Extreme Climate Change And Its Impact On Vegetation In The Mongolian Plateau

Global warming has become an irreversible trend,and the research on climate warming has become an important topic in the field of climate research.When the rate of climate change exceeds the range of climate change an ecosystem can withstand,it puts pressure on the growth of plants and animals in the ecosystem.These climate changes beyond the capacity of the ecosystem are called extreme climate,because extreme climate has the characteristics of sudden and destructive,so it has attracted the attention of experts from different fields at home and abroad.The Mongolian Plateau belongs to the arid and semi-arid climate transition zone,with rich vegetation types and fragile and sensitive ecological environment.Therefore,it is of great significance for the ecological protection of the Mongolian Plateau to study the change characteristics of extreme climate and its impact on vegetation.Based on the temperature and precipitation reanalysis data,GIMMIS NDVI data and CMIP6 future climate data of The Mongolian Plateau,this paper analyzed the spatio-temporal variation characteristics of extreme climate and NDVI in The Mongolian Plateau from 1982 to 2012,and explored the impact of extreme climate on NDVI.Secondly,The spatiotemporal variation of extreme climate in 2021-2080 was estimated by using CMIP6 data,and the future vegetation change trend was predicted by using historical extreme climate and NDVI model.The main conclusions are as follows:(1)From the perspective of the historical trend of extreme climate,the extreme climate in the Mongolian Plateau during 1982-2012 mainly shows as follows: The extreme temperature indexes TN90P,TX90P,SU25,TR20,TNn,TNx representing temperature warming showed an upward trend,while the indexes TX10P,TN10P representing temperature decline showed a downward trend.The extreme precipitation index R20 showed an upward trend,while SDII and R95 P showed a downward trend.In terms of spatial distribution,the regions with rising temperature are mainly in the west and northwest of The Mongolian Plateau,while the regions with decreasing temperature are mainly in the central part of the Mongolian Plateau.The frequency index of extreme precipitation increased in the northeast and northwest of the Mongolian Plateau,but decreased in the central part of the Plateau.The extreme precipitation intensity index increased in the northeast and southwest of the Mongolian Plateau,but decreased in the northwest.(2)The variation trend of NDVI in The Mongolian Plateau mainly shows an upward trend.From the regional scale,the increasing trend of NDVI in Inner Mongolia is greater than that in Mongolia.From the perspective of spatial scale,the increasing trend of NDVI in the northeast and a few areas in the north of the Mongolian Plateau is obvious.However,NDVI in the southwest mainly shows an increasing trend and a slowing down trend.The contribution of different vegetation types to NDVI is also quite different.Broadleaf forest,coniferous forest and meadow grassland have higher contributions,while alpine grassland,desert grassland and Gobi desert have lower contributions.The study on the relationship between extreme climate and NDVI shows that extreme precipitation has a greater impact on NDVI than extreme temperature.It is found that R20,SU25 and TNx have a greater impact on NDVI by using full subset regression.(3)Based on the full subset regression model,the future spatial-temporal changes of extreme climate indexes that greatly affect NDVI are studied.It can be concluded that the extreme precipitation indexes in SSP126,SSP245 and SSP585 during 2021-2080 all show an increasing trend.The indices SU25 and TNx,which represent temperature warming in extreme temperature index,showed an upward trend.In terms of the stability of its change,the change of extreme climate is relatively stable in SSP126 and SSP245 modes,while it fluctuates greatly in SSP585 mode.(4)In terms of future NDVI changes,the model is established to try to predict the change trend of NDVI in 2021-2080.Although the change trend of NDVI in different situations in the future shows an upward trend,compared with historical NDVI,the value of future NDVI is lower than that of historical NDVI in any situation.The spatial variation of NDVI in the future shows that with the increase of radiation intensity,the areas with increasing trend gradually decreases,while the areas with decreasing trend gradually increases.