共查询到20条相似文献，搜索用时 437 毫秒
1.
Food security in cold and arid regions in the world is threatened by stressful and unpredictable environments.The sus-tainable and economically viable solution for increasing stability of food productivity in cold and arid regions is genetic improvement of crops towards high resistance to abiotic stresses,mainly cold and drought resistance.It is often empha-sized that crop genetic improvement lies in exploiting the gene pools of the wild relatives of the crop plant.Wild barley,H.spontaneum,the progenitor of cultivated barley,is a selfing annual grass of predominantly Mediterranean and Irano-Turanian distribution that penetrates into desert environments where it maintains stable populations.Wild barley is also found in cold regions,such as in Tibet.The adaptation of wild barley to the arid region in Israel and Jordan,and the cold region in Tibet has accumulated rich genetic diversities for drought,salt,and cold resistances in wild barley,which is the genetic resource for barley and other crop improvement in arid and cold regions.These genetic diversities are revealed by allozymes,DNA-based molecular markers,and morphological and physiological traits of wild barley plants.Quantita-tive trait loci(QTLs) related to drought resistance were identified in wild barley via the QTL mapping approach.Drought resistance genes such as dehydrins,hsdr4,and eibi1 were identified in wild barley based on the candidate gene approach,gene differential expression approach,and molecular genetic approach,respectively.Genetics and genomics of wild bar-ley cold resistance have not been exploited yet,remaining a huge treasure for future crop improvement of cold resistance.Advanced backcross QTL analysis,the introgression libraries based on wild barley as donors,a QTL approach based on wide crosses using wild barley,and positional cloning of natural QTLs will play prevailing roles to help us understand the molecular control of cold and drought tolerance.Integration of QTL information into a breeding pipeline aimed at im-proving tolerance t 相似文献
2.
Jeremy S. Johnson Keith D. Gaddis David M. Cairns Charles W. Lafon Konstantin V. Krutovsky 《自然地理学》2016,37(2):93-119
Global change has become a major ecological concern that has the potential to dramatically alter plant distributions and assemblages worldwide. The specific response of plants to global change will depend on their ability to move, evolve, or adjust through phenotypic plasticity. Advances in biogeographic research are on the verge of a giant leap forward if we can take advantage of emerging tools in genetics and genomics. In this review, we appraise how new, post-Sanger, high-throughput sequencing and associated technologies can be used by next generation biogeographers to assess plant responses to global change. First, we briefly review the recent advances in genome sequencing and available approaches of genomic analysis. Secondly, we discuss the three main plant responses to global change: migration, adaptation, and phenotypic plasticity. This review is intended to spark the interest of biogeographers who do not traditionally use genetics but could benefit from including genetic and genomic tools into their research. Our goal is to illustrate that their use can contribute to new perspective and add an additional level of resolution into future biogeographic research. 相似文献
3.
DMSP(二甲基巯基丙酸内盐)是地球上最丰富的有机含硫化合物之一,同时也是海洋微生物的重要营养物。浮游植物是其主要的生产者。DMSP还是海洋中DMS(二甲基硫)的重要来源和前体,而DMS的排放与全球气候变化存在密切关联。细菌在DMSP的降解及DMS的生成方面扮演着重要角色。有关DMSP生物合成、代谢及其生态影响的研究已开展了近70年,但涉及高纬度极地低温海域的相关研究却为数甚少。本文在简要介绍DMSP生物合成与代谢,以及DMSP降解途径中的关键酶基因及其产生菌的基础上,结合笔者的工作实践,对近年来在极地低温海域的相关研究进行了介绍并展开了部分讨论。随着国内对微生物驱动水圈地球元素循环的重视,有关极地海域细菌参与DMSP/DMS代谢的研究工作将极大地增进人们对于微生物在极地海洋生态系统中生态地位的认识,也对评估极地海洋微生物群落对全球气候环境变化的响应与反馈具有重要的参考意义。 相似文献
4.
专题地图符号构成元素的研究* 总被引：10，自引：0，他引：10
在分析地图传输论和符号视觉变量的基础上,提出了地图符号构成元素。指出了符号构成元素由位置、形状、色彩(括色相、纯度和亮度)、尺寸(括大小、粗细、长短和分割比例)、网纹(括排列和疏密)、方向和注记(括文字数字、字体字级)组成。研究出了符号构成元素的设计模式为:选择,叠置或匹配,强化或减弱,拉伸或压缩。并讨论了符号构成元素的设计步骤。 相似文献
5.
