烟台海岸黑松防护林种群结构及其随离岸距离的变化

在烟台海岸黑松防护林内设置42块样地(10 m×10 m),采用样方法进行每木调查获取野外资料.以空间代替时间,以种群径级结构代替年龄结构,探讨烟台海岸黑松防护林种群的结构和动态规律;同时,分析离岸距离不等的黑松防护林的种群结构窄间变化特征.结果表明:海岸黑松防护林种群径级的数量分布基本上呈倒J型分布,表明黑松种群处于稳定发展的时期;黑松生长与种群密度之间存在明显的相关关系,黑松胸径、单株生物量与密度的关系均符合负指数函数模型,树高与密度呈显著负相关;在距离海岸50～500 m范围内,黑松种群密度随离岸距离的增加而增大,平均胸径和平均冠幅均随离岸距离的增加而减小,海陆相互作用产生的环境异质化可能是造成黑松种群空间分布格局的主要原因.     

藏东南林芝云杉种群结构与数量动态

以藏东南工布自然保护区内林芝云杉为研究对象,采用样带-样方法对林芝云杉种群及群落进行调查,从种群径级结构、高度结构、冠幅结构、静态生命表、生存分析、时间序列预测等方面对林芝云杉种群结构与数量动态进行分析。结果表明:林芝云杉种群胸径结构、高度结构和冠幅结构均呈典型的"金字塔"型,林芝云杉幼苗较为丰富,天然更新能力强,种群处于稳定发展状态。林芝云杉种群不同胸径级的个体数与胸径级呈对数关系,不同高度级和冠幅级的个体数分别与高度级和冠幅级呈幂函数关系,胸径与高度呈直线关系,而胸径与冠幅及高度与冠幅的相关性不明显。林芝云杉种群在生长过程中各龄级个体存活数量相差较大,随着龄级的增加,死亡率和消失率波动性较大,Ⅵ龄级死亡率和消失率均最低,分别为20%和22.31%;Ⅹ龄级死亡率和消失率最高,分别为62.96%和99.33%,平均死亡率和消失率分别为41.03%和57.55%。林芝云杉种群的存活曲线属于Deevey-Ⅱ型B3亚型。生存函数分析表明,林芝云杉种群具有前期锐减,中期相对平稳,后期生理枯竭而衰退的特点。时间序列预测分析显示,林芝云杉种群在未来Ⅱ,Ⅴ,Ⅷ和Ⅵ龄级时间后均呈现不同幅度的增加,种群稳定性可以维持。研究结果可为林芝云杉资源的有效利用和保护提供科学依据,同时进一步丰富西藏高原国家生态安全屏障评价内容。     

人为干扰下毛环方竹无性系种群结构及动态

以仅分布在中国贵州斗篷山,属于极度濒危物种的毛环方竹为研究对象,采用样方法从龄级、径级和高度级3个方面对人为干扰下毛环方竹无性系种群的结构和动态进行初步研究。结果表明:毛环方竹无性系种群的年龄结构中,龄级为Ⅳ和Ⅴ的分株数量分别占总分株数的30.0%和34.4%。胸径的最大值5.3 cm,最小值0.3 cm,平均值1.7 cm,主要分布范围为1.1~1.9 cm。高度的最大值为9.8 m,最小值为0.4 m,平均值为4.8 m,主要分布范围为3.1~7.0 m。胸径和高度随龄级的增大而增大。毛环方竹无性系种群呈衰退趋势。     

