Refined Risk Zoning of High Temperature and Heat Damage to Greenhouse Tomato in Southern China

With the intensification of global warming, high temperature and heat damage of spring-summer occurs frequently in recent years, which seriously affects the growth of greenhouse tomato and reduces agricultural economic efficiency. The high temperature and heat damage risk zoning of tomato is especially important, but the research is not sufficient. Based on meteorological data of 359 stations from 1990 to 2019 and greenhouse microclimate measured data, the highest daily temperature in the southern greenhouse is simulated by the BP neural network. Combining high temperature control test data using correlation analysis and principal component analysis methods, the main indicators are screened out, and a high temperature stress index model is constructed. The mean-standard deviation method is used to divide three levels of high temperature stress, and then the temperature with duration corresponding to the critical value of different levels of high temperature stress index are determined respectively, and the risk index system is established. Using geographic information system (GIS) software and other mathematical statistical methods, the characteristics of the year-over-year changes in the frequency of high temperature and thermal damage of tomatoes in the research area are analyzed, and a comprehensive risk index is established to assess the trend of risk development of high temperature and heat damage to greenhouse tomato in the past 30 years. The results show that the frequency of mild and severe high temperature and heat damage is increasing from 1990 to 2019, while the frequency of moderate high temperature and heat damage shows a different pattern (insignificant decrease trend). Among them, the frequency of mild high temperature and heat damage is the highest, followed by moderate high temperature and heat damage. The frequency of heat damage of various grades varies greatly from year to year. There are obvious differences in the distribution of the risk of high temperature and heat damage in space. High-risk areas of heat damage in southern greenhouse tomato are mainly distributed in the western and eastern parts of Guangdong, the eastern and western parts of Guangxi, and the northern, central, and southern parts of Yunnan. The second high-risk areas are mainly distributed in southern Hunan, most areas of Guangxi, central and northern Guangdong, southern Jiangxi, and most areas of Fujian. Areas with moderate heat damage are mainly distributed in north-central Hunan, northwestern Jiangxi, Zhejiang, Anhui, Hubei, and Chongqing. And the risk in western region is low.