Studies on variations in chilling and heat accumulation in apple trees and their effects on first flowering date under climate change are important for guiding apple planting and productions. In this study, we carried out experiments in representative stations of apple planting areas in the northern China, including Fushan of Shandong, Wanrong of Shanxi, Xifeng of Gansu and Akesu of Xinjiang. The first flowering data and hourly temperature data during 1996-2018 were used to calculate the daily chilling and heat accumulation units by applying the dynamic model and growing degree hour model. Partial least squares regression (PLS) correlated daily chilling and heat units with the first flowering dates was used to identify the chilling and heat accumulation periods for apple flowering. We evaluated the impacts of temperatures during these periods on apples' flowering. Our results showed that the chilling accumulation period of apple trees in the examined sites started at October 1, ended in late February or mid-March, with chilling accumulations of 74.1-89.3 CP (chill portion). The heat accumulation periods were from late January to the first flowering dates with the heat accumulation of 4010-5770 GDH (growing degree hour). The chilling accumulation at Xifeng and Akesu was correlated positively with mean temperature during the respective accumulation period, with 3.8 and 5.0 CP enhancement following 1 ℃ increase during the accumulation period. Heat accumulation at all stations correlated positively with mean temperature during the respective accumulation period, with 725-967 GDH enhancement following a 1 ℃ increase during the accumulation period. Compared to the effects of chilling accumulation on tree flowering, the first flowering data of apples in the main planting areas were mainly affected by mean temperature during the heat accumulation period. Climate warming is beneficial for apple blossom and production in the areas with low mean temperature during the chilling accumulation period.
开展气候变化背景下苹果冷热积累变化及其对始花期的影响研究,对指导苹果种植及生产具有重要意义。本研究选取山东福山、山西万荣、甘肃西峰和新疆阿克苏代表中国北方苹果主产地,利用1996—2018年红富士苹果的始花期观测资料和逐时气温数据,采用动态模型、生长度小时模型分别计算逐日冷积累量(CP)和热积累量(GDH),并利用偏最小二乘回归法,对逐日冷、热积累量和各地苹果始花期进行相关分析,以明确各地苹果冷、热积累起止日期和积累量,以及冷、热积累期内温度变化对始花期的影响规律。结果表明: 我国北方主产地苹果冷积累时段集中于10月1日前后至2月中下旬或3月中旬,积累量为74.1～89.3 CP;热积累时段集中于1月下旬前后至始花期,积累量为4010～5770 GDH。西峰和阿克苏冷积累期内平均气温每升高1 ℃,冷积累量将分别增加3.8和5.0 CP;各地热积累期内平均气温每升高1 ℃,热积累量将增加725～967 GDH。与冷积累期内温度变化的影响效应相比,热积累期内温度变化主控我国北方主产地苹果始花期,且气候变暖总体有利于冷积累期内平均气温较低地区的苹果开花和生产。.
Keywords: Fuji apple; chilling requirement; first flowering date; heat requirement.