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  • 2012 Volume 67 Issue 5
    Published: 20 May 2012
      
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  • Impacts of Cropland Transformation on Agricultural Production under Urbanization and Grain for Green Project in China
    YAN Huimin, LIU Jiyuan, HUANG Heqing, DONG Jinwei, XU Xinliang, WANG Junbang
    2012, 67(5): 579-588. https://doi.org/10.11821/xb201205001
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    In this study, the changes of agricultural production from cropland transformation in the periods of the late 1980s-2000 and 2000-2005 were estimated based on: 1) the cropland transformation results derived from Landsat TM imagery by artificial interpretation method, and 2) net primary productivity (NPP) data from the light use efficiency models of Global Production Efficiency Model (GloPEM) and Vegetation Photosynthesis Model (VPM). Changes of regional grain production capacity were mainly from two aspects of cropland transformation: cropland conversion (e.g. urbanization, converting cropland into forest) and land reclamation (e.g. converting grassland into cropland). The impacts of different cropland transformation types on agricultural production within the two periods were evaluated, a series of comparisons were conducted between the two periods as well as different regions. Results indicated that the agricultural production loss due to urban sprawl accounted for more than 60% during both stages (1980s-2000 and 2000-2005) in the total loss. In the first stage, generally, agricultural production increased evidently. The increased production from land reclamation was 87% higher than production decrease from cropland conversion. However, in the second stage (2000-2005) the agricultural production loss due to cropland conversion was 31% higher than the production increase from land reclamation, in other words, the production decrease due to cropland loss could not be compensated by limited land reclamation, as unban expansion and Grain for Green (GFG) project played an important role in cropland transformation since around 2000. Production losses from GFG project and urbanization were 57 % and 85 % higher than that in the previous stage, respectively. Due to GFG project, the states of agricultural production equilibrium changed from positive balance from the 1980s to 2000 into a negative balance during 2000-2005. the loss of agricultural production mainly occurred in Northeast China, Inner Mongolia, Yunnan and Zhejiang provinces from the 1980s to 2000, and then transferred to Inner Mongolia, Shaanxi, Gansu, Sichuan and Guizhou provinces from 2000 to 2005. The production loss due to urbanization mainly occurred in Jiangsu, Hebei, Anhui, Shandong, Henan and Guangdong provinces from the 1980s to 2000, then changed into provinces of Zhejiang, Guangdong, Shandong, Fujian and Jiangsu during 2000-2005. The land reclamation foci transferred from Northeast China to Northwest China in the two stages, the greatest contribution regions to agricultural production shifted from the Xinjiang Uygur Autonomous Region from the 1980s to 2000 into Heilongjiang Province during 2000-2005. Due to the cropland transformation from urbanization and GFG project, two thirds of provinces showed a significant change in agricultural production balance state in the two stages.
  • The Distribution and Drivers of Land Degradation in the Three-North Shelter Forest Region of China during 1982-2006
    HUANG Senwang, LI Xiaosong, WU Bingfang, PEI Liang
    2012, 67(5): 589-598. https://doi.org/10.11821/xb201205002
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    It is important to conduct studies on spatio-temporal distribution and drivers based on remote sensing for quantitative estimation of large-scale regional land degradation. In this paper, we analyze the land degradation trend in the Three-North Shelter Forest region of China from 1982 to 2006, using the remotely-sensed data of NOAA/AVHRR Normalized Difference Vegetation Index (NDVI) based on the Sen +Mann-Kendall trend analysis method, and assess the combined effect of human activities and precipitation on the regional land degradation by using the Residual Trends model. The results indicate that the land degradation have a declining trend as a whole, with the significant increase and the significant decrease being 13.00% and 17.29%, respectively. Land degradation in most of the provinces tends to be relatively slight, especially in Inner Mongolia, Qinghai and Xinjiang, while Gansu witnesses the opposite trend. Human activities contributed 11.93% to the significant vegetation increase, and 6.19% to the degradation. This means that in the arid or semi-arid regions, the temporal change of precipitation is not significant, so the obvious vegetation change is mainly affected by human activities.
