A comparative analysis of the spatio-temporal variation in the phenologies of two herbaceous species and associated climatic driving factors on the Tibetan Plateau

- Spatial-temporal variation in the phenologies of two plant species was compared.
- Variation in phenology was mainly driven by the temperature gradient with altitude.
- Phenological sequence between the two species changed with temperature/altitude.
- Variation in autumn phenology of both species can be explained by cold degree days.

Studying the differences in phenology among plant species is important for understanding their physiological and reproductive responses to climate change and complex inter-species interactions. This study conducted a comparative analysis of the spatio-temporal variation in the phenologies of two herbaceous species (Plantago asiatica and Taraxacum mongolicum) and associated climatic driving factors on the Tibetan Plateau (TP) based on ground-observed phenology data during 2000-2012. The results indicated that both spring and autumn phenology of the two species showed strong dependences on altitude, latitude and longitude, although the magnitudes of the variation with geographical factors were different among species. Change in altitude contributed the most to the spatial variation in phenology for both species. In addition, strong dependences on altitude were also observed for the phenological differences between the two species. With the increase of altitude, the same phenophases of the two species tended to occur synchronously at first and then the chronological order of the same phenophases between the two species changed. Spring and autumn phenophases showed significant negative correlations with the growing degree-days (GDD) and the cold degree-days (CDD) (p < 0.001), respectively. Moreover, the phenophases of T. mongolicum were more sensitive than those of P. asiatica in response to GDD or CDD, which explained the spatial variation in the phenological difference between the two species. The divergent phenological responses to climate change and the spatial variation in phenological differences between P. asiatica and T. mongolicum may alter the inter-species interactions between the two species.