Landscape Evolution And Fragmentation Process Of Cultivated Land In The Middle Reaches Of Heihe River

Cultivated land,as a type of landscape that people have been engaged in agricultural production activities for a long time on the basis of natural landscape,is an important part of land use change research.Farmland plays an irreplaceable role in safeguarding national food security and ecological security,promoting social and economic development.Due to rapid economic development and urbanization,Chinese cultivated land is facing a declining problem.Against the backdrop of the continuous reduction of cultivated land in the country,the cultivated land in the arid region of Northwest China has shown a clear trend of increase.This not only changed the spatial distribution pattern of cultivated land in our country,but also exacerbated the contradiction between supply and demand of water resources in the process of socio-economic development in the arid region of Northwest China.Therefore,the study on the dynamic evolution of cultivated land landscape and its driving mechanism in the arid region of northwestern China helps to clarify the process and mechanism of cultivated land evolution in the region.It makes a lot of sense for ensuring food security of the country,promoting the sustainable development of the ecological environment and social economy in the region.Taking the middle reaches of the Heihe River as an example,this paper analyzes the spatial characteristics of cultivated land landscape changes in the middle reaches of the Heihe River using the methods of change trajectory analysis and land-use conversion models.By using the type change tracking model based on the moving window technology and spatial morphological criteria,the appropriate scale and the optimal window scale of the landscape fragmentation model of the middle reaches of the Heihe River.Meanwhile on this basis,the spatial fragmentation pattern of cultivated land landscape in the middle reaches of Heihe River is analyzed.The spatial regression model was used to analyze the impact factors of cultivated land landscape evolution.The main results show that:(1)During the study period,the landscape of cultivated land in the middle reaches of the Heihe River continued to expand and shrink.The expansion of cultivated land is the main trend of its evolution.The spatial self-adjacency of the cultivated land landscape shows an increasing trend,and the degree of spatial distribution agglomeration is further strengthened.The transfer of cultivated land is mainly grassland and unused land.In the later stage of the study,unused land has become the main reserve for expansion,leading to an overall increase in spatial co-ordination between cultivated land and unused land.The conversion of cultivated land is mainly forest land and construction land.The demand for ecological environment construction and the advancement of urbanization have enhanced the transformation of cultivated land to construction land and forest land.(2)Using the type change tracking model to represent the spatial fragmentation of cultivated landscaping,finally,the optimal scale for the study to determine the model for crushing farmland landscape in the middle reaches of the Heihe River is 150 m × 150 m ~ 450 m × 450 m,and the best scale is 350 m × 350 m.The area of core farmland during the evolution of the fragmentation pattern of cultivated land landscape continues to increase,and marginal and patchy cultivated land continue to decline.The fragmentation type of cultivated land landscape presents a spatially inverse fragmentation process of "non-cultivated land? patchy cultivated land? marginal cultivated land,porous cultivated land? core cultivated land".(3)It can be known from the spatial econometric regression model that the landscape evolution process of cultivated land has a significant impact on the spatial pattern.At the same time,the water resources factor is an important factor that affects the spatial fragmentation pattern of arable land landscape,and it is also the key factor of the arable land landscape fragmentation.The closer the cultivated land is to the residential area,the easier it is to be occupied.Thus,it can result in fragmentation of cultivated land.This is due to the fact that the agricultural production in the study area has a relatively high comparative advantage,which encourages agricultural operators to expand the scale of agricultural production and leads to a counter-fragmentation of the spatial pattern of cultivated land landscape.