  • Influences of Terrace Construction and Check Dam Silting-up on Soil Erosion
    GAO Haidong, LI Zhanbin, LI Peng, JIA Lianlian, ZHANG Xiang
    2012, 67(5): 599-608. https://doi.org/10.11821/xb201205003
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    To research the terrace construction and check dam silting-up soil erosion effects, this paper firstly established a generalized model consisting of terrace, slope land, steep slope grassland, and check dam land in hilly and gully region of Loess Plateau, defined the pioneer phase, transitional phase and climax phase. Then it used the revised universal soil loss equation (RUSLE) to analyze soil erosion modulus in different periods. The results showed that pioneer phase and climax phase are the limit state of soil and water conservation. In pioneer phase, soil erosion modulus is 299.56 t×hm-2×a-1 and 136.64 t×hm-2×a-1 in the upper and lower parts of demarcation of hill and gully slope, respectively, and the average erosion modulus is 229.74 t×hm-2×a-1. In climax phase, soil erosion modulus is 39. 10 t×hm-2×a-1 and 1.10 t×hm-2×a-1 in the upper and lower parts, and the average erosion modulus is 22.81 t×hm-2×a-1. In the transitional phase, with the increase of the ratio of the terrace, soil erosion modulus index is reduced at upper Mao sideline; with the increase of the sedimentation of the height, soil erosion modulus shows a linear decrease at lower Mao sideline.
  • Influence of Human Activities on the Riverbed Evolution in Yalu River Estuary during Recent One Century
    CHENG Yan, LIU Yue, GAO Jianhua, ZHANG Chunpeng, LI Fuxiang, LIU Jingwei, ZHANG Liang
    2012, 67(5): 609-620. https://doi.org/10.11821/xb201205004
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    The two cores of modern sediments lying in the West-branch-way of Yalu River estuary is characterized by better continuity, higher time resolution and most gulf sediments. The deposition rate, grain characteristics, detrital minerals and heavy metals were measured and analyzed. The depositing process from 1920 with an average rate of 0.98 cm/a in the upstream of West-branch-way was recorded in the core. The vertical distribution of grain parameters, indicative detrital minerals and heavy metals shows that the sediments were mainly from the estuarine deposit of marine phase alternated with the deposit of fluvial phase. In comparison with previous studies, the result reveals the impact of human activities on the riverbed evolution in Yalu River estuary during recent 100 years. The influence of water conservancy projects was mainly in the early period, which led to a great change in riverbed landform. The evolution caused by land reclamation occurred in the middle period and it also exerted a significant effect on riverbed landform and made the terrestrial area bigger and water area smaller continuously. The influence of human activities such as waterway regulation appeared in the middle and late period, during which there was no obvious change in the riverbed landform. The influence of latest human activities needs to be further studied.
  • Regional Climate and Its Change in the Nujiang River Basin
    FAN Hui, HE Daming
    2012, 67(5): 621-630. https://doi.org/10.11821/xb201205005
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    Long time series of monthly air temperature and precipitation data, which were recorded at 16 meteorological observation stations in the Nujiang River basin and its adjacent areas, were employed to analyze spatial distributions and changes of these meteorological elements in this basin during the past decades. In this research, TFPW-MK (Trend-free Pre-whitening Mann-Kendall) test and BFAST (Breaks For Additive Seasonal and Trend) were used to determine trends in climate data and to detect abrupt changes within the trend and seasonal components, respectively. The results show that air temperature and precipitation increased southward along the Nujiang River and heavily negatively correlated with altitude. The regional difference in PCD was obvious and higher PCD values, more than 60%, were observed in the Nujiang River basin in Tibet Autonomous Region. Precipitation-concentration time (PCT) in the study area (except for Gongshan) mainly from late July to late August. Generally speaking, the Nujiang River basin has become warmer in the past decades. The annual mean air temperature increases at a rate of 0.36 ℃/10a.
