Study On Dynamic Change Characteristics And Driving Forces Of Land Use Landscape Fragmentation In The Mid-Sichuan Hilly Region

Landscape fragmentation is a significant manifestation of human activities on the natural environent.Quantitative analysis of its evolution process and driving force can reproduce the dynamic changes of the surface landscape,and provide ideas and references for the optimization of land use landscape patterns and efficient and rational use of land resources.The Mid-Sichuan hilly region is the most typical Fangshan hilly region in China.It has a large population and high land utilization rate.It is the main agricultural and economic zone in Sichuan Province.However,the ecological and environmental probles such as soil erosion and over-slope reclamation are serious.This study takes Yanting County,a typical county in the Mid-Sichuan hilly region,as the research object,based on the theories of landscape ecology,and uses the remote sensing images of 1987,1997,2007,and 2017 as data sources,use RS and GIS spatial analysis technology to extract land use landscape type data.Use spatial overlay analysis,land use dynamics,and transition matrix model to analyze land use landscape dynamic changes and terrain gradient effects;use landscape indices to analyze land use landscape fragmentation patterns characteristics;use principal component analysis to analyze the primary and secondary driving forces of landscape fragmentation.The main conclusions of the study are as follows.(1)The forest land accounts for more than 59%of the study area,which is the matrix landscape of Yanting County.From 1987 to 2017,the total amount of cultivated land and construction land changed most significantly.The areas of cultivated land,forest land,and grassland decreased by 3179.99hm~2,715.95hm~2,and 23.13hm~2,and water area,construction land,and unused land increased by 581.13hm~2,3329.73hm~2,and 6.21hm~2.The relationship of the transfer change between cultivated land,forest land,and construction land is particularly close.The rapid increase in construction land is mainly due to the expansion of central urban areas and administrative towns and the construction of Chengdenan and Mianxi expressways.The increase in water area is mainly due to the construction of large reservoirs such as Lianhuahu Reservoir.(2)Land use landscape types in Yanting County have obvious terrain gradient effects.Unused land,construction land,and water area are dominantly distributed at elevation grade 1.Water area,cultivated land,grassland,and construction land are dominantly distributed at slope grade 1.Cultivated land and forest land are dominantly distributed at elevation grade 2.Cultivated land is dominantly distributed on elevation grade 2.On the elevation grades 3 and 4 and on the slope grades 3 and 4,the forest land is absolutely dominant.Yanting County should continue to implement the policy of returning farmland to forest on elevation grade 4 and slope grade 4 to continuously enhance the distribution advantages of forest land,and implement protective reclamation of cultivated land on slope level 3,and strengthen water and soil conservation measures.(3)From 1987 to 2017,the fragmentation of the land use landscape in Yanting County continued to deepen,the dominance of the matrix landscape declined,and patches were scattered.Every land use landscape type has different degrees of fragmentation and deepening trend.Forest land is the least fragmented.Affected by human activities,economic development,and urbanization,the number of patches on construction land and cultivated land has increased,and the shape of patches has become more complicated,with fragmentation being the most serious.(4)In this study,18 driving indicators were selected for principal component analysis,and 3 principal components were extracted,with a cumulative contribution rate of91.695%.The first principal component contribution rate is 54.001%,which is highly correlated with 10 indicators that reflect the situation of infrastructure construction and economic development level.The second principal component contribution rate is20.713%,and the third principal component contribution rate is 16.982%,which is highly correlated with indicators that reflect the level of agricultural development and urbanization.The primary driving force of the landscape fragmentation in Yanting County is economic development and basic construction,and the secondary driving force is agricultural development and urbanization.The synthesis scores of driving forces showed an overall upward trend.After 2007,the synthetic score was positive and showed a rapid growth.The influence of human activities on landscape fragmentation has greatly increased.