Analysis Of NDVI Changes And Its Climate Driving Factors In The Three River-Headwater Region During 2000-2014

Since the 1970 s,the grassland of Three River-Headwater region has been degraded seriously.In order to restore the ecological environment of the Three River-Headwater region,The Three River-Headwater region Nature Reserve has been established since 2000,and the vegetation cover in the Three River-Headwater region has been effectively restored,but the interaction between vegetation cover change and climate change remains to be in-depth studied.In this paper,The NDVI data of MOD13Q1 and the air temperature and precipitation data of 41 meteorological stations in the Three River-Headwater region and the surrounding area,combined with the maximum value method,the trend analysis method and the correlation analysis method are used to explore the vegetation and climate dynamics,the impact of climate change on vegetation cover and the driving factors of climatic factors on vegetation growth in Three River-Headwater region from 2000 to 2014.The main conclusions are as follows:(1)In general,the vegetation coverage in the Three River-Headwater region from 2000 to 2014 is as follows: the spatial distribution of vegetation cover is decreasing from southeast to northwest.The changes of vegetation cover show a trend of improvement.In the case of vegetation types,the trend of several vegetation types is basically the same.The trend of vegetation NDVI is higher than that of alpine shrub> coniferous broad-leaved forest> alpine meadow> alpine vegetation> alpine steppe,and vegetation cover is the most obvious Alpine steppe.For the aspect of elevation,the vegetation NDVI in different elevation area show a significant growth trend.The elevation area below 3500 m is the most obvious.(2)The air temperature and precipitation in the Three River-Headwater region show a significant upward trend in the past 15 years.Nearly 15 years the air temperature change tendency rate is 0.41?/10 a,precipitation change tendency rate is59.52 mm/10 a.The average air temperature has a downward trend from the southeast to the northwest.The distribution of precipitation is generally less in the north and west than that in the south and east,and the precipitation distribution is obviously decreased from the southeast to the northwest.(3)The correlation between NDVI and air temperature in the Three River-Headwater region is higher than that of precipitation.The partial correlation by0.05 significance test area between NDVI and air temperature are mainly distributed in the central of Zhidoi county.The partial correlation by 0.05 significance test area between NDVI and precipitation are mainly distributed in Xinghai county and Tongde county northeast of the source area of the Yangtze river.In the case of different types of vegetation,the most significant relative correlation with air temperature and precipitation is the cold grassland.In terms of elevation,the area of NDVI,which is less than 3500 m,has the most significant correlation with precipitation,which is more significant than the area of 4500 m.(4)The vegetation in the Three River-Headwater region is driven by air temperature more than precipitation.The non-climatic factors driven area distribute in the whole of the Three River-Headwater region,which occupies most of the research area.For climate factor driving,the region driven by the air temperature patchy distribute in the central and western area of the source region of Yangtze river,such as the northwest of Golmud city,the central of Heteropoly county,the northwest of Song malai county and the northwest of Chindu county.The region driven by precipitation distribute in the northeast of the Yellow River source area,mainly in north of Madoi county,north of Xinghai county and north of Tongde county.The strong driving area of air temperature and precipitation is in the western region of Yangtze river,namely,the southeast of the Golmud city,the central part of Zhidoi county,and the west of Song malai county.