Table of Content

    15 July 1978, Volume 33 Issue 2 Previous Issue    Next Issue
    Zhang Yong-zu
    1978, 33 (2):  85-101.  doi: 10.11821/xb197802001
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    The zoogeographical characteristics of China as reflected by the faunistie composi-tion of terrestrial vertebrates has resulted from the successive differentiations from the Hipperion group since late Tertiary (Pig. 1). In the Palaeoarctic realm, the adjust-ment to the diversification of environment between the west and the east of the country has brought about further regionanization. On the other hand, the discontinuous distribu-tion of some species over China in the east arid Europe in the west (Fig. 3) may bear evidence of how the Pleistocene glaciation influencing the animal distribution in N. Eurasia. Of the Oriental realm, the transitional character shown by the tropical animals (Fig. 4) has been consequent to the southward recession (Fig. 2), which, as far as some genus and species are concerned, has been in progress ever since Pleistocene. The Tibetan and the Mongolia-Sinkiang Begions approximate in components, particu-larly so in the steppe areas. Their close relationship, as well as the recency of the uplifting of Tibetan plateau, might explain the slight differentiation (on the level of species or lower) from each other. Between Taiwan and Hainan, a similarily lies in the slight differentiations due to the recency of being separated from the mainland, but a dissimilarity stands out when the temperate and the subtropical elements in Taiwan are compared with the completely tropical elements in Hainan. This distinc-tion may have been descended from their respective affinities to the neighboring parts of the mainland. The uniqueness of the Southwestern Region with parallel ridges and gorges being unaffected by the last glaciation is expressed by its function, of preserving some animals or forming centers of distribution.From an ecological viewpoint, 3 main groups of vertebrates have been observed in China (Fig. 7), i. e., the monsoonal group of hygrocoles, the Sinkiang-Mongolian group of Xerocoles, and the Tibetan group of cryocoles. The components of each group vary as the habitates, and they intermingle in the boundary areas. The intersper-sion is particularly obvious (1) in the Southwes tern Eegion of ridges and gorges (Fig. 8), where the vertical zonation far exceeds the horizontal, zonation; and (2) the region between the Tibetan and the Sinkiang-Mo ngolian groups (Fig. 7), where the palaeogeographic process has drawn close with each other.A scheme of subdividing these 3 groups into 7 in accordance with the vegetation formations has been suggested (Fig 9). Groups 4 (desert and semidesert) and 7 (humid tropical) represent the two extremes (contimental dry on one hand and mari-time humid on the other) with their respective endemic animals, while other groups are transitional both in faunistie composition (Table 2) and ecological characteristics (Table 3).
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    Gao Guo-dong, Lu Yu-yong, Li Huai-jin
    1978, 33 (2):  102-111.  doi: 10.11821/xb197802002
    Abstract ( )   PDF (711KB) ( )   Save
    In this paper the various methods used for calculating the maximum possible evaporation (M. P. B.) are discussed. The M. P. E. of more than 300 stations in China, calculated with Budyko’s formula, using the component values of radiation and heat balance calculated by the authors and the other related climatological data, is analysed.It is found that both the time and space variations of M. P. E. in China are chiefly determined by the thermal condition and moisture condition. They are minimum in winter and maximum in summer. In the Eastern China the M. P. E. value dicreases with latitude from 1000 mm in south to 500 mm in Northeast. In the Western China, there is a low value region with a minimum value ’about 500mm around the Tibetan plateau, and a high value region with a maximum value about 1200 mm around the Tarim Basin in Sinkiang province. The annual range of the M. P. E. is quite small along the southeastern coast, only about 70 mm, but more than 130 mm, in the Northwestern China.