山西庞泉沟自然保护区辽东栎种群生命表研究

辽东栎是我国华北地区分布广泛的森林群落建群种和优势种,研究山西庞泉沟辽东栎生命表对于揭示其种群年龄结构和动态具有一定的科学意义。笔者基于野外调查数据,构建了山西庞泉沟自然保护区辽东栎种群的静态生命表并对其进行了分析,包括年龄结构图、存活曲线、死亡曲线等、消失率曲线、生存函数曲线、累积死亡率函数曲线、危险率函数曲线和死亡密度函数曲线。结果表明,辽东栎低龄级(1龄级～2龄级)种群数量较少,年龄结构呈衰退类型;种群死亡率随龄级增加逐渐增加,在最高龄级达到最大;种群存活曲线趋于Deevey-Ⅱ型,与年龄结构反映的衰退类型相同。总体上,死亡率和消失率随龄级增加,在高龄级阶段(7龄级～9龄级)生物量和消失率迅速上升;生存函数与累积死亡率函数呈负相关关系,生存率随龄级的增加而减小。死亡密度函数变化不明显,危险率函数变化趋势随龄级增加而增加,与死亡率变化趋势类似。因此,庞泉沟辽东栎种群年龄结构属于衰退型。     

粽粑竹无性系种群结构及空间分布格局

从年龄结构、径级结构、高度级结构3方面分析了粽粑竹无性系种群的结构特征,采用Greig-Smith的相邻格子样方调查法和方差/均值比率法、聚集度指标法分析了粽粑竹无性系种群的空间分布特征。结果表明,Ⅱ龄级的分株所占比例最高(42.3%),其次是Ⅰ龄级的分株(28.9%),表明粽粑竹无性系种群年龄结构呈增长型;地径主要分布在0.81~1.40cm,占总分株数的88.54%;高度主要集中在169.1~229.0 cm,占总分株数的51.8%。粽粑竹无性系种群空间分布格局与龄级有关,除Ⅰ龄级呈随机分布外,其余均为聚集分布。     

桥山林区3种麻栎群落类型的种群动态与幼苗特征

【目的】对比分析黄土高原南部桥山林区3种林分类型麻栎群落的种群结构与幼苗生长过程,阐明麻栎种群在不同群落类型下的数量和结构动态,为该地区麻栎林科学经营和恢复提供依据。【方法】采用样地调查法,调查12块样地(麻栎阔叶混交林、麻栎油松混交林和麻栎纯林3种林分类型,每种林分类型设置4块样地)内所有胸径大于4 cm个体的胸径(幼苗地径)、树高和冠幅等特征;在每块样地采集幼苗或幼树标准株,测定各器官生物量。以径级结构和高度级结构代替年龄结构,编制不同林分类型麻栎种群静态生命表,根据各径级麻栎种群存活量绘制存活曲线,并分析3种林分类型中1～10年生麻栎实生幼苗的高度、基径、冠幅及生物量分配差异。【结果】3种林分类型麻栎种群均呈现出随年龄增加个体数减小趋势,低龄级个体具有绝对数量优势,桥山地区麻栎种群年龄结构呈进展型。种群静态生命表表明,麻栎种群存活量随年龄增加呈降低趋势,低龄级死亡最高,为生活史脆弱期;Ⅲ、Ⅳ龄级期望寿命最高;在Ⅲ～Ⅶ龄级,麻栎阔叶混交林和麻栎油松混交林中的麻栎种群死亡率远远低于麻栎纯林。不同林分类型麻栎种群的存活曲线皆呈Deevey-Ⅲ型。实生苗基径在1～5年表现为麻栎纯林混交林,随着年龄增加,麻栎油松混交林实生苗基径略高于其他2种林分类型,但3种林分类型间差异不显著;实生苗冠幅在2～10年表现为混交林纯林,且3种林分类型间实生苗冠幅差异在4年后开始显著(P0.05);麻栎油松混交林实生苗高度在2～10年均高于其他2种林分类型,3种林分类型间实生苗高度差异在5年后开始显著(P0.05)。不同林分类型麻栎实生苗叶、干、根、侧枝生物量均随年龄增加而增长。3种林分类型间,实生苗叶生物量在1～6年差异不显著,干生物量在1～4年无显著性差异,侧枝生物量在1～2年差异不显著;随着年龄增加,3种林分类型间叶、干和侧枝生物量差异越来越显著;根生物量则随年龄变化没有太大差异。【结论】桥山林区3种林分类型麻栎种群发育良好,均具有一定的更新能力。麻栎纯林中大径级麻栎个体数较麻栎油松混交林和麻栎阔叶混交林少,麻栎纯林虽然早期幼苗数量较多,但幼树期死亡率较高,且高年龄幼苗的生长特性和各构件生物量均低于混交林,未来可将发展群落结构更稳定的混交林作为森林培育和经营的主要方向。     

