Abstract: Regionalization of frost damage risk on spring tea is helpful for optimizing the distribution of high-quality tea planting. Based on the phenology data of Longjing 43 spring tea in 2015-2020 and the meteorological daily data of Hangzhou National Reference Climatological Station in 1951-2020 and 263 regional automatic weather stations in 2010-2020, we estimated early germination date of spring tea in the missing years using an effective accumulated temperature phenology model, and analyzed the spatiotemporal variation of frost damage in spring tea production in Hangzhou City. The spatial distribution maps of frost damage risk for spring tea were developed by conducting the weighted average model of frost damage rate of spring tea. Results showed that the dates for early germination of spring tea and final frost were advanced during the past 70 years, with the advance of final frost date being faster than that of early germination date. The frost years of spring tea were decreasing due to decreasing years of mild frost, whereas severe frost years had a light increasing. The inter-annual variation of moderate frost damage was not obvious and fluctuated greatly among different decades. The variations of frost damage days at different grades were basically consistent with frost damage years. The occurrence frequency of mild, moderate, severe, and extra severe frost was 31.4%, 18.6%, 4.3% and 1.4%, respectively. There was no significant variation in the annual damage rate. For every 100m elevation rising, the early germination date of spring tea and the last frost date were delayed by about 1.3 and 2.6 days, respectively, and the frost damage rate of spring tea increased by about 1%. Generally, the risk of spring frost damage would be higher with increasing altitude. The frost damage on spring tea production showed regional variation in Hangzhou. The frost-free area of spring tea (its damage rate was less than 10%) accounted for 25.2% of the total area of Hangzhou, which was mainly distributed in the Qiandao lake region, the West Lake region, the Qiantang River valley and areas surrounded by large water bodies. Those regions were the priority areas for spring tea planting. The areas with the high risk of frost damage only accounted for 6.3% of total area of Hangzhou. Our results indicated that Hangzhou is suitable for planting high-quality and famous teas-because of the small frost damaging areas of spring tea and the light disaster level.

Key words: Longjing 43, early germination date, spring tea frost, risk zoning, Hangzhou.