Spatial-temporal Changes Of Ecological Benefits In Mountain Cities Based On GEE Cloud Platform

Since the 21 st century,with the rapid economic development,the process of industrialization and urbanization accelerate gradually,a lot of ecological space has been invaded and caused a series of ecological environmental problems such as resource waste,environmental pollution,ecological destruction and so on,which seriously restricts the sustainable development of our economy.Mountainous area accounts for about one third of China’s national land area,with large topography and complex natural environment,and weak ability to bear prone ecological problems.Monitoring and analyzing the change of ecological benefits of mountainous cities using multi-period remote sensing data can provide data support for regional sustainable development.Most of the existing analyses on the change of ecological benefits focus on simple elements such as relatively single land class and service,or the research scale is small,and there are few research results on complex ecosystems in large-scale regions..In this thesis,Chongqing was selected as the research area.Firstly,Landsat and Sentinel-2 remote sensing images from 2010 to 2022 were used as the main data sources,and land use classification was conducted based on GEE cloud platform and random forest method.Then from the perspective of ecosystem service,according to the construction principle of evaluation index system and the natural ecological environment of the research area,the ecosystem service function and value evaluation index system are established.Finally,the temporal and spatial changes of ecological benefits are reflected through the quantitative analysis of ecosystem service function and its value.The main conclusions of the thesis are as follows:(1)From 2010 to 2022,the spatial distribution of land use types in Chongqing was generally consistent.The change trend of forest land area is increasing year by year,which is the most widely distributed and the largest land type in Chongqing city.The grassland area is in dynamic change,the cultivated land area shows a trend of decrease year by year,the building land shows a trend of increase year by year,and the water area is in a basic equilibrium state.Based on the analysis of land use transfer matrix in the past 12 years,the five land use types in Chongqing showed the characteristics of "one to more" changes,among which the transfer changes of grassland,cultivated land and building land were more significant.(2)From 2010 to 2022,the overall level of ecosystem service function showed an increasing trend year by year.The distribution pattern of soil conservation service function levels was consistent with the spatial distribution of vegetation factors,which showed that soil conservation function was higher in areas with high vegetation coverage and lower in areas with low vegetation coverage.From 2010 to 2022,the function grade of water conservation service with the largest area proportion increased year by year.The area of areas with good biodiversity service function levels showed an obvious growth trend during 2016-2022.From 2010 to 2022,the net primary productivity and vegetation coverage decreased from southeast to west,and the ecosystem quality increased year by year.According to the trend of change,the ecological quality of more than half of Chongqing showed an increasing trend.(3)From 2010 to 2022,the value of ecosystem services and the total value of ecosystem services showed an increasing trend year by year.In the study area,the forest land had the highest soil conservation service value,followed by the grassland,and the building land had the lowest soil conservation service value.In 2022,the total value of ecosystem services was 757.208 billion yuan,an increase of 386.172 billion yuan compared with 2010,mainly from the increased value of water conservation services,accounting for more than half of the value,while soil conservation services and biodiversity services accounted for about 20% of the value.To sum up,Ecosystem services such as soil conservation,water conservation and biodiversity were evaluated by index and equation model,and the value of ecosystem services was quantified by equivalent factor method to comprehensively analyze the temporal and spatial changes of ecological benefits in Chongqing.This thesis analyzes land use change based on multi-source sequential remote sensing images.Compared with the previous analysis by direct use of product data,it has advantages of strong current situation and rich monitoring period,which can better grasp the trend of land use change in the research period.Based on the analysis of land use change and the results of ecosystem service function and value assessment,it can reflect the rationality and implementation of ecological protection policies in this region in the past 12 years,and also provide data basis for the subsequent formulation of ecological protection policies and the realization of regional sustainable development.