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Table of Content

    15 January 1985, Volume 40 Issue 1 Previous Issue    Next Issue
    ON THE CLASSIFICATION AND CAUSES OF FORMATION OF DIFFERENT CHANNEL PATTERNS
    Qian Ning
    1985, 40 (1):  1-10.  doi: 10.11821/xb198501001
    Abstract ( )   PDF (720KB) ( )   Save
    Based on the plain view, manner of channel shifting, stability and bank credibili-ty, channel patterns of alluvial streams a.re divided into four categories, namely, (1) wandering, (2) anabranched, (3) meandering, and (4) straight pattern.Streams, as an integrated part of a drainage ibasin, assume their characteristics in accordance with the amount and hydrograph of wafer and sediment and the type of ma- terial carried to the reach from the upstream watershed. The type of sediment manife-sts its effects in two aspects, i.e., the material which fronis the boundary of the channel and the ’bed material load which governs the formation of the channel. Whenever the conditions of the drainage ibasin change, the morphologic character of the river do-wn-streaxn will vary conformably. Such an adjustment is aoeomplished through the proce-sses of erosion, ’transportation and deposition of the sediment. The interrelationships between (1) the oncoming bed material load and. the sediment carrying capacity of the flow, and (2) the erodiblity of the river banks and the erosive power of the water decide essentially the general direction of the adjustment.Based on the concepts as depicted abov. it is argued that the production rate of tlie ’bed material load in relation to the water production rate of the watershed and the relative credibility of the stream banks are the two governing factors which control the-formation of different ohaomel patterns. Subsidiary factors in channel patterns forma-tion are given in Table 2. The existence of certain subsidiary factors may prove to be beneficial to the development of a certain chrannel pattern, or may even play a deciding-role when the stream is in a critical state of geomorpbologic (channel pattern shifting) threshold.
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    CHARACTERISTICS OF THE DISTRIBUTION OF TEMPERATURE VARIABILITY IN CHINA
    Sun Anjian, Fan Jianhua
    1985, 40 (1):  11-19.  doi: 10.11821/xb198501002
    Abstract ( )   PDF (577KB) ( )   Save
    Records of 432 weather stations in China fnom 1951 to 1980 are taken in this paper to study the characteristics of spatial and temporal distribution of temperature variabi-lity. The conclusions can be drawn as follows:1. Annual temperature variability is relatively small at lew latitude and increases with latitude.2. The position of high temperature variability center is almost identical with the position of climatic fronts and main patlies of cyclone and anticyclone activities. ’3. High center of temperature variability over the Xizang Plateau can be related to the trough activities in westerlies. There is more unanomialous corresponding rela-tion-ship between high temperature variability center of the southern Xizang mounta-ins and seasonal activity of subtropical jet.4. The maximum of temperature variability is evident in winter and the minimum in summer. Interannual temperature variation ;s very severe in winter at high latitu-de.
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    THE SIGNIFICANCE OF ASPECT IN MOUNTAIN GEOGRAPHY
    Lin Chao, Li Changwen
    1985, 40 (1):  20-28.  doi: 10.11821/xb198501003
    Abstract ( )   PDF (644KB) ( )   Save
    Aspect is a significant feature in mountain geography. It is one of the factors that ause the differentiation of mountain landscape and diversity of land use in mountain region. In ancient Chinese literature it is known as the "yinipo" (shady slope) and ""yangpo" (sunny slope). The equivance of these terms have also beging found in the geographical literature of many countries.The basic element that leads to the differentiation of the landscape is climate, e.g. -solar radiation, temperature, humidity are different on different aspects. Under the in-fluence of climate, other physical attributes such as vegetation, soil, hydrology and land-torm are manifested. The differentiation of landscape is the result of the interaction of these physical features.The difference of physical characteristics of the aspect is also significant in econo-mic activities, e.g. agriculture, forestry, husbandry and engineering. In classification of land types aspect shoud also be. considered.
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    ORIGIN AND SPREAD OF PADDY RICE CULTIVATION IN CHINA
    Wu Weitang
    1985, 40 (1):  29-36.  doi: 10.11821/xb198501004
    Abstract ( )   PDF (431KB) ( )   Save
    Concerning the problem of the origin of paddy rice cultivation there are two aspe- cts: 1. where and when the paddy rice cultivation originated; 2. how the cultivated spe- cies evolved.Up to now .there are 40 neolithic cultural sites in which a great amount of remains of paddy rice have been discovered. Two of there, Lujiao and Homodu sites, along the Hanigzhou Wan (Hangzhou Bay) dated as early as 7000 B.P.. The delta plain from the Hangzhou Wan to Taihu Lake appears to be the earliest centre for the cultivation of paddy rice in China.The spread of paddy rice cultivation is a process of cultural exchange between dif-ferent regions. It spread from the Hangzhou Wan area to the neighbouring regions fo-uowing the river courses lakes and sea coast. Among these the Chang Jiang (Yangtze River) was the mest important artery. Paddy rice cultivation spread westward to the Chang Jiang Gorges area about 5000 B.P., southward to the Zhu Jiang (Zhujiang Ri-ver) basin about 4500 B.P., south-westward to the highlands of yunnan and northward to the Huang He basin about 3000 B.P.. It spred also eastward to Taiwan about 3000 B.P..Differention and variation of the speci?s of paddy rice are the results of cultivation and spreading. Oriza sativa L., subsp. Keng Ting and O. s. L. sabsp. Hesin Ting were differentiated from the wild plants when they were domesticated. The plain surround- ing the Hangzhou Wan was the centre of differentiation.
