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1.
下木在森林群落中的作用 总被引：1，自引：0，他引：1
森林群落具有成层结构,一般分为乔木层、下木层、草本层、地被层。这样完整的层次,能保持生态平衡,促进体木的生长。然而,当前营造各种人工林时,忽视了这样层次的配置,只注重乔木树种的建群,不注意下木的营造。为了引起人们对下木的重视,加速林木生长,维护生态平衡,现根据我们的调查和有关资料,谈谈我区下木的种类和作用,供参考。据调查,我区下木主要有:山茶科的黄端木、柃木、油茶、茶、扬桐;豆科的大叶黄檀、胡枝子、美丽胡枝子、紧穗槐、山槐、宜昌木兰、华东木兰、锦鸡儿;蔷薇科的山桃、木梅、陷脉、石楠、石斑木;马鞭草科的大青、紫珠、华紫珠、广东紫珠、臭黄荆;樟科的 相似文献
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地处苏南沿江发达地区的张家港市,是一座年轻、充满活力的新兴港口工业城市,市域面积999平方公里,总人口95万人。近年来,在加强发展经济的同时,紧紧围绕建设最适宜人居、创业的现代化城市目标,以加强城市生态建设,创造良好的人居环境,促进城市可持续发展为中心,以创建国家园林城市为抓手,大力弘扬“团结拼搏、负重奋进、自加压力、敢于争先”的张家港精神,坚持政府组织、群众参与、部门共建、因地制宜、讲究实效的原则,高起点规划、高标准建设、高质量管理,加大力度、加大投入、城乡联动、狠抓落实,整体推进公园绿地、附属绿地、防护绿地、… 相似文献
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河南省太行山北起林县,西抵济源,南濒黄河,东至京广铁路线,地跨安阳、鹤壁、焦作和新乡四个市,包括林县、鹤壁市郊区的全部,辉县、济源二市的大部,安阳县、安阳市郊区,汤阴、淇县、浚县、卫辉、修武、焦作市郊区,博爱、沁阳、孟县的一部分,共涉及15个县(市、 相似文献
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《山西林业科技》1974,(3)
西山地区,西临黄河,东倚吕梁山,为一由东北向西南方向的狭长地带,长630余公里。包括雁北地区的左云、右玉、平鲁三县;忻县地区的河曲、保德、偏关、神池、五寨、岢岚、宁武、静乐八县;太原市的娄烦县;吕梁地区的兴县、岚县、临县、方山、离石、中阳、交口、柳林、石楼九县;临汾地区的隰县、吉县、蒲县、永和、汾西、大宁、乡宁七县,共五地(市)的28个县,(?)西山地区,总面积7067万亩,286.41万人,人均土地25亩多。这个地区总的特点是:地广人稀,风沙干旱,植被稀少,水土流失严重,导致土壤瘠薄,农业产量低而不稳。本区属于大陆性气候,年降水量由北向南350—500毫米,无霜期120—180天,西 相似文献
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我爱妍丽的红花,更爱金色的硕果。然而,作为一个林业工作者,我酷爱那朴实无华的绿叶。资料表明,全球有记载的高等植物约三十万种,我国约三万种。在整个植物群体中,叶子是一个庞大的家族,形态各异,种类繁多。根据叶的形态特征,一般分为鳞形、锥形、刺形、条形、针形、披针形、匙形、卵形、园形、菱形、三角形、心形、扁形等二十余种。根据叶的种类,可分为单叶、复叶。复叶又分为单身复叶、二出复叶、掌状复叶、奇数羽状复叶、偶数羽状复叶等数十种,尽管她们的形态和种类有别,但是她们的奋斗目标是一致的,就是通过自己的辛勤劳动促使植株加速生长,早日开花,尽快结果。 相似文献
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贵州毛竹林类型与林分结构的研究 总被引：5，自引：0，他引：5
一、自然概况毛竹林是贵州竹林中面积最大,分布最广,价值最高的一种竹林。天然林分主要分布于黔北的赤水、习水的赤水河流域,其次,黔东南和黔东的黎平、天柱、锦屏、溶江、从江、江口、铜仁、松桃及雷山、剑河、印江等县亦有成片或零星分布。六十年代以来,黔中地区的贵阳、平坝、惠水、修文、遵义、仁怀、湄潭、风冈、余庆、丹寨、麻江、三都、水城等地,先后均有引造毛竹林,逐渐成林,生长良好。 相似文献
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王贞虎 《绿色中国(综合版)》2014,(11):54-55
每年的5至7月,在庭院或公园里,常可见到一种开一串串白色的尤如风铃的花的植物,它宛如一位13岁少女,叫人欣赏的同时,又净化人的心灵,带给人纯洁。这种植物叫铃兰,别名君影草、山谷百合、风铃草、草玉玲、君影草、香水花、鹿铃、小芦铃、草寸香、糜子菜、芦藜花等。早先,朝鲜、日本等北温带地区是它们快乐无忧的地方,后来,姐妹多了,有的就到了欧洲和北美洲,有的则来到我国黑龙江、吉林、辽宁、内蒙古、河北、山西、山东、河南、陕西、甘肃、宁夏、浙江和湖南等地栖身,它们特喜欢在海拔850~2500的山区出没,深山幽谷、林缘草丛是它最快乐的玩耍地。 相似文献
