Impact of climate changes on apple’s phenophases in the main producing areas of the Loess Plateau in China

Abstract：【Objective】The apple producing area of the Loess Plateau is the largest apple growing and yielding area in China, and also the most significant area affected by climate changes. This article primarily analyzes the effect of climate changes on the apple’s phenophase dates. The most important meteorological factors and the intensity of their influence on phenophase dates will be identified, which could potentially provide a theoretical basis for coping with the climate changes and guiding for fruit production in the region.【Methods】Wanrong, Luochuan and Xifeng were selected as the observed stations of the apple producing areas in the Loess Plateau, representatively, and apple’s phenology data and climate factors were collected from 3 stations during 1994—2018. Apple’s phenology data included the bud break (BO), first leaf unfolding (LU), first flowering (FF)，fruit maturing (FM), end of leaf color conversion (LC) and end of leaf fall (LF), and the length of fruit growing period (FG) and tree growing season (TG) , and the climate factors included daily mean temperature and precipitation. The linear fitting method was used to analyze the interannual trends of climatic factors, phenophase dates and the two different growth stage lengths, and the partial least squares regression (PLS) was applied to identify the impacts of climate changes on different phenology events affected by the daily mean temperature and precipitation.【Results】( 1) Over the past 25 years, the annual average temperature of Wanrong, Luochuan and Xifeng consistently showed an upward trend. The heating degrees per 10 a were0.86, 0.01 and 0.47 ℃ , respectively. The heating degrees per 10 a in spring (MarchMay) were 1. 12, 0.29 and 0.83 ℃ , which were higher than the annual average temperature and other seasonal heating rates. Except for Wanrong’s decreasing trend in summer and winter, the annual and seasonal precipitation increased, with annual precipitation increasing by 13. 1 mm/ 10 a, 27.2 mm/ 10 a and 68.3 mm/ 10 a, respectively. (2)The phenoph