共查询到20条相似文献，搜索用时 46 毫秒
1.
林业公路的养护，在没有装载机与其它养路机具配套的情况下，砂料的装车工艺只能靠木制的固定式推土台通过推土机来完成，本文就结合松岭林业局研制的移动式推土台在使用和效益上进行了分析。 相似文献
2.
3.
1987年下半年,我们根据黑龙江省林科院丽林实验林场的实际条件,研制出TDJ—50型多用机。该机以旧J—50型拖拉机改制而成,前端装置推土铲,车上按设两节液控吊臂。其特点是安装容易,零部件加工简单,改装费用低;具有归、装、卸木材,推土,推雪和其他重物吊运等多种作业功能。现将有关情况介绍如下。一、确定设计方案的依据丽林实验林场木材生产方式属季节性作 相似文献
4.
近年来，国内进口了一定数量的俄产Ｔ３３０型推土机。该推土机功率大、推土能力强，适用于繁重的土石方工程。但其发动机（部分）故障率很高，配件购买困难，而且价格大约是国产的３～４倍，有的在８～１０倍左右。为此，我们于１９９５年末用国产１２Ｖ１３５ＪＺＤ发动... 相似文献
5.
一、问题的提出大兴安岭呼中林业局为了改进营林生产作业条件,曾投资近百万元购进了一批金龙—252型营林拖拉机,用于山坡和少量平地作业。因金龙—252型拖拉机离地间隙小,且前部负载推土铲、后部负载液压起重抓爪,单位地面压力较大,重心较高,通过性能较低,易翻车,夏季作业,尤为严重。因而,影响了该机在营林生产作业中的应用。 相似文献
6.
本文概述了TDJ—50型多用机的研制过程和使用情况。指出该机具有结构简单、造价低廉、适应性强、移动灵活、拆装方便等特点。可用于推土、推雪、集材、装车等多种作业,其机械式折叠主副臂臂架结构设计有独到之处。经过一年的使用,取得了显著的效益。 相似文献
7.
到过伊金霍洛旗的人,都会称赞公路两旁整齐的行道树。地处毛乌素沙漠边缘的伊金霍洛旗,是怎样取得公路绿化的好成绩呢?这还得从呼志明老汉说起。 1658年,呼志明退伍复员后被安排在伊旗公路段当养路工人。当时,伊旗境内唯一的一条东榆简易公路经常被沙埋没。养路工的工作十分辛苦,一年四季与风沙搏斗,铲沙、推土、填坑、垫路。这样的工作, 相似文献
8.
一兵 《林业机械与木工设备》1967,(6)
Л-101林用轻型轮式拖拉机主要用于间伐作业,由于其后部装有鞍式悬挂机构、集材搭载板、绞盘机、推土板等设备,还可用于幼龄林、中龄林甚至成过熟林冠下进行原木、原条或伐倒木集材,归楞,平整场地以及整地、植树、森林抚育和森林保护、防火等作业。 相似文献
9.
《林业机械与木工设备》2000,(1)
鉴于我国农机产品的结构性过剩已越来越明显，天津有关专家根据农民的实际需求，建议农机企业开发生产１５类农机产品。①节能增效农业机械。如谷物耕播联合作业机械、分层深施化肥机械、精密喷药机械等。②中低产田改造工程机械。如大功率履带拖拉机、推土平地联合机械、... 相似文献
10.
高速公路园林化存在的问题与对策 总被引：1，自引：0，他引：1
近年来,我国高速公路园林绿化建设迅猛发展。但从目前的绿化状况来看,除东部经济发达地区和京、津等大城市高速公路园林化程度较高以外,其他地区还存在一些不足之处。 一是植被恢复欠完善,绿化覆盖盲点多。只对出入口的一小段路重点绿化,中途则实行降级绿化,废弃物没有妥善处理,大面积的岩石墙、推土层、沙石沟等裸露面没有及时 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.
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
15.
《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
16.
《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
17.
《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
18.
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
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