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Land cover changes and the effects of cultivation on soil properties in Shelihu wetland,Horqin Sandy Land,Northern China

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Journal of Arid Land 2013年第1期5卷 71-79页

作者： Jie LIANI XueYong ZHAO XiaoAn ZUO ShaoKun WANG XinYuan WANG YongQing LUO Naiman Desertification Research Station Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China University of Chinese Academy of Sciences Beijing 100049 China

Land cover change plays an essential role in the alternation of soils properties. By field investigation and applying satellite images, land cover information in the Shelihu wetland was carried out in an area of 2,819 hm2 in 1985, 1995, 2000, 2005, 2010 and 2011, respectively, in Horqin Sandy Land. A total of 57 soil sampling sites across Shelihu were chosen in wet meadow （CL0）, cropland （CL） and sandy land （SL） according to the spatial characteristics of water body change. Soil texture, organic carbon （SOC）, total nitrogen （TN） and total phosphorus （TP） contents, electrical conductivity （EC） and pH were measured at the soil depths of 0-10, 10-20 and 20-40 cm to examine the influence of agricultural conversion and continuous cultivation on soil properties. The results showed that the study area was covered by water body in 1985, which gradually declined afterwards and then reclaimed rapidly at a mean annual rate of 132.1 hm2/a from wet meadow to cropland since 1995. In 2011, water body was drained and the area was occupied by 10.8% of CL0, 76.9% of CL and 12.3% of SL. Large amounts of SOC, TN and TP were accumulated in the above depths in CL0. Soil in CL0 also had higher EC and silt and clay fractions, lower pH than in SL and CL. Soil in SL was seriously degraded with lower contents of SOC, TN and TP than in CL and CL0. SOC, TN content and EC in CL decreased with the increase of cultivation age, while pH showed a reverse trend with significance at plough horizon. The agricultural conversion in Shelihu was driven by the comprehensive factors of precipitation reduction, economic development and intense competitions for irrigation water. continuous cultivation in this process is not sustainable because of SOC degradation and nutrient content reduction. The key point is that conventional tillage and removal of residuals induced further land degradation. Wetland reclamation for immediate economic interests led to greater costs in the long-term environmental restoration i

关键词： wetland soil degradation wetland reclamation continuous cultivation Horqin Sandy Land

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Miniaturized Bioreactor for Cell cultivation in Space

Miniaturized Bioreactor for Cell Cultivation in Space

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第二届仪器科学与技术国际学术研讨会

作者： Pang Changlin Wang Xiaohao Zhou Zhaoying Zhu Liang Wang Tiejun Ku Guoxian Dept. of Precision Instruments and Mechanology Tsinghua Univ. Beijing

＜正＞ The new miniaturized bioreactor designed for continuous cultivation of cells or tissues in space, is described in detail. The bioreactor is composed of flow control system, temperature control system and air pressure control system. A new kind of precision screw mini-pump was designed and fabricated for the purpose of supplying fresh nutrient medium at an adjustable rate. Temperature control system and air pressure control system are all closed-loop systems and can be used to achieve high control precision. The instrument is automatically controlled by microcontroller. Cell cultivation experiment used by this bioreactor is successful on earth.

关键词： Bioreactor Microgravity continuous cultivation

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