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    Liu Chong-ming, Chung Chun-hsiang
    1978, 33 (2):  112-127.  doi: 10.11821/xb197802003
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    In order to investigate the influence of forest cover upon the annual runoff in detail, we map the annual runoff isogram with the observed data of 1222 station-years from (94) hydrometric stations and the annual precipitation isogram with the observed data of 1534 station-years from 118 raingauge points in the middle reaches of the Yellow River.The annual runoff map shows that the 4epth of mean annual runoff in the wooded areas of the Plateau are less than that of the adjacent woodless areas. It is lower than 25 mm. in wooded area, and 30-40 mm. in woodless areas. Runoff coef-ficient expresses the ratio between runoff and precipitation and reflects the character of runoff formation. The calculation of annual runoff coefficient shown that the annual runoff coefficient in the wooded area is about 30% less than that in the woodless area.We also made a comparison of water balance analysis between five pairs of forested and unforested watersheds.For the purpose of analyzing the influence of fewest cover upon the annual runoff quantitatively, we correlate the forest cover ratio and the mean annual runoff (as well as annual underground runoff) for forested watersheds in Loess Plateau.The results obtained show four pairs in the north of Shensi province having mean annual runoff of the forested watershed less than that of the woodless one. Only one pair of comparative watersheds, the rivers of Venyu and Chongyuan which are of unforested watershed. The geographicals contrary, that is, the mean annual runoff of forested watershed is greater than that of unforested watershed. The geographical condition of this pair differs from other four pairs in that it is covered with stony soil instead of loess.The results obtained by the calculation also prove that the forest cover in Loess Plateau has a negative role for the annual runoff, and in some degree, an active effect on the underground water, that is an action of compensation.
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    1978, 33 (2):  128-141.  doi: 10.11821/xb197802004
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    SYNOPSISThere are in general two different types of braided stream. One has large num-bers of cross-channels with an ever shifting thalweg from place to place. The chan-nels can easily be silted up and abandoned by the flow, but new channels will be formed in some other places at will. The lower reaches of the Yellow River is typical of this type of braided stream. On the other hand, there are braided streams which assume a relatively stable pattern with not many cross-channels. Although periodic evolutions are noticed among these channels, but they seldom lose their existence as a result of sediment accretion. The middle and lower reaches of the Yangtze Eiver belong to this group.Based on experimental studies as well as on field observations, this paper deals with the characteristics of the flow, the effects of the nodes along the banks on the fluvial processes, the geometric shape of the river channels and the geomorphology of the bed of the braided Yangtze River. The results can be summarized as follows:1. The flow conditions of the braided stream are unique for the existence of a zone of division of the flows and a zone of re-union of the cross-channels. The zone of division can be classified into two catagories, one as division through a relatively straight channel and the other through a curved one. In the former case, the surface flow is directed towards the main channel with bottom flow moving towards the side channel. The opposite is true for the latter case. Evolution of the channel patterns will lead the division through straight channel towards the type of division through curved channel. The junction of two channels or more can be distinguished in the zone of re-union. When two curved thalwegs with opposite direction join together, two opposite spiral flows towards the middle of the channel are created. If more channels take place in the re-union, then a correspondingly increased number of spiral flows will be established.2. The nodes along the river banks are the important boundary condition for the formation of braided stream. Once the nodes are exposed by the flow, alternative wide and narrow reaches along the river course will be developed. Experimental re-sults indicate that as the width and length of the expanded reach become twice of and six times respectively the width of the reach with nodes, bars and islands will be formed in the expanded reach which will lead eventually to the creation of a braided stream. If there are nodes along both banks of the river and the reach is so long such that its length equals to its width, then the main flow will be kept in the middle of the reach and the effect of directing the flow towards the opposite bankby the nodes will be lessened. If the length of the reach with’ nodes along both banks is smaller than its width, then the flow coming from the left side upstream of the reach will be directed towards the right side