沙漠-黄土边界带沉积层有机质的环境指示意义

沙漠-黄土边界带堆积了自末次冰消期以来的第四纪沉积物,其沉积物泥炭是良好的地质档案,具有高分辨率,环境指示意义明确的优点.选取毛乌素沙地东南缘LSW剖面,探讨了该剖面有机质的分布特征及其古环境指示意义.结果表明:①剖面有机质含量变化:泥炭层>沙炭层>粉砂层>粘土层>细砂层;②LSW剖面的有机质可作为古气候研究的代用指标...     

1.8 内蒙古第四纪

1.8.1 古地理和古气候 第四纪是地质历史上最新的一个纪,它是地质历史上发生过大规模冰川活动的少数几个纪之一,又是哺乳动物和被子植物高度发展的时代,人类的出现是这个时代最突出的事件.因此,亦有人称第四纪为人类纪或灵生纪.[14]     

花开花落话苏铁

苏铁是极为古老的裸子植物，对于研究动植物进化、古地质和古气候变迁等具有重要意义。     

神农架地质构造环境演化分析

指出了神农架地区地处扬子淮地台和秦岭褶皱系两个一级构造单元,经历漫长的地质演变过程形成了神农架独特的构造类型并且完整地记录了华中区域的地质构造和演变发展历史,在全球地质构造上具有特殊的大地构造意义。参照区域的勘察研究成果,对神农架地区的地质构造背景和演变历史进行了分析,揭示了古气候、古地理环境面貌,对其地质构造背景提出了新的认识。     

为山水添异彩 为古今增回味

每一棵古树，都是一种景观：每一株名木，都记载着一段历史。这些亘古孑遗、珍贵稀有的古树，对研究古生物、古气候、古地理、古地质、古文化、古风俗等意义重大，具有极高的经济、历史、科学、文化、旅游、生态和社会价值。     

华南五针松在舜皇山国家森林公园完好保存的原因浅究

从古地理、古气候、古地层、法制保护、当地民俗、生境条件等方面探究了华南五针松在舜皇山国家森林公园延续完好保存的内因和外因，为植物学家研究华南五针松生态学特性、开发和利用华南五针松提供了重要依据。     

中国幽天牛族昆虫分布、寄主分析及国外种类潜在入侵威胁

幽天牛族是一类重要的林业害虫,我国已记载昆虫4属26种.幽天牛族昆虫的寄主多为针叶类裸子植物,已记载的寄主植物有7科15属36种,其中以松科松属的种类最多,占所有记录到种的寄主植物的30.56％,而且危害松属的幽天牛数量也最多.对我国目前分布的26种幽天牛族昆虫进行区系分析,发现幽天牛族昆虫以古北区成分为主,这可能与古北区针叶植物较多有一定关系.我国的地理环境及生态植被,均可以满足幽天牛族非中国种的分布及寄主需求,非常适宜幽天牛族非中国种的生存和繁衍,因此应该提高警惕,严防国外种类传入我国,以保护我国树木安全.     

记录千年尺度气候变化载体研究进展

冰芯、深海沉积物、黄土、石笋、湖相沉积物、珊瑚以及树木年轮等都可以作为记录过去气候的载体,能够让学者从中提取过去全球变化的信息,以此来掌握当今气候变化的机理以及预测未来气候变化的态势。为了准确把握在这一领域的研究现状与动态,对前人关于千年尺度全球变化的研究进行了梳理。     

黄土高原土壤中细菌在侵蚀和沉积干扰下的群落分布特征

为研究侵蚀扰动对土壤中细菌群落构成的影响,探究细菌群落特性与土壤理化参数的关系.在中国黄土丘陵沟壑区选择了4个具有代表性的采样点:未开垦侵蚀地、未开垦沉积地、刺槐坡地侵蚀点和刺槐坡地沉积点.采用MiSeq测序技术研究了土壤中细菌群落的丰富度、多样性和组成变化.测序结果显示刺槐坡面细菌多样性和丰富度明显低于未开垦坡面(P...     

中国黄土滑坡灾害概述

中国的黄土面积约占国土总面积的6.63%,是世界上黄土分布最广的国家。由于自然条件的限制,滑坡灾害频繁发生,已成为黄土地区社会经济发展的主要障碍。本文通过不同分类指标,把黄土地区滑坡概化为9种类型,并重点分析黄土地区滑坡灾害的时空分布特点以及黄土地区滑坡的影响因子即滑坡机理。指出黄土地区的滑坡在空间分布上与地质构造、地形地貌、地震发育情况、降水密切相关;从地形地貌、地层岩性、新构造运动和地震活动情况、水的影响以及人类活动不同方面对黄土地区滑坡的发生机理进行了分析,发现黄土地区存在易发生滑坡的先天自然条件,而人类活动又加速了滑坡的发生。本文指出控制黄土地区滑坡灾害,寻找最佳防治对策是当前的紧迫任务。表1参14。     

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.