| Drought disaster is one of the most common natural disasters in China,which has the most serious impact on agricultural production.Under the trend of global warming,drought events occur frequently in China,which seriously hinders the development of agricultural production and national economy.Songnen Plain,located in Northeast China,is one of the most important grain producing areas in China.Spring Maize is the main grain crop in Songnen Plain.Due to its special geographical location,Songnen Plain is significantly affected by climate change.With the aggravation of global warming,drought events in this region will be more frequent in the future,drought disaster risk of Spring Maize will be more serious,and national food security will be seriously threatened.Therefore,the research on drought disaster of Spring Maize in Songnen Plain has important practical significance for drought disaster monitoring,disaster prevention and mitigation strategy formulation and national food security under the background of abnormal climate change in the future.Based on the national key R&D project"key technologies for quantitative monitoring of global major meteorological disasters by Multi-source Satellite Remote Sensing"(2018YFC1506503)and"disaster risk assessment and prevention technologies and countermeasures for sensitive industries and key regions"(2019YFC1510205),this paper took Songnen Plain in Northeast China as the research area,took Spring Maize drought as the research object,and comprehensively used meteorological observation data and multi-source remote sensing data,on the premise of accurately grasping the characteristics of climate change in Songnen Plain,this paper studied the drought disaster monitoring and risk assessment of Spring Maize in Songnen Plain by improving the meteorological drought monitoring index of Spring Maize,constructing the remote sensing drought index model of each growth period of Spring Maize and constructing the drought risk assessment model of Spring Maize,so as to provide scientific basis for disaster prevention and mitigation and disaster management in Songnen plain.The main contents of this paper are as follows:(1)Based on the meteorological observation data of the study area from 1981 to2018,the potential evapotranspiration was calculated by Penman-Monteith method,and 14 extreme climate indexes were calculated by RClim Dex software.The spatial and temporal variation characteristics of precipitation,temperature,potential evapotranspiration and extreme climate events in the study area were analyzed by univariate linear regression,Sen trend analysis and M-K mutation test.The characteristics and development trend of climate change in Songnen Plain were revealed.(2)In view of the insufficient applicability of existing crop drought monitoring indicators,combined with the construction principles of crop water deficit index(CWDI)and standardized precipitation evapotranspiration index(SPEI),the standardized crop water deficit index(SCWDI)was constructed based on three parameter Log-Logistic probability distribution function with accumulated water deficit as the basic quantity.And the standardized crop water deficit index(SCWDI)was compared with the drought index(Pa,MI,SPI,SPEI,CWDI,CWDIa),the distribution characteristics of vegetation drought stress and the record of actual drought events,and the index was suitable.Based on this index,the temporal and spatial evolution law and trend of Spring Maize drought in Songnen Plain were studied.The results showed that:the SCWDI of Spring Maize in Songnen Plain had a small change trend during the whole growth period,and the spatial drought trend was mainly decreasing.The drought frequency of each growth period was mainly light drought in most regions,and the frequency of severe drought was relatively high in the northwest and southeast during the whole growth period.REOF analysis showed that the drought change of Spring Maize in Songnen Plain was mainly north-south reverse distribution;Morlet wavelet analysis showed that the drought of Spring Maize in each growth period in Songnen Plain was controlled by the first main cycle,and in the next few years,the drought years in other growth periods may increase except the milk-maturity period.(3)In order to solve the problems of vegetation index(NDVI)hysteresis under drought stress and can not reflect the risk of crop yield reduction in the construction of remote sensing drought model,solar-induced chlorophyll fluorescence(SIF)was introduced as the growth state of crops under drought stress.In order to solve the problem that there is less drought monitoring for specific crop growth period in remote sensing drought monitoring,multi-source remote sensing data(SIF,TRMM,LST,etc.)were synthesized and processed according to each growth period of Spring Maize.In order to make the spatial resolution of the remote sensing data consistent,the geographically weighted regression model(GWR)was used to downscale the SIF data and TRMM data,which provides an effective data set for the construction of remote sensing integrated drought model.(4)Based on multi-source remote sensing data,the comprehensive drought index model(CDI)of Spring Maize in each growth period was constructed by using random forest algorithm,and compared with other drought indexes(SCWDI,VCI,VCISIF),Spring Maize yield and soil relative humidity in typical agricultural stations.The effect was better.Finally,the drought information of each development period was extracted from the annual Spring Maize planting area,and the drought monitoring analysis was carried out.The results showed that:during the study period,the drought affected areas of Spring Maize in Songnen Plain were mainly in 2001,2004,2007 and2017.Compared with the national statistical drought affected areas,the change characteristics of remote sensing monitoring results and statistical results were consistent in time series.In Songnen Plain,the drought barycenter of Spring Maize in each development stage mainly tends to the South;in jointing-heading stage,the correlation between drought area and statistical yield of Spring Maize was relatively high,which indirectly indicates the effectiveness of drought monitoring results in this study.(5)Based on the Spring Maize itself and the natural disaster risk theory,the drought related factor indexes of Spring Maize were re-integrated,and the risk assessment model of Spring Maize drought disaster in Songnen Plain was established from the risk of disaster causing factors,vulnerability of disaster bearing body and sensitivity of disaster pregnant environment by using AHP and weighted comprehensive evaluation method.The results showed that in heading-milk maturity period,milk-maturity period and whole growth period,the risk of drought disaster in the west of Songnen Plain was high,so the disaster prevention and mitigation plan should be made in time.And the spatial distribution of high-risk area was similar to the average yield reduction rate of Spring Maize,which indicated that the drought risk zoning scheme in this study was feasible.The innovation of this paper is as follows:This study from the perspective of Spring Maize drought,on the premise of mastering the characteristics of climate change in Songnen Plain,constructed a new Spring Maize meteorological drought index,proposed a method to improve crop remote sensing drought monitoring,formed a set of Spring Maize drought monitoring and risk assessment research technology and method system from meteorological drought monitoring remote sensing drought monitoring drought risk assessment,which realized the effectiveness of drought disaster monitoring and risk assessment of Spring Maize in Songnen Plain,clarified the distribution and evolution trend of drought change of Spring Maize in Songnen Plain,and provides an important scientific and technological means for drought disaster monitoring,disaster prevention and mitigation and disaster management of Spring Maize in Songnen Plain,and also escorts the sustainable development of regional agriculture and food security. |
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