Construction and Analysis of Freezing Damage Indices for Winter Wheat During the Overwintering Period in Northern Xinjiang, China

Abstract

Freezing damage indices of winter wheat during snowfall in the overwintering period in northern Xinjiang, China, were constructed using six climate factors: the negative accumulated temperature, average temperature, maximum cooling range, average snow depth, extreme minimum temperature, and average wind speed. A snow depth data processing method was designed. The principal component method was used to construct the freezing damage indices. The freezing damage indices were constructed and analyzed separately using three different sources of data: freezing damage conditions recorded by 49 meteorological stations during 1960 − 2020; freezing damage conditions recorded by 11 wheat observation stations during 1960 − 2020; and freezing damage conditions recorded by 83 meteorological observation stations during 2016 − 2020. Before the analysis of disaster factors, Kaiser–Meyer–Olkin measure of sampling adequacy and Bartlett's test of sphericity were applied to test the suitability of factor selection. The results were analyzed to determine freezing damage according to a Mann–Kendall mutation test. Historical freezing damage data were used to test the freezing damage indices. The results showed that the indices did reflect the freezing damage in northern Xinjiang. In the last 60 years, the interannual variation of the freezing damage indices in northern Xinjiang displayed a significant downward trend.The freezing damage indices changed abruptly around 1985, and the frequency, extent, and scope of severe freezing damage in northern Xinjiang significantly decreased under climate warming. At the same time, instability was apparent due to climate change, with an increase in freezing damage from 1990 to 2009, a decrease from 2010 to 2020, and an increase in the area over which mild and moderate freezing damage occurred in the past 5 years. The analysis of wheat observation stations showed that the maximum cooling range and extreme minimum temperature during the overwintering period had the greatest influence on freezing damage of winter wheat. A large part of the winter wheat crop experienced frequent freezing damage, and it is therefore necessary to predict and prevent freezing damage in advance, and adjust the regional planting regime according to climate change.