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1.
东北红豆杉是一种濒临绝迹的珍稀树种,其具有抗癌等重大医药价值。根据其生物学特性及其在本溪县兰河峪林场天然林冠下造林的实际情况,进而阐述东北红豆杉在我国东北广大地区野外人工培育的可能性。 相似文献
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2005年4月对黑龙江省穆棱东北红豆杉(Taxus cuspidata Sieb.etZucc.)天然林分的组成结构、立地条件、及种群年龄结构。进行了调查研究。结果表明,该地区东北红豆杉种群生存的林分结构以天然针阔混交林为主,土壤含水量较高(40%-60%),pH值偏酸(4.7~5.5);野生东北红豆杉的种群结构不合理,属于衰退种群,这也是导致野生东北红豆杉种群下降的原因之一。虽然穆棱地区的立地条件适合东北红豆杉野生种群的生长,但目前成年东北红豆杉树干中空、腐烂,中等胸径的健壮成年树被盗伐,而且幼树经常被野生动物啃食,该地区东北红豆杉的种群仍然是下降趋势,处于濒危状态。 相似文献
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红豆杉是一种珍贵药用树种,同时亦具有观赏价值,近年来受到人们的广泛关注。在黑龙江省森工林区一些地方人工栽培东北红豆杉已获得成功,通过实践证明,在人工培育红豆杉过程中科学、适量的灌水很重要,通常会使树木生长比自然状态下提高2-3倍。 相似文献
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选择东北红豆杉为研究对象,根据野外74条样带的调查结果、14块野外植被样地调查结果和6株东北红豆杉解析木资料,系统研究黑龙江穆棱东北红豆杉自然保护区的天然东北红豆杉种群的资源特征、群落特征及生长规律。 相似文献
11.
国内外松褐天牛天敌的研究利用进展 总被引:25,自引:0,他引:25
本文系统地介绍了国内外在松材线虫病媒介昆虫松褐天牛天敌的研究利用方面所取得的成就和新进展。综述了日本、美国和我国松天牛的寄生性、捕食性、微生物、寄生线虫及鸟类等天敌种类的组成和它们的控制作用、利用途径及技术。 相似文献
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Arno P. Schniewind 《Wood Science and Technology》1968,2(3):188-206
Summary The literature on wood rheology published during the last decade is reviewed. Creep, relaxation, and response to dynamic loading are discussed in relation to stress, moisture content, and temperature. Work on creep-rupture life and on wood-based materials and mechanical wood-joints is included. It is pointed out that in the future more critically designed experiments, more emphasis on quantitative information, and more work on wood-based materials are needed.
Zusammenfassung Das über die Rheologie des Holzes innerhalb der vergangenen 10 Jahre publizierte Schrifttum wird eingehend referiert. Kriechen, Relaxation und Verhalten unter dynamischer Beanspruchung werden im Zusammenhang mit Spannung, Holzfeuchtigkeit und Temperatur erörtert. Arbeiten über Zeitstandfestigkeit, über Holzwerkstoffe und mechanische Holzverbinder werden in die Betrachtungen mit einbezogen. Der Verfasser weist darauf hin, daß es in Zukunft notwendig sein wird, exakter geplante Versuche durchzuführen, daß mehr Wert auf die Gewinnung quantitativer Daten gelegt werden muß und die Kenntnisse über das Verhalten von Holzwerkstoffen erweitert werden müssen.相似文献
13.
2006年四川发生了百年一遇的特大干旱。按照自然地理条件相近、森林覆盖率有较大差异的原则;同时,在同一行政区内按森林覆盖率的高低分成对照组。在县层面上,共3对对比县,在乡层面上共7对对比乡。对比县中,森林覆盖率高的一组森森覆盖率为34.20%~52.29%,平均为43.16%,森林覆盖率低的一组为16.60%~27.28%,平均为20.84%;对比乡镇中,森林覆盖率高的一组森林覆盖率为28.50%~56.23%,平均为41.29%,森林覆盖率低的一组为10.70%~19.12%,平均为14.61%。在干旱后期,调查了四川盆地丘陵区9个县14个乡镇主要农作物(水稻、玉米和红薯)的受灾率、成灾率和绝收率。调研结果表明,森林对农业的旱情具有一定的缓解作用。在县层次上,与森林覆盖率低的相比,森林覆盖率高的主要农作物(水稻、玉米和红薯)的平均受灾率、成灾率、绝收率分别降低16.6%、16.2%、4.0%;在乡镇层次上,与森林覆盖率低的相比,森林覆盖率高的主要农作物(水稻、玉米和红薯)的平均受灾率、成灾率、绝收率分别降低20.3%、19.7%、12.7%;与无农田防护林网相比,有农田防护林网的水稻平均受灾率、成灾率分别降低5.8%、22.8%,没有绝收现象,而无防护林的水稻平均绝收率为6.5%。 相似文献
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E. T. Craswell A. Sajjapongse D. J. B. Howlett A. J. Dowling 《Agroforestry Systems》1997,38(1-3):121-137
Steeply sloping lands are widespread in the tropics. An estimated 500 million people practice subsistence agriculture in these
marginal areas. Continued population growth has led to the intensified cultivation of large areas of the sloping lands, exacerbating
the problem of soil erosion. Although research shows that alley cropping and other contour agroforestry systems can stabilize
the sloping lands, these systems have not been widely adopted by farmers.