汶川地震引发的次生灾害链 总被引：1，自引：0，他引：1
汶川地震造成了大量的滑坡、崩塌,并诱发了多种地质和生态灾害链式发生.2008-2009年期间,在汶川地震震区开展了野外调查与试验,研究了各种不同的灾害链的形成条件及其链生机制.识别出了4种类型的灾害链,并重点研究了7起灾害链事件.发现灾害链中,每一级灾害事件都由其前一级灾害事件诱发.各级次生灾害造成的物质搬运量都远小于其上一级灾害所造成的物质搬运,灾害性沿灾害链呈现逐级衰减的趋势.由此定义灾害链衰减率为灾害链中某级次生灾害所造成的物质搬运或者灾害影响区面积与其上一级灾害所造成的物质搬运或灾害影响区面积之间的比值.汶川地震引起的次生灾害链衰减率在2％～30％.采用底栖动物作为指示物种,评价次生灾害链对震区河流生态造成的影响,发现受灾害链影响的河道中,底栖动物物种数急剧降低,生物多样性下降. 相似文献
6.
中国电子地图发展中的可视化问题 总被引：2，自引：0，他引：2
1IntroductionSpatial data can be visualized and explored in various ways. Developments in hardware and software have led to and will surely continue to stimulate novel methods for visualizing spatial data and creation of electronic atlas information syste… 相似文献
7.
In this paper, we discuss the development of electronic atlas in China, with focus on the issues of visualization. We particularly categorise this development into four periods, and then analyse the characters in each period and discuss the visualization issues. The four periods are highlighted: 1) Infant period (<1990) characterized as computer assisted mapping with products of screen maps; 2) Starting period (1991-1995) characterized as object-oriented mapping with products of interactive maps/atlases; 3) Advancing period (1996-2000) characterized as integrated mapping with products of multimedia cartographic maps; 4) New era (> 2001) characterized as web mapping and adaptive map design with products of Internet maps and atlas as well as adaptive maps. It is obvious that the development follows the logical way from static to dynamic, and even real time visualization, from single user to multiple users, from presentation to exploration for effective communication and knowledge construction. Current research and development projects are focused on customisation of atlas information systems for real-time tasks, Internet operability, small displays and mobile environments. The major challenges involved in each of such customisation processes are identified and commented in relation to the further development of visualization. 相似文献
8.
9.
This study evaluates the potential of 8-band high resolution WorldView-2 (WV-2) panchromatic (PAN) and multispectral image (MSI) data for the extraction of polar geospatial information. We introduce a novel method based on a customized set of normalized difference Spectral Index Ratios (SIRs), incorporating multiple bands, to improve the accuracy of land-cover mapping in the Antarctic. Most recently available WV-2 data are classified into land-cover surfaces such as snow/ice, water bodies, and landmass using the customized normalized difference SIRs. A novel multi-fold methodology is used to evaluate the effect of pan-sharpening algorithms on spectral characteristics of satellite data, and on subsequent land-cover mapping using an array of SIRs. A set of existing pan-sharpening algorithms was implemented in order to fuse PAN with MSI data, followed by estimation of multiple SIRs to extract target land-cover classes. These algorithms were compared on the basis of their effectiveness in extracting target classes using a defined set of SIRs. Our results indicate that the use of 8-band WV-2, customized SIRs, and appropriate pan-sharpening can greatly improve the extraction of land-cover information. 相似文献
10.
Eliot M. Tretter 《The Professional geographer》2013,65(1):34-54
The importance of commemorative place-naming has been the focus of numerous studies that explore the relationship between memory and political representation. Few studies, however, have systematically examined regional geographical patterns of racial minorities in the United States. Using a variety of Internet-based mapping tools, I have collected a data set on the regional variation of the commemoration of thirty famous African-Americans (fifteen men and fifteen women). The research presented here explores how there are regional characteristics associated with where African-Americans are commemorated, particularly pertaining to cities. I also explore the geographic dispersal of these commemorations and whether there is a gender bias in the process of commemoration. Additionally, I focus on the duality of commemorations as an index of both African-American and the dominant white power structures. 相似文献
11.
《Applied geography (Sevenoaks, England)》2007,27(3-4):131-149
For the past 25 years, non-governmental organizations (NGOs) have sponsored an increasing number of sustainable development projects in poor rural areas, but the overall pattern of NGO development efforts has remained too difficult to discern. This paper tries to clarify the geographic dimension of NGO led sustainable development efforts through a mapping of NGO sponsored sustainable forestry projects in Ecuador. The mapping and associated analysis reveals considerable unevenness in NGO efforts with people intensive projects clustering near cities and government assisted projects spread more evenly across all rural areas. 相似文献
12.
