Study On The Response Of Grassland Vegetation On Climate Change In The Eastern Mongolian Plateau

Based on the observation data of 32 meteorological stations in eastern Mongolian Plateau from 1971 to 2015 and combined with ASTER GLOBAL DEM grid,the precipitation and temperature change in the eastern Mongolian Plateau were analyzed by time series using a regression analysis method.The Holdridge life zone index and Kira Tatsuo hydrothermal characteristics in the eastern Mongolian Plateau were calculated out.The vegetation index based on MODIS was established and its relationship with climatic factors was analyzed.Based on these work,by analyzing on the change of 2000-2015 climatic factors(including precipitation,temperature,bio temperature,evapotranspiration rate,warmth-coldness index and humidity index)and of MODIS normalized difference vegetation index(NDVI),the relationship between the El Nino event year and the La Nina event year was drawn out.The following results were obtained:(1)The average annual precipitation(234.8 mm)shows a decreasing trend.Among them,the precipitation in the winter and spring showed an increasing trend,while it was significantly decreased in summer and autumn.For the decadal variability,the precipitation in the 80 s was increased by 10.1 ~ 23.8 mm than in the 70 s,and the precipitation in the 21 st century was decreased by 24.1 ~ 44.9mm than in the 70 s.It fluctuated strongly.(2)The average annual temperature(1.9 ?)showed a significant increasing trend in the study period.The increasing rate is 0.5 ?/10 a.Among them,the summer temperature was increased significantly with a rate is 0.1?/10 a.For the decadal variability,the temperature in the 80 s was increased by 0.6 ~ 1.2 ? than the 70 s,the temperature in the21 st century was increased by 1.0 ~ 1.4 ? than in the 70 s.(3)The BT value of Holdridge life zone is from 6.5 to 9.5 ?.For the decadal variability,the BT value in 80 s was increased by 0.3~0.4? than the 70 s,the BT value in the 21 st century was increased by 0.8~0.9? than in the 70 s.PER value is 1.1 mm-6.3mm.For the decadal variability,the BT value in the 80 s was decreased by 0.6 mm than the70 s in DornoGobi grassland,it was increased by 0.1~0.2 mm in the other grassland.The BT value in 21 st century increased by 0.2~0.7 mm than the 70 s.(4)Kira Tatsuo WI value is 49.5 ~ 79.4 ?/month.For the decadal variability,the WI value in 80 s was increased by 1.8 ~ 3.4 ?/month than in the 70 s,while the WI value in the21 st century increased by 6.5 ~ 9.2 ? /month than in the 70 s.CI value is 127.1 ~67.3 ?/month.For the decadal variability,the CI value in the 80 s was increased by 4.3 ~12.5 ? than the 70 s,the CI value in the 21 st century was increased by 6.3 ~ 8.7 ? than in the 70 s.HI value is 1.3-7.9 mm/?/month.For the decadal variability,the HI value in the80 s reduced by 0.1 mm/?/month than the 70 s in Xilin Gol-Hulunbuir prairie.The HI value in the other grassland area was increased by 0.1 ~ 0.4 mm/?/month.The HI value in the 21 st century was reduced by 0.2 ~ 1.4 mm/?/month than in the 70 s.(5)The maximum temperature of Xilin-Gol League in China and DornoGobi Province in Mongolia were come in the El Nino year.The maximum and minimum values of temperature in Chinese Hulunbeier City and Mongolian Dornod province,Sukhbaatar province appeared in the La Nina year.The impact of the El Nino event on the annual mean temperature is weaker than the La Nina event.The impact of the El Nino event on the annual precipitation is stronger than the La Nina event.The maximum and minimum annual precipitation levels are all present in El Nino year in the Hulunbeier City,Xilin-Gol League,DornoGobi province,Dornod province and Sukhbaatar province.(6)Between 2000-2015,the annual average NDVI was 0.329,and the high value area was mainly found in the eastern section of the study area.In the correlation between climate factors and vegetation,T,BT,PER,WI,CI are negatively correlated with and NDVI.While P,HI are positively correlated with NDVI.The maximum value of correlation coefficient with NDVI were 0.818,0.786,0.751,0.709,0.691 and 0.651 in precipitation,humidity index,evapotranspiration rate,temperature,coldness index,biotemperature and warmth index,respectively.All of them have reached extremely significant level.(7)In normal years,the annual average NDVI is 0.27.The minimum value is 0.01 and the maximum value is 0.69.In El Nino event year,the annual average NDVI was 0.17.The minimum value is 0.05 and the maximum value is 0.39.In La Nina event year,the annual average NDVI was 0.26.The minimum value is 0.08 and the maximum value is0.72.