The Framework for Evaluating Sustainable Land Management (FESLM) has been tested in sloping land areas in the Philippines.
Sustainable land management must be productive, stable, viable, and acceptable to farmers, while protecting soil and water
resources. Farms on which contour hedgerow intercropping has been adopted meet the multifaceted requirements of FESLM, whereas
the farmers' current practice does not. Appropriate land management measures for particular locations depend on a complex
suite of social, economic, and biophysical factors, and need to be developed in participation with farmers.
The role of agroforestry in sustainable management of sloping lands is the subject of networks coordinated by the International
Board for Soil Research and Management (IBSRAM) in seven countries in Asia (ASIALAND) and four countries in the Pacific (PACIFICLAND).
We review selected outcomes from a wealth of network data. From these results the following conclusions about the sustainability
of various agroforestry systems for sloping lands can be drawn:
• In the Pacific, soil loss from sloping lands due to water erosion under farmers' current practices is episodic, unpredictable,
and possibly not severe;
• Agroforestry systems that utilize legume shrubs, fruit trees, coffee (Coffea spp.) or rubber (Hevea brasiliensis) provide
useful economic returns, but are not an essential component in terms of soil protection because grass or pineapple (Ananas
comosus) planted on the contour are equally effective in reducing erosion;
• Agricultural intensification will lead to nutrient mining, reduction of aboveground biomass, declining yields, and less
soil protection unless external sources of nutrients are used;
• nitrogen can be effectively supplied using legumes;
• Cash derived from hedgerow trees and/or shrubs may providean incentive for their adoption by farmers, as well as funds to
purchase external inputs such as fertilizers;
• Labor may be a major constraint to the adoption of complex agroforestry systems.
We also discuss the information management systems required to effectively manage and utilize the extensive sets of experimental
and indigenous data being accumulated. We believe such information systems can facilitate technology transfer across and between
regions, and improve the efficiency of research into agroforestry and other land-management approaches.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
15.
Carbon storage of artificial forests in rehabilitated lands in the upper reaches of the Yellow River
Jianzhong Hu 《Frontiers of Forestry in China》2006,1(3):268-276
We studied 10-to 27-year-old artificial forests on rehabilitated lands in the upper reaches of the Yellow River with the objective
of comparing the carbon densities of various artificial and natural forests. Under artificial plantations, the vegetation
layer (including roots) had a mean carbon density of 111.3 t/hm2, the litter layer a density of 5.1 t/hm2, and the soil layer a density of 64.9 t/hm2. These values accounted for 28.6%, 13.8%, and 61.0% of their respective counterparts in the natural secondary forests under
the same site conditions in the region. The ratios of carbon density among vegetation, litter, and soil pools were 39.6:1.8:58.6
for artificial forests and 57.4:2.7:39.9 for natural forests. The carbon densities of the vegetation and litter layers increased
exponentially with forest age. The total carbon density ratios were also increasing gradually. Although the mean total carbon
density of the artificial forests in the rehabilitated lands was 281.2 t/hm2 in the experimental area, it accounted for only 41.5% of the carbon density of the natural secondary forests (677.4 t/hm2). The annual increase in total carbon density of artificial forests was as high as 15.2 t/hm2, which was 11.7% more than that of natural forests and 6.8 times higher than that (1.95 t/hm) of artificial forests in the
entire country as measured during 1994–1998. This indicates that growth and carbon storage capacity of artificial forests
in the rehabilitated lands were higher than those of forests on the barren hills and the secondary forests. We concluded that
the conversion project from croplands to forests and grasslands based on scientific principles is very important in the formation
of carbon sinks for reducing greenhouse effects.
