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1.
We examine the sequence of changes in the structure of the geosystems of the Primorsky Range (Baikal region) for the last 6000 years, based on a continuous recording of fluctuations of the vegetation reconstructed from spore-pollen complexes of a high peat bog. We determined the chronological timeframe of paleogeographical events. The study showed that there occurred a radical structure transformation of the geosystems in the mid-late Holocene, along with a recurrence of similar landscape transformations caused by the instability of natural conditions.  相似文献   

2.
刘恕 《中国沙漠》1983,3(4):22-27
我国北方东起黑龙江省嫩江地区, 吉林白城地区及辽宁西部, 包括内蒙兴安盟东南、哲里木、昭乌达、锡林郭勒、乌兰察布、伊克昭等盟的大部地区, 直至河北坝上、陕西榆林北部约26.7万平方公里的幅员范围内, 由于自然条件的特殊性(地表组成物质质地松散、沙粒成分比重很大及气候干旱、多大风, 且年内季风与周期性干旱相吻合), 加上人类不合理开发活动的影响, 成为我国目前沙漠化发展最活跃的地区, 其沙漠化土地近16.5万平方公里, 占全区总面积的61.5%。该地区有较长的经济开发史, 农、牧业相互影响, 交错分布的情况, 在历史上业已形成。据粗略统计, 该区范围内, 有旱作耕地近5, 000万亩, 多以传统的粗放的撂荒种植制进行经营, 长年遭受不同程度的风沙危害, 属于生产水平较为低下的农田类型。这些农田急待整治, 以便提高生产力。由于本区年均降水量在350-450毫米之间, 客观上具有发展旱作农业的可能性。如能合理经营、科学利用其自然资源, 将可能发展成为农、牧业结合的发达地区。从而对我国北方地区农业发展起促进作用。为了深化对沙漠化农田的认识, 揭示其生态失调的实质, 本文将就生态系统观点对其进行分析以寻求有效的整治沙漠化农田的途径。  相似文献   

3.
Summary. It is known that flow in the mantle can produce preferred orientation in olivine crystals with seismic anisotropy as a consequence. Flow in the subcrustal lithosphere is unlikely because of the high viscosity. Lenses of high temperature and low-viscosity ( anomalous mantle ) are located under the crust in many tectonically active regions, and viscous flow can easily arise in such material resulting in seismic anisotropy. After cooling, such anomalous mantle acquires high viscosity and becomes incorporated into the lithospheric layer preserving the anisotropy produced by the flows which existed previously. The interaction of the stresses with cracks in the upper crust can be one of the causes of anisotropy in this layer.  相似文献   

4.
Summary. Previous geomagnetic measurements in the Rhinegraben have led us to assume that the responsible currents have the properties of direct currents and that they all flow in the sediments filling the graben. In order to verify these conclusions, we have performed measurements in a mine at a depth of 650 m. By comparing the field simultaneously recorded at the surface, in the mine and at the reference station, it is possible to deduce that the anomalous currents have the above mentioned properties.  相似文献   

5.
城市化的开发区模式研究   总被引:14,自引:1,他引:13  
我国许多城市通过开发区建设,在短时间内完成了产业和人口的集聚,实现了城市地域空间和人口规模的跳跃性增长和产业结构的转型。由于在这种城市空间增长过程中,开发区建设起了决定作用,因此,这种以开发区带动整个地区城市化的方式可称为"开发区模式"。开发区驱动城市化的机制表现在开发区自身区域的城市化和开发区带动周围农村地区城市化两个层面,并具有快速跳跃性、外驱性和不稳定性、人为性、经济增长模式的单一性和基础设施建设的高标准性等特征。针对开发区建设中出现的问题,提出了促进其健康发展的建议。  相似文献   

6.
7.
The influence of air emissions from the enterprises of the city of Norilsk on the vegetation cover of adjacent territories was revealed. The categories of resistance of some plant species and communities to technogenic loads have been ascertained. The protective role of overmoistening of habitats was observed for plants.  相似文献   

