Characteristics of Environment Factors in Secondary Poplar-Birch Forests after Mutual-Belt Selective Cutting

The mutual-belt selective cutting was conducted in the secondary poplar-birch forests. The changes of environmental factors after cutting were observed. The environmental factors of effect belts(cutting belts) of 15m in width had great changes. 10-m effect belts had unnoticed changes in environmental factors. The reserved belts with 10-m effect belts had a greater increase in DBH growth rate and volume growth rate. The reserved belts for 6-m and 8-m effect belts had lower increase in DBH and volume. The environmental factors of 6-m and 8-m effect belts did not change much. comparing with their reserved belts. Cluster analysis and principal component analysis for environmental factors between each two belts were also made. and the results proved that 10-m cutting belt is the best way for management of the secondary poplar-birch forests.

杨树天牛生态阈值的初步研究

在简要评述经济阈值在森林有害生物,尤其是蛀干害虫综合治理中的局限性和特点的基础上,针对不同林种的主要经营目标,首次提出了防护林生态阈值的概念,分析了生态阈值与经济阈值的区别和特点.对宁夏青铜峡市防护林中的杨树天牛生态阈值进行了初步的研究.结果表明:羽化孔可以作为合作杨生态阈值的特征指标值;在甘城子乡,树龄为8～10a,合作杨与新疆杨的混交比例为1∶3,并在其它病虫危害甚轻和非生物因素的不良影响可忽略不计时,合作杨的杨树天牛生态阈值是48个羽化孔,其区间值为[4,6].

通道绿化杨树丰产林建设潜在威胁分析研究

在杨树速生丰产林的经营过程中存在着人工林地力衰退和林带胁地的问题。笔者从轮作、更换品种、林下间作农作物3个方面对杨树丰产林建设中存在的问题进行了研究。研究表明,杨树多代连作,从第3代开始,生长量明显下降;同一代次条件下更换品种之后对林地土壤肥力有明显影响,林地土壤有机质增加40%～65%,速效N增加77%～155%,速效K增加7%～23%;间作大豆对改善连作林地土壤养分的作用更加明显。

云斑天牛成虫在杨树林带中扩散特性的研究

云斑天牛的发生及危害与林分类型，林中位置，虫源地距离及杨树品种等因素有关。观测了成虫在杨树林带中的自然扩散距离、方向及特点。成虫的扩散方向与林下植被丰富度，特别是利、充营养寄主的多寡有关。成虫具有较强的飞翔能力，测定了成虫一次持续飞行的时间、距离、高度、速度及方向等。

杨树林带施肥效应及其收获量

在杨树林带中进行同价值不同种类肥料施肥试验,对其林带生长历时13年跟踪调查,试验结果表明,施肥对其胸径、树高生长有明显的促进作用,收获量及木材等级明显提高,其经济效益十分显著。