共查询到20条相似文献，搜索用时 62 毫秒
1.
我国山区发展的历史表明，山区经济的发展、良好生态环境的维持都与森林的枯荣盛衰密切相关，所以，山区综合开发建设要以林为本．山区综合开发要在增加农民收入、发展地方经济与保护森林资源、改善生态环境的结合点上找出路，而出路就是发展社会林业．社会林业是山区综合开发建设最稳妥、最可靠、最有效而快速的途径． 相似文献
2.
内蒙古草原带的山地，山杨分布面积欠于白桦，或于白桦以不同的比例组成混交林。它是山地森林的主要类型之一，是护坡林及痧资源涵养林的重要树种，为增强水源涵养，防止水土流失，保护生态环境，加速三弱防护林体系的建设，实现要业可持续的发展，应加强内蒙古山区山杨更新措施的研究。经多年试验，采取开沟进行山杨人工促进天然更新，是一个可以大力推广的适用技术。 相似文献
3.
呼和浩特地区的大青山、具有立地生产力较低,人工林和天然林年龄小等特点。大青山林业的发展,对涵养水源,调节气候,改善生态环境,维护生物多样性,供应城乡居民所需的用材、烧柴及果品、提供游乐场所等方面起着重要作用。其发展方针是：把山区的水源涵养、水土保持和生态环境建设列在首位;以林为主、协调农、果、林、牧的关系,森林的培养,要采取封山育林和人工造林并重的政策;把经济林的发展和其他林种结合起来,重视自然保 相似文献
4.
5.
陈炳浩 《绿色中国(A版)》1998,(5)
探讨了1998年长江、松花江和嫩江流域发生特大洪涝灾害的原因，有自然因素的影响，但人为因素诸如滥伐森林、围湖造田和在河滩地搞违章建设等促成此次洪水灾害的严重性。山区林区生态环境恶化，山下平川地区遭殃，历来如此。应强化保护森林，加快长江中上游防护林体系生态工程建设，充分发挥山地森林的水文生态效应机制，对江河湖泊及其流域进行综合治理，协调行动。 相似文献
6.
罗顺宏 《云南林业调查规划》2000,25(3):12-14,52
转龙镇森林资源具有宜林荒山荒地面积少，覆盖率高；森林质量差；中幼林比重大，可采资源少；森林类型单一，单位面积蓄积小等特点。其山区面积占总面积的９０％以上，山区脱贫致富的最大优势在于山，为此提出林业发展措施；①采取有效的技术措施把现有的近万亩板栗其地管理好，并适度发展鲜果类经济林；②加强幼龄林的抚育和林分的封山育林工作；③进行山区林业综合开发，大力开发以华山松为主，旱冬瓜、云南松为辅的用材林造林和低产林改造工作；④利用区位优势，发展森林旅游业。 相似文献
7.
8.
云南是典型的山区省份,全省94%的国土面积是山区,近3400万人居住在山区半山区,占全省总人口的70%。念好"山"字经,做好"林"文章,是"三农"工作的重要内容,也是社会主义新农村建设的重要支撑。省委省政府高度重视山区特色林产业的发展,作出了加快林业发展建设森林云南的决定,出台了《加快木本油料产业发展的意见》,把以核桃为主的木本油料产业发展,作为发展山区经济,改善农村生态环境,加快社会主义新农村建设的重大举措。 相似文献
9.
南岳之胜在山，山之胜在林。森林既是构筑南岳生态环境的主体，又是南岳旅游经济发展的基础。作为以旅游立区的南岳区，其主要任务：一是建设好生态林业，改善旅游环境，培育旅游资源；二是发展旅游经济，把生态林业变为经济资本，让森林在经济发展中发挥最大的效益。随着我国加入WTO，党中央、国务院非常重视生态环境的建设，把改善生态环境提高到关系到中华民族生存和发展的长远大计来抓。省委、省政府对我区生态环境建设非常重视。省委书记杨正午先后作了重要指示，省林业厅葛汉栋厅长多次莅临南岳研究、考察林业工作。由于领导重视，… 相似文献
10.