8.
Field observations showed that the characteristics of chemical composition of waters and the development of plankton algae in the lakes within the delta of the Selenga river are determined by their flowage. The most open Lake Nekipelovskoe communicates with the Selenga outlets throughout a year, and Lake Zavernyaikha only at the period of an open channel. Lake Semenovskoe and Lake Khlystov Zaton are located in the islands and are isolated from the outlets. According to composition of main ions, the lakes under investigation refer to the hydrocarbonate class, the calcium group. The sum of ions in the water of Lake Nekipelovskoe approaches the one in the Selenga (86?221 mg/dm3), and the highest sums of ions were recorded in the wintertime in the lakes isolated from the outlets (446?743 mg/dm3). The lakes of the delta are characterized by a high trophicity. The maximum concentrations of total phosphorus in Lake Nekipelovskoe and Lake Zavernyaikha were 68 and 122 μg mg/dm3, and in Lake Semenovskoe and Lake Khlystov Zaton ?0.8 and ?0.63 μg mg/dm3, respectively. The most intense development of algae is observed in Lake Zavernyaikha, which is due to the high population of Baikal endemics. Lake Zavernyaikha showed a close negative correlation between the concentration of NO 3 ? , mineral phosphorus and phytoplankton biomass; the correlation coefficient was ?0.8 and ?0.63, respectively. The lakes exhibited increased contents readily hydrolysable organic matter, and a decrease in dissolved oxygen concentration in winter; hydrogen sulfide was repeatedly recorded in Lake Khlystov Zaton. The water quality in the lakes during the springtime varies from “quite clean” to “weakly polluted”; at low-water periods, especially in winters, it can drop to the category of “exceedingly dirty”. The water quality of the Selenga can be influenced by the lakes during spring floods when material accumulated during the wintertime is transported to the river outlets and further to Lake Baikal.  相似文献   

9.
孙松  王荣 《极地研究》1996,7(2):87-93
孙松,王荣StudyontherelationshipbetweenthediameterofthecompoundeyeandthegrowthoftheAntarctickrill¥SunSongandWangRongInstituteofOce...  相似文献   

10.
胡小猛  蔡顺  陈美君 《地理学报》2016,71(5):864-872
目前对含大荔人化石的地层年代认识仍存很大争议。采用黄土—古土壤序列定年法广泛调查渭河盆地东北部区域和大荔人化石点附近洛河上下游河段过去的河湖环境演变历史;在此基础上,结合产出大荔人化石的地貌沉积体特征,分析其形成时所处的区域演化阶段及其中含化石的沉积层位堆积年代。结果显示,区域曾在S14、L9、L6、S2、L2和L1SS发育或堆积时期发生过数次古湖湖退或河流下切;含大荔人化石的沉积层是在区域发生于L6晚期的一次湖退后,洛河于出露至气下的古湖湖底上堆积而成的,其堆积时代与S5古土壤发育时代相当,平均年龄约0.55 Ma BP。由该研究结果推论,学界对北京猿人年龄估计的老的年龄框架可能偏年轻。  相似文献   

11.
Recent mooring-based observations at several locations along the continental slope of the Arctic Ocean's Eurasian Basin showed a transformation of the Boundary Current (BC) from a mostly barotropic flow in Fram Strait to a jet-like baroclinic current northeast of Svalbard, and the reemergence of the barotropic structure of the flow in the eastern Eurasian Basin. This transformation is accompanied by a weakening of the flow from ~24 cm/s in Fram Strait to ~5 cm/s at the Lomonosov Ridge. The maximum of the baroclinic component of the BC at an intermediate depth (~200–370 m) is associated with the Atlantic Water core. The depth range of the baroclinic current maximum is controlled by cross-slope density gradients above and below the baroclinic velocity maximum as follows from the geostrophic balance of forces. According to the model simulations, the BC splits into shallow and deep branches in the proximity of Svalbard due to a divergence of isobaths, confirming topographically-controlled BC behavior. The shallow branch is located at a shelf break with a typical bottom depth of ~200 m and current speed of up to ~24 cm/s. The discussed results, which provide insight on some basic aspects of the dynamics of the BC (the major oceanic heat source for the Arctic Ocean), may be of importance for understanding of the ocean's role in shaping the arctic climate system state.  相似文献   

12.
13.
The Passive Influence of the Oceans upon the Rotation of the Earth   总被引:2,自引:0,他引:2  
A general theory is developed which allows the exact numerical computation of the static equilibrium response of a non-rotating spherically symmetric Earth model covered by thin oceans with geometrically irregular coastlines to the action of an imposed static tidal or centrifugal potential. The theory is self-consistent, and takes into account the gravitational self-attraction of the oceans and the elastic-gravitational response of the Earth model to both the applied potential and the equilibrium oceanic tidal load on the surface. The results are used to determine the influence of an equilibrium pole tide on the free period and the associated rotational eigenfunction of the Chandler wobble. If the pole is globally well represented by this equilibrium approximation, its effect is to increase the Chandler wobble period by 27·6 days. It is shown that a fully self-consistent theory of the rotation of an Earth model with oceans predicts that changes in spin and wobble will be coupled, and that the Chandler wobble should, as a result, be accompanied by an associated periodic change in the length of day. The consequences of spin-wobble coupling are explored quantitatively, and found to be slight.  相似文献   