  • Temporal and Spatial Changes of Precipitation in Qilian Mountains and Hexi Corridor during 1960-2009
    JIA Wenxiong
    2012, 67(5): 631-644. https://doi.org/10.11821/xb201205006
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    Based on daily precipitation data of 18 weather stations in Qilian Mountains and Hexi Corridor during 1960 to 2009, the spatial and temporal changes of day number and intensity for different grades of precipitation were analyzed by the methods of linear trend, five-year moving trend, IDW, Morlet wavelet and Mann-Kendall. The results indicated that the spatial distributions of day number and intensity for different grades of precipitation changed from east to west and from south to north. In the last 50 years, the annual variations of day number of different grades of precipitation were increasing in most of the regions and the increasing scales are decreasing from east to west, which is consistent with the intensity of heavy rainfall events. However the annual variations present an increasing trend in some parts or decreasing in other parts in terms of the intensities of light rain, moderate rain and extreme rain. The annual changes of day number of different grades of precipitation showed an increasing trend, and they are significant for light rain, moderate rain and heavy rain. Intensity of light rain and heavy rain prohibited an unobvious decreasing trend, but it is opposite to intensities of moderate rain and extreme rain. The main change cycles of day number of different grades of precipitation have quasi-periods of 2a, 5a, 8a, 11a and 19a, and those of intensity of different grades of precipitation have quasi-periods of 2a, 5a, 11a, 15a and 25a. Except for the abrupt decrease in intensity of light rain, the day number and intensity of different grades of precipitation increased abruptly.
  • Evaporation Paradox in the Yellow River Basin
    MA Xuening, ZHANG Mingjun, WANG Shengjie, MA Qian, PAN Shukun
    2012, 67(5): 645-656. https://doi.org/10.11821/xb201205007
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    Based on the data of 72 meteorological stations in the Yellow River Basin from 1960 to 2010, this paper analyzed the changing trends in potential evapotranspiration and air temperature, and the main factors affecting the decrease of potential evapotranspiration. It also discussed the existence of the "evaporation paradox" (the contract between expectation and observation of evaporation). The results are indicated in the following aspects. (1) In the past 51 years, the air temperature increased significantly and the potential evapotranspiration decreased, therefore the evaporation paradox actually existed in the Yellow River Basin. (2) The "evaporation paradox" is not consistent spatially or temporally: as the temperature increased, potential evapotranspiration decreased in spring, summer and winter over most parts of Shanxi and Henan, and some parts of Gansu, Ningxia, Inner Mongolia, and Shaanxi. In the past 51 years, the changing trend of potential evapotranspiration is not significant from 1960 to 1979, and the changing trends of temperature and the potential evapotranspiration were negatively correlated at most of the stations. (3) In the past 51 years, the changing trends of annual, summer and autumn precipitation are not obvious, and the precipitation and potential evapotranspiration exhibit a contrary trend. (4) In terms of the contribution rate of meteorological elements change to potential evapotranspiration change, a significant decrease of wind speeds in the 51 years is the dominating factor leading to the decrease of potential evapotranspiration in the Yellow River Basin.
  • Quaternary Glacier Development and Environmental Evolution in Qianhu Mountain, Northwestern Yunnan Province
    ZHANG Wei, LIU Beibei, LI Yonghua, FENG Jun, ZHANG Bing, WANG Zhilin, LI Dapeng
    2012, 67(5): 657-670. https://doi.org/10.11821/xb201205008
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    The Qianhu Mountain, one of the regions with Quaternary glacial remains in the Hengduan Mountains, is intensively influenced by the southwestern monsoon and has the important scientific significance in the research not only on glacial characteristics in western and eastern China, but also on the relationship between the climate change and tectonic uplift in the bordering mountains of eastern Tibetan Plateau. Field investigations show that the Quaternary erosion and sediment geomorphology are preserved above 3500 m in the main peak of the Qianhu Mountains and its surrounding areas. Glaciers mainly depended on the planation surface (3900-4000 m) and its relevant valleys, and the glacier type belongs to the small ice cap and the valley glacier entered the branch valley. Using geomorphology method and the lab optically stimulated luminescence (OSL) dating of glacial periods, this paper confirms the glacial advance only occurred during the last glacial cycle (LGC), that is, last glacial maximum (LGM, 22.2 ± 1.9 kaBP) in the mid-last glacial cycle (MIS3b, 37.3 ± 3.7 kaBP, 45.6 ± 4.3 kaBP), and in the early stage of last glacial cycle (MIS4). The glacial extent of the MIS3b is larger than that of last glacial maximum. This might be caused by different climate events alternated with wet and dry conditions during different glacial stages. Compared with the multi-glacier sequences in the Hengduan Mountains, the Qianhu Mountain only experienced the glacial advance during the last glacial cycle. It is the tectonic uplift coupled with the climate change that led the Qianhu Mountain to the snowline and witnessed the glacial advance.
