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    25 July 2007, Volume 62 Issue 7 Previous Issue    Next Issue
    The Type and Evolution of the Gr anite Landforms in China
    CUI Zhijiu, YANG Jianqiang, CHEN Yixin
    2007, 62 (7):  675-690.  doi: 10.11821/xb200707001
    Abstract ( 924 )   PDF (4310KB) ( 697 )   Save

    With the subtropical monsoon climate in southern China, the planation surface and the crust of weathering developed into many particular granite landform types, such as that on Mt. Huangshan and Mt. Sanqingshan, as a result of the uplift and down-cut in the following tectonic movements. In this paper, the temporal and spatial development discipline of the granite crust of weathering and landform was discussed, and the close relationship between the landform age and planation surface was studied. The connections of the granite landform and the crust of weathering were also put forward in different uplift background. Based on that, the uplift extent of massifs can be presumed, which would be ~200 m at coastal region, and increase to 1600-2000 m at the Nanling Mountains or Dabie Mountain and Funiu Massif.

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    Formation and Development of the Potholes Formed in a Gorge River in Guangdong
    WANG Wei, HUANG Shan, LIANG Mingzhu
    2007, 62 (7):  691-697.  doi: 10.11821/xb200707002
    Abstract ( 766 )   PDF (2336KB) ( 725 )   Save

    Pothole geometries were measured in a reach of Dabu river bed at the head of a gorge that more than 200 m deeply incised into a 650-750-m high planation surface formed in the middle Miocene in northern Guangdong, China. Geometric and derivative data of the potholes obtained from the field study were interpreted using standard statistical methodologies. The statistical analysis combining with related field observations revealed the origins of river potholes and the processes of pothole formation and development. The study shown that the formation and development of a river pothole were only related to the localized conditions, such as geology, geomorphology and water fluid styles at a spot where the pothole occurred; the weaknesses, which were usually intersected fractures, typically interconnected vertical joints, or triangular pits generated by hitting of rock fragments during floods, initiated pothole development on a river bed at this site; the geometrical dimensions of the potholes were controlled by the features of the tectonic joints developed in river bed rock; the radius and the depth of potholes were strongly (log) positive correlated; the shape of a pothole and the style of stream flows forming the pothole were not always the same in the processes of pothole growth; as an important role for channel incision, a pothole could create quickly in a gorge river undergoing powerful vertical erosion, but did not have enough time to fully develop and could not be maintained for a long time as well.

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    Influence of Gr azing on the Char acter istics of Longitudinal Dune Sur face in the Southern Par t of Gurbantunggut Deser t
    WANG Xueqin, ZHANG Yuanming, JIANG Jin, YANG Weikang,CHEN Ming, ZHANG Jikai, CHEN Junjie, SONG Chunwu
    2007, 62 (7):  698-706.  doi: 10.11821/xb200707003
    Abstract ( 613 )   PDF (2599KB) ( 499 )   Save

    The Gurbantunggnt Desert is the largest fixed and semi-fixed desert in China, where the main dune type is longitudinal dune. The distribution of biological crusts and plants, sand surface stability and physicochemical characteristics of soil on the dune surface in the southern part of Gurbantunggut Desert were monitored and studied in 2002 (no grazing) and 2005 (following grazing). The results showed that over 80% of the total area of the dune surface was covered by well-developed biological crusts and plants in 2002, when the interdune and middle to lower part of the slopes were stabilized and only the crest had 10-40 m wide mobile belt. Affected by heavy grazing in 2005, over 80% of the total cover of the biological crusts was destructed and the plants coverage only reached 1/5 of that in 2002, especially, the ephemeral plants cover had a great change. The value of sand transport potential in 2005 only reached 1/3 of that in 2002, but the total surface activity in 2005 was 1.6 times stronger than that in 2002. Meanwhile mobile area began to expand from dune top to the whole dune surface following grazing. Compared with 2002, the medium sands content of the dune surface soil increased 13.9%, while that of fine and extra-fine sands decreased 7.4% and 8.0% in 2005. The soil organic matter in 2005 was only about 1/2 of that in 2002. It is obvious that grazing made excessive damage to some protective conditions in Gurbantunggnt Desert, such as the biological crusts and the ephemeral plants. Intensive activity of dune surface occurred and led to great losses of fine sands and organic matter, which will influence continuance development of the desert ecosystem.

