Vegetation Patterns And Dynamics In Response To Climate Change Across The Mongolian Plateau

Global climate change and its impact on terrestrial ecosystems have attracted widespread attention of the academic community in recent decades.Mongolian Plateau is located in the inland region of Eurasia and highly sensitive to climate change and external disturbances as its larger area belongs to arid and semi-arid regions with the ecological environment extremely fragile.Under the combined action of climate change and human activities,the balance and stability of the Mongolian Plateau ecosystem have been seriously disturbed and destroyed in the recent 50 years,thus the functions of productive and ecological service reduced significantly.Therefore,it is of great significance to study systematically the climate change and its influence on the ecosystem in the region for the economic and social sustainable development and ecological security in the China,Mongolia,Russia and Asia even the global.This paper integrated meteorological observation data,satellite TRMM and AVHRR NDVI,based on the vegetation type area of Mongolian Plateau,using Sen's slope,Mann-Kendall test,spatial interpolation,spatial trend analysis,geostatistical method and synchronization and lag correlation analysis method.We aims to reveal the evolution of climate and vegetation coverage of the Mongolian Plateau at different spatial and temporal scales,and to clarify the impact of regional climate change on vegetation growth,and verify the adaptability of TRMM data for the temporal and spatial evolution of regional climate.The main conclusions are as follows:The annual mean temperature increased significantly during 1961-2014 across the Mongolian Plateau with increasement of about 2?,which is about twice the increase rate of global average temperature,the annual precipitation decreased overall.It was a cold period before 1989,mainly warm and humid in the 1990 s,and warm and dry after 2000.Seasonal mean temperature showed a significant upward trend(winter > spring > autumn >summer),and the spatial difference in temperature increase rate is not obvious(except some local areas).Influenced by the intensity,arrival time and duration of E ast Asian monsoon,Arctic airflow,westerly jet,the spatial and temporal variations of precipitation are significant.Precipitation increases significantly in spring and winter,but decreases significantly in summer and does not change obviously in autumn.The spatial variation results showed that annual and summer precipitation decreased in the southeastern and northern regions,and increased in the northeastern,southern and northwestern regions.The precipitation in spring increased as a whole,and increased significantly in the southeast and northwest of study area.Autumn precipitation decreased significantly in the north and southeast of MP.Winter precipitation increased significantly in the northern(northeast,north,northwest)and southern region.There were high consistency between the TRMM data and meteorological data and can be applied to the precipitation study at the different temporal and spatial scales.2)Regional averaged growing season(April-October)accumulated NDVI displayed increasing trend for the Mongolian Plateau and its each ecoregion during1982-2013,but the difference was obvious at different periods.The change trend in seasonal NDVI for each ecoregion was significantly different.In spring and autumn,NDVI increased in all vegetation areas except desert.In summer,vegetation NDVI decreased in coniferous forest,meadow steppe and desert,but increased in deciduous broadleaf forest,typical steppe,desert steppe and steppe desert.The proportion of seasonal NDVI change trend area differed by seasons.In summer,vegetation NDVI decreased significantly in most areas except increasing in the south and southeastern regions.In spring,vegetation NDVI increased in most areas,while significantly in the north and northwest.In autumn,vegetation NDVI increased significantly in south,southeast and surrounding mountainous forest areas.3)The response of vegetation to climate change is complex at different time scales.In most vegetation areas except coniferous forest and desert areas,interannual variations of growing season NDVI were positively correlated with precipitation in the same period(p < 0.05)and negatively correlated with mean temperature in the growing season,which implying that the accumulated precipitation during the growing season is the main factor driving the interannual variation of vegetation growth in most vegetation areas of the Mongolian Plateau.From the intra-annual change,the monthly NDVI was significantly correlated with the temperature and precipitation of the same period(p < 0.05),and the correlation between vegetation NDVI and temperature was greater than that of precipitation.In terms of seasonal response,spring NDVI in coniferous forest,meadow steppe,and typical steppe was influenced significantly by spring(April-May)temperature,indicating that spring warming promoted vegetation growth,while NDVI in desert steppe and steppe desert was significantly affected by spring precipitation.In summer,the vegetation change of steppe and desert was affected significantly by precipitation.The degree of influence of precipitation varies by vegetation types due to the differences in physiological and ecological characteristics.The vegetation growth of desert steppe is the most sensitive to precipitation in summer,followed by meadow steppe and typical steppe.The vegetation change in summer is not significantly affected by temperature,and the increase of temperature in summer inhibits vegetation growth by promoting water evaporation.In autumn,the vegetation growth of meadow steppe is closely related to the seasonal temperature change(r = 0.25,P < 0.05).The increase of autumn temperature promotes vegetation growth by prolonging the growing season.NDVI in autumn was negatively correlated with precipitation in coniferous forest(r=-0.32,P < 0.05).Excessive precipitation in autumn reduced temperature by affecting solar radiation,thus inhibiting vegetation growth.4)Vegetation growth has a lagging effect on temperature and precipitation,especially on precipitation.Its significance varies with vegetation types and growth stages.There was a positive correlation between NDVI in June-October and precipitation in the preceding 1-month and 2-month in all vegetation types except coniferous forest.The vegetation NDVI from June to September were negatively correlated with temperature in the preceding 1-month,while the vegetation NDVI in April,May and October were positively correlated with the temperature in the preceding 1-month.