Abstract
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.
Highlights
IntroductionSeed germination plays a vital role in the propagation and renewal of plant communities [1], which represents a predictable ecosystem function in response to changes in biotic and abiotic factors [2,3]
Seed germination plays a vital role in the propagation and renewal of plant communities [1], which represents a predictable ecosystem function in response to changes in biotic and abiotic factors [2,3].Generally, seed germination characteristics differ among species
The only significant differences in seed germination percentage (SGP) between the temperature treatments occurred in F. coelestis, where SGP was approximately 15% lower under the optimal treatment than under the control or warming treatments (Figure 2)
Summary
Seed germination plays a vital role in the propagation and renewal of plant communities [1], which represents a predictable ecosystem function in response to changes in biotic and abiotic factors [2,3]. It is generally believed that low temperatures and short growing seasons result in high seed mortality and low seedling survival [8,9]. This indicates that seed germination contributes little to vegetation renewal and seedling establishment in an alpine ecosystem [10] because the process of alpine vegetation renewal is mainly achieved through clonal propagation [11]. Sexual propagation might be vital in the renewal and establishment of alpine plants
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