| With the acceleration of urbanization,problems such as contradiction between man and land,ecological deterioration and environmental pollution have appeared one after another,and study on land use change,regional ecological quality and regional ecological security pattern have emerged.How to ensure the ecological security and quality of the region as much as possible in the process of promoting urbanization in an orderly manner has become an urgent problem to be solved.On this basis,China’s first inland new area,Liangjiang New District in Chongqing,is regarded as a research area,based on the regional reality,and the remote sensing image data of the three phases of 2001,2010,and2018,combined with land use changes,the regional ecological environment constructs the ecological security pattern of the study area,and the changes in the ecological environment and the evolution of the ecological security pattern in the Liangjiang New Area during the different research stages were analyzed.Therefore,some optimization suggestions were put forward to provide reference for the urban ecological planning and construction of the study area and the improvement of the environment.The main research conclusions were as follows:(1)From 2001 to 2018,arable land and construction land accounted for the largest proportion of land use types in the study area,followed by woodland,water area,grassland and unused land.In terms of land use types,the largest land type in the study period was cultivated land,which accounted for 79.58%in 2001,70.17%in 2010 and decreased to 53.98%in 2018,the annual decline rate of cultivated land area was about1.79%.The construction land increased from 58.32km~2 in 2001 to 359.63km~2 at the end of the study period,with an average annual increase of 16.74km~2 and an average annual growth rate of 28.70%.Forest land,water area,grassland and unused land change slowly during the whole study period,and the range is basically stable at about 0.2%.From the perspective of land use dynamic attitude,the land use dynamic attitude of construction land reached 28.7%from 2001 to 2018,with a rapid change rate and an increase as the main trend.Waters and woodlands have smaller changes,and the absolute value of dynamic attitude is less than 1%.The study of landscape pattern indicators showed that the landscape pattern of Liangjiang New Area tends to be broken and the landscape richness was increased.From the overall landscape level index,the landscape heterogeneity of the study area has been enhanced,showing that the fragrance diversity index has increased from 0.7161 to 0.9095,with an annual growth rate of about 3.01%,and the fragrance uniformity index has also increased from 0.3996 at the beginning of the study to 0.6000 at the end of the study,with an overall annual growth rate of about 2.95%.The landscape types of cultivated land,woodland and grassland are fragmented to varying degrees,which further affects the species energy balance in the ecosystem of the study area.The average patch area and maximum patch index of construction land increase with the increase of years,and the spatial distribution changes from scattered to concentrated.(2)From 2001 to 2018,changes in the ecological quality of the Liangjiang New Area have shown a decline.The ecological quality of the study area in 2001,2010 and 2018was quantitatively analyzed by constructing remote sensing ecological index with four indexes of green degree,humidity,heat and dryness.The results showed that among the four indexes,dryness and heat index had negative effects on the regional ecological environment,and the increase of green degree and humidity index could effectively improve the regional ecological quality.During the study period,the dryness and heat index were increased,while the green index decreased year by year,so the average value of RSEI decreased from 0.7704 to 0.6577.Modeling the RSEI and four indicators through stepwise regression analysis found that the dryness and greenness indicators have a greater impact on ecological quality.The RSEI was divided into five grades,the areas with excellent and good grades have decreased,and most areas in the study area have a one-level decline in ecological quality.From 2001 to 2010,the ecological environment quality of every street in Liangjiang New Area decreased,especially Dazhulin Street(decreased from 0.7306 to 0.5836),Yuanyang Street(decreased by about 42%)and Yuelai Street(decreased by about 0.1209 in RSEI value).From 2010 to 2018,the RSEI average of some streets(towns)increased to varying degrees,but the overall ecological quality level of the study area still declined mainly.(3)During the study,the overall ecological security level of Liangjiang New District has been reduced.During the study period,the proportion of ecological sources decreased from 10.78%to 10.63%,and the spatial distribution was mainly concentrated in the four major mountain ranges(from left to right:Zhongliang Mountain,Tongluo Mountain,Mingyue Mountain,and Longwangdong Mountain)and along the Liangjiang.The administrative units along the coast mainly include Caijiagang,Fuxing Town,Muer Town,Gulu Town,Guojiatuo,Tieshanping,Longxing Town,Shichuan Town,Yufengshan Street,etc.,while Cuiyun Street,Huaxin Street,Longshan Street,Tiangong Street,Renhe Street are rarely distributed,which is consistent with the spatial distribution of forest land,waters,and some arable land of a certain scale.The ecological resistance value was divided into 5 grades,and the total area of areas with high resistance has increased by16.30km~2 from the beginning of the study period to the end of the study period,while the areas with low resistance have decreased by 6.17km~2.The number of ecological corridors has been reduced from 12 in 2001 to 8 in 2018,and the total length has been reduced by about 41.35km~2.The ecological nodes have also been reduced from 18 first-class ecological strategic points in 2001 to 11,and second-class ecological strategic points have decreased from 33 reduced to 18.(4)After studying the land use change,ecological quality and ecological security level of Liangjiang New District in Chongqing,it’s suggested that ecological components such as ecological source,corridor and strategic point should be considered in urban planning and construction,so as to create alternate distribution between construction land and small ecology in the city,maintain the advantages of natural landscapes such as forest land and water area as much as possible,repair the fragmentation of regional patches and enhance the connectivity between patches such as forest land and arable land.Delineate the"ecological red line",strengthen the protection of ecological sources to optimize the ecological security pattern at the source,protect different resistance areas to slow down the further expansion of ecological resistance,and strengthen the construction of ecological corridors,radiation channels and ecological strategic points to improve the connectivity between ecological sources,urban areas and natural ecology. |