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    STUDY ON THE RELATIONSHIP BETWEEN SOLUMSTRUCTURE PATTERNS AND GROWTH OF CROPS IN FARM-LAND OF NORTH CHINA PLAIN
    Ye Wenhua
    1985, 40 (1):  37-49.  doi: 10.11821/xb198501005
    Abstract ( )   PDF (883KB) ( )   Save
    North China Plain is an alluvial plain. The alluvium are alternatingly deposit. In-vestigation shows that the soluni structure patterns of North China Plain are very complex and diversified. The interstratified solum pattern and the loam (apposite) solum pattern are much fertile than the clay solum pattern, dispersed sandy solum pattern and sandy gravel solum pattern.There is a close relationship between the solum structure patterns and the growth of crops. The differences in function and effect of the solum patterns depend on the presence or absence of the barried-layer in the soil profile of 0-100 cm. When there is no such layer, the supply of water and fertilizer will be higher and crops yield is ge-nerally high and stable.The barrier layer or barrier factors in solum of farm-land of North China Plain include thin cultivated horizon, hard plowpan, lower content of waterstable aggregate, hard calcic horizon, alkali-saline soil and pollute etc. All these are unfavorable to the growth of crops.
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    FLUVIAL PROCESS OF THE FORK AND BRAIDED CHANNEL AND ITS EFFECTS ON EACH OTHER IN THE SOUTH-NORTH WATERWAY OF THE YANGTZE ESTUARY
    Zhong Xiucheng
    1985, 40 (1):  51-59.  doi: 10.11821/xb198501006
    Abstract ( )   PDF (525KB) ( )   Save
    The South-North "Waterway is a main fork reach of Yangtze River, it consists of three regions: (1) the fork reach; (2) the main braided channel; (3) the mouth bar re-gion.Based on the historical charts and hyddrological surveys, this paper dealts with the characteristics on the distribution of discharge and bed material load transported and analyzes fluvial process of the fork and braided channel.The paper points out that the oscillation of the main channel in the fork reach-brings about the change of the transported bed material load distribution ratio in the South-North "Waterway, thus causes the banks in the South-North Waterway subject to scouring and silting, Furthermore it also causes the flow condition changes in the-fork reach and conversely makes the main channel oscillates.According to the analysis, the basic reason which causes all of the changes descri-bed above is that the equilibrium condition between the flow and sediment transporta-tion is destroyed. In addition, wide river b?d and sandbank with characteristic loose material boundarv condition of channel in fork reach are other reasons.
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    SOME PROBLEMS ON THE [ALTITUDINAL BELTS IN SOUTHEASTERN QINGHAI-XIZANG (TIBETAN) PLATEAU
    Zheng Du, Yang Qinye
    1985, 40 (1):  60-69.  doi: 10.11821/xb198501007
    Abstract ( )   PDF (698KB) ( )   Save
    The study area is mainly covered by montane coniferous forests, alpine scrubs and meadows. It is the most humid region in the Qinghai-Xizang Plateau. In general, four types of the altitudinal belt, all pertaining to the oceanic system, may be recognized.The differentiation of the altitudinal belts is correlated with the basal belt. Prom southeastern margin to the interior of the study area, with increasing altitude, in addi-tion to differences of the basal belt there is a decrease in number of altitudinal belts and a simplification of spectra. The regional variation of zonal structures and their al-titudinal limits is conspicuous. Compared with other parts of the world, the upper for-est limit in the eastern Tibet is the highest.A number of dry valleys located in the gorge ’bottoms is one of the striking geo-ecologieal phenomena. The extent, distribution and upper limit of the dry valleys as well as their relationship to the horizontal zonation are discussed.Altitudinal belts of the study area are economically important in providing different areas for agriculture, animal husbandry, forestry, fuel supply and others. The long-term’ results of human impacts on fragile mountain environments may be summarized as the expansion of scrubs belt of the dry valley, the lowering of upper forest limits, de-forestations, and dramatical acceleration of soil erosions.Although the population pressure is one of the underlying causes of environmental and natural resource problems in the mountainous areas, the deforestation and misma-nagement of forests are directly responsible for ensuing environmental problems.
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