Variation characteristics of high temperature and drought compound events during the main growth stage of soybean in Liaoning Province and their effects on yield

Utilizing daily meteorological data collected from 51 stations across Liaoning Province from 1961 to 2020,combined with soybean development stage observation information,this study systematically identifies high temperature and drought disasters based on threshold temperatures for soybean development and employing the Standardized Antecedent Precipitation Evapotranspiration Index (SAPEI) on a daily scale.The spatiotemporal distribution characteristics,variation trends,and impacts on yield of high temperature and drought compound events during the entire growth period and different developmental stages of soybean are analyzed.The results show that these events have had significant impacts on soybean yields.Specifically,the occurrence range of high temperature and drought compound events during the entire growth period exhibits a trend of initial decline followed by an increase,with a multi-year average occurrence range (IOC) of 0.37.The frequency of occurrence gradually decreases from northwest to southeast,with the majority of areas experiencing an occurrence frequency of ≥50%,corresponding to approximately once every two years.During the development stages of soybean,from sowing to branching stage,a large range of high temperature and drought compound events were prone to occur,and the IOC showed a fluctuating upward trend,with a high frequency of occurrence,about once in 5 years.From branching to mature stage,the occurrence frequency of high temperature and drought compound events is low and the occurrence range is small.In 2000,a high temperature and drought compound event occurred in the critical period of soybean water demand in Liaoning Province.The IOC value of the occurrence range was 0.78,the HDD was 86.25 ℃·d,and the drought accumulation index was -23.42,which had a significant impact on the final yield of soybean,with a yield reduction rate of 7.7%.In summary,the high temperature and drought events of soybean in Liaoning Province have obvious regional differences and developmental stage differences.