融水苗族自治县地处桂北山区 ,是国定贫困县 ,林业在全县国民经济中占有很重要的地位 ,林业可持续发展是全县山区可持续发展的重要基础。融水县山区林业可持续发展的内涵和特点第一 ,融水县位于珠江流域的上游 ,是国家确定的首批５０个“珠江防护林工程”建设重点县之一 ,广西三大暴雨中心之一 ,要求山地森林具有更高的水分涵养和土壤保持功能 ,水土保持要求渗透到一切山地森林的所有经营活动中去。第二 ,具有由山地生态环境的立体性和多样性衍生的森林生态系统本身的多样性以及森林生态系统中的动物、植物、微生物的多样性以及这些物种遗传… 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage. 相似文献
13.
Contour hedgerows of multipurpose tree species in the sloping tea lands of Sri Lanka are expected to reduce soil erosion and
also add significant amounts of plant nutrients to the soil via periodic prunings. The objective of this experiment was to characterize the biomass decomposition pattern and quantify the
amount of nutrients added through prunings of six tree species (Calliandra calothyrsus, Senna spectabilis, Euphatorium innulifolium, Flemingia congesta, Gliricidia sepium and Tithonia diversifolia) currently being used in hedgerows associated with tea. Withered leaf and stem prunings (50 g) were enclosed in 2-mm litter
bags, placed at 5-cm depth and retrieved after one, three, six, nine and 12 weeks. Loss of initial dry weight, N, P and K
was measured. Single exponential decay function adequately described both dry weight and nutrient loss. Tree species differed
significantly in their rate of breakdown with decomposition constants (k) varying from 0.0299 to 0.2006 week−1 for leaves and from 0.0225 to 0.0633 week−1 for stems. Gliricidia showed the highest k for leaves with the rest in the following descending order: Senna > Tithonia ≥ Euphatorium > Calliandra > Flemingia. A similar pattern was observed for loss of all nutrients with Calliandra and Flemingia always having lower k values than the rest. Although N immobilization was not observed, immobilization of P and K was observed
during the first week of incubation in some species, particularly in stem prunings. Annual biomass of prunings differed significantly
between tree species in the following descending order: Calliandra > Senna > Flemingia > Tithonia > Gliricidia > Euphatorium. Calliandra added the greatest amount of nutrients annually to the soil with Euphatorium adding the least. Calliandra prunings provided the annual total K requirement and 49% of the N requirement of mature tea. However, none of the species
provided more than 5% of the P requirement. It is concluded that among the tree species tested, Calliandra and Flemingia are the most suitable for contour hedgerows in tea plantations of this agroclimatic region because of their higher soil nutrient
enrichment capacity and slower decomposition rates which would minimize leaching losses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland. 相似文献
15.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions. 相似文献
16.
《Scandinavian Journal of Forest Research》2012,27(2):118-130
The effects of seed weight and seed type on seedling growth of Pinus sylvestris (L.) were studied by seeding individually weighed orchard and stand seed in different mixtures under harsh (direct seeding in field) and optimal (seeding in nursery) conditions. In the nursery experiment an increase in the seed weight from 3 to 7 mg increased the seedling height by 10-27% and total weight by 27-113%, and decreased the height/diameter ratio by 5-6% after 2 yrs. With elimination of seed weight effects, orchard seedlings were 2% taller than stand seedlings in year 2. Without elimination of seed weight effects, orchard seedlings were 7-13% taller. In the field experiment an increase in the seed weight from 3 to 7 mg increased seedling height by 18-65%, stem volume by 81-274% and the number of top-buds by 23-34% in year 5. After elimination of seed weight effects, orchard seedlings were 7-13% taller than stand seedlings and without elimination of seed weight effects 20-21% taller after 5 yrs. Even after elimination of both seed weight and genetic effects orchard seedlings were 3-9% larger than stand seedlings in the field experiment. In conclusion, the influence of seed weight and seed type on growth traits and slenderness is highly significant and the influence seems to be greater in harsh conditions. 相似文献
17.
