中国省域森林生态安全与林业产业结构时空耦合测度

在探讨森林生态安全与林业产业结构耦合特征的基础上,分别构建森林生态安全与林业产业结构评价指标体系,并运用耦合协调度模型对2007,2010,2013,2016年中国大陆各省域森林生态安全与林业产业结构的耦合协调发展关系进行分析。结果表明:从耦合协调发展阶段来看,大部分省域在4个年份分别处于磨合、磨合、磨合、协调阶段,部分省域发展过程出现了跃进或倒退现象;从相对发展状态来看,大部分省域在4个年份分别处于超前、超前、超前、滞后状态,当前森林生态安全较林业产业结构仍存在一定差距;从耦合协调发展类型来看,大部分省域在4个年份分别为类型Ⅵ、Ⅵ、Ⅵ、Ⅶ,当前森林生态安全滞后于林业产业结构,二者处于低度协调阶段。     

北京山区森林健康的多尺度评价

北京山区森林是北京市重要的绿色屏障,其健康状况事关首都生态安全等重大问题。基于森林资源二类调查数据和样地调查数据等,利用多层模糊综合评价法,从林分、景观和区域多尺度对北京山区森林健康状况进行耦合评价。结果表明:在区域尺度上,北京山区森林整体处于亚健康状态;在景观尺度上,18类森林景观要素类型中,健康的森林4类,亚健康的12类,不健康的2类;在林分尺度上,30164个森林经营小班中,亚健康的最多,数量为12226个,面积比例42.21%;不健康和疾病的数量为9534个,面积比例27.57%。因此,北京山区森林急需进行健康经营和管理以提高健康等级。     

景观生态学与森林景观生态规划初探

随着景观生态学的发展,结合景观规划的概念,对森林景观进行景观生态规划,可以协调森林在生态、社会、经济方面的功能.同时森林景观生态规划使得森林经营和资源管理活动不再局限于某一尺度上的决策,而是在景观、区域尺度上的进行综合分析.应用地理信息系统的原理以及相关软件可以为森林景观生态规划的实施提供技术支持.     

森林生态补偿标准体系研究

构建科学的生态补偿标准体系,能够实现以生态补偿带动精准扶贫,将生态环境退化与经济贫困恶化的困局兼而治之。目前,对森林补偿标准的研究主要集中在局地层面,国家尺度补偿标准体系研究尚不多见。将经济水平、营林成本、生态区位和林分质量等因素引入补偿标准模型,应用森林长期定位观测数据和31省森林经营成本等基础数据,构建效益法和成本法的补偿标准区间体系,结合皮尔(R.Pearl)生长曲线模型和经济发展阶段设计我国适度补偿标准体系。结果表明:效益法补偿标准均值是1 605.90元/(hm~2·a),成本法补偿标准均值是615.15元/(hm~2·a),各地适度补偿标准的均值为783.60元/(hm~2·a);效益法和成本法分别能够解释实际补偿标准变异的38.5%和41.4%;补偿标准区间和适度补偿标准体系的构建能够响应多种异质性要素,有利于实现森林生态补偿制度的激励相容。     

黑龙江省林火规律研究Ⅲ.大尺度水平林火与森林类型之间的关系研究

林火是森林生态系统中重要的生态因子.森林作为可燃物主体对林火的影响具有尺度性.虽然这种影响与尺度之间的关系研究较少,但在具体尺度上的研究却很多.在实验室小尺度上同质可燃物床层与火行为的关系可用Rothemel模型(Rothemel, 1972)来描述.在林分尺度上关于森林对林火的影响的研究,包括森林可燃物含水率的变化及其与林火发生和林火行为的关系等,国内外研究都很多.在景观斑块尺度上(GCTE 1990年定义)的研究较多,尤其是关于火作为一个扰动因子与景观格局的相互影响.在景观尺度(100km2,GCTE 1990年定义)上,特别是对景观之间的火系统(fire regime)关系研究较少.在景观以上尺度的研究国内尚未进行.介于景观和区域之间的尺度(100～10000km2)与我国的各省区内由不同森林类型形成的异质区的尺度相近.在该尺度上主要是对林火统计特征与区域可燃物、气候等属性之间的关系进行研究,采用自上而下的方法 ,注重统计规律,较少考虑自下而上的机理.它与区域尺度上的研究是进行大尺度规划,如国家火险等级区划的基础.     