14.
The author discusses "varying strategies of urbanization and city growth for the Soviet macroregions--European USSR, Siberia, and Central Asia." Several important research areas are outlined, including global aspects of urbanization, forecasts of urban growth in the USSR, formulation of a theory and methods for categorizing urban formation, urbanization and environmental concerns, mathematical modeling of urban systems, and research on specific urban systems.  相似文献   

15.
全球化时代的地缘政治形态分析   总被引:1,自引:0,他引:1  
地缘政治形态是由各种地缘政治关系有机组合而形成的综合体,它反映特定时空条件下地缘政治现实的总体面貌和特征。本文在简要介绍地缘政治形态概念和研究方法基础上,着重剖析当今世界以全球化为特征的地缘政治形态的内部结构。全球化打破了以往以民族国家为基本单元的地缘政治结构,表现出明显的多元化趋势;同时,国家之间边界越来越模糊,相互依赖日渐加深,地缘政治的全球整体性进一步加强,世界地缘政治形态展现出新的风貌。  相似文献   

16.
On the basis of analyzing long-term field data, we investigated the vertical thermal structure of 66 lakes of the North-West of Russia during the freeze-up period. The largest variability in thermal structure is characteristic for low-drainage shallow water bodies. Detailed data were obtained at self-contained buoy stations located in a small Lake Vendyurskoe (southern Karelia) were used to identify water temperature changes at the depths for a winter season as well as making assessments of het flows at the water–bottom and water–ice interfaces. The interannual water temperature variability at the depths reaches 2°C. The main geographical factors influencing the formation of thermal stratifications in the 66 lakes used in the study during the winter period are their mean depth, area, water residence time and geographical latitude. The largest vertical water temperature gradients are characteristic for the group of the smallest and shallow lakes, in the bottom layers of which the water temperature exceeds the temperature of maximum density, whereas in the deep lakes (more than 15 m) the water temperature is below 4°C. The lowest values of water temperature are observed in large lakes. The water temperature in the upper layer (up to 10 m) of drainage water bodies also decreases to 0–1°C as the result of the removal of heat with the river discharge. According to the thermal stratifications, the lakes are categorized as small (shallow, deep and drainage lakes), medium-sized and large shallow and large deep lakes. The suggested regression model permits a typical water temperature to be assessed at standard depths at the end of a winter season for any water body in the study region using available geographical information. The verification of the model is done from independent data for eight lakes of Finland.  相似文献   

17.
人地关系优化调控必须落实到具体的区域。区域具有层次和结构,不同类别的区域、同一类别区域的不同层次,人地关系演变和面临的矛盾受不同规律支配。文章从自然区域层次、文化区域层次、人类活动地域单元层次3个界面上探讨人地关系优化调控的可行性。  相似文献   

18.
本文将氚的测定方法应用于察尔汗盐湖抽卤过程中晶间卤水氖含量变化趋势的研究,以多次的测试数据研究和探讨了大气降水、周边水、地下水对察尔汗盐湖晶间卤水的影响,特别是开渠后湖水对晶间卤水的影响,从水平和垂直两个面讨论察尔汗首采区晶间卤水氚含量的变化规律。  相似文献   

19.
松嫩平原资源开发对湿地生态环境的影响研究   总被引:5,自引:2,他引:5  
文章论述了松嫩平原湿地生态系统的结构特征、资源潜力和生态功能,针对资源开发存在的诸多问题,探讨了不合理资源开发对湿地生态系统的影响。研究表明:松嫩平原湿地生态系统对区域农业经济可持续发展具有重要作用,不合理开发湿地会带来严重的生态后果,只有合理开发利用湿地才是维护生态平衡、实现区域生态经济持续发展的有效途径。  相似文献   

20.
Psychoanalysis has profoundly influenced those social theories that inform qualitative methodology in human geography. Yet many geographers are skeptical about the value and viability of psychoanalytic methodology because of its alleged reductionist causal explanations and relativistic interpretations of data. Drawing on the work of Slavoj ?i?ek, which affirms Jacques Lacan's undermining of the dualism of causality versus sense, this article illustrates the potential value of Lacanian psychoanalysis as a qualitative methodology in geography. Using a methodological case study from my research on Jamaican tourism, I illustrate how we can locate a Lacanian understanding of the drives in the interactions between tourists and hotel workers. In so doing, the article provides new insights into the enduring allures of tourism's commodity-form by focusing on how the object petit a—a chimerical object that incites desire and an unattainable object that the drives encircle—takes place in customer service and entertainment activities.  相似文献   

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