| Monitoring the change of vegetation coverage and evaluating its ecological effect have important reference value for the government to rationally plan urban development and improve the ecological environment.In this paper,Lanzhou New Area was selected as the research area and Landsat8 OLI/TIRS satellite images for 2013 and 2017 were used as main data sources.Combined with the characteristics of semi-arid climate in the study area,the Soil Adjusted Vegetation Index(SAVI),the Normalized Difference Moisture Index(NDMI),the Land Surface Temperature(LST)and the Normalized Difference Soil Index(NDSI)were represent of greenness,wetness,heat and dryness to measure the regional ecological environment quality.Then,the remote sensing ecological index(RSEI)was established by principal component analysis method and it was used to analyze the spatial and temporal characteristics of the ecological quality in the research area.Finally,the ecological effects of regional vegetation coverage were discussed by analyzing the differences in ecological quality levels of vegetation coverage and establishing linear regressions model on the vegetation coverage and the surface temperature,the normalized humidity index,the remote sensing ecological index.The main conclusions are as follows:Firstly,the overall vegetation coverage of Lanzhou New Aear has declined slightly,but the construction of local ecological green space has begun to take effect.The vegetation coverage of the research area decreased by 21.0152% from 2017 to 2013,and the internal dispersion increased by 3.8640% from 2017 to 2013.This indicates that the vegetation environment in the area has become more fragile,and the difference of vegetation coverage distribution in the area increased,which will affect the stability of the ecosystem.According to the spatial and temporal variation characteristics of vegetation coverage,the increase of vegetation coverage level in the research area was lower than the decline,and the surface area with medium vegetation coverage is mainly turned to low vegetation coverage.The change of vegetation coverage level in the research area showed that the northwest increased and the southeast decreased,the central and western regions remained the same,but the local areas were accompanied by big change.In particular,areas with high increase in vegetation coverage were concentrated in the northern ecological agriculture and forestry areas,green belts on both sides of the roads,and wetland parks.Secondly,the overall ecological quality of Lanzhou New Area has declined,but the ecological quality of ecological green areas has increased.Compared with 2013,the greenness and the wetness of the research area decreased by 10.8207% and 15.7620% respectively in 2017,while the heat and the dryness increased by 11.5901% and 12.4456% respectively,which caused the RSEI to decrease by 18.6462%.The ecological environment quality of the research area has declined.Meanwhile,The northern mountainous areas,urban roadside and wetland park have been affected by greening,and their ecological quality has shown a turning trend.Thirdly,the remote sensing ecological index in this paper can reflect the change of ecological quality in Lanzhou New Area.The greenness and wetness have a positive effect on the ecological environment of the research area,while the heat and dryness have a negative effect on the ecological environment of the research area.In addition,the dryness has more influence on the change of the remote sensing ecological index value of the research area.Fourthly,there is a positive relationship between vegetation cover and ecological quality change in Lanzhou New Area.Increased vegetation coverage in summer is beneficial to alleviate thermal environmental effects and increase surface moisture.The vegetation coverage is higher,the ecological environment quality is better,and it more sensitively affects the ecological quality changes.The ecological quality of low vegetation coverage areas is relatively unstable.Therefore,rational control of impervious surface area and scientific planning of urban green space play an important role in improving the ecological environment quality of Lanzhou New Area. |
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