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<正> 湖北省地处长江中游,浩荡的长江江水由四川奉节经秀丽壮观的翟塘峡、巫峡奔流而下,从巴东县鳊鱼溪河口流入湖北,流经巴东、秭归、宜昌、宜都、枝江、松滋、江陵、沙市、公安、石首、监利、洪湖、嘉鱼、汉阳、武昌、武汉、新洲、黄冈、鄂洲、浠水、黄石、大冶、蕲春、阳新、广济至黄梅滨江出口,共26个县、市,境内流长1061km,占长江全长约16%,最大流量为8万m~3/s,宜昌以上江狭流急,宜昌以下逐渐平缓,世界著名的葛洲坝现代化水电枢纽工程在宜昌拦江筑坝发电,从而结束了江水白流的历史,湖北省属长江流域面 相似文献
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为纠正植物学专著对传统名花“绣球”和“粉团”的错误考订,恢复它们的本来面目,进行了文献考证和实物比对。结果表明,《中国植物志》中的粉团Viburnumplicatum Thunb．实乃典籍中的绣球;而该书的绣球Hydrangeamacrophylla（Thunb．）Ser．,才是真正的粉团（该种曾称“八仙花”,更谬甚）。本文还对它们混淆的根源作了探讨。 相似文献
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Else Jahn 《Journal of pest science》1973,46(3):37-43
Zusammenfassung Die Zentren des Schadauftretens verschiedener untersuchter forstschädlicher Insekten dürften nach zahlreichen Testungen Reizzonen umfassen, welche wieder als eine Kombination von elektrischen und magnetischen Feldern und durch diese freigelegte Metalleffekte erscheinen. Untersuchungen zur möglichen Wirksamkeit dieser Komponenten auf Vitalität und Fertilität vonLymantria monacha führten zu folgenden Ergebnissen. Es erscheint möglich, daß innerhalb von Reizzonen Sterblichkeit und Fruchtbarkeit vonLymantria monacha auch von niederfrequenten elektromagnetischen oder auch konstanten magnetischen oder elektrostatischen Feldern beeinflußt werden, die direkt oder auch über die Pflanze auf die Lebenskraft der Nonne von Wirksamkeit sind. Reizzonenbereich und Normalbereich zeigten hinsichtlich der Mortalität der Versuchstiere gegensätzliche Verhältnisse. Die Anfangsmortalität innerhalb von Reizzonen war gegenüber jener der Zuchten im Normalbereich erniedrigt, die Endmortalität vielfach erhöht. Futter aus Normalbereichen setzte in den Reizzonen, Reizzonenfutter im Normalbereich die Sterblichkeit herab und erhöhte im Normalbereich die Fruchtbarkeit. Im Normalbereich mit Normalfutter gezogene Nonnen wiesen die geringsten Zahlen an abgelegten Eiern auf, was sich besonders bei an Pflanzen eingebeutelten Tieren deutlich zeigte. Die wesentlich höhere Fruchtbarkeit von Nonnen an Pflanzen im Reizzonenbereich mag zusammen mit der hier erniedrigten Anfangsmortalität eine Erklärung zum gehäuften Auftreten vonLymantria monacha innerhalb von Reizzonen geben. Freigesetzte Metalleffekte könnten innerhalb von Reizzonen die Sterblichkeit aber auch die Fruchtbarkeit erhöhen.
