Monitoring and estimation of late spring frost and its impact on winter wheat through multi-temporal GF-1 remotely sensed imagery

Abstract

Frost events pose a threat to normal development of winter wheat and increase risk of production loss, even given the context of global warming. Henan province, which is the largest region of winter wheat cultivation in China, late spring frost damage has been one of the major meteorological catastrophes. For systematical and accurate monitoring and estimation of single-event frost damage of winter wheat, serial GF-1 remotely sensed imageries were collected during the winter wheat growth with field investigations and yield measurements in Yanjin county, Henan. Field investigation across Yanjin county based on five grades (normal growth, frost damage grade I to frost damage grade IV) defined by the agricultural indicators was conducted on 15 April and in which 133 ground samples were collected. Based on the investigation, the remotely sensed monitoring and estimation indicated that frost-affected areas accounted for 87.71% of the winter wheat planting area in the whole county. From frost damage I to frost damage IV, the frost-affected areas accounted for 55.52%, 15.79%, 2.90% and 16.32%, respectively. The frost-affected regions were distributed from northeast to southwest of the county, showing zonal distribution; and the severe frost damage regions showed scattered and irregular distribution. Based on the agronomic freezing indicators, it can be concluded that the frost damage III and frost damage IV would cause yield loss of the winter wheat. In an average year, the yield of winter wheat in Yanjin county was about 6750-9000 kg/ha. In 2018, the yield of winter wheat for normal growth and mild frost damage (grade I) was about 6750 kg/ha according to the field investigation; whereas, the yield of winter wheat was 3000-4500 kg/ha for slight frost damage (grade II) which did not form a disaster; and the yield of winter wheat was 600-2250 kg/ha for the severe frost damage (grade III and IV). According to the proportions of areas affected by the frost damage and the yield for different grades, the yield reduction of winter wheat caused by this late spring frost was about 24%-33% in 2018. Our findings reveal region-specific changes in the spring-frost risk that can inform decision-making in land management, forestry, agriculture, and insurance policy.