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1.
"The author discusses the distinctive demographic trends among Soviet Moslems, whose numbers are projected to rise from 44 million in 1979 to 64 million in the year 2000. This group is distinguished by high rates of natural increase, little mobility and low rates of linguistic assimilation. The rapid population growth among Moslems, especially those in Central Asia, poses problems of employment and of integrating these people into the Soviet economy."  相似文献   

2.
"The related topics of regional net migration and ethnic Russian population redistribution and change in the USSR are investigated for the intercensal period 1970-79 in comparison to 1959-70 by economic regions and subdivisions. The results reveal that the main migration and Russian shifts continued to be from internal to peripheral regions. However, compared with the 1959-70 period, regional rates for 1970-79 were more equalized, and a south-to-north shift seemed to be occurring in both cases." The author notes that "aggregate measures...suggest that the traditional eastward movement of Russians is slowing. Correlation analysis indicates that migration and ethnic Russian change patterns are associated with selected indices of modernization. The south-to-north shift, in particular, has been fairly strong in relation to changes in capital investment. Prospects of a northward migration of Turkic Moslems from Central Asia are also discussed."  相似文献   

3.
"Population density is one of the most widely-used statistics in human geography. Maps showing areas of high and low density illustrate stark contrasts which result from the interplay of numerous forces. In South Africa political developments during the apartheid era have left a long-lasting impression upon population distribution and density. Conditions in one former homeland, Ciskei, are examined."  相似文献   

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7.
近20年来北京都市区人口增长与分布   总被引:42,自引:6,他引:42  
冯健  周一星 《地理学报》2003,58(6):903-916
利用第5次人口普查数据,研究1982~2000年北京都市区人口增长与分布规律。首先分析都市区人口增长特征,并提炼不同阶段人口增长的空间模型,发现:开始于20世纪80年代的人口郊区化,在90年代幅度加大;80年代北京都市区人口空间增长过程的相似性大于差异性,整体上呈现出一定的同质性特点;而90年代则差异性大于相似性,异质性特征日渐突出。继而,通过数学模型的回归研究北京都市区人口分布及空间结构的演化趋势。单核心模型的回归表明,Clark模型在拟合北京城市人口分布方面占据优势,而Smeed模型拟合都市区人口分布的效果更好,参数变化说明当前郊区化的主体仍属“近郊化”。多核心模型的回归表明,1990年都市区双中心结构刚刚发育,2000年多核心结构比较明显但并不成熟;主要的次中心在影响人口分布方面起到重要作用。近20年来,基于人口分布的北京都市区空间结构渐趋复杂。  相似文献   

8.
Based on monthly evaporation of two meteorological stations in the Gulang River Basin of China, the inter-annual variation of evaporation during 1959-2013 were analyzed using Mann-Kendall and wavelet analysis. The results demonstrated that the annual evaporation show a fluctuating increase over the past 50 years approximately, with an average increase rate of 4.26 mm per decade. The overall trend was decrease-increase-decrease. According to the cumulative anomaly curve,the turning point of the annual evaporation occurred in 1979, in which the evaporation increased in the early stage and decreased in the later stage. Meanwhile, the seasonal variation of the evaporation shows that it decreased in Spring and Autumn, and increased in Summer and Winter, especially obvious for the later. The evaporation abruptly changed in Spring and Summer in 2008 and in Winter in 1994. In addition, all evaporation increased after the changes. However,the evaporation in Autumn abruptly changed in 1986 and 1999, which show a trend of increase-decrease-increase.Wavelet analysis shows that evaporation in Summer and wet season would decrease in the next few years, and in the other seasons would increase. Based on the aforementioned analysis, it can be concluded that increased evaporation is mainly induced by increase of evaporation in dry season, especially in Winter, and this trend to be continued in the future for the Gulang River Basin.  相似文献   