  • The Holocene Palaeoflood Events in the Yunxi Reach in the Upper Reaches of Hanjiang River
    ZHA Xiaochun, HUANG Chunchang, PANG Jiangli, ZHOU Yali
    2012, 67(5): 671-680. https://doi.org/10.11821/xb201205009
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    Through field investigation in the upper reaches of Hanjiang River, palaeoflood slackwater deposits (SWD) were found in the bedrock gorges in the Yunxi reach. Based on field observation, laboratory analysis including grain-size distribution and magnetic susceptibility, and comparison with modern flood deposits, this SWD is identified as the most typical Holocene palaeoflood deposits in the Hanjiang River basin. By using stratigraphic correlation and OSL dating method, the palaeoflood events were dated to 3200-2800 aBP at the turn from the middle to late Holocene. According to the palaeoflood peak stages and hydraulic parameters, the peak discharges of the palaeoflood were reconstructed to 48830-51710 m3/s by using the slope-area method. At the same time, the flood peak discharges of 1983, 2005 and 2010 extraordinary floods were reconstructed with the same method and hydraulic parameters in the same cross-section. The error between the reconstructed and gauged discharges is 1.99%-4.21%. This shows that the reconstructed palaeoflood peak discharges are reliable. The flood peak discharge-frequency relationship at 10000-year time scale is established by a combination of the data of gauged flood, historical flood and palaeoflood hydrology.
  • Gullies Evolution and Fault Activities in Dushanzi, Xinjiang
    QIAN Mang, LI Youli, SI Supei, LU Shenghua, WANG Yiran
    2012, 67(5): 681-688. https://doi.org/10.11821/xb201205010
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    Dushanzi anticline is the northwestern fold of the three fold belts in north Tianshan Mountains. A thrust fault has developed in the north limb of the fold. The fault movement caused scarps with a height of less than 20 m in the terraces and alluvial fans of Kuitun River. Gullies have developed on the upper stream alluvium of the scarp, which can be divided into 7 groups by length. Trenches revealed two latest faulting events of the north limb fault in Dushanzi anticline, the former occurred at 3110?40 a BP. The headwater erosion rate is 38 mm/a, deduced from the average length of gullies triggered by faulting. Based on the headwater erosion rate, the time of formation can be calculated for each group of gullies (1169 a BP, 3110 a BP, 7203 a BP, 12573 aBP, 14992 a BP, 30568 a BP, and 37745 a BP), which may coincide with occurrences of faulting events. The latest faulting age derived from headwater erosion rate is consistent with that discovered from trenches, and another three latest events are consistent with the previous studies on trenching. This result shows that under specific conditions it is applicable to estimate the time of faulting based on headwater erosion rate of gullies on uplift wall.
  • Changes of Kusai Lake in Hoh Xil Region and Causes of Its Water Overflowing
    YAO Xiaojun, LIU Shiyin, SUN Meiping, GUO Wanqin, ZHANG Xiao
    2012, 67(5): 689-698. https://doi.org/10.11821/xb201205011
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    Based on topographic maps, Landsat TM/ETM+ images, China Environment and Hazards Monitoring and Prediction Satellite (HJ1A/B) CCD images and meteorological materials observed at Wudaoliang meteorological station, we explore the change causes of Kusai Lake using geographical information techniques and mathematical statistics method. The results show that water overflowing Kusai Lake occurred in September 20-30 in 2011, and the direct reason was the flood from Zhuonai Lake flowing into Kusai Lake. In addition, Kusai Lake has been growing in recent decades; especially after 2006 it experienced a quick increase that formed the foundation of lake water overflow. The main factor resulting in the flood from Zhuonai Lake was the steady precipitation. Specifically, the heavy precipitation on August 17 and 21 made Zhuonai Lake water outflow on August 22, 2011; then continuous precipitation during August 31 to September 9, 16 and 17 subsequently formed a serious flood from September 14 to 21. Accordingly, there was a sudden drop in area of Zhuonai Lake. As of November 29, the lake decreased to 168.07 km2 (a reduction of by 104.88 km2), accounting for 62% of the area on August 22. The outflow water from Kusai Lake flowed into Haidingnuoer Lake, then into Yanhu Lake. The latter occurred during October 6-20. Due to sudden rapid flow, both Haidingnuoer and Yanhu lakes suffered a quick expansion from October to November, 2011.
