共查询到20条相似文献，搜索用时 31 毫秒
1.
Brian Huntley 《第四纪科学杂志》1990,5(2):103-122
Pollen data are the most important source of information with respect to late Quaternary vegetation history. Broad-scale palaeovegetation patterns have been subjectively inferred from mapped pollen data by previous authors. In this study, multivariate classification was applied to European pollen data for the last 13 000 yr. The resulting clusters are mapped at millennial intervals and can be equated with vegetation units. The maps portray the changing vegetation of Europe since the last glacial. They reveal the impermanence of the assemblages of species that ecologists recognise as communities. The dominant patterns in the maps also change through time, indicating important changes in palaeoenvironmental conditions and in the alignment of major environmental gradients. Human impact upon European vegetation history is seen to be relatively unimportant when the vegetation is viewed at a continental scale. 相似文献
2.
S.B. Lavrov M.K. Bandman K.P. Kosmachev G.V. Sdasyuk S.S. Artobolevsky L.M. Shevchenko 《Geoforum》1979,10(3):333-344
A major field of research since the 1920s has been methods and theories of economic regionalization. The territorial-production complex is now recognized as a key developmental tool within the framework of economic-planning regions. Recently, there has been a more marked growth of study into problems of natural-resource development, social progress and change in the U.S.S.R. as well as into the spatial structure of other nations, particularly other socialist countries and non-socialist developing countries. 相似文献
3.
V.V. Vladimirov 《Geoforum》1984,15(1):19-23
Regional planning in the U.S.S.R. is part of a comprehensive and hierarchical spatial and sectoral planning system. Four levels are described: (a) the national level, involving the total settlement system; (b) the major regional level, handling major development schemes; (c) the minor regional level, with plans for administrative districts; and (d) the urban level, where city master plans are produced. The amount of detail and scale of working increased downwards through the hierarchy. The most pressing problem is planning for the emergence and growth of cities of 100,000 population or more. Moscow city-region is used as an illustration. 相似文献
4.
《International Geology Review》2012,54(11):1335-1346
A detailed classification of regional metamorphic rock facies is presented along with the results of compiling a small scale Map of Metamorphic Facies of U.S.S.R. It is demonstrated that typical metamorphic complexes are associated with certain large structural elements of the crust. The aspects of metamorphism are used in identifying the areas of ancient platforms, two types of mobile belts, and two types of high pressure zones at the junction of major structures of different degrees of stability.—Author 相似文献
5.
Paul F. Williams 《Australian Journal of Earth Sciences》2013,60(3):215-228
The Ordovician rocks exposed along the N.S.W. coast, near Bermagui, comprise a sequence of alternating greywacke and shale and a less abundant sequence of alternating chert and detrital beds. The only lithological boundary that can be mapped is the contact between the two sequences and it sheds little light on the large scale structure. However, due to continuity of outcrop, well‐defined vergence zones and abundant younging evidence it is possible to interpret the regional structure. Two generations of folds (B1 and B2) are recognized and the regional folds, a N/S trending anticlinorium to the east and synclinorium to the west, are interpreted as second generation structures (B2). First generation folds (B1) are refolded by B2 on the limbs of the large B2 structures and are commonly recumbent. In the hinges of the regional B2 folds, B1 axial planes are steeply dipping and the folds instead of being refolded by B2, are more tightly appressed than elsewhere. A model is described to explain these observations. 相似文献
6.
Accurate and consistent X-ray fluorescence analysis of major and trace elements using a single pressed pellet for each sample has been achieved with a wide variety of rock compositions. Counting techniques for use with data reduction and correction programs in Standard Fortran IV are described; the latter depend throughout on data developed from a wide range of standard rock compositions. A comparison of ten major and fifteen trace element analyses for U.S.G.S. standard rocks with averages taken from the literature testifies to the precision of these techniques. 相似文献
7.