9.
1984-2008年北京湿地景观格局驱动机制(英文)   总被引:3,自引:0,他引:3  
The landscape pattern of Beijing wetlands has undergone a significant change as a result of natural and artificial elements.Supported by remote sensing and GIS technology,using multi-temporal TM images from 1984 to 2008 in Beijing,this paper analyzed the dynamic characteristics of wetlands landscape pattern through selected typical indices including patch area,patch average area,fractal dimension index,diversity,dominance,contagion indices and the spatial centroids of each wetlands type were calculated.Finally,the paper explored the evolution mode and driving factors of wetland landscape pattern.The results were obtained as follows:the total wetland area increased during the period 1984-1996,then decline from 1996 to 2004.The wetland area in 1994 accounted for only 47.37% of that in 2004.The proportion of artificial wetland area was larger than that of natural wetland.The proportion of reservoir wetland was 33.50% to 53.73% and had the maximum average area.pond and paddy field wetland type with the least average area accounted for 16.46% to 45.09% of the total wetland area.The driving forces of the natural river wetland were mainly natural elements;its fractal dimension index was greater than the others.The Shannon diversity index of wetland landscape increased from 1.11 in 1992 to 1.34 in 2004,indicating that the difference between proportions of each wetland type decreased and areas of each wetland type were evenly distributed.The contagion index went down from 65.59 to 58.41,indicating that the connectivity degraded.Miyun Reservoir had the largest area and its area change had a great impact on the location of the centroid.Wetland resources degenerated gradually from the joint effects of natural and artificial factors.During the period 2006-2008,the precipitation increased and the drought condition was relieved.The government implemented series of positive policies to save water resources,and the wetland area increased.  相似文献   

10.
种群数量动态的研究是认识种群的生存现状及发展动态的前提。通过对古尔班通古特沙漠固定沙丘、半固定沙丘和流动沙丘上主要固沙灌木的样地调查,分析了固沙灌木的年龄结构,建立了3种沙丘上固沙灌木的静态生命表和存活曲线。结果表明:(1)固沙灌木的存活个体数呈逐级递减的趋势,幼龄个体占有很高的比例;固定沙丘上梭梭(Haloxylon ammodendron)呈现Ⅰ型存活曲线,种群退化,白梭梭(Haloxylon persicum)呈现Ⅱ型存活曲线,种群稳定;(2)半固定沙丘上白梭梭呈Ⅱ型存活曲线,种群相对稳定;沙拐枣(Calligonum mongolicum)和油蒿(Artemisia ordosica)均呈现Ⅰ型存活曲线,种群处于退化状态;(3)流动沙丘上沙拐枣呈现Ⅲ型存活曲线,种群有较大的增长潜力,白梭梭呈现出Ⅱ型存活曲线,种群相对稳定,油蒿呈现出Ⅰ型存活曲线,种群处于不稳定的退化状态。  相似文献   

11.
Based on air temperature observation data from 32 meteorological stations, temperature changes in the middle Qinling Mountains from 1959 to 2016 were analysed with respect to the north-south, seasonal and altitude differences. Our research mainly showed the following results. The annual temperature(TA) rose approximately 0.26℃/10 a within the past 58 years. This warming trend was stronger on the northern slope than on the southern slope, and a warming trend reversal occurred in 1994 on the northern slope, which was three years earlier than on the southern slope. The temperature changes for the four seasons were not synchronized, and the trend in spring contributed the most to the TA trend, followed by winter, autumn, and summer. The temperature difference between summer and winter(TDSW) decreased significantly over the past 58 years. The temperature change in the middle Qinling Mountains was clearly dependent on altitude. With increases in altitude, the TA increased gradually and became stronger while the TDSW decreased gradually and became weaker. Differences in temperature change between the north and south were mainly observed in low-altitude areas. With increase in altitude, the differences gradually tended to disappear.  相似文献   

