| Inner Mongolia is located in the northern border of China,mainly engaged in agriculture and animal husbandry.Spring maize is the main crop in this area.The growth of spring maize is under serious threat due to the negative impact of climate change.At present,climate change has significantly changed the climate resources in Inner Mongolia,which has a significant impact on agricultural water use for spring maize.At the same time,affected by changes in complex meteorological factors,extreme weather events such as rainstorm,flood,drought,heat wave and freezing occur frequently,which seriously restricts agricultural production in the region.In order to alleviate the pressure of climate change on agricultural water use in the region and further strengthen the capacity of agro meteorological disaster monitoring and disaster prevention and reduction.In this thesis,meteorological drought,flood and chilling damage in agricultural areas of Inner Mongolia are taken as research objects.Based on meteorological data and crop production data,the temporal and spatial variation characteristics of main meteorological factors under the background of climate change are analyzed;The effects of the change of maturity type and variety distribution of spring maize on the water requirement during the growth period of spring maize were quantified;The characteristics of drought,flood and chilling damage during the growth period of spring maize were revealed through index construction and selection;The risk assessment system of main meteorological disasters during the growth period of spring maize was constructed;Estimate the meteorological disaster hazard under RCP4.5 and RCP8.5 emission scenarios.It provides a theoretical basis for monitoring spring maize disasters in Inner Mongolia,formulating policies for disaster prevention and reduction,and ensuring food security.The main research results are as follows:（1）Spatial interpolation and Mann-Kendall mutation test were used to analyze the temporal and spatial distribution characteristics of main meteorological factors and spring maize production factors in Inner Mongolia.The results show that the average temperature in Inner Mongolia was 4.58℃from 1959 to 2018,with a significant upward trend of0.31℃/10a.The warming rate in the western region is greater than that in the eastern region,and the year of sudden change of average temperature and maximum temperature is near 1989.The precipitation showed an insignificant downward trend,and the spatial distribution showed an increasing trend from west to east.The relative humidity generally shows a downward trend,which is similar to precipitation in spatial distribution.Sunshine duration is between 6.01 and 9.33 h.The average wind speed is 3.13 m/s.The planting area and yield of spring maize have increased significantly.At present,it is the crop with the widest planting area and the highest yield proportion in Inner Mongolia.（2）By summarizing the heat resources（≥10℃）in Inner Mongolia,the spatial changes of spring maize maturity type replacement and cultivation mode（early maturity,medium early maturity,medium maturity,medium late maturity and late maturity）were analyzed,and on this basis,the spatial and temporal changes of effective precipitation and crop water requirement during the growth period of spring maize were calculated.The results showed that the accumulated temperature in Inner Mongolia showed an increasing trend from 1959 to 2018,and increased by 307℃from 2009-2018 compared with1959-1968.The accumulated temperature isoline shifted significantly,and the planting boundary line of different maturity spring maize moved northward and expanded eastward significantly.From 1959 to 2018,the average effective precipitation during the growth period of spring maize was 114 mm,showing an increasing trend from west to east.The water requirement of spring maize is 481mm,which shows a decreasing trend from west to east.The increase of ET0 in the growing season and the extension of growth period days together lead to the increase of water requirement of spring maize in this region at an average rate of 5.24 mm/10a.The coupling degree of crop water requirement with effective precipitation and groundwater recharge in different climate regions is low.In addition to the increasing trend of coupling degree in the extremely arid area,the overall trend of the other climatic areas is decreasing,which increases the burden of water resources in this area.（3）In view of the coexistence of arid areas and irrigation areas in this area,this study comprehensively considers the effects of crop water requirement,effective precipitation and groundwater recharge during the growth period of spring maize,takes the water surplus and deficit as the basic quantity,and refers to the SPEI index construction process,constructs the standardized water deficit index（SPEI-IR）,and tests and analyzes its applicability.At the same time,based on the main meteorological disasters in agricultural areas,SPEI-IR,Z index and accumulated temperature anomaly index are selected to analyze the spatial and temporal distribution characteristics of drought,flood and chilling damage during the growth period of spring maize.The results are as follows:on the time scale,the drought index in the early growth stage has a tendency to become wet,and in the middle,late and whole growth stages has a tendency to become dry.In the spatial distribution,the drought in the western region is weakened,and the drought in the eastern region is strengthened.The drought frequency in each growth stage is maintained at about33%,mainly light drought,and the drought range in other periods is mainly increasing except the early growth stage.The frequency of floods in each growth period is about 20%,mainly large floods.The scope of floods in the early and middle growth periods shows an increasing trend as a whole,and the scope of floods in the late growth period and the whole growth period shows a decreasing trend as a whole.With the extension of crop growth period,the frequency of chilling injury also shows an increasing trend,and the high chilling injury is mainly distributed in the mideast and northeast regions.（4）Based on the occurrence characteristics of disasters,collect agricultural production materials and socio-economic indicators,and establish a risk assessment system from four aspects:the hazard of disaster causing factors,the exposure and vulnerability of disaster carriers,and the ability to prevent and reduce disasters.The research shows that the comprehensive hazard is high in the midwest regions,western regions and northeast regions of Inner Mongolia.The high exposure areas during the growth period of spring maize are mainly distributed in Kezuohouqi,Wulanhaote,Kailu and Alashanzuoqi.The vulnerability level is between 0.30 and 0.86,and the vulnerability index of the eastern region is larger than that of the western and central regions as a whole.Areas with strong disaster prevention and mitigation capabilities are mainly concentrated in Bayannaoer city,the southern regions of Chifeng and Tongliao,and the vicinity of Zhalantun.In the risk assessment of meteorological disasters,the risk areas above the median value are widely distributed,mainly in the western region,the mideast and the northeast of Inner Mongolia.（5）The research on meteorological disaster prediction shows that the temperature and precipitation show a significant increasing trend under RCP4.5 and RCP8.5 scenarios.Under the two scenarios,the drought index SPEI of each station shows a downward trend,especially in the western region.The hazard assessment shows that from 2031 to 2060,the areas with high drought hazard under RCP4.5 scenario are mainly in Alashan and the western region of Hulunbeier,and the whole region is mainly in medium hazard areas under RCP8.5 scenario.There is similar spatial distribution of drought hazard in the two scenarios from 2071 to 2100.Under the two scenarios in different time periods,the hazard of flood and chilling damage is higher in the northeast.Except for 2071-2100,the high value areas of comprehensive hazard under RCP4.5 scenario are distributed in the west and the mideast,and the hazard in the east is higher in other periods. |