J. P. Cull 《Geophysical Journal International》1985,80(3):661-675
Summary. The Willyama Complex near Broken Hill represents a major exposure of the Precambrian terrain in Australia. However, the eastern limits are obscured by recent cover in the Murray/Darling basin. The nature and extent of the contact with the younger basement to the east is unknown.
Magnetotelluric data have now been obtained as an aid to regional mapping. Profiles are based on observations at 14 sites in a traverse east of Broken Hill. Apparent resistivities presented as pseudosections reflect the major structural units identified from surface geology. Continuity between sites is indicated from similarity in apparent resistivities and lateral changes east of the Block are generally gradational.
Characteristic divergences in orthogonal resistivity components are consistent with 2-D structure. The foliated Precambrian complex appears to form a semi-vertical contact at the margin of the Murray/Darling basin, thus generating the required anisotropy at depths from 15–35 km. Seismic evidence indicates an equivalent structural contact possibly extending into the mantle. 相似文献
Magnetotelluric data have now been obtained as an aid to regional mapping. Profiles are based on observations at 14 sites in a traverse east of Broken Hill. Apparent resistivities presented as pseudosections reflect the major structural units identified from surface geology. Continuity between sites is indicated from similarity in apparent resistivities and lateral changes east of the Block are generally gradational.
Characteristic divergences in orthogonal resistivity components are consistent with 2-D structure. The foliated Precambrian complex appears to form a semi-vertical contact at the margin of the Murray/Darling basin, thus generating the required anisotropy at depths from 15–35 km. Seismic evidence indicates an equivalent structural contact possibly extending into the mantle. 相似文献
13.
EULOGIO PARDO‐IGÚZQUIZA ANTONIO PULIDO‐BOSCH MANUEL LÓPEZ‐CHICANO JUAN J. DURÁN 《Geografiska Annaler: Series A, Physical Geography》2016,98(3):247-263
Dolines are the most typical landform in karst landscapes. They play an important role in karst hydrogeology; they are effective sediment traps that provide information about past climates and karst evolution, and can also be indicators of tectonic activity. The morphometic analysis of those depressions can help in their study and interpretation. However, detailed identification and delineation of dolines becomes increasingly difficult when the study area is very large, of limited access or covered by vegetation. Here, we have used a method developed by the authors for automatic identification and delineation of karst depressions based on the use of a pit removal algorithm. Next a complete morphometric analysis of the karst depressions has been carried out. The main advantage of the methodology is that by delineating and identifying the depth of each doline from its rim, many morphometric statistics can be obtained, including the relation of doline depth and area with respect to altitude, the main doline orientations, doline density, the fractal dimension of doline area and frequency, and point field analysis, among others. The results are interpreted from a geomorphological point of view and the mapped dolines can be easily integrated into geomorphological mapping. A case study is presented from the large Sierra Gorda karst massif in southern Spain, where 3100 depressions have been identified. A strong structural control of doline shape and orientation is demonstrated; the main areas of doline density are highlighted and doline size is shown to follow a fractal law. 相似文献
14.
Landslide susceptibility maps can be prepared in a variety of ways. Many geoscientists favour the use of an overlay model approach in which several map layers are combined by some arithmetic rules to determine the potential for sliding in an area or region. The resulting susceptibility maps, although based on a subjective weighting of relevant factors, can often be of high accuracy and utility. In order to obtain the relevant input data for this type of analysis, remotely sensed data are often used. To date, susceptibility mapping, just as the mapping of historic and individual landslides, has tended to require higher-resolution imagery. This has somewhat limited the application of landslide susceptibility mapping. While high-resolution air photo or satellite imagery is superior to lower resolution imagery for the purpose of mapping of historic and individual landslides, such higher levels of resolution may not be required for the development of landslide susceptibility maps. In order to determine if medium-resolution satellite imagery, such as SPOT or ASTER, could provide the needed data for landslide susceptibility mapping, a comparison was undertaken of landslide susceptibility model output resulting from the use of stereo NAPP aerial photography versus the use of data obtained from stereo SPOT imagery. The test area selected for this study consisted of two watersheds, Pena Canyon and Big Rock Canyon, situated west of Santa Monica, California, USA, along the Pacific Coast Highway. Both watersheds have a long and well-documented history of landslide activity and sufficient geologic variability and complexity to provide a good test site. The specific overlay model used in this evaluation required input data consistent with the needs of many other models of this type. The model output derived from the two different data sources and presented here in the form of susceptibility maps were virtually identical. Statistical and difference analysis confirmed that both methods of obtaining input data provide similar results and successfully identified landslide prone areas. These results suggest that satellite imagery, in this instance, SPOT images, could potentially be used in lieu of conventional air photos, to evaluate landslide susceptibility. In many situations, especially in the case of remote locations and/or developing countries, this capability should result in substantial savings in terms of time, financial resources, and overall viability. 相似文献
15.
