较高;树木生长受制于生长期的2个气候因子--温度和降水.其中降水和树木生长呈正相关,随着降水量的增加,树木生长量也随之增加;一定程度的高温会促进树木生长,但高温少雨会抑制树木生长.在温度适宜树木生长的条件下,温度和降水这2个气候因子,在某种程度上可以认为是通过对土壤含水量的制约,从而影响树木的生长速度.     

粘胶涂干防治榆紫叶甲试验

为了阻止榆紫叶甲成虫上树为害,采用无毒粘胶涂干方法对害虫进行了防治试验,并与采用无公害农药——触破进行涂毒环和直接喷洒百虫杀两种防治方法的效果进行了比较。结果显示:粘胶涂干法的防治效果最好,其防治率可达90%以上,明显高于涂毒环的防治率(32.63%)和喷药的防治率(68.90%);且粘胶涂干法的有效防治期长,在整个春季对越冬代成虫都有持续的阻隔上树作用;涂粘胶的最佳宽度为5cm,其防治率可达89.57%。     

南京市不同环境树木年轮重金属元素含量对比分析

[目的]弄清南京市城市主干道重金属元素污染状况的动态变化,为南京市环境重金属元素污染防治提供科学依据。[方法]对南京市区主要城市干道行道树和作为对照组的南京林业大学校园内的雪松、法国梧桐和水杉3个对应树种树木年轮重金属元素Cd、Cr、Cu、Fe、Mn、Ni、Eb、Ti、Zn含量进行了测试和对比分析。[结果]分析发现,自20世纪60年代以来,南京市行道树年轮重金属元素含量均呈现出明显的上升趋势,且上升速度在近几个年轮段时期内明显加快。对比还发现,校园组树木年轮重金属元素含量明显低于行道树组,且上升速度大大低于行道树组,甚至校园组某些元素含量随时间无明显的上升趋势。这说明南京市交通主干道的重金属元素污染程度和污染的上升速度明显高于非交通干道区域,这一快速上升的特点与南京市机动车拥有量快速增长相一致。[结论]研究得出,机动车暴发式增长是造成南京市主干道重金属元素污染的主要原因。