Unprecedented modern rates of warming are expected to advance alpine treelines to higher elevations, but global evidence suggests that current treeline dynamics are influenced by a variety of factors. Seasonal snow cover has an essential impact on tree recruitment and growth in alpine regions, which may in turn influence current treeline elevation; however, little research has been conducted on its role in regional treeline formation. Based on 11,804 treeline locations in the eastern Himalayas, we extracted elevation, climate, and topographic data for treeline and snowline. Specifically, we used linear and structural equation modelling to assess the relationship between these environmental factors and treeline elevation, and the climate-snow-treeline interaction mechanism. The results showed that the treeline elevation increased with summer temperature and permanent or seasonal snowline elevation, but decreased with snow cover days and spring temperature at the treeline positions (P ​< ​0.001). Importantly, spring snowline elevation (33.4%) and seasonal snow cover days (21.1%) contributed the most to treeline elevation, outperforming the permanent snowline, temperature, precipitation, and light. Our results support the assertion that the temperature-moisture interaction affects treeline elevation in the eastern Himalayas, but we also found that the effects were strongly mediated by seasonal snow cover patterns. The increasing tendency of snow cover governed by climate humidification observed in the eastern Himalayas, is likely to limit future treeline advancement and may even cause treeline decline due to the mortality of the remaining old trees. Together, our findings highlight the role of seasonal snow cover patterns in determining treeline elevation in the eastern Himalayas, which should be considered when assessing the potential for treeline ascent in snow-mediated alpine systems elsewhere.

前所未有的现代变暖速度预计会将高山林线推向更高的海拔，但全球证据表明，当前的林线动态受到多种因素的影响。季节性积雪对高山地区的树木补充和生长具有重要影响，这可能反过来影响当前的林线高度；然而，关于它在区域树线形成中的作用的研究很少。基于喜马拉雅东部 11,804 个树线位置，我们提取了树线和雪线的海拔、气候和地形数据。具体来说，我们使用线性和结构方程模型来评估这些环境因素与林线海拔之间的关系，以及气候-雪-林线相互作用机制。P < 0.001）。重要的是，春季雪线海拔 (33.4%) 和季节性积雪天数 (21.1%) 对林线海拔的贡献最大，优于永久雪线、温度、降水和光照。我们的结果支持温度-水分相互作用影响喜马拉雅东部树木线海拔的断言，但我们还发现这种影响强烈受到季节性积雪模式的影响。在喜马拉雅山脉东部观察到的受气候加湿影响的积雪增加趋势可能会限制未来林线的推进，甚至可能由于剩余老树的死亡而导致林线下降。总之，我们的研究结果强调了季节性积雪模式在确定喜马拉雅东部地区林线高度方面的作用，