XiaoYing M Chao Li AiDong Wang RuiJun Duan GenLin Jiao Eviatar Nevo GuoXiong Chen 《寒旱区科学》2012,4(6):0453-0461
Wild barley (Hordeum vulgare spp. spontaneum) is the undisputed progenitor of cultivated barley and offers considerable potential
as a genetic resource for barley improvement. Naturally occurring populations are distributed primarily across the Fertile
Crescent, but secondary areas of diversity are also found in central Asia and Tibet. The pattern of its genetic diversity is
non-random, and is structured on a global, regional and local scale. On a global scale, diversity follows ecogeography, while on a
regional and local scale, it is more strongly determined by ecology. Populations growing in areas where the climate is unreliable
and/or the soil is heterogeneous tend to retain the most diversity. A large number of accessions are currently conserved ex situ, but
a high proportion of these have originated from the Fertile Crescent. Given the likelihood of future climate change, conserving
germplasm both in situ and ex situ in the various regions where the species’ currently existing is a research priority. The value of H.
vulgare spp. spontaneum for the improvement of cultivated barley lies largely in its potential contribution to the levels of attainable
pathogen resistance and abiotic stress tolerance. 相似文献
16.
DAVID RHIND 《The Geographical journal》2000,166(4):295-305
The vast bulk of topographic mapping - the geographical framework used to underpin many activities of the state and of business - has been created and is maintained to national standards. As a consequence, what is available differs greatly from country to country. Yet there is a range of needs for globally-consistent map information. Such needs have long been recognized: the International Map of the World was an attempt to meet them. A multiplicity of factors has constrained the National Mapping Organizations from meeting this aim. However, new technologies have enhanced our capacity to create a geographical framework almost anywhere in the world. Using such technologies, commercial and other non-commercial bodies (e.g. the US military and its counterparts within NATO) have begun to produce wide-area geographical information. This paper describes the nature of the need for global mapping, the players involved and the drivers and obstacles to progress. It proposes a rapid way to enhance the current situation through public/private sector partnerships based on a combination of skills, information assets and resources. If implemented, this could lead to global coverage of a framework derived from 1:25000 scale mapping within about two years. 相似文献
17.
土壤盐渍化遥感应用研究进展 总被引：31，自引：4，他引：31
文章从地面数据的调查、盐渍土影象的目视判读特征、光谱特征和土壤盐渍化区域的植被特征以及多光谱、高光谱遥感技术等方面综述国内外应用遥感数据探测土壤盐渍化程度及其制图的研究。利用数字图象并结合野外调查数据进行目视解译和计算机自动解译、图象变换提取盐渍土信息;结合G IS方法在分类中加入非遥感数据来提高分类精度;在研究盐渍土的光谱特征的基础上应用高光谱技术定量或半定量地提取盐渍土信息。这都是制定综合治理措施、决定土地利用方向的关键,也是进行区域土壤盐渍化动态预报的重要依据。 相似文献
18.
19.
A new mapping of the world for the new millennium 总被引：1，自引：0，他引：1
Peter J. Taylor Michael Hoyler David R.F. Walker & Mark J. Szegner 《The Geographical journal》2001,167(3):213-222
A new mapping of the world derived from connections between cities is presented as a complement to the traditional world map of countries. Under conditions of contemporary globalization world cities have emerged as global service centres. These have been created by the location strategies of leading corporate service firms (e.g. in accountancy) in setting up their global office networks. Data on the offices of 46 global service firms in 55 world cities are used to define service connections between cities. Connections are converted into measures of network proximity and a multidimensional scaling is applied to these 'distances' to create a 'global service space' of cities. This new mapping of the world shows a distinctive centric structure with the major world cities (e.g. London) at the core. Investigation of this general structure reveals more subtle patterns of interacting regional and hierarchical tendencies. 相似文献
20.
传统的制图数据分级方法存在对原始数据信息的歪曲、普适性不强及计算复杂等问题。基于此,结合现实分级问题的模糊性,提出基于模糊统计分析模型的制图数据分级处理方法。首先通过专家系统获取各模糊样本集,利用统计分析方法求得样本分布函数;然后利用分布函数获得模糊隶属函数,进而求取各模糊集的最模糊点;最后根据最模糊点获得各模糊集的区域划分,从而实现对制图数据的分级处理。该方法不需要对影响级别划分的多因子进行分析和转换,降低了计算的复杂度;另外,该方法是在获得原始数据实际分布的基础上进行的,在后续的分级过程中避免了对原始数据信息的歪曲。 相似文献