Response of winter wheat to spring frost from a remote sensing perspective: Damage estimation and influential factors

Abstract Spring frost is one of the major weather-related threats to winter wheat. The damage to winter wheat caused by spring frost is aggravated by the increase in extreme weather events and the advance of spring phenology driven by a warming climate. Until recently, studies of frost damage were primarily based on controlled field experiments and crop model simulations, which cannot accurately represent the real frost damage suffered by winter wheat in the natural environment. In this study, a remote sensing-based spring frost damage index (SFDI) was proposed to rapidly and effectively quantify the impact of spring frost on winter wheat at the provincial scale. Compared with the existing methods, the SFDI is easy to implement with widely available remotely sensed vegetation index (VI) time-series data. It can be used to assess spring frost damage to winter wheat in near real-time to allow a rapid response. Although the SFDI was developed for winter wheat and spring frost, it has the potential to be extended to other agricultural hazards and crop types through careful adjustments to the design. We assessed the performance of SFDI using a spring frost event that occurred from April 3–7, 2018, in North China as a case study. The results showed that the severely damaged areas were mainly located at the junction of Hebei, Henan, and Shandong provinces, especially in western Shandong Province. The result showed good agreement with the proxy data retrieved from the national archives of regional newspaper reports about the event. The validity of the new index (SFDI) was also verified against the reduction in county-level crop production. Additionally, we used multivariate linear regression (MLR) and geographically weighted regression (GWR) to identify the key factors affecting the spatial variation in SFDI. The results indicated that the growth status of winter wheat before spring frost and the amount of precipitation during the frost event were the two major factors affecting the severity of frost damage to winter wheat, followed by the accumulated frost degree-days and soil moisture. This suggests that proper management of the crop growth rate after winter wheat greening and adequate soil moisture (from irrigation and precipitation) before and during the spring frost period could greatly alleviate the damage of spring frost to winter wheat.