《Geoforum》1988,19(1):45-54
This paper seeks to examine the destabilizing role of the U.S. in international monetary affairs by charting the changing economic and monetary policies of successive U.S. administrations. It suggests that U.S. economic policy since the beginning of the 1970s can only be explained as a reaction to the relative decline of the U.S. economy vis-à-vis Western Europe and Japan. To ward off this decline the U.S. has pursued unilateral policies of dollar devaluation and revaluation which have often worked to the disadvantage of its rivals and the Third World. In detail, this paper examines the nature and consequences of a dollar devaluation policy under Nixon and Carter, of the strong dollar policy of the first Reagan administration, and of the renewed devaluation policies of Reagan's second administration. This paper shows how these policies have evolved against a background of deepening international crisis (and with reference to U.S. geopolitical strategies and the sanction of protectionism). Lessons are drawn for the European Left and future scenarios are mapped out concerning possible geographical alignments at the turn of the century. This paper places the debt crisis in the wider context of an asymmetrical and dysfunctional economic and monetary order. 相似文献
8.
《International Geology Review》2012,54(7):1273-1278
Progress report deals with: 1) Geochronology — potassium-argon — principally Precambrian. Gives dates on Precambrian of Baltic Shield including eastern Sweden, Northeastern Norway, Finland, Karelia, and Kola Peninsula. Gives a correlation of the Precambrian for the entire European U.S.S.R. 2) Depth and origin of magmatic ore deposits using reconstructed erosion surfaces for the major periods of mineralization. The depth zones of ore formation of American and European theories is questioned. 3) Tectonic mapping in crustal studies. And in this conjunction 4) Bathy-metric map of the Pacific has been prepared, conspicuous features are major tectonic and volcanic forms of the ocean bottom, as well as minor detail. Brief mention is made of ore deposits from the ocean. 5) “Weathering Crust” studies of subaerial weathering erosion and deposition, mainly of ancient crusts. 6) Study on the origin and distribution of “agricultural areas”, mainly phosphates. 7) Compilation of a Manual of Minerals now underway.--M.A. Klugman. 相似文献
9.
Analysis of tidal marsh vegetation patterns in two Georgia estuaries using aerial photography and GIS 总被引：1，自引：0，他引：1
Aerial photographs and GIS analysis were used to map the distribution of tidal marsh vegetation along the salinity gradients
of the estuaries of the Altamaha and Satilla Rivers in coastal Georgia. Vegetation maps were constructed from 1993 U.S. Geological
Survey Digital Orthophoto Quarter Quads, 1∶77,000-scale color infrared photographs taken in 1974 and 1∶24,000-scale black
and white photographs taken in 1953, Changes between years were identified using a GIS overlay analysis. Four vegetation classifications
were identified and groundtruthed with field surveys: salt marsh (areas containing primarilySpartina alterniflora), brackish marsh (Spartina cynosuroides andS. alterniflora), Juncus (Juncus roemerianus), and fresh marsh (Zizania aquatica, Zizaniopsis miliacae, and others). There was no evidence for an upstream shift in marsh vegetation along the longitudinal axis of either estuary
over the time frame of this analysis, which implies there has not been a long-term increase in salinity. Although the inland
extent of each marsh zone was further upstream in the Satilla than the Altamaha, they corresponded to similar average high
tide salinities in each estuary: areas classified as salt marsh occurred from the mouth up to where average high tide salinity
in the water was approximately 15 psu;Juncus ranged from 21 to 1 psu; brackish marsh ranged from 15 to 1 psu; and fresh marsh was upstream of 1 psu. Approximately 63%
of the 6,786 ha of tidal marsh vegetation mapped in the Altamaha and 75% of the 10,220 ha mapped in the Satilla remained the
same in all 3 yr.Juncus was the dominant classification in the intermediate regions of both estuaries, and shifts between areas classified asJuncus and either brackish or salt marsh constituted the primary vegetation change between 1953 and 1993 (87% of the changes observed
in the Altamaha and 95% of those in the Satilla). This analysis suggests that the broad distribution of tidal marsh vegetation
along these two estuaries is driven by salinity, but that at the local scale these are dynamic systems with a larger number
of factors affecting the frequently changing borders of vegetation patches. 相似文献
10.
