Effects Of Extreme Climate Changes On Vegetation Phenology Of Inner Mongolia

The climate warming in the past century has had a significant impact on the frequency,intensity,spatial extend and duration of extreme climate events,which will continue to increase globally in the future.Inner Mongolia is a typical arid and semiarid climate transition zone and located in the northern of China.It has many vegetation types such as forest,forest steppe,desert steppe,typical steppe,and sand,but its ecosystem is extremely fragile.The global warming has led to the increase of extreme climate events in Inner Mongolia,which has a great impact on the vegetation dynamics.Therefore,the scientific analysis of the impact of different spatial and temporal scale extreme climate events on the vegetation phenology and the prediction of the future extreme climate events and the change characteristics of vegetation phenology have important guiding significance for promoting the protection of ecological environment and formulating effective disaster prevention and mitigation measures.This study analyzed the temporal and spatial characteristics of extreme climate events and vegetation phenology at different temporal and spatial scales,the annual and seasonal climate changes in different vegetation types and the impact of extreme climate changes on surface phenology,the extreme climate events that have the greatest impact on the surface phenology on different temporal and spatial scales have been identified,and the temporal and spatial characteristics of extreme climate events and vegetation phenology changes under different representative concentration pathways(RCP)scenarios in the future have been predicted,based on the daily meteorological data of Inner Mongolia meteorological stations,the GIMMS NDVI3 g data set,and the Phase 5 of the Coupled Model Intercomparison Project(CMIP5)future climate model,comprehensively using extreme climate indexes and surface phenological parameters(Start of Season,SOS and End of Season,EOS).The main conclusions are as follows:(1)On the years scale,the extreme climate events related to the lowest temperature and the highest temperature in Inner Mongolia have shown a decreasing and increasing trend,respectively,in the past 34 years.The increase rate of the number of warm days and warm nights was greater than the number of cold days and cold nights.On the seasonal scale,summer extreme temperature events have the largest rate,followed by spring and autumn,and winter has the smallest rate.The rate of change of desert steppe,forest,forest steppe and typical steppe I was greater.The extreme precipitation events showed a decreasing trend,and the decrease rate was the largest in summer,and all other seasons showed an increasing trend.The extreme precipitation events have the largest increase rate in the sand,and the largest decrease rate in the typical steppe II.The extreme precipitation day indices still have the largest increase rate in the sand,and the decrease rate was larger in the forest steppe and typical steppe II.(2)From 1982 to 2015,the SOS of forest,typical steppe ? and desert steppe was between 115 and 130 days,and the SOS of typical steppe ? and forest steppe was between 130 and 145 days.The average SOS DOY(Day of Years)was 129.The EOS of the forest and typical steppe II was between 280-290 days,and the EOS of the forest steppe,typical steppe area I and desert steppe was between 290-310 days.The average EOS DOY is 292.SOS showed a significant advanced in forest and forest-steppe,and a significant delayed in the typical steppe II.EOS showed a significant advanced in desert steppe,and a significant delayed in forest and forest steppe.(3)On the years scale,the number of warm night days and the number of cold days have the greatest impact on SOS and EOS in the entire study area,respectively,indicating that extreme temperature events promote the impact of annual mean temperature on vegetation phenology.The extreme climate events that have the greatest impact on SOS in desert steppe,forest,forest steppe,sand,steppe desert,typical steppe I and typical steppe II were cold night days,heavy precipitation,heavy rain days,cold night days,and maximum daily precipitation,cold night days and heavy rain days,respectively.The extreme climate events that have the greatest impact on EOS in different vegetation types were extremely heavy precipitation,frost days,heavy rain days,cold days,warm days,cold night days,and heavy precipitation,respectively.On the seasonal scale,the spring extreme temperature event has the greatest impact on SOS in different vegetation types,and it has a greater impact than the mean spring temperature.The greatest impact on EOS in different vegetation types was summer extreme temperature events,and the impact was greater than the mean summer temperature.(4)Compared with a single CMIP5 future climate model,Multi-Model Ensemble(MME)was more effective in simulating extreme climate events.From 2020 to 2099,under the three RCP scenarios,the extreme climate events related to the maximum temperature(minimum temperature)all have an increasing(decreasing)trend,and the extreme precipitation has an increasing trend.The rate of extreme climate events under RCP2.6,RCP4.5 and RCP8.5 scenarios is slight,rapid,and extreme,respectively.The extreme temperature events have a greater rate in the western and typical stepp II,the extreme precipitation events have the largest increase rate in the west,and the number of moderate rain and heavy rain days has a greater increase rate in the typical steppe.(5)During the period of 2021-2100,the SOS of the entire Inner Mongolia has a trend of advance,delay and delay respectively,under RCP2.6,RCP4.5 and RCP8.5 scenarios,respectively,while the EOS has a trend of advancement under the three RCP scenarios.The SOS has advance in the northeast,while has delay in the middle of study area.EOS has delay in most of the forest and the southwestern part of the study area,and EOS has advance in other areas.