Temporal And Spatial Changes Of Grassland Vegetation Coverage And Driving Factors In Qinghai Province

In the context of further warming and drying trend of global climate change,the response of grassland vegetation changes to climate change and human activities is a hot issue in ecological research in recent years.Qinghai Province is one of the most widely distributed areas of alpine grassland in China,which belongs to ecologically vulnerable areas that are sensitive to the effects of climate change and external forces.Therefore,to grasp the relationship between grassland vegetation growth and climate,human activities in Qinghai Province is scientific and practical significance.Based on MODIS EVI time series data of grassland,temperature and cumulative precipitation data for the same period of EVI from 2005-2014,this paper takes Qinghai Province as the research area,use a series of methods such as correlation analysis and residual trend method based on local regression to explore temporal and spatial Characteristics of Grassland Vegetation Coverage and Major Climate Factors in Qinghai Province and their response relationships.Then we quantitatively separating the impact of climate factors and human activities on grassland vegetation changes and get the following results:From 2005 to 2014,the EVI of grassland vegetation in Qinghai Province showed a tendency of increasing fluctuations.The spatial distribution of EVI showed high in the southeast and low in the northwest.Grassland vegetation improvement areas are concentrated in the western part of Qingnan Plateau,Hainan zhou,the Hehuang Valley of the eastern Loess Plateau,the Zhaling Lake and the Eling Lake region and the north of Qilian Mountain.The degraded areas of grassland vegetation are concentrated on both sides of Animaqing Mountain,Qinghai Lake basin area,Maduo County,and Chengduo County.According to the change of grassland vegetation coverage in different periods of Qinghai Province,the growth of grassland vegetation in certain areas of Qinghai Province has deteriorated,but the overall vegetation shows an improvement trend.According to the dynamic analysis of grassland vegetation cover in Qinghai Province,the whole from the first period to the second period was a benign evolution trend,and the second period to the third period was a malignant evolution as a whole,indicating that the quality grassland was facing the threat of degradation.The evolution types of grassland vegetation coverage are mainly invariant type,followed by single-variation type,and the third type is reversion type,and the smallest is layer variation.The average annual temperature in Qinghai Province has shown a tendency of fluctuation increase.The temperature increases in the central and eastern parts of the province are obvious,and the temperature in the southern and northern parts of the province has a clear trend of cooling.The annual average accumulated precipitation in Qinghai Province is on the rise,but it is not significant.The precipitation in the south has a significant increase trend,and the precipitation in the north has a significant decrease.The grassland EVI in the growing season was closely related to temperature and precipitation in Qinghai Province.Overall,the grassland EVI in the growing season was positively correlated with the mean temperature and cumulative precipitation.Among them,31.34% of the pixels had a significant positive correlation with the average temperature,and 24.67% of the pixels had a significant positive correlation with the accumulated precipitation.To a certain extent,temperature and precipitation are the main limiting factors for the growth of grassland vegetation,and the relationship between temperature and EVI is even closer for Qinghai Province in high-cold regions.The change of grassland vegetation in Qinghai Province is mainly due to the combined effect of climate factors and human factors.The Qaidam Basin(Levels II,III,and IV),Huanhu and Qilian Mountains(Levels I and IV),and the Qinghai Plateau(Levels II and III)are mainly driven by temperature and precipitation;The eastern Loess Plateau area(levels III and IV)is mainly driven by precipitation;Lakes and Qilian Mountains(Level III)and Qingnan Plateau(Level IV)are mainly driven by temperature;Other regions are mainly driven by non-climatic factors(human factors).The impact of human activities on grassland vegetation change in Qinghai Province from 2005 to 2014 gradually changed from a negative impact to a positive one,which improved the coverage of grassland vegetation in Qinghai Province to some extent.In areas where grassland vegetation has changed significantly,human activities play a major role in the restoration and destruction of grassland vegetation.