大兴安岭落叶松种群生态特征研究

文章以大兴安岭呼中区兴安落叶松林为研究对象,结合径级结构、静态生命表、存活率曲线、死亡率曲线和消失率曲线,对兴安落叶松种群的年龄结构和生态特征进行了研究。研究发现在不同龄级下落叶松种群的个体数量有明显差异,I~Ⅲ龄级落叶松种群个体数占绝大多数,IV~VI龄级落叶松种群个体数相对较少;落叶松种群的存活曲线呈DeeveyⅡ型(对角线型);消失率和死亡率曲线变化趋势基本一致,均呈现单峰型,I~Ⅲ龄级落叶松种群的消失率和死亡率逐渐增加,IV~VI龄级落叶松种群消失率和死亡率逐渐减少。     

冷箭竹更新幼龄无性系种群结构的研究

本文分析了卧龙自然保护区冷箭竹更新幼龄无性系种群的龄级结构、径级结构和高度结构及其与生境条件的关系。结果表明;冷箭竹更新幼龄无性系种群为一增长种群;径级处于小径阶区域,主要位于０．００－０．１５ｃｍ之间;高度结构呈倒“丁”字型,随着高度级的增加,植株数量表现出递降趋势。同时,不同林分类型和海拔高度内冷箭竹的种群结构具有不同的分布格局,这与微生境、林分郁闭度、群落结构和野生动物影响密切相关。     

西江中下游针阔混交林优势种群的结构及分布格局研究

以西江中下游的针阔混交林为研究对象,通过固定样地、每木调查和林下更新层调查法获得野外资料,采用径级代龄级的方法,研究主要优势树种的种群结构,以及应用方差／均值比、平均拥挤度指数、聚块指数、丛生指标、负二项式参数等5个指标分析其种群格局状况。结果表明不同优势种群的径级结构差异明显：马尾松和烟斗柯缺失或缺乏幼苗,为衰退型种群;福建青冈幼苗充足,中龄级立木占绝对优势,表现为增长型种群,但结构不稳定;鸭脚木幼苗数量丰富,径级分布呈倒J字型,为稳定的增长种群。种群的格局动态因树种和发育阶段而不同,表现为马尾松由均匀分布过渡到集群分布,福建青冈始终为群集分布,鸭脚木和烟斗柯则由幼苗的集群分布向成树阶段的随机分布转变,4个种群的格局动态呈现出聚集强度降低的扩散趋势。     

冷箭竹无性系种群结构的初步研究

本文分析了三种林分类型下冷箭竹种群的年龄结构和表现结构，结果表明，卧龙自然保护区森林植被下的冷箭竹种群处于腿衰退状态，其林随年龄而变化；高度结构和径级结构因群落生境，干扰程度和大勇猛的取食不同而有明显差异。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

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.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

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.     

Decomposition and nutrient loss from prunings of different contour hedgerow species in tea plantations in the sloping highlands of Sri Lanka

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.     

Effects of Seed Weight and Seed Type on Early Seedling Growth of Pinus sylvestris under Harsh and Optimal Conditions

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.     

Modelling of adequate pretwist for obtaining straight timber

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.     

Potential to harness superior nutritional qualities of exotic baobabs if local adaptation can be conferred through grafting

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.     

Growth of Phlebiopsis gigantea in wood of seven conifer species

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.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

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.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

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.     

CAD与建筑设计的关系

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。