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901.
902.
闽东桉树品系造林效果综合评价研究 总被引:2,自引:0,他引:2
选择福建省有一定栽培面积的7个桉树品系,在永泰县的三个海拔带分别采用随机区组,3次重复的试验设计,运用多目标决策原理,进行综合评价研究,结果表明在永泰山地造林综合指标表现最好的为尾赤桉201;其次为尾园桉184、尾巨桉3229、赤桉9号、巨尾桉C6、;比较差的为巨桉A5、柳窿桉9号。在本地区,包括整个闽东Ⅱ08桉树引种小区,发展桉树宜提倡使用尾赤桉201。 相似文献
903.
904.
905.
土壤含水量对三种阔叶树苗光合作用的影响 总被引:1,自引:0,他引:1
研究了在温室内用盆栽法,其土壤含水量对茶条槭、山梨和山桃三种阔叶树苗光合作用的影响,以及各树种在土壤相对含水量为75.0%时光合作用的日变化. 相似文献
906.
A half-scale model of a light-frame shear wall was developed to evaluate the racking performance of a fullscale shear wall (prototype). The effect of nail size on the performance of the shear wall was also investigated using models constructed with three types of nail. Materials for the model were determined through experimental methods, which included nail-head push-through, stud-to-sheathing nail connection, and static bending tests. Materials with which the model was made to be in similarity to the prototype were three-layer 4.8-mm plywood, 39.72-mm long nails, and 1 × 2 lumber cut from 2 × 4 studs. In accordance with ASTM E 72 and ASTM E 564, racking resistance tests were conducted on 20 shear walls. The results showed that the maximum load capacities of the prototype walls could be evaluated by the model without significantly different failure modes. Tests on the effect of nail size revealed that increasing the nail head diameter may improve the performance of shear walls.Parts of this paper were presented at the International Conference on Effective Utilization of Plantation Timber (ICEUPT'99), Chi-Tou, Taiwan, May 1999; and the World Conference on Timber Engineering (WCTE2000), Whistler, Canada, July–August 2000 相似文献
907.
Open pollinated progenies from 15 clones of Japanese black pine (Pinus thunbergii), that had been selected for their tolerance to pine wilt disease, were tested by artificial inoculation with pine wood nematode
for six years at a nursery of Kyushu Regional Breeding Office. Family variations in the respective year were all significant.
An analysis of variance across the six years’ tests confirmed highly significant effect of year and of families; however,
the year by family interaction was significant also. Phenotypic and genetic variances estimated from each year’s result were
fitted to a quadratic regression using their mean survival ratio as an independent variable. The variances were greatest at
around 0.5 of the mean survival ratio. Estimated heritability showed a similar trend of change, whereas the peak of the expected
amount of improvement shifted toward the lower survival range: around 0.4, where a greater selection differential was anticipated.
It was concluded that a useful amount of genetic improvement that may be reduced by 30% due to the interaction, would be expected
by prescreening seedlings where the mean survival ratio after inoculation was around 0.25 to 0.6. 相似文献
908.
本研究报道沙棘(胡颓子科)对雄性白化病白鼠由铬诱导氧化胁迫的抗氧化活性。氧化胁迫通过对小白鼠进行强制性喂养30 d,以浓度为30 m g/kg的铬相对体重比例的重铬酸钾盐实现。铬促使体重下降,而却明显增加了器官与体重比例。铬处理明显减少了谷胱甘肽的降低,增加了丙二醛和肌氨酸磷酸激酶的水平;而且它还加强了血清中谷氨酸草酰乙酸转移酶和谷氨酸丙酮酸转移酶的浓度。用不同剂量的沙棘叶子提取物(乙醇提取)对保护铬元素诱导的氧化胁迫进行了评估,结果表明叶子提取物在浓度为100到250 m g/kg铬与体重比的情况下可以明显保护动物避免由铬所诱导的氧化伤害。 相似文献
909.
Bare-root seedlings of Eucalyptus nitens frequently exhibit water stress after planting resulting in leaf lamina damage and reduced leaf area. Two trials examined effects of root exposure and desiccation between lifting and transplanting on post-planting water relations, leaf retention and root growth. Plants with roots exposed on a glasshouse bench initially lost water rapidly. In one trial 1 declined to around –2.0 MPa within 2.5 h, after which there was no further change with exposure up to 7.5 h. In the second trial, the initial decline in 1 was more rapid, reaching below –2.0 MPa in the first hour, before remaining stable with continuing exposure up to 4.5 h. A further decline then continued to –4.0 MPa after 7.5 h.Two days after transplanting into potting mix, day – time leaf water potentials in all desiccation treatments had declined to near –2.0 MPa. Hydraulic resistivity, measured as leaf specific resistivity two days after transplanting, increased following exposure for greater than 2.5 h, but there was no further increase between 4.5 and 7.5 h. The increase in resistivity corresponded with leaf water potential declining below –2.0 MPa during exposure.In the second trial, increasing root exposure time resulted in decreased leaf area due to lamina necrosis. Root growth, measured three weeks after planting, was also reduced. and there was also a positive curvilinear relationship between leaf area remaining at three weeks and new root growth. The results are discussed in terms of hardiness and the management of E. nitens seedlings from nursery to plantation. 相似文献
910.
This paper explores the influence over time of past policies on people’s attitudes towards the use of forestland in Bangladesh.
The discourses of the attitudes of people were captured from the observed social tradition towards forest resources. Forests
were reserved systematically and solely through the Forest Department. The conservation processes were not participatory,
and rights and tenure were strictly controlled. People were socially excluded and alienated from the forest, and the socio-political
factors stimulated negative attitudes among people. Forests were considered to be government property, and therefore managing
forests was the responsibility of the government. People only used forest resources to meet their own requirements, either
with formal permission or illegally. This situation continued even after the independence of Bangladesh in 1971. As a result,
the forests of Bangladesh have been degraded heavily in recent decades. 相似文献