Herrn Prof. Dipl.-Ing. Dr. ERWIN SCHIMITSCHEK zum 75. Geburtstag.
A 1130 Wien XIII, Fasangasse 5-7, 1/8 相似文献
Summary The centres of damages by different forest insects, examined in this research, seem to be in zones of Earth radiations (Reizzonen), which again seem to be combinations of magnetic or electric fields and metal effects, set free by them. Examinations for possible influences of these components on vitality and fecundity ofLymantria monacha showed the following results: It seems possible, that inside of zones of earth radiations mortality and fecundity of this butterfly could be directed from magnetic or electric fields also of low frequency or electrostatic, which either directly or indirectly by the nutrients (plants) influence the vital power ofLymantria monacha. Zones of Earth radiations and normal zones showed different conditions in respect of the mortality. Mortality of larvae of first developmental stages inside of zones of Earth radiations was decreased, such of late stages increased contrary to larvae in normal zones. Plant-food of normal zones decreased the mortality of larvae in zones of Earth radiations and food of zones of Earth radiations decreased the mortality of those of normal zones and increased fecundity in the latter cases. Female butterflies reared in normal zones showed the lowest number of developed eggs, especially when reared encaged on living plants (spruce). The essentially higher fecundity ofLymantria monacha reared on plants inside of zones of Earth radiations together with the decreased mortality of first instar larvae there, may give an explantation for the increased population ofLymantria monacha inside of zones of Earth radiations. Metal effects set free inside of zones of Earth radiations could increase there the mortality but also the fecundity.
Herrn Prof. Dipl.-Ing. Dr. ERWIN SCHIMITSCHEK zum 75. Geburtstag.
A 1130 Wien XIII, Fasangasse 5-7, 1/8 相似文献
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Changes in the physical and chemical properties of six Japanese softwoods caused by lengthy smoke-heating treatment 总被引：1，自引：0，他引：1
Futoshi Ishiguri Noritaka Masubuchi Shinso Yokota Nobuo Yoshizawa 《Journal of Wood Science》2005,51(2):161-166
The effects of prolonged smoke-heating treatments on wood quality were investigated. Six Japanese softwoods were smoke-heated for 100 and 200h at a temperature of 75° ± 5°C, which was recorded inside the log. After smoke heating, wood quality, including moisture content, amounts of chemical components, relative degree of crystallinity (RDC) of cellulose, and sapwood color were examined. Moisture content decreased as a result of smoke heating, especially in sapwood, leading to a uniform distribution of moisture content within a log. Almost no difference was found in the amounts of chemical components between the control woods and the woods that were smoke-heated for 100h. However, in the wood that was smoke-heated for 200h, the amounts of holocellulose decreased, suggesting that thermal deterioration and/or degradation of hemicelluloses had occurred. We assume that the increase in RDC was caused by smoke heating with the crystallization of cellulose and/or thermal degradation of hemicelluloses. Almost no differences were found in sapwood color between the control woods and the woods that were smoke-heated for 100h. In the wood that was smoke-heated for 200h, however, L*decreased, whereas a* and b* increased. As a result, E*ab, showing the total color change, increased, resulting in a deeper color. These results suggest that thermal degradation of hemicelluloses was caused by smoke heating for over 100h. Therefore, smoke heating of softwood logs using a commercial-scale kiln should not exceed 100h. 相似文献
