Responses of 12 plant species flowering phenology to nitrogen and phosphorus nutrient additions in alpine grassland of Haibei, Qinghai

Elucidating the effect in nitrogen and phosphorus nutrient supply changes on the flowering phenology of alpine plants and plant communities is essential when studying the responses of alpine grassland ecosystems to global change. To predict the evolution and pattern of flowering phenology of alpine plants and plant communities in alpine grassland under the continuous increase of atmospheric nitrogen and phosphorus deposition, we observed the flowering phenology of 12 species using the fixed plant marker method under nine different nitrogen and phosphorus nutrient addition treatments in alpine grassland in Menyuan County, Qinghai Province. Results showed that: 1) The effect of nitrogen and phosphorus addition treatments on the overall flowering phenology of alpine plants was mainly to advance the first flowering date and prolong the flowering duration; however, the end flowering day did not change significantly (P > 0.05). 2) The influence of nitrogen and phosphorus additions on the flowering phenology was consistent with each other. There was no significant interaction between nitrogen and phosphorus addition on the flowering phenology of alpine plants (P > 0.05). 3) At the species level, most species are characterized by earlier first flowering date and prolonged flowering duration, while the end flowering day showed no consistent trend. Thus, under the continuous intensification of atmospheric nitrogen and phosphorus deposition, the flowering period of the alpine plant community in the study area tends to advance and extend. For different species, although the changes of the first flowering date and flowering duration were relatively consistent, there will be a certain divergence in the response of the end flowering day.