12.
1959-2008年新疆阿尔泰山友谊峰地区冰川变化特征   总被引:2,自引:0,他引:2       下载免费PDF全文
 利用1959年地形图、2008年ASTER数字遥感影像及数字高程模型,在地理信息系统技术支持下分析了新疆阿尔泰山友谊峰地区冰川的变化特征。研究表明:1959-2008年该区冰川整体呈萎缩趋势,且变化幅度相对较大。相对于1959年,2008年冰川面积和数量分别变化-32.5%和-27.9%。其中,小于1 km2的冰川面积平均变化率为-66.7%,面积小于0.5 km2的冰川面积变化率大于-70%,面积大于1 km2以上的冰川面积变化率为-35.0%,1~5 km2的冰川面积变化率为-27.9%。冰川末端平均后退253 m,末端退缩比例为-18.3%,且南坡冰川末端变化率大于北坡。分析发现,研究区冰川面积亏损较大主要缘于该区小冰川分布数量较多(面积小于1 km2的冰川数量达75%),对气候变化的响应较为敏感。  相似文献   

13.
本文基于黄土高原地区1959-2008 年51 个地面气象台站的逐日降水资料, 计算了降水集中度(PCD)和集中期(PCP), 并结合EOF、趋势分析以及相关分析等方法对我国黄土高原地区年内降水不均匀性特征及其趋势进行了分析。结果表明:①黄土高原地区PCD在0.53~0.75 之间, 自东南向西北逐渐增加, 而PCP变化不大, 主要集中在7 月中旬和下旬;②近50a 黄土高原地区PCD主要以南北反向型分布为主;③从变化趋势来看, PCD增加趋势较明显的区域主要分布在宁夏的同心和山西的五台山等地, PCD减小比较明显的区域主要分布在山西的阳泉以及青海的门源等地区;而PCP整体上呈现提前趋势, 只有青海的门源站附近有小幅推迟趋势;④年降水量与PCD有较好的相关性, 大部分地区都通过了显著水平为0.05 的检验;而年降水量与PCP的相关性并不显著, 通过显著水平0.05 检验的区域仅分布在山西的兴县、陕西的洛川以及宁夏的固原等地。  相似文献   

14.
东北地区最高、最低温度非对称变化的季节演变特征   总被引:9,自引:4,他引:9  
孙凤华  袁健  关颖 《地理科学》2008,28(4):532-536
选用东北地区剔除迁站次数较多的观测站后的74个代表站1959~2002年44年的月平均最高气温和最低气温观测数据,建立了东北地区近44年来的年、四季最高气温和最低气温序列。在所建序列基础上,分析了东北地区最高气温和最低气温的年和季节变化规律;采用Mann-Kendall和Yamamoto方法对经过滑动平均的最高气温和最低气温序列进行了突变分析。计算了所有测站的年和各个季节最高气温和最低气温的趋势系数,分析增温趋势在各季节的地域分布特征。结果表明,近44年最高气温和最低气温均表现为明显的增温趋势,最低气温的增温趋势明显高于最高气温,前者的年气候倾向率为后者的2倍; 最高气温和最低气温都表现为冬季增温最强,春季次之,秋季最弱;在研究区域的中心部位,即内蒙古、吉林和黑龙江三省交界处有一范围较大且稳定的最低气温强增温区;最高气温和最低气温的突变点发生时段基本一致,强突变发生在80年代后期,较弱的一次发生在70年代初。  相似文献   

15.
As in previous years Norsk Polarinstitutt has carried out mass balance investigations on Storbreen and Hardangerjøkulen in mainland Norway and on Broggerbreen and Lovenbreen in Svalbard. More than 20 years of measurements show that the glaciers both in mainland Norway and in Svalbard are retreating.
Both in 1985 and in 1986 the glaciers in Norway had a negative net balance. At Storbreen the mean annual net balance value 1949-86 is -0.30 m in water equivalents, while on Hardangerjflkulen the mean value 1963-86 is -0.02 m.
The two glaciers measured in Svalbard also had negative net balance in 1985 and in 1986. Both measured glaciers have had negative balance nearly all years since the measurements started in 1966. The mean value is close to -40g/cm2 or -0.4 m on both.  相似文献   

