鄂西三峡库区生态安全综合评价

从生态安全涵义理解出发,以鄂西三峡库区为例,建立了包括气候条件、林种结构、社会经济发展水平、土地利用结构、生态环境状况等方面的区域生态安全评价指标体系,并进行了数量化评价。研究结果表明:库区生态安全处于相对稳定的状态,4个(区)县中,夷陵区生态安全整体情况较好,巴东县和兴山县一般。库区在水土保持、林种结构、土地利用等方面存在一定的生态安全问题,应采取科学合理的措施加以改善,构建鄂西三峡库区安全的生态系统,保障库区生态安全,实现区域可持续发展。     

艾比湖湿地生态系统健康评价研究

从状态的健康、恢复能力的健康、所在环境的健康三个方面建立涵盖22个指标的艾比湖湿地生态系统健康评价指标体系。以艾比湖周边区域的统计年鉴数据和遥感解译数据为基础,用2000—2012年时间序列数据,分析艾比湖湿地生态系统健康状况。运用综合评价及划分的等级标准对13年间艾比湖湿地生态系统健康水平进行量化分析。结果表明:艾比湖湿地生态系统在2000—2001年处于较健康状态,2002—2003年处于健康状态,2004—2009年处于较健康状态,2010—2011年处于一般病态,2012年处于较健康状态。艾比湖湿地生态系统健康总体呈恶化趋势,健康状况不容乐观。     

廊坊市建成区森林生态系统生态资产动态分析与预测

使用市场价格替代法、影子工程价格法及现行市价法等评价方法,对廊坊市建成区森林涵养水源、保持土壤、净化空气、固碳制氧等服务功能进行了初步估算。以2000年为基准年,以2001—2005年、2006—2010年及2011—2015年为估算时段综合分析、预测廊坊市建成区森林生态系统生态资产的动态变化趋势。结果显示:廊坊市建成区森林生态系统生态资产2000年、2005年、2010年及2015年分别为1 448.818 6万元、2 733.072 4万元、4 098.457 6万元及4 692.988 4万元,人均生态资产占有量分别为43.573 5元/人、74.268 3元/人、90.076 0元/人及86.427元/人;2001—2005年、2006—2010年及2011—2015年3个评价时段中生态资产增长率依次为88.641 5%,49.957 9%及14.506 3%,而同期人均生态资产占有量增长率依次为70.443 7%,21.284 6%及-4.051 0%。     

云南哈巴雪山生态系统时空变化分析

利用遥感和GIS技术方法,对哈巴雪山2000—2010年TM影像进行人工目视解译得到研究区域的生态系统分类数据,并对研究区生态系统格局时空变化特征进行分析。结果表明:1研究区生态系统的格局变化主要集中在2000—2005年,而2005—2010年变化剧烈程度减缓,生态类型的变化主要集中在人为活动最为集中的金沙江流域的河谷区域;2生态格局分布的总体变化特征是:农地转化为居住用地、冰川/永久积雪和河流湖泊转化为草地或林地。人为因素对森林生态系统环境保护产生了积极影响,而对农业生态系统稳定性造成了一定干扰。     

基于PSR模型的中国生态文明建设国际比较

引入“压力—状态—响应(PSR) ”模型,从生态系统视角构建包括生态系统压力、生态系统健康和生态环境管理3个子系统共21个指标的生态文明评价指标体系; 采用全球60个主要国家(地区)的数据,从国际比较的视角考察中国生态文明建设水平和生态文明协调度。结果显示:中国生态文明综合指数排名第50位,与发达经济体的差距较大,在发展中经济体中位居中游,与我国当前的经济发展水平总体相适应; 中国生态环境管理表现相对优异,但生态系统压力和生态系统健康水平滞后,导致我国生态文明协调程度偏低。实证分析表明,一国生态文明建设水平与生态文明协调度存在显著的正相关性。我国在加强生态文明建设的过程中,应着力提升各子系统间的协调互动水平,特别是生态环境管理的实施效果。     

基于土地利用变化的福建省自然保护区生态系统服务价值研究

以福建省自然保护区为例,依据2000年、2005年和2010年福建省土地利用数据,利用ArcGIS软件分析各类型土地利用的面积及其变化特点,并参照谢高地的生态系统服务价值计算方法,分析了福建省自然保护区内土地利用变化与生态系统服务价值之间的关系。结果表明:(1)2000—2010年,土地利用发生了较大的变化,各类型之间转换比较频繁,且林地面积逐渐在减少,园地和建设用地面积逐渐在增加,其他土地类型面积先增加后减少;(2)2000—2010年,林地主要转变为园地和耕地,园地主要由林地和草地转换而来,林地为自然保护区最主要的土地利用类型;(3)2000—2010年,自然保护区生态系统服务价值逐渐减少,且土地利用变化与各类型的生态系统服务价值变化相对一致。     

城市生态系统可持续发展评价研究——以北京市为例

从对生态系统健康概念的质疑入手,提出了用“可持续发展”代替“生态系统健康”的合理性。参照先辈们关于城市可持续发展及生态系统健康评价指标体系的成果,进一步简化、完善了城市生态可持续发展评价指标体系,并采用模糊数学的方法,借助相对隶属度矩阵和信息熵权法评价了北京城市在某一特定时间内(1999—2004年)的生态可持续发展状况。     

基于熵权物元模型的城市生态安全评价研究——以韶山市为例

以韶山市为例,选取人口增长率、人口密度、城市化率等指标构建了城市生态安全评价指标体系,综合熵权法和物元分析建立城市生态安全评价模型,对韶山市2011年-2015年生态安全状况进行了定量评价和分析,结果表明:韶山市生态安全状况逐年上升,目前稳定在安全水平。     

旅游城市生态评价方法比较分析与实证研究——以广西桂林为例

旅游活动的开展依赖于良好的生态环境,对旅游城市生态评价可以了解其生态系统健康、平衡、良性循环状态,明晰其生态发展变化的特点和未来趋势。对旅游城市生态综合指数评价法、旅游城市生态安全模糊综合评价法、旅游城市生态足迹评价法进行比较分析研究,认为这3种方法同时使用,可以克服单一评价方法本身的一些缺陷,能从不同角度互为补充、较完整地反映旅游城市的生态状况。利用这3种评价方法,对桂林旅游城市进行生态评价,结果为:桂林旅游城市生态状况处于"临界安全"状态。     

要闻

<正>全国生态状况变化调查评估启动环境保护部和中国科学院于2月27日在北京联合启动"全国生态变化(2010—2015年)调查与评估"。这一项目是继"全国生态环境十年变化(2000—2010年)调查评估"之后,两部门开展的第二次对全国生态环境情况的摸底调查,将科学认识全国生态系统、生态问题与生态资产现状与变化趋势,以满足我国生态文明建设以及国家与区域经济社会发展规划的重要科技需求。     

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。