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1.
井冈山罗浮栲群落种群生态数量场特征 总被引：4，自引：0，他引：4
以江西井冈山自然保护区天然罗浮栲群落为研究对象,应用植物生态场理论,对罗浮栲种群生态数量场进行研究.结果表明: 罗浮栲优势种群的生态数量场主要有如下特征:1)数量场的作用范围为半径为60 m的圆;2)β"驼峰"值的时间延续长度为100年;3)罗浮栲种群生态数量场的梯度在规范距离 (r为 0～28.8 m)表现为:在3.6～14.4 m 场势增强,在18.8～28.8 m场势减弱;4)罗浮栲种群生态数量场具有周期震荡的特征,震荡的周期为2个世代,时间长度为50年;振幅处于较大值的时间较长,即250年,说明现在的罗浮栲群落并未进入衰退阶段;罗浮栲种群数量场具有阻尼震荡的特点,表明罗浮栲群落在325年以后将进入衰退期,到那时罗浮栲群落的优势树种地位将被其他树种取代. 相似文献
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研究了不同人为干扰强度对甜槠天然群落中主要种群甜槠和赤楠的分布格局的变化动态.结果表明,人为干扰会使甜槠种群的聚集性加强,而赤楠种群的聚集性降低.干扰强度对甜槠聚集性的影响随树龄的增大而逐渐减小,而对赤楠聚集性的影响则是随林龄增大呈现由小→大→小的规律. 相似文献
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东兰县绿兰林场借西部大开发东风，为保护生态环境平衡，大力营造生物防火林带隔离火源。 东兰县绿兰林场是森林火灾常发区域，目前经过精心营造建成的以白克木为主、荷木为辅的生物防火林带已初见成效。全场原有防火线87．7公里，现已种白克木生物防火林带60公里，占全场防火线的68．41％。白克木长势最高5米，最低1．5米，已成一条绿色纽带。其中分布于县界边缘的有5公里，乡镇界有25公里，内界线有30公里。目前该场2001年规划营造10公里白克木生态防火林带，2002年补造和新造20公里，争取在2003年把该场全部防火线转换为生物防火林带… 相似文献
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采用有限空间种群增长的逻辑斯谛方程,研究天然针阔混交林建群种的种群优势度增长规律。研究结果表明,群落建群种马尾松和丝栗栲的种群优势度最大增长速度的径级范围是36～40cm 和24～28cm,此外还对该群落的演替趋势进行了分析。 相似文献
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对江西、广东等地不同纬度、不同演替阶段的19个类型常绿阔叶林群落的种群多样性进行了调查分析,探讨了有关理论和实践上的规律,即种群多样性与群落的结构、类型、发展动态以及地理纬度有关。 相似文献
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通过踏查、样地调查相结合的野外调查方法,结合群落重要性指数、相似性指数分析方法,对大山冲森林公园天然的针阔混交群落进行研究,了解其亚热带典型天然混交林的更新和演替规律。结果表明:群落物种组成结构差异在随着时间增加而增大,但总体变幅小,乔木层物种种类增加33.3%,平均胸径、平均树高和林分密度变幅小;4年演替过程中,山矾在群落乔木层中几乎消失,山矾种群数量下降94.4%,青冈栎种群数量相差小,但种群重要值从第三到第五,下降23.4%,丧失了原来的优势地位;群落中,常绿阔叶树种类和针叶树种类变化小或不变,落叶树种类增加了12.5%,但在数量及重要值两方面,常绿阔叶树和针叶树一直处优势地位,石栎和马尾松仍是群落优势种;群落乔木层相似性系数为0.4;在不出现天灾或人类有意干扰下,群落将继续朝顶级群落-常绿阔叶林方向更新演替。 相似文献
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星斗山自然保护区珙桐繁殖方式及生长分析 总被引：10，自引：0，他引：10
星斗山自然保护区珙桐繁殖方式及生长过程分析结果显示：珙桐种群在天然群落中为集群分布,以根萌蘖繁殖为主,胸径、树高平均生长量和连年生长量随年龄增加呈规律性变化。 相似文献
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民勤连古城自然保护区绵刺种群的结构与动态研究结果表明：绵刺种群在群落中地位和作用非常突出，其重要值为206．92，远远大于其他灌木物种，灌木层为群落的优势层片。绵刺具有2种典型的克隆生长构型：由劈根形成的密集性克隆生长构型和枝条下垂受损产生不定根形成的游击性克隆生长构型，这种特性在很大程度上影响了种群的分布格局、年龄结构和生命曲线。分布格局为集群分布。绵刺的年龄结构为下降型锥体，年龄越大，种群数量越多，但并不表示该种群为衰败种群，而为一个比较稳定的种群。生命曲线呈反对角线性上升，达到生理寿命前很少有个体死亡。 相似文献
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《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
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《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
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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
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《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
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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
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《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
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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
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《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
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《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
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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