| Using the meteorological data from 7 counties (districts), and the phenological records and output data from 6 counties (districts) in Pingliang City, Gansu Province, the indicators for frost damage during apple bloom period, the output loss caused by frost damage and the occurrence frequency for different damage degrees were analyzed. According to field investigations of frost damage in recent years, the grades for frost damage during apple bloom period were classified into three levels: serious (T≤-3.5℃), moderate (T≤-1.5℃) and slight (T≤0℃), which corresponded to different rates of output loss. In the 7 counties (districts) in Pingliang, frost damage was most serious in Huating where the occurrence frequency of frost damage with different
levels was 1-2 times per year, and it was most slight in Chongxin where the occurrence frequency of frost damage with different levels was 1 time every 3 years, while the occurrence frequency was 1 time every 1-2 years in other counties (districts). The frequency distribution of frost damage for different levels was ordered as: slight > moderate > serious. Furthermore, the regional division of
damage risk for apple was made by using loss rate. The whole city could be divided into 3 regions including high risk region, mid risk region and low risk region, and most part of the city belonged to the mid or low risk region. Serious frost damage occurred rarely, but moderate and slight frost damage occurred frequently in Pingliang. It is suggested that, on the basis of current layout of orchards, the planting area be further expanded in the middle and eastern part of Pingliang where belongs to the low risk region. |