The Time Variation Characteristics Of Comple Geographical Vegetation Cover Index (NDVI) In Multi-climate Belt And Its Relationship With Environmental Factors

Global climate change is increasingly affecting the sustainable development of the human economy and society.From climatological records,global temperatures have risen by0.3-0.6?in the past 100 years,and combined with the industrialization process,there has been a trend of rapid increase in atmospheric temperatures.It is predicted that by 2100,the global average temperature will likely increase by 1.4-1.8?,which will cause a series of ecological environmental problems.Vegetation cover change is an important indicator of the environmental change of the region and even the ecosystem.Vegetation cover is also an important influence factor of soil erosion and soil erosion,and it is also the most important indicator to measure the situation of surface vegetation.Vegetation coverage has been widely used in soil and water conservation research and ecosystem research.The development of remote sensing technology provides a way to accurately obtain the information of vegetation cover and its change,and to reveal the spatial and temporal variation of vegetation cover.Based on the data of MODIS/NDVI,combined with remote sensing and geographic information system,this paper adopts the methods of maximum value synthesis,difference method,linear regression analysis,etc.The spatial and temporal characteristics and dynamic changes of vegetation NDVI in Gansu province from 2000 to2015 were analyzed in terms of time,horizontal space,vertical space and quantity.In this paper,the temporal variation characteristics of vegetation cover index in Gansu province(hereinafter described as NDVI)and its relationship with environmental factors are analyzed.Gansu Province is located at 32~o11'—42~o57'north latitude and 92~o13'—108~o57'East longitude.The geographical form is complex and spans 8 climatic zones.This paper discusses the time variation of NDVI in Gansu province,the multi-scale characteristics of NDVI wavelet and the relationship between NDVI and environmental factors.Studies have shown that,The time phase change of vegetation growth with time series is more due to the phenological characteristics of ecological factors,and the difference in quantity and quality displayed in the spatial distribution is the common result of structural factors and random disturbances.In Southeast Gansu province,NDVI and precipitation showed significant positive correlation.However,the distribution of NDVI in the northwest of Gansu Province,whether it is temperature or precipitation,has little effect on the distribution of NDVI.In small areas,NDVI is more sensitive to terrain factors.This is mainly due to the small differences in the large climate environment in small areas,and the elevation,slope,and slope effects of terrain factors determine the distribution trend of NDVI.This paper concludes that it is of practical significance to evaluate the spatial and temporal changes of vegetation cover index in Gansu province and their impact on ecological environment.