Temporal And Spatial Variation Of Desert Steppe Vegetation And Its Response To Climate Change

Desert steppe is the xerochemical buffer zone between desert and typical steppe.Affected by climate change,its ecosystem is inherently sensitive and fragile.Analyzing the rules of the temporal and spatial dynamic changes of vegetation and its correlation with climate change is of great significance for probing the formation and degradation mechanism of desert steppe,effectively maintaining the stability and ecological carrying capacity of its ecosystem,and improving steppe productivity.The representative arid and semi-arid desert steppe in Sonid Youqi was taken as the research area in this paper.The dynamic change data of steppe vegetation height,coverage,fresh grass yield,hay yield,vegetation community composition and other indicators in the region were used,combined with meteorological statistics.The temporal and spatial dynamics of the steppe vegetation indicators in the whole area over the past 10 years and their response to changes in climate factors were analyzed,and the best fitting models of vegetation and temperature and precipitation factors were constructed.The main conclusions are as follows:（1）The growth quality of vegetation shows a decreasing law from southeast to northwest.The growth statu of grass vegetation in Zhurihe Town and Saihanwuliji Sumu was the best,and the growth statu of vegetation in Wurigentala Town and Erennaoer Sumu was the worst.The growth statu of steppe vegetation in the southernmost and easternmost parts of Sonid Youqi is better than that in the middle part,and the growth statu of steppe vegetation in the northwest part is the worst.（2）The vegetation of arid and semi-arid desert steppe of the whole Sonid Youqi is dominated by Stipa tianschanica,Cleistogenes songorica,Allium,Caragana,Salsola collina and Corispermum mongolicum.Compared with 2003,the proportion of high-quality grass increased,the proportion of miscellaneous grass and poisonous grass decreased,and the species diversity of community increased.The vegetation height,coverage,fresh grass yield and hay yield all showed an upward trend,and the steppe showed positive succession in 2013.（3）The overall climate of the whole area showed a trend of cold-dry from 2003 to 2013.The annual variation of temperature and precipitation both showed a unimodal type,and both reached their maximum in July.The fluctuation of annual average temperature is mainly driven by the fluctuation of temperature in autumn and winter.The increase and decrease of annual precipitation is mainly driven by the increase and decrease of precipitation in summer and autumn.（4）The annual maximum vegetation height,coverage,and grass yield are positively correlated with precipitation,and negatively correlated with temperature.The correlation with temperature is weaker than the correlation with.Rising temperature will inhibit the growth of steppe vegetation,while the increase in precipitation has an important role in promoting the growth of vegetation,and precipitation has a greater impact on the arid and semi-arid desert steppe in Sonid Youqi.（5）The annual maximum vegetation coverage,height and grass yield have a two-month time lag effect with temperature and precipitation,and have the highest correlation with temperature and precipitation factors in June,while they have no significant correlation with temperature and precipitation in August and July.（6）The models with the highest fitting degree between vegetation height,fresh grass yield and hay yield and climate factors are binomial models,while the model with the highest fitting degree between vegetation coverage and climate factors is power exponential model.The best fitting model between vegetation height and average temperature in June is y=0.629x²-28.547x+333.76,the best fitting model between vegetation fresh grass yield and June precipitation is y=0.3359x²-8.4857x+629.43,and the best fitting model between vegetation hay yield and June precipitation is y=0.1608x²-5.4645x+228.74,the best fitting model of vegetation coverage and precipitation in June is y=6.0011x^0.2924.