<b>Indirect effects of warming via phenology on reproductive success of alpine plants</b>

1. Climate warming has induced pronounced shifts in the phenology of alpine plants worldwide, yet the impact of these changes on plant reproduction remains unclear, although phenology plays a vital role in reproduction.2. Based on a 7-yr field warming and altered precipitation experiment initiated in 2017, we measured three reproductive phenological events and seven reproductive traits of six dominant species, belonging to two flowering functional groups, to assess the effects of climate change on reproductive phenology and the reproductive consequence of changing the phenology in an alpine meadow on the eastern Tibetan Plateau from 2021 to 2023.3. Warming significantly advanced the start of flowering in early-spring flowering (ESF) and mid-summer flowering (MSF) plants, while the fruiting period of ESF plants remained stable. Furthermore, warming led to a decrease in the number of seeds and productivity of alpine plants, while seed size remained stable. Phenological changes regulate the reproductive success of alpine plants. Specifically, the start of flowering for ESF plants and the start of fruiting for MSF plants regulated the number of seeds and productivity of the two flowering functional groups, respectively. The increase in phenological niche overlap and intensification of interspecific competition, caused by different phenological responses of the flowering functional groups to warming, also are key factors contributing to the decline in seed production of alpine plants.4. <i>Synthesis.</i> These results demonstrate that the reproductive success of alpine plants would be decreased by earlier reproduction under climate warming, and alpine plants tend to maintain stable seed size in response to climate change. Our study emphasizes the important regulatory and indicative role of reproductive phenology in the sexual reproduction of alpine plants under future climate change.1. 全球范围内，气候变暖已引发高山植物物候（phenology）的显著改变；尽管物候对植物繁殖至关重要，但此类变化对植物繁殖的影响仍未明确。2. 本研究依托2017年启动的为期7年的野外增温与降水调控实验，于2021—2023年间在青藏高原东部（eastern Tibetan Plateau）的高山草甸中，针对隶属于2个开花功能群（flowering functional groups）的6个优势物种，测定了3项繁殖物候事件与7项繁殖性状，以此评估气候变化对繁殖物候的影响，以及物候改变所带来的繁殖后果。3. 增温显著提前了早春开花型（early-spring flowering, ESF）与盛夏开花型（mid-summer flowering, MSF）植物的开花始期，而ESF植物的结实期则保持稳定。此外，增温导致高山植物的种子数量与繁殖产量下降，但种子大小维持稳定。物候变化可调控高山植物的繁殖成功。具体而言，ESF植物的开花始期与MSF植物的结实始期，分别调控了两个开花功能群的种子数量与繁殖产量。开花功能群对增温的物候响应存在差异，由此引发的物候生态位重叠（phenological niche overlap）增加与种间竞争（interspecific competition）加剧，同样是导致高山植物种子产量下降的关键因素。4. 综合分析。本研究结果表明，在气候变暖背景下，繁殖提前会降低高山植物的繁殖成功，而高山植物倾向于通过维持稳定的种子大小来应对气候变化。本研究强调，在未来气候变化场景下，繁殖物候对高山植物的有性繁殖（sexual reproduction）具有重要的调控与指示作用。