共查询到20条相似文献,搜索用时 78 毫秒
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恒续林经营研究经过了100多年, 但至今仍然没有被广泛应用于生产实践, 其主要原因是尚没有很好地回答“什么样的林地适合经营恒续林?” “恒续林经营的理想林分是什么样的?” “恒续林经营是否更具经济效益?”这3个基本问题。在基本问题不解决的情况下开展的研究均存在局限性, 因此文中建议在构建恒续林立地综合评价指数的基础上确定恒续林经营适宜区, 以对人的效用为目标函数构建模型来规划经营目标及经营行为, 借鉴和综合现有的相关理论方法, 全面系统地开展恒续林研究, 并做准确的经济成本效益分析, 为经营单位开展森林经营和政府制定政策提供依据。 相似文献
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通过对日本国有林管理基本情况进行的介绍,比较分析我国国有林管理与日本的差异,提出重新准确定位国有林业的建设方向和目标任务、理顺国有林场管理体制和运行机制、完善国有林场政策体系、加强森林经营、建立精干高效的国有林管理队伍、加大宣传力度,提高全民生态保护意识等建议。 相似文献
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介绍了河北省木兰林区针对不同树种、起源的林分,分别采用转化利用林、均质经营林、苗材兼用林、绿化苗木基地4种森林培育方向,阐述了其适用林分类型、培育目标和经营技术措施。 相似文献
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杉木人工林地力衰退研究概述 总被引:6,自引:0,他引:6
介绍了我国杉木人工林地力衰退的现状,从森林土壤条件、杉木人工林的营养循环特点和人为经营措施等方面分析了导致杉木人工林地力衰退的原因,提出营建人工复层林、林地施肥、适当延长轮伐期,加强植被管理和进行定位观测等措施防止地力衰退。 相似文献
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This study investigated the dynamic modulus of elasticity (DMOE) of wood panels of Fraxinus mandshurica, Pinus koraiensis, and Juglans mandshurica using the natural frequency measurement system of fast Fourier transform (FFT). The results were compared with the static
modulus of elasticity (E
S) tested by a mechanical test machine. The results show a significant correlation between E
S, transverse vibration DMOE (E
F), and longitudinal vibration DMOE (E
L). For all of these species, the correlation between E
S, E
F and E
L is more significant than the individual species, which indicated that the FFT method is universal. The correlations between
E
S and sample’s density (ρ) are significant, but the correlation coefficient of E
S and ρ is lower than those between E
F, E
L and E
S. The E
S of wood is more accurately tested by the analysis based on FFT measurement than by the estimation based on density.
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Translated from Scientia Silvae Sinicae, 2005, 41(6): 126–131 [译自: 林业科学, 2005, 41(6): 126–131] 相似文献
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Bacterial blight is considered one of the most serious diseases affecting the genus Juglans. Artificial inoculations with Xanthomonas campestris pv. Juglandis were performed in the field by spraying seedlings of Juglans cinerea, Juglans hindsii, Juglans mandshurica, Juglans nigra, Juglans regia and Juglans sieboldiana. Juglans nigra, J. cinerea ana J. sieboldiana proved to be the most resistant. The multiplication ability of Xanthomonas campestris pv. corylina, X. c. pv. juglandis, and X. c. pv. campestris was evaluated by injecting 2-year-old seedling leaves of J. mandshurica, J. nigra and J. regia. The bacterial growth was monitored in the infected tissue over 12 days. Xanthomonas c. pv. juglandis exhibited a high growth rate and induced black greasy spots in J. mandshurica and J. regia; X. c. pv. campestris grew in leaf tissues without inducing symptoms, X. c. pv. corylina showed a very low growth rate. None of the tested bacterial strains multiplied in the leaves of J. nigra. This confirms the results obtained in the field tests. Juglans regia was the most susceptible among the walnut species tested. 相似文献
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Wu Xingyin Zhang JinghuaForest Pest Control Quarantine Station of Archeng City of Heilongjiang ProvinceXiang Cunti Li Guisheng '''' Shao Zhongwen Liu Xiaoguang Ma LiyaNortheast Forestry UniversityZhang Xianwen Li Zhuo Xie Guicai Dang WenqiangArcheng Forestry Bureau of Heilongjiang Province 《林业研究》1991,2(2):7-16
The poplar bacterial canker caused by Erwinia sp is a serious disease spreading inmost parts of Northeast China,where poplars are cultivalted.The disease seriously infects thosepoplars belonging to section Aigeiros or the intersection hybrids of section Tacamahaca and section Aigeiros and their clones.Five fine poplar cultivars resistant to the bacterial canker have been ob-tained by screening tests.They are Lz_2(Populus simonii×nigra var.italica),A_(15)(P.×sp.)613(P.×sp.),A_(102)and A_(98)(P.simonii×sp.)T following chemicals are obviously effective,such as:50%DT germicide ,40% XF-136 and 10% C.C.M.A.or 12.5% ramphencol and 50,000 ppm/mlvalidamycin,with which the stems or roots can be watered. 相似文献
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Summary The wood, composed of alternate earlywood and latewood lamellae, forms a statically indeterminate system with two redundants. The redundant forces are the shearing forces arising at the edge of the boundary between earlywood and latewood in the longitudinal and in the tangential directions of wood. By determining the redundant forces according to the theory of statically indeterminate systems, we know the state of stress and the state of detormation of the wood element and thus can determine its shrinkage and stresses in the longitudinal, tangential and radial directions.