11.
Delaware Bay is one of the largest estuaries on the U.S. eastern seaboard and is flanked by some of the most extensive salt marshes found in the northeastern U.S. While physicochemical and biotic gradients are known to occur along the long axis of the bay, no studies to date have investigated how the fish assemblage found in salt marsh creeks vary along this axis. The marshes of the lower portion of the bay, with higher salinity, are dominated bySpartina spp., while the marshes of the upper portion, with lower salinity, are currently composed primarily of common reed,Phragmites australis, S. alterniflora, or combinations of both. Extensive daytime sampling (n=815 tows) during May–November 1996 was conducted with otter trawls (4.9 m, 6 mm mesh) in six intertidal and subtidal marsh creek systems (upper and lower portions of each creek) where creek channel depths ranged from 1.4–2.8 m at high tide. The fish taxa of the marsh creeks was composed of 40 species that were dominated by demersal and pelagic forms including sciaenids (5 species), percichthyids (2), and clupeids (7), many of which are transients that spawn outside the bay but the early life history stages are abundant within the bay. The most abundant species wereMorone americana (24.3% of the total catch),Cynoscion regalis (15.4%),Micropogonias undulatus (15.3%),Anchoa mitchilli (12.0%), andTrinectes maculatus (10.8%). Non-metric Multi-Dimensional Scaling ordination of catch per unit effort (CPUE) data indicated two fish assemblages that were largely independent of the two major vegetation types, but generally corresponded with spatial variation in salinity. This relationship was more complex because some of the species for which we could discriminate different age classes by size had different patterns of distribution along the salinity gradient. 相似文献
12.
招远金矿区植被异常及遥感找矿意义 总被引：3，自引：0，他引：3
提出了一种新的综合型替代方法:基于廉价的Landsat-7 ETM 遥感数据揭示植被异常与热液蚀变区的潜在关系。在研究过程中,使用了招远金矿区夏季的ETM 遥感数据来分析和展示植被异常与热液矿化蚀变是否存在上述关系。该方法包括以下几个步骤:(1)数据预处理;(2)植被指数(Veg.In-dex、TNDVI、SQRT(IR/R)、NDVI、IR/R等)和波段比值指数;(3)主成分分析(PCA);(4)非监督分类;(5)监督分类。最后,经过综合解译成图发现,该图很好地展示了招远金矿区部分区域的植被异常,同时经过野外验证,在招远其它地区的植被异常都与热液蚀变区域有关。研究结果表明,这种综合型方法在植被覆盖区利用ETM 遥感数据提取植被异常信息非常有效。 相似文献
13.
14.
《International Geology Review》2012,54(8):1387-1396
A very interesting and informative paper on widespread occurrence of a thermal hydrosphere. Geothermal power uses are discussed. Distribution of heated waters, some up to 150° C is discussed in considerable detail, especially with reference to possible power utilization of the geothermal energy. Seven hydrothermal regions of the U.S.S.R. are discussed and delineated. Chemical quality of waters is referred to. There is a summary listing of locations in the U.S.S.R. where thermal waters could be utilized for generation of electric power. — B. N. Cooper. 相似文献
15.
《International Geology Review》2012,54(1):23-26
On October 12, 1962, a joint session of the Presidium of the U.S.S.R. Academy of Sciences and the Collegium of the U.S.S.R. Ministry of Geology and Mineral Reserves adopted a resolution “On the present state of the geological sciences in the U.S.S.R. Academy of Sciences and the U. S. S. R. Ministry of Geology and Mineral Reserves and their prospects for the future.” Important contributions of Russian geologists are acknowledged, but attention is drawn to many shortcomings. Future goals of geological study and work are given in detail. Twenty-one lines of research to be concentrated on are given, covering all phases of geology, geophysics, and geochemistry. In discussing the failings of the geological profession in Russia, it is of interest to note the following comment: “Geological research in other countries is still insufficiently studied and applied, and we are not making adequate use of geologic information from abroad.” The list of the Russian geologists' shortcomings sounds vaguely familiar. —J. R. Hayes 相似文献
16.
