排序方式: 共有7条查询结果,搜索用时 218 毫秒
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目的 获取毛白杨的静态压缩力学性能.方法 针对含水率为14.6%,密度为0.544 g/cm3的毛白杨木材试件进行静态压缩实验,通过实验获得毛白杨顺纹、横纹径向和横纹弦向的抗压模量、准静态压缩应力-应变曲线,并对不同方向的吸能特性进行分析.结果 毛白杨木材顺纹、横纹径向和横纹弦向抗压弹性模量分别为10.49 GPa、887和504 MPa;顺纹方向加载试件破坏形式表现为轴向屈曲,横纹径向为沿径向的裂纹及破坏,横纹弦向的破坏模式则为沿木纹纤维间的分离破坏.结论 在相同变形(应变相等)情况下,毛白杨木材单位体积吸能沿顺纹方向压缩吸收的能量最大.在应变小于0.45情况下,横纹径向和弦向压缩吸能曲线基本重合,随着应变继续增加,横纹弦向压缩吸能略大于横纹径向压缩吸能. 相似文献
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三倍体毛白杨引种育苗试验研究 总被引:4,自引:1,他引:4
何秀伟 《湖南环境生物职业技术学院学报》2002,8(2):93-97
采用2000年引进的三倍数体毛白杨73、80、96、330、331及本地繁育的303、304、305等品种在不同土壤上进行育苗、造林试验.育苗试验表明:土壤质地及肥力对育苗成活率无明显影响,成活率引最高69.4%,苗木高、径生长8月达到高峰,最高达0.93 m (331号)和0.51 cm (96号);造林试验表明:造林成活率与土壤湿度、地下水位密切相关,生长量与品种及土质密切相关,造林密度为89-110株/667㎡,截干高度1.8-2.3 m为宜,综合表现以96号最佳. 相似文献
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在调查塔里木河地区不同混交模式林分生产力、生物量及其分配状况、林分土壤养分分配状况、混交距离对胡杨生长的影响与不同林分土壤水源涵养能力的基础上,研究不同混交模式的结构与功能关系.结果表明,胡杨—柽柳块状混交林的生产力、生物量及其分配状况均好于胡杨—柽柳带状混交林与胡杨纯林.胡杨—柽柳块状混交林林下枯落物分解速度较快,积累量明显少于胡杨—柽柳带状混交林与胡杨纯林,说明胡杨—柽柳块状混交林具有较好的改良土壤作用,胡杨—柽柳块状混交林的土壤物理、化学性质及其涵养水源功能好于胡杨—柽柳混交林与胡杨纯林.此外,25 a胡杨—柽柳混交林混交距离应大于900 cm;混交方式采用块状混交能起到较好的效果. 相似文献
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Joakim Hjältén Anna Lindau Anders Wennström Patrik Blomberg Johanna Witzell Lars Ericson 《Chemoecology》2008,18(4):227-231
Summary. There is an increased interest for the use of GM trees in forestry and several commercially promising lines are now available.
However, the ecological implications of the use of GM trees, e.g. effects on non-target natural enemies, have rarely been
explored. The aim of this study was to determine if modification of non-defensive traits in GM poplars unintentionally can
influence plant chemistry in a way that has consequences for palatability to voles. In a greenhouse experiment, we used two
lines, SPS33A and SPS26, of GM hybrid poplars (Populus tremula x tremuloides) with 1.5 and 4 times, respectively, over-expression sucrose-phosphate synthase (SPS). This enzyme plays a central role in
sucrose synthesis, affecting cold acclimation, mesophyll sucrose content and biomass production. As a control we used the
isogenic unmodified wild type. Stems of these poplars were presented to bank voles and field voles in cafeteria experiments.
The concentration of condensed tannins was higher in leaves of lines SPS33A and SPS26 than in the isogenic wild-type and the
concentration of nitrogen was higher in line SPS33A than in both the wild-type and line SPS26. Although the bank voles consumed
slightly less bark from SPS33A, there were no significant differences in the preference of bank vole or field vole for the
different poplar lines. This indicates that the changes in plant chemistry were insufficient to produce any strong herbivore
response or that alteration in tannins and nitrogen counteracted each other. Still, changes in the interactions between mammalian
herbivores and GM trees are important to consider in future cost-benefits analyses of GM trees. 相似文献
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胡杨是一个古老的第三纪孑遗树种,胡杨林生态系统在绿洲演替与发展的不同阶段发挥着主要作用.通过对叶尔羌河流域胡杨林的生存现状、演变规律的调查,总结和分析当前胡杨林存在的一些生态环境问题,结合其流域特征和流域总体规划,对叶尔羌河流域开发中胡杨林的保护对策进行探讨. 相似文献
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