青海省柴达木盆地沙漠化治理途径研究

柴达木盆地现有沙漠化土地1659.9万hm2,是全省沙漠化最严重的地区之一。40年来,当地在治沙试验研究方面取得了一批科研成果,应用推广后,建立起香日德、诺木洪、格尔木、德令哈等一批绿洲,近10年来,随着治沙工程项目的实施,加快了治理速度,局部地区生态环境得到改善,但是整体在扩大。为更有效地防治沙漠化,根据沙漠化土地在柴达木盆地的分布现状,文章提出了以防治为主,防与治相结合的对策,及综合防治沙漠化的生物和工程技术措施。     

新疆土地沙漠化现状及综合治理对策

治理沙漠化土地必须坚持“统一规化,分工负责,水利先行,以防为主,防治结合,综合治理,因地制宜,因害设防,突出重点,讲求效益”的工作方针.     

辽宁省沙化土地治理对策

该文详细分析了辽宁省2009、2014年两次沙化土地监测报告,通过对沙化状况、危害及治理效果进行分析评价,有针对性地提出防治的对策及政策建议,探索土地沙漠化演替规律,掌握沙漠化演替过程,探索出治理沙化成功经验,以期为辽宁省防沙治沙工作提供建议,为国家和辽宁省宏观决策提供依据。     

豫东沙区生物治理与效益评价

通过对豫东地区沙漠化土地变化动态监测,生物治理实地考察和资料收集,分析了本区沙化土地的生物治理方法和产生的多种效益,结果表明：本区的生物防护体系和农业改良措施促进了沙漠化土地的逆转,取得了防风,固沙,改良土壤,改善小气候和农业增产等多种效益。     

内蒙古兴安盟土地沙漠化的调查与分析

由于自然和人为原因,在半干旱的内蒙古兴安盟地区,存在较为严重的土地沙漠化问题。文章通过查阅资料,了解兴安盟沙漠化的现状及治理沙漠化存在的问题,并结合对兴安盟部分常住人口的问卷调查的结果,总结出兴安盟土地沙漠化的防治及治理的建议。     

浅谈河西走廊土地沙漠化的根源与防治

针对河西走廊土地沙漠化、荒漠化发展现状,根据有关土地沙漠化理论和研究进展,归纳总结了河西走廊土地沙漠化的表现形式,分析和评价了流动沙丘(地)、固定、半固定沙丘(地)、戈壁、重盐碱地、潜在荒漠化土地等不同类型沙漠化土地的特点。提出了河西走廊土地沙漠化主要成因和防治土地沙漠化的关键措施。     

浅论发展生态农业与沙漠化土地的综合治理

鄂尔多斯市达拉特旗多年的生态建设实践证明,发展生态农业,是治理沙漠化土地的重要途径之一。一沙漠化土地治理与开发利用过去,有些人错误地认为治理沙漠化土地,     

朝阳市土地荒漠化现状及动态变化分析

通过对朝阳市1999年、2004年两次荒漠化普查结果以及相关历史资料的综合分析,对朝阳市土地荒漠化现状及治理成效作出定性的评价;对土地荒漠化的动态变化做出定量的分析;分析社会和自然因素对土地沙漠化进程的影响。结果表明:朝阳市荒漠化土地有逐年减少的趋势;但总体上,现处于治理与恶化相持阶段。     

防治土地沙漠化要高度重视生态系统的保护和恢复——关于我国防治土地沙漠化问题的一点思考

我国是世界土地沙漠化危害严重的国家之一,防治土地沙漠化,扼制风沙灾害,建设良好生态环境,是一项长期而重要的战略任务。这些年来,在党中央、国务院的重视和领导下,我国土地沙漠化防治工作取得了重大成就,局部地区沙漠化土地初步得到治理,生态环境明显改善,风沙灾害受到抑制,促进了沙区社会经济的发展。但从总体上看,我国土地沙漠化仍呈不断扩展的趋势,形势依然严峻。据有关部门的资料,20世纪70年代,我国土地沙化面积年均扩展约为1560平方公里;80年代增至2100平方公里;90年代上升到2460平方公里;90年代末竟激增至3436平方公里,可以说防沙治…     

彰武县土地沙漠化现状及治理对策

通过彰武县2004年沙漠化土地调查以及相关历史资料,分析了彰武县沙漠化土地形成的主要原因,并提出土地沙漠化治理对策建议。     

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.