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181.
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The development of cracks and changes in appearance have been investigated on radial and tangential sections of pine (Pinus sylvestris L.) and spruce (Picea abies Karst.) after exposure outdoors for 61 months. The degradation of the sections has also been studied at the micro-level. The annual ring orientation was the most important factor affecting crack development on weathering. After 61 months of outdoor exposure, the tangential sections of spruce had 1.7-2.2 times greater mean total crack length per area unit than the corresponding radial sections. In pine, the total crack length per area unit on the tangential sections was 2.2-2.6 times greater than that on the radial sections. Tangential and radial sections show the same colour change as a result of weathering. Tangential sections have more and deeper cracks than radial surfaces. The cracks on the tangential sections occur frequently in both earlywood and latewood. On radial sections, cracks occur primarily at the annual ring borders, but to a certain extent also in the earlywood. Decomposition of the cell wall takes place in both radial and tangential cell walls, and cracks tend to follow the fibril orientation in the S2-layer of the cell wall. The radial cell wall of the earlywood has a large number of pits which are degraded at an early stage. 相似文献
183.
The cutting technic for thePinus elliottii plantation of the multi-benefit management pattern in the hilly region of Jiangxi Province was studied by establishing the
model of growth progress according to Richards function and simulating the tending cutting on computer by use of dynamic programming.
The results showed that the best time for the initial thinning was at tree age of 8–10 and final cutting was at tree age of
25. The optimal thinning project was 3 times of thinning cutting including the first thinning, and the thinning time was at
tree ages of 8, 12 and 16, respectively. Their thinning intensities were separately 950, 700 and 300 trunks per hectare, and
the preserved density was 550 trunks per hectare until the final cutting
Foundation item: This study was supported by Natural Science Foundation of Jiangxi Province (A grant 0330023)
Biography: WANG Qing-chun (1970-), male, Ph. Doctor, Senior Engineer in Academy of Forest Inventory & Planning, Jiangxi, Nanchang 330046,
P.R. China.
Responsible editor: Song Funan 相似文献
184.
Stergios Gakis Konstantinos Mantzanas Dimitrios Alifragis Vasilios P. Papanastasis Athanasios Papaioannou Dimosthenis Seilopoulos Panagiotis Platis 《Agroforestry Systems》2004,60(2):149-157
The interaction between understorey plants and trees in a young silvopastoral system was studied in a sub-humid Mediterranean
environment with cold winters in northern Greece. The experimental design was a split-split plot with three replications and
included: three understorey treatments (grass, legume and control), two tree species (Acer pseudoplatanus and Pinus sylvestris) and two spacings (2.5×2.5 m and 3.5×3.5 m). The competition between herbaceous plants and trees resulted in significant
differentiation in tree growth while their spacing did not produce any significant differences. The influence of trees on
herbage yield either by plant species or spacing was not significant. During the early stages of establishment, a significant
positive correlation was observed between sycamore growth and soil moisture, leaf weight, leaf area and leaf number as well
as nitrogen and potassium concentration in leaves. Six years after planting the height increase of the sycamore trees was
largest in the control treatment (415%), lowest in the grass treatment (134%) and intermediate (192%) in the legume treatment.
Much higher was the increase obtained for the diameter, 161%, 207% and 536% respectively for the grass, legume and control
treatments. The Scots pine trees grew faster than sycamore over the course of the experiment. Height increased by 397%, 351%
and 400% and diameter by 518%, 443% and 683% respectively for the grass, legume and control treatments.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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马尾松针叶中挥发性成分的鉴定及其对马尾松毛虫的触角电位反应 总被引:24,自引:6,他引:24
马尾松Pinus massoniana针叶的挥发物由溶剂提取和真空蒸馏制得。用气相色谱和气相色谱-质谱,由挥发物中鉴定出了20种成分。它们主要是单萜烯、单萜烯醇、单萜烯乙酸酯和倍半萜烯。用正常和剪除触角的雌蛾研究针叶挥发物在马尾松毛虫Dendrolimus punctutas产卵场所选择中的作用。试验表明正常雌蛾在针叶上的产卵量要比剪除触角的高得多。触角电位(EAG)研究表明无论是交配的还是未交配 相似文献
188.
The effects of j-rooting on water stress and growth of loblolly (Pious taeda L.) and eastern white pine (Pious strobus L.) were examined over three growing seasons in the field. Seedlings were planted in an area with severe herbaceous competition with either their roots planted straight or bent into a j shape. All seedlings were planted with their root collars placed at the soil surface. During the first year j-rooted seedlings consistently had lower water potentials but never statistically significant. Since both treatments were planted with the root collar at the soil surface, this trend was likely due to an initial shallower root system in j-rooted seedlings. In year three no differences in water potential were significant and no trends were evident. Growth did not differ significantly by treatment at any time but, by year three, j-rooted plants were consistently larger for both species. 相似文献
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