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Water And Heat Balance And Its Coupling Simulation At Transitional Region Between Oasis And Desert

Posted on:2003-09-24Degree:DoctorType:Dissertation
Country:ChinaCandidate:B WangFull Text:PDF
GTID:1100360092496830Subject:Ecology
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The oasis ecosystem is a typical fragile terrestrial ecosystem, whose ecological balance is badly demolished in the recent years. After long-term evolvement and human disturbance, Minqing oasis located at the transitional belt between Tenggeli desert and Badanjilin desert, has become a typical arid area in the northwest part of China. Many researches show that water and heat can restrict the restoration of degraded ecosystem, and the restoration process of degraded ecosystem is the gradual improvement process of environmental conditions. Therefore, it is imperative to research water and heat conditions, analyze the laws of water and heat balance, enhance utilization efficiency of water source on the basis of adjusting water and heat resources to optimize water and heat structure in order to promote the restoration and reconstruction of the ecosystem as soon as possible for preventing and curing desertification.The research targeted minqin oasis area, at the transitional belt between Badanjilin desert and Tenggeli desert, where a 2km sample belt, was established, along the prevailed direction of wind causing desertification. With 3 different gradient types of vegetation coverage (Tamarix ramosissima shrub sand dune, Nitraria sibirica shrub sand dune and shifting sand dune) as the research subjects, such ecological factors as water, soil, cliamte and physiology were observed with 3 automatic meteorological stations. Then their laws of water and heat balance were studied; coupling simulations were made on SPAC water and heat transfer, exchange, and soil water and heat flow in the oasis transitional region. All of these will provide scientific theoretical basis for development on the optimized model of water and heat structure and the prevention and cure of desertification in the region. The content and the main conclusions were as following:1) The conditions of water resources in the region and the neighbouring areas were surveyed and the process and characteristics of oasis-desert hydrology were analyzed. According to the character of water scarcity in the arid and semi-arid regions, water conditions, temporal and spatial patterns as well as dynamic law of soil moisture at the oasis transitional belt were systemically analyzed, Some analysis results are as follows: â‘ The change of soil water contents among years was not obvious in Tamarix ramosissima sand dune and Nitraria tangutorum sand dune, but it was great in Shifting sand dune, with the maximum of 2.538%; â‘¡The order of average monthly soil water contents in the depth of 0 to 80cm at different places is Tamarix ramosissima sand dune (5.61%) > Nitraria tangutorum sand dune (5.47%) > shifting sand dune (5.22%). The seasonal dynamics can be divided into three periods: accumulating period, consumptional period, stable peorid;â‘¢Vertically, along with the depth adding increases soil water content, which is influenced by such exoterical factors as vegetation, weather, and human activities. The vertical distribution of soil water in shifting sand dune is terribly uneven, with the largest difference of 13.81%. By comparison, the distribution in Tamarix ramosissima sand dune is very even, showing that Tamarix ramosissima sand dune has a better hydrological effect; â‘£Soil water contents are different on different slopes. In general, soil water content on the lower slope is obviously higher than the ones on the upper slopes as well as on the middle slopes,with maximum at 15.408%. 2)And the variational characteristics and laws of actual evapotranspiration of the vegetation-covered surface were emphatically studied. In the diurnal process of evapotranspiration, the maximum or minimum evapotranspiration of Tamarix ramosissima sand dune or Nitraria tangutorum sand dune come 1 to 2 hours earlier than that on the shifting sand dune. The order of maximum evapotransipirations on different places is: Tamarix ramosissimasand dune (0.24mm/h) > Nitraria tangutorum sand dune (0.20mm/h)> shifting sand dune (0.18mm/h). Through grey correlation anal...
Keywords/Search Tags:Minqin, oasis area, water and heat balance, evapotranspiration, water and heat transfer, coupling simulation
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