Spatio-temporal Changes Of Vegetation And Its Driving Factors Covered In Poyang Lake Basin

Vegetation uses photosynthesis,surface reflectance,and roughness to regulate the energy conversion and carbon cycle in the biosphere,and has an indication of climate change.In this paper,we considered the Poyang Lake Basin as the research area.The vegetation coverage and vegetation of the Poyang Lake Basin are analyzed using MODIS NDVI datasets,meteorological data,and statistical data from 2000 to2016 using some methods such as S-G filtering,one-dimensional linear regression model,and correlation analysis.Not only explored the characteristics of spatio-temporal changes of vegetation coverage and vegetation phenology in the Poyang Lake Basin,but also their response to changes in meteorological factors.The main results are as below:(1)From 2000 to 2016,the overall change of NDVI in the Poyang Lake region was dominated by an upward trend,and the NDVI multi-year average was 0.63.Among them,there is a difference in the increase rate in different seasons,which are summer> autumn> spring in descending order.The annual variation of the vegetation index in the Five River Basins shows an increasing trend.Spatially,the NDVI change trend of the vast majority of areas in the Poyang Lake Basin is not obvious,and there is a slight improvement in vegetation coverage in a few areas..(2)The period of vegetation growth season in the Poyang Lake Basin from 2000 to 2016 was mainly distributed on the 50 th to the 106 th day.The overall trend was an early trend,which was about 3.8 days ahead of schedule.Spatially,the period of vegetation growth began earlier in the northern,northeastern,and southwestern parts of the Poyang Lake Basin,while a few areas in the middle and most of the southern regions started later.The end of vegetation growth period and vegetation growth cycle showed a trend of delay during 17 years.Among them,the end of the growth season was delayed by 3.9 days every ten years,and the length of the growth period was delayed by 7.7 days every ten years.Spatially,it showed that most of the areas in the Poyang Lake Basin showed a postponing trend,and the growth period of the Poyang Lake,the Central Plains,and a few parts of the south ended earlier.The spatial distribution of the length of the vegetation growth period is quite different.It shows that the vegetation growth period is short in a few areas in the south,most of the central plain,and the edge of Poyang Lake,and the growth period is longer in thenorthern and southwest mountainous regions.(3)On the whole,the average annual temperature of the Poyang Lake Basin during 2000-2016 showed a fluctuating upward trend,which increased at a rate of0.24°C/10 a.The multi-year mean temperature in different seasons differed more greatly,showing summer> autumn> spring.The average annual temperature variation in the five river basins remains generally the same,and the annual average temperature changes in the Xinjiang River Basin and the Raohe River Basin are basically the same;the average annual precipitation in the Poyang Lake Basin generally fluctuates and declines,and the precipitation decreases by 131.5 mm every10 years;The average annual radioactivity in the lake basin is 1292.94KWh/m2,showing a slight downward trend.(4)From the entire study area,the correlation between annual average NDVI and precipitation was not significant,and negative correlation was observed in some areas.However,annual average NDVI was positively correlated with temperature;solar radiation was positively correlated with annual average NDVI,and few areas were not clearly presented.Negative correlation.The sensitivity of vegetation NDVI and meteorological factors are in order of temperature> precipitation> solar radiation.(5)During the period from 2000 to 2016,the change of vegetation phenology parameters was more sensitive to temperature than precipitation in the correlation of phenology and meteorological factors.The beginning of the growing season was advanced with the increase of temperature,while the late growth season was followed by the increase of temperature;The increase leads to a delay in the beginning of the growing season and an earlier ending period;an increase in the solar radiation will cause the beginning of the growing season to be advanced and the end of the growth period to be delayed.Temperature and solar radiation play a prolonged role in the growing season of vegetation,but precipitation inhibits the growth of vegetation.