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    Accr etion/erosion of the Subaqueous Delta at the Yangtze Estuary in Recent 10 Year s
    LI Peng, YANG Shilun, DAI Shibao, ZHANG Wenxiang
    2007, 62 (7):  707-716.  doi: 10.11821/xb200707004
    Abstract ( 612 )   PDF (2820KB) ( 660 )   Save

    Based on the sediment supply from the Yangtze River and the analysis of the accretion/erosion of the subaqueous delta at the Yangtze Estuary in recent ten years, the accretion/erosion response of the subaqueous delta to the sharp decline of the sediment supply from the Yangtze River to the sea and the impoundment of the Three Gorges Reservoir was preliminarily discussed. The results show that (1) because of the impoundment of the Three Gorges Reservoir, the sediment supply from the Yangtze River to the sea decreased at an order of magnitude 1×108 t/a; (2) the proportion of accretion area to the total area is 75.5%, 30.5% and 14% in the three periods. The accretion/erosion rates of the three periods (1995-2000, 2000-2004, 2004-2005) are 6.4 cm/a, -3.8 cm/a and -21 cm/a respectively in the study area; and (3) the accretion/erosion response to the decrease of the sediment discharge from the Yangtze River in the study area has significant spacial different results in the influence of topography, the change of hydrodynamics and the engineering projects. The conclusions are that the impoundment of the Three Gorges Reservoir accelerated the decrease of the sediment from the Yangtze River which is the main cause for the change from accretion to erosion of the subaqueous delta. Attentions should be paid to the future evolution processes of the Yangtze River Delta in view of the further decrease of sediment supply of the Yangtze River, which is due to the more dam construction and land conservation in the future, and the consequent further erosion in the subaqueous delta.

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    Impact of Urbanization on Regional Temper atur e Change in the Yangtze River Delta
    XIE Zhiqing, DU Yin, ZENG Yan, SHI Yafeng, WU Jingang
    2007, 62 (7):  717-727.  doi: 10.11821/xb200707005
    Abstract ( 565 )   PDF (2504KB) ( 710 )   Save

    Based on non-radiance-calibrated DMSP/OLS nighttime light imagery from 1992 to 2003, urban land area statistical data, meteorological data and land surface temperature data retrieved by MODIS and NOAA/AVHRR data, the influence of urbanization on regional climate trend of temperature in the Yangtze River Delta was analyzed. Conclusions are as follows: (1) There is a significant urbanization process from 1992 to 2003 in the Yangtze River Delta, and the annual mean air temperature increased at a rate of 0.28-0.44 oC/10a in mega city. (2) The urban heat island (UHI) effect on regional mean air temperature in different seasons is summer > autumn > spring > winter. (3) The UHI intensity and the urban total population logarithm are creditable correlated. (4) The UHI effect made the regional annual mean air temperature increased 0.072 oC from 1961 to 2005 and 0.047 oC from 1991 to 2005, and the annual maximum air temperature increased 0.162 oC and 0.083 oC from 1991 to 2005, all indicating that the urban expansion in the Yangtze River Delta from 1991 to 2005 may be regarded as a serious climate signal.

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    The Relationship between Autumn- time Eur asian Snow Cover and Winter - time NH Cir culation
    ZHANG Tianyu, CHEN Haishan, SUN Zhaobo
    2007, 62 (7):  728-741.  doi: 10.11821/xb200707006
    Abstract ( 507 )   PDF (2680KB) ( 627 )   Save

    The relationship between the autumn-time and winter-time Eurasian snow cover anomalies and the distributions of winter-time NH circulation has been investigated by using comparative analysis of the correlation and synthetic methods based on the data of the snow cover in Eurasia from NOAA and reanalyzed data from NCEP/NCAR for the period 1973 through 2004, and the results show an observational fact: there is a significant correlation between the Eurasian autumn snow cover and the high-latitude atmospheric circulation of late winter in Northern Hemisphere. Especially it shows an obvious negative correlation between the Eurasian autumn snow cover and the main model Arctic Oscillation (AO), or the North Atlantic Oscillation (NAO) of the winter-time NH circulation. The relationship between the autumn-time snow cover anomalies and the following winter-time circulation is closer than that between the winter-time snow cover anomalies and the winter-time circulation based on observational analysis. Finally, a link between the Eurasian autumn snow cover and the winter-time NH circulation is mentioned. The Eurasian autumn snow cover may be a major factor which forces the variability of the following winter-time NH circulation.

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    Hor izontal Var iations of Climatic Response of Qilian Juniper (Juniperus przewalskii) in the Anyemaqen Mountains
    PENG Jianfeng, GOU Xiaohua, CHEN Fahu, ZHANG Yongxian,LIU Puxing, ZHANG Yong, FANG Keyan
    2007, 62 (7):  742-752.  doi: 10.11821/xb200707007
    Abstract ( 645 )   PDF (2820KB) ( 652 )   Save

