Vegetation Growth And Its Response To Climate Change In Different Eco-regions Of Inner Mongolia

Located in the northern frontier of China,the Inner Mongolia is an important ecological security shelter,with its unique natural habitats and abundant natural resources.Terrestrial vegetation plays pivotal roles on land-atmosphere interactions,and even global climate change.Monitoring the tempo-spatial distribution,changing trend and driving mechanism of the vegetation growth is of great significance for ecological environment assessment and protection of the Inner Mongolia.This paper constructed a vegetation growth index(GI)model based on MODIS remote sensing data,and analyzed the temporal and spatial variation characteristics of vegetation growth in forest eco-region,grassland eco-region and desert grassland eco-region in Inner Mongolia from the years of 2001 to 2017.Combined with the data of air temperature and precipitation in the study area,the correlation analysis method is used to study the time lag of vegetation growth to climate change.The study area is finally zoned into different parts according to the driving climatic factors to vegetation growth on the basis of lag analysis.Based on the results of lag analysis,the climate-driven zoning of vegetation growth was preliminarily divided,and the spatial and temporal characteristics of vegetation growth response to different climate factors were quantitatively demonstrated and evaluated.The main conclusions are as follows:(1)The vegetation GI showed an uptrend with a growth rate of 0.037/10 a in recent 17 years in Inner Mongolia.The differences of variation rate and fluctuation range are significant in the eco-regions.The eco-regions orders of increased rate are desert grassland eco-region(0.048/10a),grassland eco-region(0.034/10a)and forest eco-region(0.032/10a).The spatial distribution of the mean GI showed the characteristics of south-high and north-low during the growing season,with significant regional differences.The eco-regions orders of vegetation growth were desert grassland eco-region,forest eco-region and grassland eco-region.(2)As a whole,the vegetation GI was dominated by no significant change(54.70%)and increase(43.93%)in Inner Mongolia in the last 17 years.The vegetation GI in the forest eco-region in the last 17 years was dominated by increased significantly.There was no significant change in vegetation GI in most regions of the grassland eco-region and desert grassland eco-region.The overall vegetation growth in the study area showed positive persistence(95.63%).In the future,about 50.47% of the regional vegetation GI will continue to have no significant change,and 43.83% of the regions will continue to increase.The trend of future vegetation GI changes in each eco-region is different,among them,the trend of future vegetation GI change in the forest eco-region will continues and increas significantly,both the grassland eco-region and the desert grassland eco-region are continuous and no significant change.(3)In the past 17 years,the mean of air temperature and precipitation were 17.18? and 265.10 mm in the study area,respectively.The air temperature decreased at a rate of 0.018?/10 a,and the precipitation increased at a rate of 26.055mm/10 a.There are significant differences in the variation rate of air temperature and precipitation in the eco-regions,among them,the grassland eco-region is the only region in the eco-regions where the air temperature has shown a downward trend for many years.And the desert grassland eco-region is the only region showing a downward trend for years of precipitation.The air temperature generally showed the spatial characteristics of decreasing from southwest to northeast in the study area,and the precipitation was opposite.(4)In general,the vegetation growth in the growing season does not lag behind air temperature,and there is a lag time of 1?2 months for precipitation.Vegetation growth in different ecological zones is slightly different to the lag time of air temperature and precipitation.the correlation coefficient between vegetation GI and air temperature in April-September reaches the highest,and there is a lag time of one month for precipitation.the lag time of air temperature in grassland ecological area and desert grassland ecological area is not obvious,but it lags 1 month and 2 months for precipitation,respectively.(5)The vegetation growth in the study area was negatively correlated with air temperature and positively correlated with precipitation.the vegetation GI in forest ecological area was affected by air temperature and precipitation.and the vegetation GI and precipitation in grassland ecological area and desert grassland ecological area were more closely related.The average complex correlation coefficient is 0.56 in the study area,28.99% and 11.67% of the study area passed the significance level of 0.05 and 0.01 respectively.In general,the complex correlation coefficient in different eco-regions from high to low is grassland eco-region,desert grassland eco-region,forest eco-region.(6)The GI areas driven by air temperature,precipitation,air temperature and precipitation account for 3.17%,27.99% and 6.39% of the total area in the study area respectively.The vegetation growth of forest eco-region was affected by both air temperature and precipitation,while the grassland and desert grassland eco-regions were mainly influenced by precipitation.On the whole,the vegetation growth was affected by non-climatic driving factors in most study areas.