| 摘 要： |
Phenological changes in global vegetation are often attributed to climate warming. However, climate warming and elevated atmospheric CO 2 concentration ( e CO 2 ) are two co-occurring global change factors, and how e CO 2 would affect vegetation phenology has received less attention. The partial pressure of atmospheric CO 2 on the Tibetan Plateau (TP) is lower than that in regions of lower altitudes. Consequently, the growth and phenology of alpine plants in this region could be more sensitive to e CO 2 , but this hypothesis is not yet supported by empirical evidence. Here we explored the effect of e CO 2 on plant phenology (including phenophases of green -up, budding, and flowering) through a 5 -year field manipulation experiment in a high -altitude (4600 m above sea level) alpine grassland on the TP. Our results showed that e CO 2 significantly advanced the spring phenology of an earlyflowering species ( Kobresia pygmaea ), while it had no impact on the phenology of two mid -flowering species ( Potentilla saundersiana and Potentilla cuneata ). Compared to other low -altitude regions, plant phenology on the TP underwent greater alterations under e CO 2 , which supports our hypothesis that the growth of high -altitude plants is more sensitive to e CO 2 . Furthermore, we found that e CO 2 significantly reduced the overlapping of flowering between contrasting plant species, mainly due to the phenological advancement of the K. pygmaea induced by e CO 2 . The observed advancement of the spring phenology in K. pygmaea under e CO 2 was associated with increasing ecosystem water -use efficiency (WUE), thereby advancing its subsequent phenological development, such as budding and flowering. Our findings provide experimental evidence that atmospheric CO 2 enrichment can accelerate plant growth processes in high -altitude regions, and suggest that large-scale model simulations should consider the effects of elevated atmospheric CO 2 concentration on plant growth and phenology. |
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