三亚市生态补偿区森林生态评价

以三亚市生态补偿区生态公益林为研究对象,从森林的结构、稳定性和功能性3个方面构建了森林生态评价指标体系,在此基础上,以小班为评价单元,对研究区的森林生态水平进行了评价。结果表明:森林生态评价的6个指标层因子权重由大到小分别为:森林蓄积量(0.25)、森林自然度(0.20)、森林群落结构(0.20)、森林健康等级(0.15)、郁闭度(0.10)、平均树高(0.10)。4个区域整体生态水平处于中等水平,而抱安区的生态水平是最高的,4个区域的森林生态水平大小为抱安区那会区青法区扎南区。     

实施工程治理提高森防管理水平

辽宁省是一个少林的省份,现有林地面积451万hm2,森林覆盖率30.95%.由于中幼龄人工纯林比例较大和生态环境质量不高等原因,致使森林病虫害发生危害十分严重.长期以来,省财政厅每年都安排一部分资金用于森林病虫害防治,但由于病虫种类多,危害面积大,森林病虫害防治一直处于灾后救灾和被动控灾的局面.为了寻求有效控制森林病虫害严重发生的途径,省林业厅和省财政厅在认真总结经验教训和调查研究的基础上,于1992年在辽西地区松毛虫的防治上,以生态经济理论为依据,采取以营林技术为基础的生态措施和生物、仿生药剂防治技术,开展了“三生工程”,省财政厅拿出专款用于试点,取得了明显的防治效果.     

涉及邻近关系的多尺度林业数据图形综合方法

科学的森林经营管理是在研究结构与功能的基础上,考虑林分、景观和地理区域3个尺度,在林分小尺度上强调森林直接利用价值,在景观和地理区域大尺度上突出森林整体功能(亢新刚,2001)。Franklin(1994)和Egan等(1999)较早呼吁把更宽空间尺度作为森林生态系统管理的特征之一(谢剑斌等,2005)。目前,林分尺度的数据源大多为森林资源调查和外业调研数据,景观尺度数据源多为遥     

我国森林覆盖率的时空分布规律及对空气质量的影响

该文通过研究我国各省、市、自治区森林覆盖率的时空分布和演变过程,对第六、七、八次森林资源清查期间的森林覆盖率进行时空特征分析,并探究空气质量与森林覆盖率间的相关性。经过对时间(纵向)上的发展变化及空间(横向)上的区域差异进行对比分析,发现我国森林覆盖率有随时间增加的趋势,在地域分布上具有较明显的聚集效应,其中西部地区的森林覆盖率始终处于全国最低水平,森林覆盖率最高的区域主要集中在我国最南部的几个省份以及华东地区南部。另外,从空气质量与森林覆盖率间的关系来看,森林覆盖率对空气质量具有一定的影响,特别是对SO_2浓度和PM_(10)浓度影响较大。     

呼和浩特市森林承载力综合评价研究

森林是生态系统的重要组成部分,在提高和改善环境质量方面发挥着重要作用。以呼和浩特市森林资源二类调查相关数据为依据,运用层次分析法、综合指数法等方法,对呼和浩特市森林承载力指数进行计算,结果表明:目标层森林承载力指数(FCC)为0.8585,其中4个准则层承载指数分别是森林结构承载指数(FCC1)为0.9279,森林生态承载指数(FCC2)为0.5120,经济发展承载指数(FCC3)为0.7866,社会发展承载指数(FCC4)为1.8652,社会发展需求承载力最好,结构发展需求承载力次之,经济和生态需求承载力较弱;同时,运用森林资源可持续评价划分标准对呼和浩特市森林状态进行评价,表明呼和浩特市森林承载力处于弱中等承载状态;准则层森林结构需求的权重为0.4424,是加强森林承载力的关键因素,今后要更加注重森林结构的优化。     

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.     

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。     

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.     

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.     

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.     

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.