Study On Ecological Water Requirment Of Vegetation In Xinjiang Region Based On GIS

Xinjiang has typical continental arid climt characteristics, including rich sunlight, longtime-sunshine, big diurnal variation of temperature, small rainfall and big evaporation. Andclimt characteristics have signifisent difference in temporal and spatial. Lack of water re-source caused by arid is the main limiting factor of economic construction. So it is really im-portant to exploit and use the limited water resource. Humen overemphasizes the target ofmeeting economic water need and neglects ecosystem water requirement seriously, for vege-tation is an important part of ecosystem, so it is necessary to make study on ecological waterrequirement of vegetation in arid and semiarid areas. Xinjiang, which is a typicalarid-semiarid area in northwest of china, was chosen as the study area.In this paper, meteorological dates of42weather stations in Xinjiang and Pen-man-Monteith equation were used to estimate ET0at daily and monthly time scales. Multi-ple-variable regressions between ET0and4main climatic elements(temperature, wind speed,sunshine hours, relative humidity)were conducted to obtain empirical equations for calcu-lating ET0. The ET0combined with soil moisture parameter and plant parameter can calculatevegetation ecological water requirement quota of three typical plants in Xinjiang. Then com-bining vegetation ecological water requirement quota with vegetation growth periods, waterrequirements in unit area of three typical plants in different growth stages were obtained.Making use of software ArcGIS' spatital analysis function, the spatital distribution of ET0andvegetation ecological water requirement quato of three typical plants in Xinjiang can be ob-tained. In addition, using software ERDAS9.2to deal with the remote sensing images, areasof three typical plants in Urmuqi, Habahe, Jimunai and Aletai can be obtained. Combinedwith unit area vegetation eclolgical water requirements of three typical plants in differentplaces, ecological water requirements of vegetation in different places can be obtained, thenminus rainfall between March and November, the vegetation ecological water shortage in dif-ferent places are obtained. The main conclusions were as follows:(1) The overall trend of annual ET0's spatial distributions were roughly the same at daily and monthly scales. Both of them had significantly lagere ET0value in southern part than thatin northern part and the ET0value showed a trend of increasing from northern to southern. ET0value had significant coorelations with temperature, wind speed, sunshine hours and relativehumidity both at daily and monthly time scales, so both of the two multiple-variable regres-sion formulas are reasonable and reliable and both of them can be used as empirical formulasto estimate ET0in different parts of Xinjiang.(2) Annual soil moisture limit coeffcient changed in a small range, and its spatital distri-bution showed a trend of discrease from north to south. The plant parameters in differentplaces were significantly different in initial growth stage and the difference in middle and lategrowth stages is small. Spatital distribution of plant parameter in initial growth stage was se-miliar to that of ET0, but the spatital distribution of plant parameters in middle and late growthstages were semiliar to that of wind speed and relative humidity.The variation of unit area vegetation ecological water requirement of three typical plantshad semiliar trend in every growth stages: all of them discreased from north to south in the in-itial growth stages, increased from north to south in middle and late growth stages. The varia-tion of unit area vegetation ecological water requirement in whole growth stage was semiliarto that in middle and late growth stages.(3) Grass ground was the main vegetation in Urumqi, Habahe, Jimunai and Aletai, treesand shrubs accounts for a small percentage of the total vegetation area. Habahe county had thelargest vegetation cover rate, with a coverage rate of58.2%. Jimunai county had the smallestvegetation cover rate, with a coverage of27.8%. The vegetation ecological water requirementshowed a trend of increase from west to east in Habahe county etc, in northern part of Xinji-ang. Except in Aletai county, the effective rainfall could't meet the need of shrub eclolgicalwater requirement, there was no vegetation ecological water shortage for grass and shrubs inWulumuqi, Habahe and Jimunai counties. And all of the four counties existed vegetation eco-logical water shortage for tree.(4) In the region of Habahe-Jimunai-Aletai, spatital distribution of vegetation ecologicalwater requirement of three typical plants all showed a trend of increase from west to east, andspatital distribution of total vegetation ecological water requirement also showed a trend ofincrease from west to east.