Spatio-Temporal Characteristics Of High Temperature Heat Damage And Heat Damage Risk Zoning Of Rice In The Eastern Sichuan Basin

Under the background of climate warming,high temperature heat damage occurs frequently,which seriously affects regional agricultural production and food security.Sichuan Province is one of the 13 major grain producing areas in China,and rice is the most important grain crop in Sichuan Province.Due to the complexity and diversity of meteorological disasters in Sichuan Province,the increasingly frequent high temperature and heat damage events have become one of the main factors restricting the yield and quality of rice.Based on the meteorological data of 26 meteorological stations in five cities in the eastern Sichuan Basin during the heading and flowering period(July to August)from 2000 to 2018,this paper used annual anomaly and cumulative anomaly method to identify the high temperature anomaly years.The cumulative index of high temperature heat damage was calculated,and the spatial distribution pattern of high temperature heat damage was extracted by using meteorological interpolation software ANUSPLIN.Based on the risk analysis model of high temperature heat damage,the risk of the hazard factors,the exposure and vulnerability of the carrier were considered comprehensively,and the high temperature heat damage risk of rice in the study area was zoned.The results show that:(1)2006 was an abnormally high temperature year,which was the year with the most intense high temperature heat damage in the study period.2017 was a year with significantly higher temperature.2016 and 2018 were warmer years.The cumulative anomaly calculation results of annual mean daily maximum temperature show that the average daily maximum temperature in 2010-2018 is generally higher than that in 2000-2010,and the cumulative anomaly value in 2015-2018 is increasing year by year.It can be predicted that the frequency and intensity of extreme high temperature events will continue to increase in the future.(2)Spatial interpolation was carried out by using ANUSPLIN according to the calculation results of cumulative index of high temperature heat damage over many years and cumulative index of high temperature heat damage in one year.The results showed that the spatial distribution of high temperature heat damage in the study area was significantly different and was significantly affected by topography and terrain.The high temperature heat damage of rice was almost rare in the mountainous area above 500 m,and the cumulative index of high temperature heat damage over many years was less than 20.In the southern part of the study area,the cumulative index of heat damage over the years in Jialing District,Gaoping District,Quxian County,Dazhu County,Dachuan District,Wusheng County,Huaying City,Fengxian District,and Yuechi County in Nanchong City,reaches more than 80,and some areas even reach151.2.The results show that 2006 is the year with the highest intensity of high temperature damage and the most extensive impact area in recent 20 years.The intensity of high temperature damage in 2017 and 2018 is second.In 2016,the occurrence intensity of high temperature heat injury was the least,and the influence range was limited.Most of the cumulative index values of high temperature heat injury in a single year in the affected area were between 0-5 or 5-10.(3)Based on the two phase images synthesized by Google Earth Engine cloud platform,the variation characteristics of rice time series NDVI index and NDWI time series index were used to construct a decision tree to extract rice area with a high precision and a relative error of 7.8%.Dazhou,Nanchong and Guang ’an are the cities with the most extensive rice planting area in the study area,with nearly three quarters of the rice planting area distributed in these three cities.Guang ’an City and Nanchong City are the two cities with the most intensive rice planting in the study area,and each county(district)has a large area of rice planting.(4)The maximum EVI(Maximum EVI,IEVI)data were used as the observation data of rice growth status,and the agricultural gas records of grain number per spike,actual yield of mu and empty shell rate in agricultural gas stations were used as the measured data;Correlation analysis showed that IEVI value extraction of rice planting range in the study area could be used to judge the growth status of rice.The variation anomaly degree of rice IEVI value under different high temperature heat injury years was calculated by grid scale,and the response of rice growth to different high temperature heat injury in different regions could be better identified.(5)The spatial unit of 2.5×2.5km grid was used to analyze the risk of high temperature heat damage of rice in the study area,considering the risk of the hazard factors,the exposure and vulnerability of the carrier.Among them,the high risk areas are mainly distributed in the south and southeast of the study area.The second highest risk areas were mainly distributed in Nanchong City,and some were also distributed in the southern counties of Dazhou and Bazhong City.First,the middle risk area is distributed in the border area between Jiange County,Guangyuan City and the south of Nanchong City.In addition,the middle risk area is concentrated in Enyang District,Bazhong District and Pingchang County to the south of Bazhong City.The low risk area is located in the northern and northeastern mountainous areas of the study area.In this area,the rice planting area is small and the probability of high temperature heat injury is small,so the risk is low.