Study On The Driving Force Analysis And Suitable Scale Of Oasis In The Manas River Basin

Oasis is the basis for human survival in arid and semi-arid regions.With the increase of climate change and human activities,the oasis ecological environment in the arid regions is deteriorating.The establishment of a sustainable oasis has become the primary goal of humans in the arid regions.Based on the remote sensing interpretation,hydrological data,meteorological data and socio-economic data,this paper analyzes the changes of the artificial oasis,natural oasis and oasis total area in the Manas River Basin.Principal component analysis was used to construct the oasis change driving index system from natural and human factors.The driving force of artificial oasis,natural oasis and oasis total area change was discussed.The evolution process of hydrological drought in the basin was further analyzed.The stability of the basin oasis under the influence of drought,based on the suitable scale of the constructed oasis,determines the suitable scale and suitable cultivated land area of the Manas River Basin oasis.Research results can provide a scientific basis for the sustainable development of the Manas River Basin oasis.The main conclusions are as follows:(1)Analyzed of the changes of artificial oases,natural oases and oasis in Manas River Basin and their driving forces.The results show that from 1990 to 2015,artificial oasis increased by 3118.47 km~2 and natural oasis decreased by 2310.40 km~2.The main sources of the increase of artificial oasis area are cultivated land,construction land and water.The increase of cultivated land is the most obviously.In 26years,cultivated land area increased by 2841.19 km~2,with an average annual increase of 109.28 km~2.The main source of reduction of natural oasis area was grassland and woodland,of which grassland decreased most obviously.In 26 years,the area of grassland decreased by 2287.91 km~2,with an average annual decrease of 87.99 km~2.From the whole basin point of view,the oasis area of Manas River is much larger than reduced the oasis area,and the Manas River Basin oasis is developing towards an increasing trend.Among them,2010-2015 is the peak period of oasis area growth,followed by 1990-2000,and the oasis growth is the slowest in 2000-2010.The change of oasis is the result of population growth,agricultural technology improvement and socio-economic development.Among them,population growth and agricultural technology improvement are the dominant factors affecting the increase of natural oasis and artificial oasis in Manas River Basin.(2)Revealed of the evolution process of basin drought under different time scales.The results show that the drought in the Manas River Basin has a weakening trend on the monthly,seasonal and annual scales,and the drought has weakened significantly after 1995.The frequency of drought on the monthly scale is 33.05%,mostly in light drought and moderate drought,and March and October are frequent periods of drought.The seasonal scale is prone to autumn drought and winter drought,and the frequency of occurrence is 35.00%and 31.67%,respectively.The frequency of drought on the annual scale is 28.81%,mainly in light drought and moderate drought.The main cycle of the 32-44 year scale and the main cycle of the 44-year scale exist in the seasonal and annual scales respectively.In the next cycle,the basin-scale and annual-scale droughts will increase.(3)Analyzed of the stability of the oasis under the influence of drought in Manas River Basin,and the suitable scale and suitable cultivated land area of the Manas River Basin oasis were determined.The results show that from 1990 to 2015,the oasis in the Manas River Basin has been in a metastable state,and the form of oasis stability is not very optimistic.With the influence of the 44-year main cycle drought in the basin,the stability of the basin oasis will be further threatened.The application of the Oasis Appropriate Scale Model to the Manas River Basin Oasis Research found that the suitable scales of the Manas River Basin oasis in 1990,2000,2010 and 2015 were 4132.04 km~2,32.5.86 km~2,4481.06 km~2,3942.28 km~2,respectively.suitable arable land area is 1652.82 km~2,1450.35 km~2,1792.42 km~2,1576.91 km~2,respectively.Compared with the actual area and actual cultivated land area,the suitable scale and suitable cultivated land area of oasis are much smaller than the actual scale and actual cultivated land area.In order to ensure the stability of the oasis,the Manas River Basin should reduce the scale of the oasis and strictly control the continuous growth of the cultivated land area.