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17.
蒸发是水文循环的一个重要过程,也是影响区域水资源量的重要因素。通过选取黄土高原50个气象站1959-2015年的逐月气象资料,应用FAO修正的Penman-Monteith模型计算黄土高原潜在蒸发量,采用Mann-Kendall检验与空间插值分析其时空变化特征,探讨各气象要素对潜在蒸发量的影响。结果表明:黄土高原多年平均潜在蒸发量在780~1 470 mm之间,由西北向东南递减。1959-2015年,黄土高原潜在蒸发量变化率为5.64 mm·(10 a)-1;春季变化率最大,其次为夏季和秋季,冬季最小。从空间分布看,西部、中北部地区和东南部地区潜在蒸发量均呈非显著性增加趋势。太阳净辐射量增加是黄土高原潜在蒸发量增加的主导因子,其次为实际水汽压、风速和温度。  相似文献   

18.
《Basin Research》2018,30(Z1):532-549
The Podolia region is located along the western border of the Eastern European Craton, which is also known as Ukrainian Shield. From the Ordovician to the Miocene, this area formed part of an epicontinental basin system. In order to investigate the effects of orogenic cycles occurring along the plate margin, a multi‐disciplinary approach was used in this study. Paleotemperature analysis and low‐temperature thermochronometry were combined with stratigraphic data to obtain a burial model for the Paleozoic succession exposed in the study area. Maximum burial for Silurian and Devonian rocks occurred during the Devonian and Early Carboniferous at depths of 4–5 km, as constrained by vitrinite reflectance and illite content in mixed illite‐smectite layers. Thermochronometric data indicate that exhumation through the 45–120 °C temperature range took place between the Late Triassic and the Early Jurassic, and that no significant burial occurred afterwards (temperatures characterising the stratigraphically lowermost units remaining below ca. 60 °C). These results point to a major exhumation event coeval with the Cimmerian orogenesis, which took place a few hundreds of kilometres away from the study area. On the other hand, no significant effect of the Alpine orogenesis was recorded, although the collisional front was located <100 km from the Podolia region. This work shows how paleothermal and thermochronometric analyses can be successfully integrated with stratigraphic data to reconstruct the burial history, and how the burial history of a basin located on a plate margin can, in some cases, be independent from the distance of the margin from the collisional fronts.  相似文献   

19.
Based on daily surface climate data and weather phenomenon data, the spatial and temporal distribution and trend on the number of consecutive days of severe weathers were analyzed in China during 1959–2014. The results indicate that the number of consecutive days for hot weathers increased at a rate of 0.1 day per decade in China as a whole, while that for cold weathers, snowfall weathers, thunderstorm weathers and foggy weathers showed significant decreasing trends at rates of 1.4, 0.3, 0.4 and 0.4 day per decade, respectively. Spatially, there were more consecutive hot days and rainstorm days in southeastern China, and more consecutive cold days and snowfall days in northeastern China and western China. Consecutive thunderstorm days were more in southern China and southwestern China, and consecutive foggy days were more in some mountain stations. Over the past 56 years, annual number of consecutive cold days decreased mainly in most parts of western China and eastern China. Consecutive thunderstorm days decreased in most parts of China. The trend of consecutive hot days, snowfall days and foggy days was not significant in most parts of China, and that of consecutive rainstorm days was not significant in almost the entire China.  相似文献   

20.
NECT样带1984~1996土地利用变化分析   总被引:30,自引:6,他引:30  
康慕谊  江源  石瑞香 《地理科学》2000,20(2):115-120
在分区选择典型样点的基础上,从土地利用结构类型和土地利用强度等方面对中国东北带(NECT)近年来的土地利用变化进行分析,揭示出样带上土地利用发生变化较剧烈的区域为农牧交错带,变化的原因主要是人类活动强度的增加。此结论对样带上的生态敏感区域制定土地利用开发与管理下策应具有意义。  相似文献   

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