Abstract: To reveal the characteristics of apple phenology changes and its response to climate warming on the Tibetan plateau, with a view to providing basic scientific and technological support for local apple cultivation, management, breeding and coping with climate change. Both phenological data and meteorological items measured in the period of apple growth in Tsedang agrometeorological station from 2001 to 2020 were analyzed, which include phenological dates and the daily mean value of several meteorological factors such as mean temperature(T_m), maximum temperature(T_max), minimum temperature(T_min), diurnal temperature range(DTR), precipitation(Pr), relative humidity(RH), sunshine duration(S), and accumulated temperature above 0℃(∑T₀) et al. Statistical methods, including linear regression, Pearson correlation coefficient and stepwise regression, were used to reveal the trends and identify the leading factors caused the changes in apple phenology in south-central Tibet in the past 20 years. The results indicated that: (1) all of the apple phenological dates were postponed in a range from 2.83 to 7.64d·y⁻¹ in south-central Tibet from 2001 to 2020 except for the fruit maturing date (FMD), which exhibited an advanced rate of 1.28d·y⁻¹. The length of fruit growing period (LFG) and flowering duration (FD) were shortened by 8.92d·y⁻¹ and 5.98d·y⁻¹, respectively, while the length of tree growing season(LTG) was slightly extended at an increasing rate of 0.65d·y⁻¹. These results were different from the main apple producing areas in northern China where the autumn phenophase was delayed and the spring phenophase was advanced, and may be attributed to the reduction of ∑T₀ during the growth seasons. (2) For all of apple phenological stages, the T_max has increased with T_min decreasing, leading to a significant larger value of DTR. For most of the phenological stages, RH and S have reduced significantly, while Pr increased before FMD and decreased afterwards. (3) In spring, temperature was identified as the dominant factor with negative correlation with the phenophase in south-central Tibet. In contrast, Pr was the leading factor causing changes in autumn phenophases, which was positively correlated with the FMD and negatively correlated with both the end of leaf coloring date (LCD) and the end of leaf fall date (LFD). (4) For most of the phenology, ∑T₀ has been revealed as the leading factor influencing the length of phenological period. However, Tm has played the dominant roles influencing the length of the whole period and the period from the FMD to LCD, and S can be viewed as the leading factor influencing the length of the period from the LCD to LFD. It has been identified that the first flowering date was advanced by 2.32 days when T_max increased by 1°C in early March, and the LFD was advanced by 8.55 days when Pr changed with 10mm in late October in this study region.

Key words: Malus pumila, Phenology, Climatic factor, Change trend, Tibet