Both advanced and delayed shifts of different magnitude in flowering phenology, based on limited controlled experiments and ground-based observational studies, have been reported on the Qinghai–Tibetan Plateau (QTP). To clarify flowering phenological changes, we collected 1646 ground-observed phenological records of 21 species, from 27 stations, for 78 time series, and daily average air temperature data from 1983 to 2017 on the QTP. Trends in the first flowering date (FFD) and changes with temperature increase were analyzed using regression models. The FFD of early flowering time series showed an overall trend for significant advance (-0.371 ± 0.149 days/year, p < 0.001), whereas the mid-to-late-flowering showed a delayed trend (0.158 ± 0.193 days/year, p = 0.108). This finding is in contrast with the stable trend for early flowering species and the advanced trend for midsummer and late-flowering species in high latitude and Arctic regions, where the low-temperature environment is similar. The growing degree days from 1 January to the day of the observed occurrence of the FFD for early flowering time series kept stable (p = 0.531) and FFD showed a positive regression with chilling days; however, the growing degree days of mid-to-late-flowering time series increased significantly at a rate of 5.375 ± 2.519°C-days/year (p < 0.001), indicating the limitation on FFD from other related climatic factors except for forcing temperature may strengthen, and FFD showed no relationship with chilling days. The mid-to-late-flowering time series showed vernalization sensitivity in the spring of the flowering year, whereas the early flowering time series did not. This indicated that retarded vernalization completion may be responsible for the delayed flowering phenology of mid-to-late-flowering species. The FFD of early flowering species, with flower preformation in the preceding autumn, was mainly controlled by forcing temperature in spring; decreased chilling days indicating warmer winter were also beneficial for development and fitness of preformed floral organs, and thus, temperature increase significantly advanced the FFD. These findings suggest that divergent flowering phenology shifts may alter the species composition and ecosystem services of alpine ecosystems, causing challenges in grassland management.

根据有限的对照实验和地面观测研究，在青藏高原 (QTP) 已经报道了开花物候不同幅度的提前和延迟变化。为阐明开花物候变化，我们收集了来自27个站点、78个时间序列的21个物种的1646条地面物候记录，以及1983年至2017年青藏高原日平均气温数据。使用回归模型分析第一个开花日期 (FFD) 的趋势和随温度升高的变化。早花时间序列的FFD总体趋势显着提前（-0.371±0.149天/年，p < 0.001），而中晚花时间序列呈延迟趋势（0.158±0.193天/年，p = 0.108）。这一发现与低温环境相似的高纬度和北极地区早花物种的稳定趋势和盛夏和晚花物种的提前趋势形成鲜明对比。从 1 月 1 日到早花时间序列观察到 FFD 发生日的生长期天数保持稳定（p  = 0.531），FFD 与寒冷天数呈正回归；然而，中晚花时间序列的生长度天数以5.375±2.519°C-days/年的速度显着增加（p< 0.001)，表明除强迫温度外，其他相关气候因素对 FFD 的限制可能会加强，而 FFD 与寒冷天数无关。中晚花时间序列在开花年份的春季表现出春化敏感性，而早花时间序列则没有。这表明春化完成延迟可能是中晚花物种开花延迟的原因。早花品种的FFD主要受春季强迫温度的控制；寒冷天数减少表明冬季变暖也有利于预形成的花器官的发育和健康，因此，温度升高显着促进了 FFD。