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Translated from Journal of Beijing Forestry University, 2005, 27(6): 1–8 [译自: 北京林业大学学报, 2005, 27(6): 1–8] 相似文献
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This paper describes some recent experimental and theoreticalwork on the growth and spread of fire in the open and discussessome examples of field data in terms of the theoretical calculationspresented. The lengths of flames from laboratory fires have been relatedto the size and rate of burning of the fuel by formulae derivedfrom a simplified dimensional analysis. The effects of a windblowing across a long fuel bed on the length and orientationof flames are also described. The scaling laws for flame heightsuggest that in the horizontal spread of fire, heat transferfrom the flames above the fuel bed is important primarily withshallow fuel beds. It is suggested that the main effect of a wind on crib firesis aerodynamic. The wind deflects the advancing fire front fromthe vertical, but perpendicular to this deflected front therate of spread of fire, at least for cribs, is roughly the sameas in still air. However, a theory of spread allowing for heattransfer through the fuel bed and radiation from the flamespredicts that there can be a stable fast spreadas well as a slow spread. In fastspread the flames are thick and control the spread. In slow spread radiant heat transfer from theburning zone is usually responsible for the spread. The flamesare thin and of low emissivity. The most important factors determiningthe rate of slow spread R are pb the bulk densityof the fuel bed and ø the deflection from the verticalof the front of burning fuel which varies with wind speed. Rpb cos ø is approximately constant over a wide rangeof conditions with an order of magnitude of 510 mg cm2s1. 相似文献
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According to the requirements of the conversion of farmland to forests project (CFFP), we investigated the vegetation factors
and environmental factors from more than 6,105 sub-compartments in Liangcheng County, Inner Mongolia by using the Matlab,
analytic hierarchy process (AHP), and the hierarchical cluster method (HCM). The site conditions were classified quantitatively.
The results show that CFFP at this site comprises five site-type groups and 19 site types. A quantitative site classification
system method has been established in this paper.
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Translated from Journal of Beijing Forestry University, 2005, 27(6) [译自: 北京林业大学学报, 2005, 27(6)] 相似文献
18.
Mohammad Mahfuzur Rahman Md. Abdullah Al Mahmud Mohammad Shahidullah Tapan Kumar Nath Mohammed Jashimuddin 《Journal of Sustainable Forestry》2013,32(6):431-450
ABSTRACTMany forest reserves in Bangladesh have been converted to protected areas (PAs) to conserve the forests resources from further depletion. This study has investigated if such initiatives have improved the state of biodiversity of these PAs amid tremendous anthropogenic pressure on forest resources. We have assessed the phytosociological attributes of the PAs in the country through a case study at Kaptai National Park (KNP) and compared the attributes with those of the adjacent areas and of the tropical forests across the world. We have identified 52 species belonging to 45 genera and 28 families. The most dominant species in KNP was Dipterocarpus spp. and the adjacent area was dominated by Tectona grandis. Unexpectedly, the Shannon-Wiener index of KNP has dropped down from 2.98 in 2000 to 0.90 in 2014. However, in terms of relative density, relative dominance, and relative frequency, KNP was better than the adjacent areas. In contrast, the mean Shannon-Wiener index in KNP (0.90) was smaller than that in the tropical countries (2.99). We recommend strengthening effective comanagement of PAs and enabling nonforestry income generation activities for the forest-dependent people so that the biodiversity of the PAs can be enriched while people’s livelihoods are ensured. 相似文献
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Sap flow of the major tree species in the eastern mountainous region in northeast China 总被引:1,自引:0,他引:1
This study is based on Quercus mongolica, Fraxinus mandshurica, Phellodendron amurense, Juglans mandshurica, Tilia amurensis, and Pinus koraiensis trees of the same age (12 years) and seedling origin under the same site conditions. The sap flow density, water consumption,
and related environmental factors were also measured using thermal dissipation method and ICT-2000TE (Transpiration-Environment)
automatic measuring system for tree transpiration and environmental factors. On clear days during the growing season, the
sap flow density exhibited mono-peak diurnal patterns, mostly between 10:00 and 14:00, except for Phellodendron amurense, whose sap flow showed two peaks during the daytime three times. The photosynthetically active radiation (PAR) and vapour
pressure deficit (VPD) were the major factors influencing diurnal changes in sap flow, which explained 60%–74% variations
in sap flow density for all species except Phellodendron amurense. Maximum sap flow densities for F. mandshurica, Phellodendron amurense, Q. mongolica, J. mandshurica, T. amurensis, and Pinus koraiensis were 516.36, 234.00, 625.93, 945.83, 507.93, and 286.21 cm3/(cm2·h), in July, June, September, August, August, and July, respectively. Water consumption during the whole growing season for
J. mandshurica, T. amurensis, F. mandshurica, Pinus koraiensis, Phellodendron amurense, and Q. mongolica was 3,840, 2,820, 2,710, 2,120, 1,470, and 1,390 kg/sapling, respectively.
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Translated from Scientia Silvae Sinicae, 2005, 41(3): 36–42 [译自: 林业科学, 2005, 41(3): 36–42] 相似文献