本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。 相似文献
18.
Astra Zaluma Lauma Bruna Darta Klavina Natalija Burnevica Kristine Kenigsvalde Andis Lazdins Talis Gaitnieks 《Forest Pathology》2019,49(6)
Heterobasidion parviporum and Heterobasidion annosum are widely distributed root‐rot fungi that infect conifers throughout Europe. Infection of conifer stumps by spores of these pathogens can be controlled by treating fresh stumps with a competing non‐pathogenic fungus, Phlebiopsis gigantea. In this study, growth of three Latvian strains of P. gigantea and the biological control agent ‘Rotstop’ strain was evaluated in stem pieces of Norway spruce, Scots pine, lodgepole pine, Douglas‐fir, Weymouth pine, Siberian larch and Sitka spruce. The growth rates of one H. parviporum and one H. annosum isolate were also measured in the same stem pieces. The growth rate of P. gigantea varied greatly in wood of different conifer species. It was higher in the three pine species, lower in Norway spruce and lowest in Sitka spruce and Siberian larch, and in Douglas‐fir, this fungus did not grow. The largest area of wood occupied by P. gigantea was in lodgepole pine. Growth of Latvian isolates of P. gigantea in the wood of Pinus and Picea species was comparable to that of the Rotstop isolate. Consequently, stump treatment with local P. gigantea isolates should be recommended. However, our results suggest that Douglas‐fir stump treatment against Heterobasidion by P. gigantea may be ineffective and other stump treatment methods should be considered. 相似文献
19.
Steven Maranz Amadou Niang Antoine Kalinganire Djeneba Konaté Bocary Kaya 《Agroforestry Systems》2008,72(3):231-239
Baobab leaves form an important part of the local diet in Sahel countries and elsewhere in Africa. Existing leaf nutritional
data and agroforestry performance information are based solely on Adansonia digitata L., the baobab of continental Africa. The introduction potential of Adansonia species from the center of diversity in Madagascar and from Australia remains untapped. To assess this potential, the mineral
contents and B1 and B2 vitamin levels of dried baobab leaves were determined for five-year old trees of A. digitata, A. gibbosa (A. Cunn.) Guymer ex D. Baum, A. rubrostipa Jum. & H. Perrier (syn. A. fony Baill.), A. perrieri Capuron and A. za Baill. grown in an introduction trial in Mali. Nutritional data were evaluated against survival and vigor to identify promising
germplasm. Leaf vitamin and crude protein contents were highest in the Madagascar species, especially A. rubrostipa (B1 88 mg 100 g−1, B2 187 mg 100 g−1, protein 20.7% dry weight). However, the local species far outperformed the introductions in survival, tree height, basal
diameter and resistance to termites. We suggest grafting as a way of harnessing the vigor of well-adapted local baobab varieties
to the superior nutritional profiles of A. rubrostipa and others. Cross-species grafting tests in Adansonia were successful, thus creating new agroforestry possibilities with different scion/rootstock combinations. 相似文献
20.
《Wood material science & engineering》2013,8(2):76-84
Abstract Wood in general and wooden studs in particular are often distorted owing to uneven shrinkage during the drying process in the sawmill. Twist is often the most detrimental of all types of distortion, and it is caused by spiral grain in combination with variations in moisture content. For sawmills, the objective is to produce dried, straight boards, and one method of dealing with boards with excessive spiral grain is to sort them out and then dry them in a pretwisted position to obtain straight boards after drying. A model using the finite element (FE) method for the simulation of drying twist distortions was first calibrated against laboratory experiments in which boards were dried with and without restraints and pretwists. After the calibration, the FE results were compared with industrial test results for boards that were dried without restraints or with restraints with zero pretwist, i.e. straight restraints. The FE model used an elastic–ideally plastic material model to obtain permanent deformations. The calibration was to set the yield stresses so that there was a good match between FE results and results from the laboratory experiments. The comparison between the industrial test results and the FE results showed that the FE model is capable of realistic simulations of drying boards with and without restraints and presumably also pretwists. 相似文献