  • Annual Variations in Climatic and Hydrological Processes and Related Flood and Drought Occurrences in the Poyang Lake Basin
    GUO Hua, HU QI, ZHANG QI, WANG Yanjun
    2012, 67(5): 699-709. https://doi.org/10.11821/xb201205012
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    Observational data from 1960-2008 were analyzed to obtain the mean annual climate and hydrological variations in the Poyang Lake basin, China. These variations were explained by the surface water and energy budgets, and the characteristics of these variations and the budgets were further used to deduce the rhythms of flood and drought developments in the lake basin. Some conclusions can be drawn as follows. (1) The precipitation in the lake basin increases at a large rate from January to June, reaching the annual maximum in late June. Amplifying monthly precipitation, particularly from April to June, coupled with weak surface evaporation and transpiration (ET), saturates the soils and produces a large amount of surface runoff which raises the lake level. In July, rainfall decreases sharply with clear sky and high ET, which reduces surface runoff and reverses the hydrological processes developed in the first half of the year. These drying processes continue through October, making the basin dry again. (2) When June and July have above average monthly precipitation the lake basin becomes supersaturated, and floods develop. In such conditions, if July rainfall in the middle and upper reaches of the Yangtze River basin is above average, the Yangtze River blocking (or reversed flow) effect can trigger, intensify, and prolong Poyang Lake floods. Thus, Poyang Lake floods generally occur in July and August. (3) Because the lake basin is drying after July with strong ET, if there is below average rainfall in July and the months afterwards, ET would be greater than rainfall, causing drying. Drought could occur in fall. This fall drought can persist through the winter and into the following spring and result in severe spring drought in the lake basin. Thus, the droughts occur in the fall and spring months in the lake basin. (4) The Yangtze River effects on the floods and droughts in the lake basin are most significant during the "river-lake coupling period" from July to August. Strong effects can lead to floods in the lake basin. Lack of river effects would help lower the lake level and dry the basin, leading to drought in fall.
  • Impact of Soil Water Variations on Wheat Yields on the Loess Plateau of Gansu
    PU Jinyong, WANG Runyuan, LI Xiaowei, ZHANG Moucao
    2012, 67(5): 710-718. https://doi.org/10.11821/xb201205013
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    Based on the data of wheat fields and soil moisture at the Xifeng Agrometerological Experiment Station from 1981 to 2010, the variation law of soil water and the relationship between the yield factors and soil water were discussed. The results showed that the maximum soil water storage occurred in growth stage before winter, followed by reviving to jointing stage, and the minimum in booting to mature stage. The maximum soil water consumption was observed in booting to mature stage, followed by growth stage before winter, and the minimum in reviving to jointing stage. It is also shown that the soil water storage at depths of 200 cm and 100 cm decreased and water consumption at depths of 200 cm and 100 cm increased with trend of fluctuations. The utilization efficiency of soil water increased in a linear trend and the turning point occurred in 1998. There is significant relationship between the infertility spikelet rate and soil water storage at depths of 200 cm and 100 cm. The correlation between soil water storage in different layers and TKW (thousand kernel weight) can be estimated through the method of hypothesis testing, and the deeper the layer of soil water storage, the higher the correlation coefficient was. The correlation between ear number and soil water storage in different layers in growth stage before winter and the period of reviving to jointing could pass 0.1 and 0.01 reliability testing respectively. The soil water storage in different layers in growth period and actual yields in test field were correlated prominently. The value of aj(t) was 20 kg in 1 ha at a depth of 1 mm in soil water during the second ten days in May. There is negative correlation between water consumption at 100 cm depth and infertility spikelet rate. The TKW and water consumption in different soil layers was closely correlated.