Abstract: Elymus nutans and Stipa aliena are typical clonal plants in the alpine grasslands of the Qinghai-Tibet Plateau. Reproductive strategies of both species are influenced by climate change, which in turn affects reproductive success and overall fitness. However, how these strategies respond to temperature changes over different temporal scales, as well as the role of functional traits in regulating these strategies, remain unclear. Based on reciprocal transplant and common garden experiments conducted at three elevations (3200, 3400, and 3800 m) along a mountain slope, we investigated the reproductive traits and the responses of aboveground and belowground functional traits in these two species to short-term and long-term temperature changes. The results showed that: (1) Although short-term warming increased the number of reproductive branches of S. aliena, the ratio of reproductive to vegetative branches in both species significantly changed only under longterm treatments, indicating a delayed response in reproductive strategy. (2) Under long-term warming, for every 100 m decrease in elevation within the range of 3200 m to 3400 m, the ratio of reproductive to vegetative branches of E. nutans decreased by 54.5% (P=0.001), while that of S. aliena increased by 98.4% (P<0.001). Under long-term cooling, for every 100 m increase in elevation, the ratio of reproductive to vegetative branches of E. nutans decreased by 21.6% (P=0.038) within the range of 3200 m to 3800 m, and that of S. aliena decreased by 58.3% (P=0.013) within the range of 3200 m to 3400 m. (3) Long-term warming decreased specific root length of E. nutans, accompanied by an increase in  clonal reproduction. The increased plant height of S. aliena was associated with  a higher proportion of sexual reproduction. Long-term cooling significantly reduced the height of S. aliena, accompanied by a decrease in sexual reproduction. In conclusion, E. nutans tends to increase clonal reproduction under both long-term warming and cooling, while S. aliena increases sexual reproduction under long-term warming but decreases sexual reproduction under long-term cooling. This study underscores the critical role of both aboveground and belowground functional traits in shaping reproductive strategies, offering valuable insights into the adaptation of alpine clonal plants to climate change. Additionally, it provides theoretical support for biodiversity conservation and the adaptive ecosystem management in the alpine grasslands of the Tibetan Plateau.

Key words: Qinghai-Tibet Plateau, reproductive allocation, sexual reproduction, clonal reproduction