Study On The Spatial And Temporal Variation Of Vegetation NDVI And Its Driving Factors In Henan Province

Vegetation is the foundation and also the important part of terrestrial ecosystem.The dynamic change of vegetation can not only measure the natural and ecological environment of a region,but also reflect the impact of climate change and human activities on natural environment.By using remote sensing and GIS technology,vegetation can be dynamically monitored in time series,better monitoring and predict the development trend of vegetation in the future.It is of farreaching significance for the improvement of the ecological environment in Henan Province and realize the sustainable development of ecological environment and regional economy in Henan province.At the same time it also could be better to provide monitoring and scientific theoretical basis and support for Henan province ecological environment.In this paper,based on MODIS-NDVI data and meteorological data sets,this paper analyzes spatial and temporal variation and changes vegetation NDVI of Henan province from 2000 to 2015 years trend.And then it uses simple correlation analysis,partial correlation analysis and residual analysis method to analyze the impact of vegetation change with factors such as precipitation,temperature,elevation,slope,aspect,and human activity and to quantify analysis of the driving factors of temporal and spatial changes of vegetation NDVI in Henan province.The results of the study are as follows:(1)Analysis of temporal and spatial changes of vegetation NDVI in Henan provinceThe NDVI value of Henan Province showed a slight upward trend during the 16 years and the trend rate was 0.0017/10 a,of which the lowest NDVI was 0.32 in January and the highest NDVI value was 0.73 in August.Through the interannual change: Henan province is in time series in the rising trend as a whole.The annual average NDVI value fluctuates between 0.44 and 0.54,and the annual average NDVI linear tendency rate is 0.0056/10 a.From the perspective of seasonal scale,the average NDVI in all seasons shows an upward trend.The seasonal mean value is summer>growth season>spring>autumn,and the growth rate is autumn>spring>growth season>summer.From the perspective of spatial characteristics,NDVI in Henan province is unevenly distributed in space,showing high in the west,east,and south,and low in the middle and north.(2)Analysis of the change of precipitation and temperature in Henan provinceThe average annual rainfall in Henan province shows a downward trend,the rate of decline is 11.304mm/10 a,the annual average precipitation is 772 mm,the highest value is 1105 mm in 2003,the lowest value is 556 mm in 2001,and the average annual rainfall is in summer >Autumnal>spring.However,the annual average temperature is on an upward trend,the trend rate is 0.0333°C/10 a,the annual average temperature is 14.49°C,the highest value is 15.17°C in 2013,the lowest value is 13.73°C in 2003,and the average annual temperature in order of summer>growth season>spring>autumn,the changing trend rate was autumn>summer>growth season>spring.(3)Time-delay analysis of precipitation and temperature on monthly and seasonal scales of NDVI in different vegetation typesThe time delay analysis of the monthly average NDVI value and monthly mean precipitation and monthly mean temperature: The NDVI value of eight different vegetation types and the maximum response time of precipitation and temperature are both in this month,and both of them have passed the P<0.01 significance test.The time delay analysis of seasonal NDVI value and seasonal average precipitation and seasonal mean temperature: The maximum response period of spring coniferous forests,broad-leaved forests,grasses,shrubs,other vegetation types,and precipitation is one month behind,while the maximum response period of cultivated vegetation,swamps,and meadows is two months behind.The maximum response time of the shrubs,grasses,coniferous forests,broad-leaved forests to the temperature is in the current season,while the maximum response period of cultivated vegetation,swamps,meadows,other vegetation types to the temperature is lagging by two months.While summer swamps,coniferous forests and precipitation have no significant correlation,the maximum response period of broad-leaved forests,cultivated vegetation,other,shrubs,grasses,meadows,and precipitation are in the current season.While cultivated vegetation,shrubs,grasses,and other summers had no significant correlation with summer temperatures,the maximum response times for marsh,coniferous forest,broad-leaved forest,and summer temperatures are in the season,and grass the maximum response period of temperature and temperature is one month behind.The maximum response period of vegetation,other meadows,grasses,swamps,and marshes in the autumn is the seasonal season,while the response period of shrubs,coniferous forests,broad-leaved forests and precipitation is one month behind.While the maximum response period of precipitation and temperature in eight plant types in the growing season is in the current season,the maximum response period of precipitation and temperature in eight plant types in the growing season is in the current season.(4)Correlation analysis between vegetation NDVI and driving factorsIn terms of elevation factors: At an elevation of <500 m to >2000 m,the average annual NDVI in Henan decreases first and then increases.In terms of slope factor,vegetation NDVI is more active in areas with smaller slopes than in more steep slopes,because smaller slopes are favorable to vegetation.The growth,but also the area where human activities are more frequent,has a greater impact on vegetation.In terms of aspect factor: Limits of natural conditions such as precipitation and temperature,the NDVI values of semi-shade slopes and semi-sunny slopes are slightly higher than those of shady slopes and sunny slopes.In terms of human activities factor:In general,the number of pixels that positively affect the growth of vegetation as a whole increases with time,the negative effect and the number of negative pixels with significant negative effects decrease with it,indicating vegetation growth shifts in a good direction in time series.Similarly,when studying the correlation of population density,GDP,urban expansion and NDVI,it was found that there are strong correlations between the three human activity factors and NDVI,and also reflect the economic growth and improvement of living standards.The requirements of the environment have also been further enhanced,which has,to some extent,promoted the improvement of the ecological environment in Henan province.