Zusammenfassung Holz ist aus Früh-und Spätholzlamellen aufgebaut und bildet damit ein statisch unbestimmtes System mit zwei statisch unbestimmten Größen. Diese statisch unbestimmten Größen sind die Scherkräfte, die in longitudinaler und tangentialer Richtung an den Kanten der Grenzschicht zwischen Früh-und Spätholz entstehen. Bestimmt man die statisch unbestimmten größen nach der Theorie der statisch unbestimmten Systeme, so kennt man den Spannungs-und Verformungszustand der Gefügeteile des Holzes und ist damit in der Lage, scine Schwindung und Schwindspannungen in longitudinaler, tangentialer und radialer Richtung zu berechnen.相似文献
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Hitoshi Sakio 《Journal of Forest Research》2005,10(4):341-346
The effects of flooding on growth of seedlings were compared over a 7-month period (April–November) among six different woody species: Aesculus turbinata, Cercidiphyllum japonicum, Fraxinus platypoda, Pterocarya rhoifolia, Pterostyrax hispida, and Quercus mongolica var. grosseserrata. Flooding reduced the shoot length of F. platypoda, P. rhoifolia, C. japonicum, P. hispida, and Q. mongolica var. grosseserrata seedlings but did not affect that of A. turbinata seedlings. Among control seedlings, shoot elongation occurred once in A. turbinata and twice in F. platypoda and Q. mongolica var. grosseserrata; the other species continued to grow from April to August. Among the flooded plants of all species, shoot elongation occurred only once at the beginning of the growing season. On August 25, flooding significantly reduced the number of developed leaves as compared with control plants except for A. turbinata. In the flooded plants except for F. platypoda, leaf fall began on June 30; in controls, by contrast, the number of developed leaves increased until August 25. Flooding reduced the total dry weight increment in all species. The survival ratio of flooded plants after the experiment differed with species. All of the F. platypoda and A. turbinata seedlings survived the flooding treatment, while only 20% of P. hispida and 30% of Q. mongolica var. grosseserrata survived. Flooding seriously affected the growth of riparian pioneer species including P. rhoifolia, C. japonicum, P. hispida, and Q. mongolica var. grosseserrata. The effects of flooding on growth of the seedlings differed with the tree species because of differences in leaf-emergence pattern and physiological flood tolerance. The responses of tree seedlings to flooding reflected species habitats and growth patterns. 相似文献
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Characterization of strength properties of branchwood and stemwood of some tropical hardwood species
The mechanical strength properties of the branchwood of Aningeria robusta and Terminalia ivorensis with diameters ranging from 10 to 25 cm were examined to determine the suitability of branchwood as raw material for downstream processing. The study precisely assessed the static bending strengths, compression strengths and shear strengths parallel to the grain of the branchwood and stemwood of T. ivorensis and A. robusta. It was observed that under static bending, the overall (sapwood and heartwood combined) modulus of rupture and modulus of elasticity of the branchwood of A. robusta and T. ivorensis were lower than that of their corresponding stemwood. The results further show that the overall compression and shear strengths parallel to the grain of the branchwood of A. robusta and T. ivorensis were higher than that of their corresponding stemwood. Under static bending, compression parallel to the grain, and shear parallel to the grain, the experimental results indicate that the sapwood of the branchwood from both T. ivorensis and A. robusta had lower strength values than that of their corresponding heartwood. Similar results were recorded for the stemwood of T. ivorensis where the heartwood had higher strength values than the sapwood. However, in the case of the stemwood of A. robusta, the sapwood had higher strength values than the corresponding heartwood. 相似文献
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Four regions of chloroplast DNA were sequenced as a prospective genetic marker to identify Japanese representatives of Cyclobalanopsis: Quercus acuta, Q. sessilifolia, Q. salicina, Q. myrsinaefolia, Q. glauca, and Q. gilva. We found that Q. gilva was distinguished from other species based on both the trnL-trnF and trnT-trnL intergenic spacers. The evidence shows good coincidence with the fact that Q. gilva has several peculiar morphological features distinguishable from those of other species. There was no difference in trnL intron and matK. Both trnT-trnL and trnL-trnF intergenic spacers are capable of being used as genetic markers to identify Q. gilva among Cyclobalanopsis species.Part of this paper was presented at the 48th annual meeting of the Japan Wood Research Society, Shizuoka, April 3–5, 1998 相似文献
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Micromorphology of the bacterial attack of wood 总被引:1,自引:0,他引:1
H. Greaves 《Wood Science and Technology》1969,3(2):150-166
Summary This paper describes fully the various patterns of bacterial attack to be observed in wood. It is based on many observations made with bacterially infected wood, both in pure laboratory cultures and in naturally attacked wood from diverse environments. Patterns of attack are described for tracheids, fibres, vessles and rays and three types of pit border decay are figured, together with attack of the pit margo and torus. A brief section also deals with the macroscopic appearances of wood subject to bacterial attack.
Zusammenfassung Auf Grund zahlreicher Versuche und Beobachtungen werden die verschiedenen Formen bakteriellen Befalles von Holz, sowohl bei inokulierten Laborkulturen als auch bei natürlich infizierten Hölzern von verschiedenen Waldstandorten, eingehend beschrieben.Im einzelnen umfassen die geschilderten Befallsformen diejenigen, von denen Tracheiden, Fasern, Gefäße und markstrahlen betroffen werden; außerdem werden drei Typen von Tüpfelwulstfäule, sowie je ein Fall von Bakterienbefall eines Tüpfelhofes und einer Tüpfelschließhaut dargestellt.Dem makroskopischen Aussehen bakterienbefallener Hölzer wird ein kurzer Abschnitt gewidmet.相似文献