17.
Jenneke M. Visser Charles E. Sasser Robert H. Chabreck R. Greg Linscombe 《Estuaries and Coasts》2002,25(6):1184-1195
In order to document the effect of the recent drought and the resulting marine intrusion event on plant-community shifts in a Louisiana estuary, we analyzed two vegetation data sets collected in Barataria estuary in 1997 and 2000 and compared community shifts to surface salinity changes at four points along the estuarine gradient within the study area. We used the major vegetation types identified in our previous research of larger data sets and tested the use of a simple vegetation classification technique. This vegetation classification technique is based primarily on the dominant and co-dominant species, and secondarily on the number of taxa observed. To distinguish vegetation types with similar dominant species but different associated species, the vegetation classification technique used a salinity score derived from the species composition. Surface water salinity increases were reflected by a change in species composition in the mesohaline to fresh marshes. The largest species composition shift observed was the shift from oligohaline wiregrass (species rich vegetation type dominated bySpartina patens) to mesohaline wiregrass (vegetation type dominated byS. patens with few other species). Shifts in vegetation composition may have been enhanced by the presence of the major dominant species at a low abundance in other vegetation types. The vegetation classification technique used could classify over 95% of the stations. This vegetation classification technique provides a simple method to classify Louisiana's coastal vegetation based on plant species composition. 相似文献
18.
MIRJAMI TOLONEN 《Boreas: An International Journal of Quaternary Research》1983,12(3):201-215
Postsettlemcnt vegetation changes beginning in the early 17th century were studied through comparing stratigraphic peat-pollen data with available historical evidence. The isolation of the site and the relatively long historical record were ideal for the study. Human disturbance of the vegetation was readily identified in the pollen diagram with a contemporaneous increase in sediment mineral matter. The effects were much the same as the changes associated with Neolithic forest clearance in Northern Europe. Settlement resulted in the introduction and expansion of several cultural weeds after grazing and cultivation of Zea mays began on the island in the first decades of the 17th century; Rumex acetosa-acetosella, Ranunculus acris type, Plantago major-media and several new Compositae and Umbelliferae species all appeared at that time. The response of the native species to settlement was varied. Because of the limitations of the palynologic method, the area of cultivated land and detailed kind of agriculture can only be estimated. The data suggest that although agriculture was intensive from time to time, it took place on a very limited local scale; fires, grazing, and lumbering were the major factors affecting natural ecosystems. 相似文献
19.
通过盆栽实验,研究了不同营养土改良的铜尾矿对旱柳(Salix matsudana)扦插枝条生长及根系特性的影响。处理方式分别为TA100(100%尾矿)、TA80(80%尾矿+20%营养土)、TA60(60%尾矿+40%营养土)、TA40(40%尾矿+60%营养土)、TA20(20%尾矿~80%营养土)、TA00(100%营养土)。研究结果发现,旱柳枝条在5种处理方式下均可生根成活,但长势存在差异。随着尾矿含量的降低,旱柳枝条的生物量呈现出增加的趋势;随着尾矿含量的降低,旱柳枝条不定根数目增多、平均根长及最长的根长增加,根系活力先增强后降低。结果表明,旱柳可用于铜尾矿废弃地植被恢复,利用营养土改良有利于柳条不定根的形成和生长。 相似文献
20.
G.A. Privalovskaya 《Geoforum》1984,15(1):39-48
The recent experience of the rising cost of exploiting new material resources in the U.S.S.R. has led to exploration of alternative methods, particularly greater intensification of exploitation. The regional variations in the balance between intensive and extensive methods is considerable and is consequently an important aspect of Soviet geographical research. This paper discusses the criteria and methodology for this crucial economic/resource regionalization of the U.S.S.R. 相似文献