Variation Trends Of NDVI In Different Underlying Surface And Its Correlation With Climatic Factors In Yangtze River Delta

At present, "global climate change and terrestrial ecosystems (GCTE)" and "land use/land cover change Chemical (LUCC)" has become the most complex and dynamic research content among global change research subjects. The climate factor such as temperature and precipitation determines the vegetation types and their distribution, and vegetation type determines the terrestrial ecosystem. However, the driving force of earth land ecosystem evolution will change with different space-time scale. Though climate is the determining factor in vegetation distribution in large range, the size of the impact has associated with the consideration of time and space.In this study, we use the NDVI data of MOD13A2 product during 2003-2013, analyse the distribution characteristics of NDVI and time-space variation of land use changes over Yangtze River Delta, and discuss the correlation between different land cover types and climate factors. We obtain the major findings below.(l) Vegetation covers in southern mountains and hilly land is higher than northern crops growing areas, and the central region is the lowest. The vegetation covers show a rising trend during the year 2003-2013. The characteristic of distribution is:the NDVI range is-0.05/10a-0.05/10a in southern forest region. There is an obvious rise in northwest area (0.3/10a-0.4/10a) while an obvious decline occour in northeast coast area. In the city, NDVI value of the old city area increased (0.02/10a～0.1/10a) while the new urban area declined (-0.1/10a～0.4/10a).(2) The average growth rate of Construction land and forest land area is 3.35%(Rr= 0.93) and 1.35%(R2= 0.76), respectively, which show the significant increasing trend. Water area change was not significant; Cultivated land reduced sharply, the change rate is 1.45%(R2= 0.88). We can find that except the water, the annual change rate of other three type land cover are pass the significance test on P<0.0001, that mean extremely significant.(3) Using the monthly average data of temperature, precipitation and sunshine during 1984-2013, we analyze the spatial and temporal variation of climate factors, we can conclude that: the average temperature appears extremely significant rise, growth rate was 0.56"C/10a, the varation is different in each area. The mean precipitation change is not big, but there is a huge difference in different season, the trend is precipitation in summer increased and decreased in spring. Sunshine time is obviously decline across the region, but linear trend exists significant differences between south and north area.(4) We use different analysis method to study the correlation between climate factors and NDVI values in different cover types, the result show a huge difference between different methods. Because it eliminates the effect of other meteorological elements, the correlation coefficient calculated by second order partial correlation analysis is more accurate to reflect the real correlation between NDVI and climate fator. The study found that:there is a different lag for NDVI value in different land cover types repond to climate fators. The NDVI in last year winter have a significant impact to the spring climate of this year, and the NDVI in summer also affect the summer climate significantly.