The effect of climate change on the apple’s initial flowering date in the eastern Gansu province

Abstract: 【Objective】This article primarily analyzes the effect of climate change on the apple’s initialflowering date. The most important meteorological factors will be identified. Two methods will be used toforecast the apple’s initial flowering date in this article. Some scientific results will be provided to betterallow for identifying meteorological disasters before they occur.【Methods】Used partial least square regression method to analyze the correlations between the apple’s initial flowering date and meteorologicalfactors. Use the improved accumulated temperature method, linear correlation method and partial leastsquare regression model to forecast the apple’s initial flowering date. Meteorological factors about light,heat, water were obtained from the Xifeng Agricultural Meteorological Station’s observations. Data aboutapple florescence were obtained from the Xifeng Agricultural Meteorological Station which is located atDongzhi Loess Plateau, Qingyang city, Gansu province. The observed variety of apples for testing was the‘Red Fuji’apple. Meteorological data was obtained from the Xifeng National Based Station in Gansuprovince. The years used for testing were all 22 years from 1994 to 2015.【Results】(1) There was a signifi⁃cant negative correlation between the date of apple florescence and the averange temperature from Febru⁃ary to early April. There was a low correlation between the date of apple florescence and the average temperature from November last year to January this year. When the average temperature was higher, the ap⁃ple blossomed earlier. (2) There was a significant correlation between the accumulated temperature (accu⁃mulated temperature≥0 ℃ and ≥5 ℃) and the apple’s initial flowering date during November 1st lastyear to April 10th this year. The larger the accumulated temperature, the earlier the apple’s initial flowering date. It indicated, with the heat condition increasing year by year, that the apple’s initial floweringdate also showed an advancing trend. The warmer winter temperatures make apple trees safer to gothrough the winter. (3) When the average temperature from March to early April was higher than the mini⁃mum temperature for the growth of apple trees, the apple’s initial flowering date was more than 20 daysbehind the first date of 5 ℃, and was closer to the first date of 10 ℃. (4) The relationship between ten daysor more of monthly precipitation and the apple’s initial flowering date had very little correlation. There⁃fore, precipitation was not the factor that restricted the blossoming date of the apples. (5) There was astrong negative correlation between the apple’s initial flowering date and the sunshine duration in earlyJanuary and March. Especially in March, the sunshine duration had passed the α0.05 significance test,which means in March, when the sunshine duration has increased, the apple’s initial flowering date willalso advance. (6) In using the improved accumulated temperature model to forecast the apple’s initialflowering date from 1994 to 2015, there was a 81.8% year forecast date which was closer to the actualdate. The maximum time difference was 16 days. The years with errors of more than 7 days reached 5years. Then forecasted date of the apple’s initial flowering date in 2013 was April 23th, while the actualdate was April 7th. When the forecasted apple’s initial flowering date was determined by using the linearcorrelation method, the difference between the forecast of the remaining 21 years and the actual date wassmaller, there was a 95.5% year forecast date which was closer to the actual date. When the forecasted ap⁃ple’s initial flowering date was determined by using the partial least square regression model, the differ⁃ence between the forecast of the remaining 21 years and the actual date was similar, there was a 97% yearforecast date which was closer to the actual date. (7) The partial least square regression model for forecast⁃ing the apple’s initial flowering date in the east of Gansu province provided much better results. By accu⁃rately predicting the apple’s initial flowering date, fruit farmers can adjust the apple flowers density andcan also determine frost damage defense in the early spring.【Conclusion】(1)The apple’s initial floweringdate was primarily effected by light, heat, water and other meteorological elements. If the meteorologicalelements are sequenced, the major factor is heat, followed by sunshine, with precipitation being the mini⁃mal effect factor. Global warming and high illumination help to make the apple’s initial flowering date ad⁃vance. (2) The research results about the apple’s flowering response to climate change was the same asother experts and scholars, but there are some differences with Lee Mi-Ying’s study results, such as, theaverage temperature during early February to early April was more important for the apple’s initial flower⁃ing date and the average temperature in March was the most important factor. Also it was concluded thatprecipitation was not the key factor effecting the condition of the apple’s initial flowering date, but LeeMi-Young’s study results show that the apple’s initial flowering date will be inhibited by excessive rain⁃fall. (3) The linear correlation method is a more reliable forecast for the apple’s initial flowering date thanthe improved accumulated method. This article primarily discussed the effect of meteorological factors onthe apple’s initial flowering date, however, the apple’s initial flowering date also was affected by appletree management (such as fertilization, pruning, watering, covering with grass or black plastic film orstraw, etc.) and tree-age, the effect of these factors needs to be further explored.