Seed Germination in Alpine Meadow Steppe Plants from Central Tibet in Response to Experimental Warming

Clarifying the effects of climate warming on seed germination is critical for predicting plant community assembly and species renewal, especially in alpine grassland ecosystems where warming is occurring faster than in other biomes globally. We collected matured seeds of 19 common species from a typical alpine meadow steppe community in Central Tibet. Seeds were germinated in three incubators with manipulated day-night temperatures to impose three treatments: (1) theoretically optimal values of 25/15 °C, (2) temperatures observed in the field (control), and (3) a warming of 3 °C above the observed temperatures. We calculated seed germination percentage (SGP) and mean germination time (MGT) per species at different treatments. Our results showed that SGPs of Stipa capillacea , Kobresia macrantha , Potentilla saundersiana , Saussurea tibetica , Pedicularis kansuensis , and Androsace graminifolia were higher under the warming treatment than under control. Among them, the MGTs of S. capillacea , K. macrantha , and And. graminifolia were significantly shortened, while the MGT of Pe. kansuensis was significantly lengthened by warming of 3 °C. Significant decreases in MGT induced by warming were only observed for Festuca coelestis and Anaphalis xylorhiza . Additionally, the treatment with theoretically optimal temperatures restrained germination of Stipa purpurea , S. capillacea , F. coelestis , and Sa. tibetica seeds but promoted germination of K. macrantha , Astragalus strictus , P. saundersiana , Potentilla bifurca , Pe. kansuensis , Swertia tetraptera , Pleurospermum hedinii , and And. Graminifolia seeds, when compared with the control and warming treatments. Therefore, the response of seed germination to warming differs among alpine species, implying that future warming could result in significant changes in community assembly of alpine grasslands on the Tibetan Plateau.