    A spatiotemporal patterns analysis of a network with 20 Qilian juniper (Juniperus przewalskii) tree ring-width chronologies from 5 slopes along a west-east gradient in the Anyemaqen Mountains on the northeastern Qinghai-Tibetn Plateau was performed by means of chronology statistics. Higher SNR and EPS values implied the more climatic information in these chronologies. Most correlations among standard chronologies taken in pairs are significant, with the mean correlation coefficient for all sites being 0.35, indicating that environment condition was consistency. The result of Hierarchical Cluster Analysis showed two well-defined groups at large, corresponding to the two groups, the eastern and the western. Scatter plots of component loadings indicated that stands growing in a similar climate environment are most important on variability of radial growth. The first component of chronologies in east-west regions implied that the center of Qilian juniper (Juniperus przewalskii) growing transplants eastwards along the Anyemaqen Mountains and the eigenvalues (narrow years) tree-growth in the western and the eastern Anyemaqen were synchronous. Correlation between the first principal component (PC1) and the second principal component (PC2) and the climatic factors revealed similarity and differences in radial growth along the west-east gradient in the study area, nevertheless the difference of PC2 is more prominent. Temperature was the main limiting factor to tree growth PC1 in the western Anyemaqen, especially the impact of current late spring and early summer the most significant , and Precipitation was very importance to tree growth, but precipitation was mainly limiting factor of tree growth PC2. Temperature and precipitation held definite commutative.

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    The Mean Annual Water Balance in the Hekou- Longmen Section of the Middle Yellow River : Testing of the Regional Scale Water Balance Model and Its Calibr ation
    ZHANG Xiaoping, ZHANG Lu, MU Xingmin, LI Rui
    2007, 62 (7):  753-763.  doi: 10.11821/xb200707008
    Abstract ( 492 )   PDF (3083KB) ( 511 )   Save

    Ecosystem health and sustainability of social and economic development in arid and semi-arid regions depends on water availability. To study the responses of water balance components to the different land cover types on mean annual scale, the data of streamflow, precipitation and Epan from 1980 to 2000 in the He-Long section (briefly for Hekou-Longmen section) of the middle reaches of the Yellow River, were used to test and calibrate the water balance model set up by Zhang in 2001. The results showed that the model was able to accurately simulate mean annual evapotranspiration, but not mean annual streamflow when compared with streamflow measurements from 38 hydrologic stations in the study area. Using the optimized parameters, the index of agreement between modeled and observed evaporation increased from 0.89 to 0.94, and the relative error and root mean square error decreased from 3.6% and 17.2 mm to 1.5% and 7.9 mm. The index of agreement for streamflow increased from 0.21 to 0.63 and the relative error decreased from 42.7% to 18.0%. Hierarchical cluster analysis showed that 3 types of water cycles exist due to the different land cover types. The parameter optimization showed that due to the effects of forest interception, the evaporation coefficient (ET/P) in the southern part of the He-Long section is fairly high so the region is suitable for the parameter w 1.61. For the influence of sandy soil and high groundwater, the evaporation coefficient in the northwestern region is low, so that for this region the parameter value of 0.10 was used. In the middle part of the He-Long section, it is fit for the parameter value of 0.45.

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    Hydro- geochemistry and the Sour ces of DIC in the Upr iver Tr ibutar ies of the Ganjiang River
    LI Tiantian, JI Hongbing, JIANG Yongbin, WANG Lixin
    2007, 62 (7):  764-775.  doi: 10.11821/xb200707009
    Abstract ( 479 )   PDF (3124KB) ( 534 )   Save

    Testing and analyzing the samples collected from the upriver tributaries of Ganjiang, we found that the river and its tributaries have low total dissolved solids concentrations and the chemical composition of river water is dominated by Na+, Ca2+, Cl-,HCO3- and Si, representing that of the river water from the typical silicate rock areas. Seawater correction approach (Cl- normalized seawater ratios) was used to estimate the contribution proportions of local precipitation to the solutes, we found that most watersheds of southern Jiangxi province were evidently influenced by precipitation. After the contributions of precipitation deducted from the total dissolved solids, on the basis of the principal composition analysis and factor analysis, the watersheds of Ganjiang were influenced strongly by silicate weathering. At the same time, the watersheds are evidently influenced by evaporates under the influence of the mineral resources. In this paper, the upriver tributaries of Ganjiang were selected for analyzing the dissolved inorganic carbon isotope composition of it. It has δ13CDIC of -8.35 to -13.74‰, with an average of -11.65‰. The key source of DIC is soil CO2 and carbonate weathering. According to carbon isotopic composition of soil CO2 and carbonate rock, 68.5% of the DIC is calculated to originate from soil CO2, respectively, and 31.5% of the DIC is calculated to originate from carbon rock. The soil CO2 consumption of chemical weathering processes is 2.11 ×105 mol/yr·km2, and about 9.6 ×104 mol/yr·km2 is from carbonate. At the same time, the tributaries have different δ13CDIC values each because of different environments and the human interference.

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