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This paper describes the salient aspects and analyses the potential of the Paraiso Woodlot System, which is becoming popular as an agroforestry alternative to land use in the degraded acid sandy soils of the humid sub-tropical Guayaybi area of Paraguay. The system consists of a combination of paraiso (Melia azedarach var gigante) with other trees, especially Leucaena leucocephala, and annual crops.The fast growth habit, deep root system, addition of large quantities of organic matter through leaf and litter fall, compatibility with agricultural crops, high value of the sawlogs and production of substantial quantities of poles and firewood make paraiso an excellent species for agroforestry combination. Preliminary results of the trials indicate that the woodlots are successful and with increasing efforts of the extension agencies, they are being accepted as a viable alternative to traditional agricultural systems.Besides discussing the potential of these woodlots based on initial results, the paper identifies the constraints of the system and highlights the priority research areas. 相似文献
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Previous papers have quantitatively indicated that the total movement of cement bonded particleboard (CBPB) is equal to the sum of the movement of its components. This paper examined the efficacy of the law of mixtures when applied to the movement of a wood-cement composite under internal swelling or shrinkage stresses. Abundant data generated in companion papers were first manipulated to develop the universal formulae for predicting the movement of components. In conjunction with previous numerical results from image analysis of the structure of CBPB, and the orientated elasticity and stress algorithms, the models for theoretically predicting mass and dimensional changes of CBPB were derived. Validation studies were conducted and these demonstrated an excellent agreement of the theoretical predictions with experimental data for both mass and dimensional changes of CBPB due to internal swelling or shrinkage stresses during adsorption and desorption. The success also implied that CBPB can be treated as a composite and its properties can be well derived by the law of mixtures even though CBPB is an unusual type of composite having a very high volume fraction of wood chips, but a very high mass fraction of cement paste.Notation ERT
Mean transverse modulus of elasticity of wood
- EL
Longitudinal modulus of elasticity of wood
- Ep
Modulus of elasticity of cement paste
- Ewa
Modulus of elasticity of embedded wood chips at angle
- E
Modulus of elasticity of wood chips at direction
- E
Modulus of elasticity of wood chips at direction
- GLRT
Mean transverse shear modulus of wood
- L(T)cp
Length/width (thickness) change of CBPB at angle
- L(T)p
Length (thickness) change of cement paste
- mpf
Mass fraction of cement paste in unit mass of CBPB
- mwf
Mass fraction of wood chips in unit mass of CBPB
- Mcpj
Mass change of CBPB at the various conditions tested
- Mpj
Mass change of cement paste at corresponding conditions
- Mwj
Mass change of wood chips at corresponding conditions
- M(L; T)w/P
Mass, length or thickness changes of wood chips or cement paste at various conditions
- t
Duration of exposure
- LRT
Mean transverse Poissons ratio of wood
- Vpf
Volume fraction of cement paste in unit mass of CBPB
- Vwf
Volume fraction of wood chip in unit mass of CBPB
- cp
Density of CBPB
- k
Density of wood chip or cement paste
- cp
Overall stresses of CBPB at angle
- L
Stress in the longitudinal direction of wood
- RT
Mean stress in the transverse direction of wood
- p
Stress of cement paste
- w
Stress of the wood chips at angle
-
Stress of the wood chips at direction
-
Stress of the chip at direction
- cp
Strain in CBPB
- p
Strain of cement paste
- WL
Strain in the length of wood chips
- WT
Strain in the thickness of wood chips
- w
Strain in wood chips
-
Angle between the longitudinal direction of wood chips and surfaces or edges of CBPB
-
Angle between wood chips and edges (length direction) of CBPB
-
Angle between wood chip and vertical coordinate
- A, B, C
Coefficients related to the feature of materials and exposure conditions
The senior author wishes to thank Professor W.B. Banks of University of Wales, Bangor for his constructive discussions and assistance and the British Council for partly financial support. 相似文献
17.
