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对安庆市南埂林场长江沿岸滩地3年、8年和20年生人工杨树林地上空间昆虫群落的种群组成和多样性进行了调查观测。结果表明,在3种不同林龄林分之间,地上空间昆虫种群组成的差异表现为:在目一级分类单元组成上,3种不同林龄林分具有很高的共性;在科和种的单元上,不同林龄林分之间的差异表现为3年生与20年生林分之间3年生与8年生林分之间8年生与20年生林分之间。随着林分林龄的增加,林内地上空间昆虫丰富度指数、Shannon-Wiener指数明显降低。不同林龄林分地上空间昆虫种群的均匀度指数与林分林龄没有明显的相关性,其中20年生林分昆虫种群的均匀度指数显著低于8年生和3年生的林分,而8年生和3年生林分之间没有显著差异。 相似文献
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对安庆市南埂林场长江沿岸滩地3年、8年和20年生人工杨树林地上空间昆虫群落的种群组成和多样性进行了调查观测。结果表明,在3种不同林龄林分之间,地上空间昆虫种群组成的差异表现为：在目一级分类单元组成上,3种不同林龄林分具有很高的共性;在科和种的单元上,不同林龄林分之间的差异表现为3年生与20年生林分之间〉3年生与8年生林分之间〉8年生与20年生林分之间。随着林分林龄的增加,林内地上空间昆虫丰富度指数、Shannon-Wiener指数明显降低。不同林龄林分地上空间昆虫种群的均匀度指数与林分林龄没：哿明显的相关性,其中20年生林分昆虫种群的均匀度指数显著低于8年生和3年生的林分,而8年生和3年生林分：之间没有显著差异。 相似文献
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章古台地区樟子松人工林土壤水分物理性质的研究 总被引：2，自引：0，他引：2
以章古台地区樟子松人工林地土壤为研究对象,依照不同立地、不同林龄、不同林型和不同林分密度研究了樟子松人工林改良土壤水分物理性质状况和林地土壤含水率。结果表明:不同林龄林地土壤含水率有明显区别:0～20年生林分土壤含水率较高,至27年生林分林地土壤含水率为最低,27年生以后林分土壤含水率有所回升。甸子地樟子松固沙林改善土壤水分物理性质优于坨子地樟子松固沙林。不同林龄间土壤水分物理性质区别不明显,但较裸沙地要好。从改良土壤水分物理性质效果来看:樟杨混交是较好造林类型,600～800株/hm2是章古台樟子松固沙林适宜的林分密度。 相似文献
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《经济林研究》2014,(2)
为给筛选抗旱性强的油茶优良单株以选育油茶抗旱砧木提供参考依据,以香花油茶、小果油茶、普通油茶、陆川油茶、博白大果油茶和广宁红花油茶这6个油茶物种的1年生实生苗为试材,采用人工控制浇水使土壤自然干旱的方法对其抗旱性进行了试验研究,并对其苗期抗旱性的强弱进行了评价。结果表明:广宁红花油茶的暂时萎蔫系数和永久萎蔫系数分别达到5.09%和3.11%,均显著高于其它油茶物种;而香花油茶的暂时萎蔫系数和永久萎蔫系数均最小,仅分别为2.42%和1.10%;6个油茶物种的抗旱能力由强到弱依次为香花油茶小果油茶普通油茶陆川油茶博白大果油茶广宁红花油茶;6个物种内不同单株间的抗旱性均存在分离情况,依其永久萎焉系数的大小可将其划分为0%~1%、1%~2%、2%~3%、3%~4%、4%~5%共5种抗旱类型,其中,广宁红花油茶的抗旱类型分布在3~5级之中;博白大果油茶分布在2~4级之中,陆川油茶、普通油茶和小果油茶均仅在2、3级之中有分布,香花油茶只在1、2级之中有分布。 相似文献
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【目的】为优化杉木栽培措施,实现杉木林可持续经营。【方法】本试验以3、6、9年生红心杉幼林为研究对象,分析了1 667、2 501、3 333株·hm-2不同造林密度林分生长及土壤理化性质的变化。【结果】结果表明：造林密度显著影响了6和9生林分生长,整体上随着林龄增加,林分密度越大,树高、胸径、单株材积及蓄积量下降幅度越大。其中,与1 667株·hm-2林分相比,3 333株·hm-2林分各生长指标下降了22.0%～65.3%。相较1 667和2 501株·hm-2林分,9年生3 333株·hm-2林分土壤容重增大、孔隙度降低,土壤中全氮、速效氮、速效钾含量均显著减少。此外,相较氮素,土壤中磷钾含量随着林龄增加均呈明显的下降趋势。【结论】供试3种造林密度中,以1 667株·hm-2造林密度林分生长及土壤性状均表现最佳,为进一步提升林地生产力,实现地力维持,应注重磷钾肥的补充。 相似文献
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《林业勘察设计》2018,(2)
通过设置18个20 m×30 m的临时样方对大田县不同年份营建的闽楠示范林进行调查和生长分析,以客观评价示范区建设成效。研究结果表明:3年生林分平均造林保存率、地径、树高、枝下高和冠幅分别为94. 4%、3. 3 cm、2. 3 m、0. 6 m和0. 9 m,不同种植模式的生长效果依次为7楠3杉 8楠2杉闽楠纯林,树高、枝下高和冠幅在不同种植模式间存在显著差异;坡位对5年生和7年生闽楠生长有一定影响,且随年龄的增大,其影响效应有增大的趋势; 5年生的林分生长低于一般栽培区的水平,而3年生和7年生的均达到中心栽培区的水平。为促进闽楠标准化示范区建设,建议优先选择中下坡且土层较厚的立地条件,并保留适宜的杉木株数和加强抚育管理。 相似文献
10.
长江中下游滩地杨树林植物多样性研究 总被引：3，自引：0，他引：3
本文以3个人工杨树林下植物群落调查样地及原始无林滩地资料为基础,从物种丰富度、均匀度和物种多样性指数等方面对长江中下游江河滩地抑螺防病林试验示范区林下植物群落多样性进行了分析。结果表明,人工林栽植后植物多样性升高了,且不同林龄人工林的植物种类及物种多样性存在差异——3年生的人工林多样性指数最高,8年生的人工林均匀度最高。说明滩地造林明显增加了植物群落的多样性,但随着林分的郁闭会限制其下植物的生长,导致多样性呈下降趋势,可见人工林林分郁闭度左右着林下植物的组成及分布。 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
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
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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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《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
19.
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
20.
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