Abstract: Abstract Aims Previous studies on the impact of climate change on plant phenology were mostly based on constant warming. However, under natural conditions, climate change shows seasonal and diurnal asymmetry. A few studies based on remote sensing or long-term observations showed that the response of plant phenology to asymmetric warming is inconsistent with that to constant warming. However, due to the limitations of remote sensing and statistical methods, these research conclusions are still uncertain, and ground-based control experiments are needed to accurately determinethe impact characterize of asymmetric warming on plant phenology. Methods An infrared automatic temperature warming experiments (2023-2024) was carried out in the typical development area of the alpine meadow in Nagqu, the heart of the Tibetan Plateau. Three common plants were selected, including the early-flowering plant Potentilla multifida, the mid- and late-flowering plants Stipa purpurea and Leontopodium pusillum, to simulate the characteristics of diurnal and seasonal asymmetric climate warming and constant warming field control experiments, while coupling the water increase factor. Important findings The main findings are that temperature is the main factor affecting the flowering phenology of alpine meadows, while water has no significant effect. Among them, early flowering plant Potentilla multifida, is more sensitive to warming. The mid- to late-flowering plant Stipa purpurea had no significant response to warming. There is no significant difference in the effects of diurnal asymmetric and symmetrical warming on the flowering phenology of all species. A comparison between seasonal asymmetric and symmetric warming revealed that seasonal asymmetric warming significantly advanced the first flowering day of Leontopodium pusillum by about 4-7 days, while there was no significant difference in the flowering phenology of the other two plants. This may indicate that asymmetric warming (especially day and night) does not change the chilling and accumulated temperature processes of plants. Our research results provide empirical data and theoretical guidance for the implementation of future warming experiments on the Tibetan Plateau and the construction of phenological models.

Key words: asymmetric warming, first flowering day, interaction between warming and water increase, alpine meadow, different species