Reconstruction Of Cultivated Land Pattern In The Manas River Basin In Xinjiang Since The Qing Dynasty

Land use and land cover changes plays a very important role in the global environment,is to adapt to the environment for the survival and sustainable development of human society one of the most direct expression of changes,changes as a global or regional prediction model parameters,is very important in the global environmental change of the research history and the future trend prediction plays an important role.The reconstruction study of land use/land cover change in historical period,especially in the past 300 years,can not only well show the development process of land in historical period,but also reveal the environmental impact and human response caused by land development in the past.High resolution and high precision land use/cover data with spatial attributes are the key to in-depth analysis of the environmental effects of land use/cover changes(especially climate effects).The Manas river basin in Xinjiang is a representative area of oasis in arid region.Since the Qing dynasty,the development of this region has been gradually strengthened.The analysis of land use/land cover changes in the historical period is of great significance to understand the development history of this region and explain the regional and even global environmental changes.In this paper,the spatial distribution pattern of cultivated land in Manas river basin since the Qing dynasty is reconstructed by revising the existing research methods according to the regional characteristics by using the documents such as gazetteers,local gazetteers and geographic information technology.The following conclusions are drawn:(1)Since the Qing dynasty,the number of settlements in the Manas river basin gradually increased,and the settlement density center gradually moved to the northwest.From the perspective of the time evolution process of settlements,the settlement growth of Manas river basin can be divided into three periods:the slow growth period(1762-1861),the rapid growth period(1862-1949)and the high-speed growth period(1950-1985),which also reflects the three processes of land development in the Manas river basin.The settlement policy,inland migration,water conservancy construction and other cultural factors are the important factors for the settlement to gradually increase over time.The evolution of settlement density centers also reflects the changes of settlements over time.From the perspective of spatial evolution of settlements,the settlements in Manas river basin are concentrated in the front of the alluvial fan in front of the mountain.The region's gentle topography,fertile soil and superior thermal and water conditions make it suitable for settlement and land reclamation.In addition,natural conditions also have a certain impact on water conservancy construction,road construction,etc.,which indirectly affects the establishment and development of settlements.The deterioration of natural environmental conditions also leads to the migration or even disappearance of settlements.(2)The cultivated land area and spatial distribution of cultivated land in historical period can be reconstructed to a certain extent based on settlement and cultivation radius.Based on the two methods of "mean tillage radius" and"reclamation coefficient",combined with settlement distribution and tillage radius,the cultivated land distribution in the Manas river basin in the 1980s was reconstructed,and the reconstruction results were compared with the remote sensing inversion results in the Manas river basin in the 1980s.Comparing the two reconstruction results,when the tillage radius is 1430m,the cultivated area in the buffer zone accounts for 53.24%of the actual sown area.When the tillage radius is calculated based on the result of reclamation coefficient,the cultivated land area in the buffer zone accounts for 55.66%of the actual sown area.Therefore,the scale of settlements,including cultivated land area and administrative area,should be taken into full consideration when reconstructing cultivated land distribution by using settlement and tillage radius.At the same time,the reconstruction results also reflect that there are some differences in the degree of agricultural development in the Manas river basin.(3)The cultivated land area of Manas river basin was rebuilt since the qing dynasty.Taking into account such factors as "private land" or "private cultivation land" in the Manas river basin,omission and concealment,this paper corrects the registered land area in the historical documents,and rebuilds the actual cultivated land area of the six time sections of the Manas river basin in 1778,1806,1819,1863,1909 and 1944.It can be seen that the change of cultivated land area in Manas river basin has a certain volatility since the Qing dynasty.The reclamation of Manas river basin is divided into three stages:development,decline,recovery and development.(4)The spatial pattern of cultivated land in two time sections of Manas river basin in 1909 and 1944 was reconstructed by using grid model.Based on the existing research results,this paper improves the model,establishes the cultivated land grid reconstruction model suitable for the Manas river basin,and establishes the cultivated land grid data of the 1909 and 1944 time sections of the Manas river basin.By comparing with the data of 1910s and 1940s Manas river basin in HYDE3.2,it was found that the reclamation rate of HYDE data was higher than the reconstruction result on the whole.