枇杷幼果冻害低温等级指标的确定

根据福建省近5a枇杷幼果低温箱试验和低温过程山坡地枇杷冻害观测试验结果，以及主产省福建、浙江历史灾情资料，采用归纳分析和对比印证等方法，对枇杷幼果冻害的低温等级指标进行研究。结果表明：枇杷幼果冻害低温等级指标可用日最低气温（Tmin）和低温持续天数（DD）表示，各级冻害指标分别为，轻度：-2.5℃＜Tmin≤-1.0℃，DD≤3d；中度：-3.5℃＜Tmin≤-2.5℃，DD≤3d或-2.5℃＜Tmin≤-1.0℃，DD＞3d；重度：-4.5℃＜Tmin≤-3.5℃，DD≤3d或-3.5℃＜Tmin≤-2.5℃，DD＞3d；极重：Tmin≤-4.5℃，DD≤3d或Tmin≤-3.5℃，DD＞3d。历史灾情资料验证结果表明，冻害等级指标在福建莆田的推算准确率为61%，在浙江临海、黄岩为87.5%，说明枇杷幼果低温冻害等级指标可应用于低温冻害预测。

Determination of Frozen Injury Grade Index for Young Fruit of Loquat

Based on the data of low temperature box experiment and climatic gradient observation at hillside land in last 5 years, and historical disaster data of the main production provinces, the frozen injury grade index for young fruit of loquat was studied by using methods of induction analysis and contrast verification. The results showed that the frozen injury grade index for young fruit of loquat could be represented by the daily extreme minimum temperature (Tmin) and the continuous days of low temperature (DD). All of the frozen injury grade index was as follows: the mild frozen injury-2.5℃3d, the severe frozen injury-4.5℃3d, the serious frozen injury was Tmin≤-4.5℃ and DD≤3d or Tmin≤-3.5℃ and DD>3d. Compared to historic disaster data, the accuracy of the frozen injury grade index was 61% in Putian region Fujian province, and 87.5% in Huangyan and Linhai region Zhejiang province, which indicated that the frozen injury grade index for young fruit of loquat could be used for frozen disaster prediction.