甘州区兔儿坝滩水土流失综合治理初探

甘州区兔儿坝滩生态环境恶化一直是困扰该区北部乡镇农村经济发展和影响着城区环境改善的重要原因,也是造成水土流失的源头。加快兔儿坝滩水土流失综合治理不仅能增加本区域的林草植被盖度,有效改善本区域的水土流失状态,逐步引导本区域生态环境向着良好的方向发展,为周边乡镇群众和企业创造良好的生活生产环境。同时也为城区环境改善建起一道天然屏障,有效阻截沙尘来源,大大改善城区环境面貌。     

浅谈黄土丘陵沟壑区生态治理之途径

黄土丘陵沟壑区梁峁起伏，沟壑纵横，植被稀少，水土流失严重，生态环境恶化，改善这个区域的生态环境是一项空前而艰巨的长期任务。多年来，各级人民政府和广大干部群众投入了大量的资金，采取了各种措施，开展了多项试验，付出了不懈努力，取得了显著的治理成效。但仍存在治理措施对位配置不够，造林种草保存率低，重点项目开发力度不大，部分工程毁坏严重，生态环境依旧恶化的问题。为了抓住国家战略重点向西部转移和加强生态建设的有利时机，     

黄土高原丘陵沟壑区退耕还林成效初探

水土流失严重、生态环境恶化是制约黄土高原半干旱地区农村经济可持续发展的重要因素,控制水土流失、改善生态环境、提高群众收入是黄土高原地区乃至全国农村经济发展的重要议题。为了改善日益恶化的生态环境,2000年,以中国西部为重点,国家     

城镇化建设中的绿色化问题及对策

分析了城镇化建设中所出现的城市生存环境恶化、生态环境恶化、心灵环境污染和污染向农村转移等绿色化中存在的问题,从加强制度建设约束城市生存环境恶化、多方合力防止污染向农村转移、加大治理力度改善和控制生态环境恶化、以人为本治理心灵环境污染等方面提出了相应对策。     

坝上地区土地利用及沙化动态原因分析

选择具有典型意义的多伦南部、围场西部、丰宁北部为研究对象,利用1987年、1999年和2004年3期Landsat TM卫星影像,采用监督分类和转移矩阵,对该地区土地利用及土地沙化的变化进行了研究。结果表明,生态环境具有恶化和逆转双重性,积极的生态建设能有效遏制生态环境的恶化。1987—1999年该区域生态环境持续恶化,沙化土地扩展,1999年在以生态建设为中心的京津风沙源治理工程实施后,生态环境恶化的趋势得到显著遏制。     

西北地区生态环境治理途径与对策

西北地区水土资源不匹配,地多水少,水资源严重短缺,是我国主要干旱缺水地区。文章在对西北地区生态环境恶化现状和生态环境恶化成因进行深入分析的基础之上,提出了西北地区生态环境的治理途径及生态环境治理的对策,旨在推动西北地区生态环境治理快速有效地进行。     

内蒙古黄河流域及京津周围地区生态环境存在问题及建设的必要性

文章分析了内蒙古自治区黄河流域及京津周围地区生态环境现状 ,认为水土流失、土地荒漠化、草原退化是这一区域生态环境恶化的主要原因。有林地面积少 ,森林覆盖率低 ,自然灾害严重 ,生态建设投入严重不足是这一区域生态环境存在的主要问题。从抓住西部大开发机遇 ,加快我区经济发展 ,使农牧民脱贫致富等几个关键问题上论述了这一区域林业生态环境建设的必要性。     

自贡市生态环境现状及建设对策

通过分析自贡市生态环境现状和导致生态环境恶化的原因，提出改善生态环境的途径，以及加强生态环境建设的对策。     

论经济林生产在长江三峡库区生态经济建设中的作用

长江三峡工程举世瞩目,其生态环境、库区经济更引人关注。三峡库区是典型的山地区,生物资源丰富,水热条件优越,土壤类型良好,是发展林业生产,尤其是经济林生产的一块得天独厚的宝地。然而,由于山多人多土地少,人地矛盾突出,人类经济活动频繁,造成森林资源锐减,土地垦殖过度,陡坡耕种突出,水土流失严重,生态环境恶化,自然灾害频起,致使区域经济长期贫困落后。正在兴建的三峡工程,给三峡库区的生态环境建设和区域经济开发注入了活力,带来了前所未有的转机.利用三峡库区开发性移民策略的实施和为三峡工程配套的生态环境建设这一千载难逢的良机,充分发挥山地资源优势,发展以经济林为主体的高效林业,是加速改善库区生态环境和振兴区域经济最为有效的捷径。     

河西地区生态安全建设与对策

通过对河西走廊地区的生态环境恶化成因的分析，认为人口的增加是影响区域生态恶化的主要辱旱，声此产生的人工绿洲不断扩大，自然绿洲缩小，又加剧了区域生态的恶化。要建立良好的区域生态安全体系必须控制人口增长、提高人口素质，依法管理水源，确定科学的生态建设目标。     

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.     

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。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.