Responses of phenology and seed production of annual Koenigia islandica to warming in a desertified alpine meadow

- Warming only significantly delayed first budding-set and complete leaf coloring.
- Warming only prolonged the durations of leaf coloring and the total activity period.
- Warming significantly increased seed number and mass per plant.

The distribution of annual plant species greatly expands with degradation and desertification of natural grasslands caused by climate change and overgrazing. However, limited understanding of how their life history traits respond to climate change limits our ability to predict their adaptive strategies in the future. Here we explored effects of warming on phenological sequences and seed production of annual Koenigia islandica using an open top chamber on the Tibetan plateau from 2014 to 2016. Our results indicate that warming significantly delayed first budding-set and complete leaf coloring, and prolonged the durations of leaf coloring and the total activity period in the alpine region. Warming significantly reduced ratio of reproductive and vegetative phases relative to no-warming in 2016. Warming significantly increased plant height at first flowering, seed number and mass, but had no significant effect on seed size in 2016. There was a positive correlation between seed germination time and seed number, and there were negative correlations between seed size and first fruiting-set and flowering duration. Soil temperatures and soil moisture in May and June had positive and negative correlations with seed number and mass per plant, respectively. Our results suggest that the annual plant primarily promotes its fitness through an increase in seed number and mass per plant due to an increase in plant height, rather than by altering phenophases or prolong duration of reproductive phase under future warming in the alpine meadow.