of the downstream reach, and vice versa.3. A complex braided channel system with a plain view look like "the head of a goose" is often a combination of straight channel, channel with slight curves, cur-ved channel and loop with the shape of a reversed "S". In the historical past, dif-ferent single channel patterns can be mutually converted, and there is always a channel the evolution of which plays a dominant role. The fluvial processes of the braided channel system as a whole depend on the changes which take place in that channel.4. Islands appeared in the braided system are often built up from the central bars. There are many ways in. which central bars can be created. If the river as-sumes a form with alternative wide arid narrow reaches due to the existence of nodes along the banks, then upstream of the nodes, the flow will be dammed up in the flood season ,and central bars will be developed due to the accumulation of sediment. Downstream of the nodes, the diversion of flow is also beneficial for the accretion of the channel and the formation of the central bars. In some times central bar is developed in consequence of the cuttin
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    Li Wen-yi, Wu Hsi-fang
    1978, 33 (2):  142-155.  doi: 10.11821/xb197802005
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    Based upon Palynological investigations on the late Tertiary and early Quarternary deposits found in the vicinity of kuenming, four developmental stages in vegetation in the central Yunnan are recognized. In the first stage, the sporo-pollen assemblage was mainly composed of temperate plants, Pinus, Quercus and Castanea, along with some warm temperate to subtropical elements, Podocarpus, Carya, Ilex, Aralia, etc. It reflects that the climate was rather warm. The age of this stage probably corresponds to late Miocene to Pliocene. In the second stage, Pinaceae and Pagaceae were predominant again. Some subtropical elements, Platycarya, Liquidambar, Pittosporum, Antidesma and Symplocos were distributed. It indicates that the climate became wetter and warmer . In the third stage, the amount of Pinaceae and Fagaceae decreased, while some subtropical Gymnosperms, Podocarpus, Dacrydium and Keteleeria, and subtropical broad-leaved trees, Ilex, Carya, Melia, Caesalpinia and Sterculia increased. It reflects that the climate was still warm. The second and third stages probably correspond to the Pliocene.In the final stage, the assemblage showed some changes, such as, increasing of some conifers (Abies, Picea and Cupressus), the broad-leaved trees (Alnus, Betula and Tilia) and herbs. It indicates that the climate became cooler and drier. This stage is tentatively assigned to early Quarternary.The flora reflected by the pollen assemblages is a mixed flora, Pinaceae and Fagaceae were present throughout the whole period. On the other hand, many subtropical and tropical elements, such as Ham xmenlidaceae Aquifoliaceae, Araliaceae, and Pittosporum were present too. On the whole, the flora is simillar to that of to-day in the same region. It shows that the vegetational type has not been much changed since late Tertiary.
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    Shieh Shiarn-chyurn, Pao Shin-chu
    1978, 33 (2):  156-162.  doi: 10.11821/xb197802006
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    This paper analyses the thermal regime of the underlying surface in the cul-tivated area of Hulun-Bir steppe and discusses the increase of atmospheric dust content over the area caused by the variation of the thermal condition of underlying surface after cultivating.The result of observation shows that after cultivating the albedo of the cultivated land is about 0.13 to 0.18, with a mean value of 0.16. The albedo for grassland is about 0.16-0.21, with a mean value of 0.19. The surface temperature of cultivated land is about 3-4℃ higher tham that of grassland during daytime, so that the effec-tive radiation of cultivated land is larger than that of grassland. The heat balance for cultivated land is quite different from that of the grassland. The net radiation on the grassland is mainly used for the evaporation, which constitutes about 60% to 70% of radiation balance, and is larger than that of the cultivated lanid. But the turbulent heat flux on cultivated land is larger than that on grassland, about 4 times larger at noon, sometimes even 10 times larger. The turbulent) heat flux on cultivated land constitutes about 60% of radiation balance so that the net radiation of cultivated land is mainly used for the turbulent transport of heat into the air.The relationship between the diurnal variation of the turbidity of atmosphere and the turbulent heat flux in spring over Pa-Kshi Farm shows that the turbulent heat flux increase rapidly following the development of turbulent thermal instability. In the meantime, the increasing turbidity of atmosphere over cultivated area is due to the increasing transport of dust particle from the surface of the earth to the air. This is the cause why there occurs frequently the dust bowls on the cultivated land of Hulun-Bir steppe during April and May.
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