Nitrogen Addition Alters the Phenology of a Dominant Alpine Plant in Northern Tibet

Abstract Among the various plant traits, phenology is one of the most sensitive to environmental changes. Nitrogen (N) has been reported to be an important factor constraining plant growth, while N deposition is an increasing concern due to social and economic development. However, studies exploring influences of atmospheric N deposition on alpine plant phenology have been barely reported. We conducted a N addition gradient experiment in an alpine meadow on the plateau to examine plants' phenological response. The results suggest that N addition plays an important role in regulating plant phenology, but only for the dominant species; specifically, the budding time of Kobresia pygmaea advanced in response to N addition. The prolonged lengths of flower phase and reproductive period of K. pygmaea were mainly ascribed to an earlier start of the growing season and more resources being allocated to reproductive growth in the N-rich soil. The N addition caused no effect on the phenology of the accompanying species. There were no obvious phenology differences among each N addition treatment. The earlier budding time and the prolonged growing season of the dominant species in response to the N addition means a longer provision duration of food sources to local herders, which can facilitate local economic development.