Abstract:

Based on the temperature data of 50 meteorological stations from 1961 to 2018 and the investigation data of winter wheat growth periods from 1997 to 2017 in central and northern Shaanxi, we analyzed the spatiotemporal variations of heat resources before the turning green stage of winter wheat under the background of climate change and their potential effects on winter wheat, by using the linear trend estimation, Mann-Kendall test and GIS technique. Meanwhile, the correlations between the key development periods of winter wheat and critical temperature were studied. The results showed that: (1) in central and northern Shaanxi, there were significant correlations between the sowing date of winter wheat and the final day ≥14℃, between the beginning date of winter wheat overwintering stage and the final day ≥0℃, and between the turning green date and the initial day ≥0℃; (2) the average sowing date of Guanzhong plain was 10 days later than that of Weibei plateau, the ten-day average temperature and the accumulated temperature ≥0℃ before winter had an increasing trend in the two regions, the suitable sowing date of winter wheat was gradually postponed with the delaying of the final day ≥14℃, and the delaying trend was particularly obvious in the late 1990s; (3) the beginning date of winter wheat overwintering stage in the southern region was earlier than that in the northern region, but the turning green date showed the opposite distribution; the turning green date of winter wheat had an obvious advance in recent 58 years, but the beginning date of winter wheat overwintering stage had no obvious change; (4) the duration and the negative accumulated temperature during overwintering decreased with the climate warming, while the annual minimum temperature showed an evidently increasing trend in Guanzhong plain. These changes are beneficial to reducing the freezing injury risk of winter wheat, but could weaken the cold resistance of winter wheat and raise the base of overwintering diseases and insect pests.

Key words: winter wheat, turning green stage, overwintering, accumulated temperature, Shaanxi