W. H. Thomas 《Wood Science and Technology》2003,37(3-4):259-268
In the assessment of the structural adequacy of oriented strand board (OSB) members by design calculation, the need for the boards Poissons ratios often becomes evident. However, mention of Poissons ratios as a relevant mechanical property is seldom made in wood-based panel test and design standards. The short-term principal Poissons ratios of a typical OSB has been determined from tension tests. Mean values of 0.23 and 0.16 have been obtained for the major and minor Poissons ratios, respectively. The experimentally determined Poissons ratios appear consistent with the values estimated from the panel shear and tension moduli of elasticity. Complementary values of the Poissons ratios in bending have been estimated from the bending moduli of elasticity and tension test results for the panel. Efficiency in the assessment of OSB by design calculation follows from knowledge of Poissons ratios. However, for this benefit to be realised in routine design, the Poissons ratios of structural grade OSB need to be available. 相似文献
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There is growing interest in research to develop potential agroforestry models for temperate climates. In Washington State, recent studies and anecdotal information suggest that agroforestry is already employed by land managers, and if so, this experience should inform future research efforts. Because this population is not well defined, a mail survey was designed to: 1) Assess Washington land manager awareness of agroforestry, 2) assess perceptions of agroforestry as a land management tool, 3) assess the perceived potential opportunities or obstacles for land managers to practice agroforestry, and 4) identify landowner groups believed to be practicing agroforestry in Washington State.Three groups of land managers were surveyed: employees of the Soil Conservation Service (SCS), Washington State University Cooperative Extension Service (WSUCE) and OTHER, consisting of university faculty, private land managers, State and Federal land managers and owners of small natural resource businesses.Agroforestry was not a new concept for most (94%) respondents, further 55% of those familiar with agroforestry were practicing agroforestry or providing advice to landowners who were practicing agroforestry. Use in (government mandated) soil conservation plans on farmland (100% of all respondents) was the most frequently cited potential application for agroforestry in the state followed by range and pasture land and managing non-commercial forest land (both 84%), use on commercial forest plantation (83%) and fruit and nut orchards (61%).Diversifies land use (25%), enhanced productivity (18%), aesthetics (13%) and income diversity (13%) were the four most frequently cited potential advantages to practicing agroforestry. Lack of information (28%), lack of technical assistance (18%), establishment costs (14%) and not an established practice (14%) were the most frequently identified potential obstacles to practicing agroforestry. Respondents suggested there is great potential for application of agroforestry throughout the state, and non-industrial private forest land owners were selected for future study of this potential. 相似文献
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生态食物链反映了生物界互相依存、互相制约的关系。对小流域(经济沟)治理意义最大的是“粮-人”食物链、“草-畜”食物链、“地-商”食物链。增强主导食物链运行强度的“加减公式原理”,扩大粮食来源的“加加公式原理”,扩大肉、蛋、奶转化的“新金字塔原理”,调整生态食物链内外循环的“能流、物流平衡与价值流不平衡原理”,是小流域(经济沟)建设的生物学基础。为使开发治理具有活力,充满稳定和有序,必须解决“粪-土短路”问题,“粮食功能转化”不力问题,主导食物链运行强度减弱问题,土地投入产出比例失调问题,“地-商”食物链受阻问题。 相似文献
20.
Mangrove forest productivity and biomass accumulation in Hinchinbrook Channel,Australia 总被引：7，自引：0，他引：7
Data on stand structure and rates of photosynthesis were used to estimate net canopy carbon fixation and carbon accumulation as living biomass in mangrove forests in Hinchinbrook Channel, Australia. Total annual canopy net carbon fixation was estimated to be about 29tCha–1yr–1. This equates to about 204,000tCyr–1 for all mangrove forests in Hinchinbrook Channel. Of this, only about 12% was stored as living plant biomass. Although it is not yet possible to present a robust carbon balance for mangrove trees, the remainder is presumably lost through plant respiration, litter fall, root turnover and exudation of organic compounds from roots. 相似文献