Accurate projections of growing-season duration of trees are crucial in evaluating the capacity of forests to mitigate climate warming through growth and CO₂ uptake. However, little is known on how and to what extent the growing season of tree height growth will change under future warming. Herein, we projected the height-growth phenology of Smith fir (Abies georgei var. smithii) along two altitudinal gradients on the southeastern Tibetan Plateau under CMIP6 climate scenarios by using process-based phenology models. The models performed well when simulating timings of height-growth onset and cessation on the plot level, with root mean square errors of less than 5.8 and 3.8 days, respectively. From the 2020s to 2090s, the onset of height growth (i.e. bud swelling date) was predicted to advance by 10 ± 6 days under four warming scenarios. The elevational gradients of onset of bud swelling would significantly decrease from 3–4 to 1–2 days 100m⁻¹ under the warmest climate scenario, suggesting future warming may result in more uniform onset of height growth along elevational gradients. Given the temporal variation of thermal requirements, the projected cessation of height growth was delayed by 3 ± 1 days in most plots. Overall, the height-growth duration was predicted to lengthen by 4–22 days by the end of the century. The extended duration of height growth predicted for Smith fir could enhance primary growth, forest productivity, and CO₂ sequestration on the southeastern Tibetan Plateau.

准确预测树木的生长季节持续时间对于评估森林通过生长和吸收CO _{2来缓解气候变暖的能力至关重要。}然而，在未来变暖的情况下，树高生长的生长季节将如何变化以及在多大程度上变化知之甚少。在此，我们预测了史密斯冷杉 ( Abies georgei var . smithii ) 的高度生长物候) 沿青藏高原东南部两个海拔梯度在 CMIP6 气候情景下使用基于过程的物候模型。这些模型在模拟样​​地层级的身高增长开始和停止时间时表现良好，均方根误差分别小于 5.8 天和 3.8 天。从 2020 年代到 2090 年代，在四种变暖情景下，高度增长的开始（即芽膨胀日期）预计将提前 10 ± 6 天。芽肿胀开始的海拔梯度会从3-4天到1-2天100m ^{-1显着降低}在最温暖的气候情景下，这表明未来的变暖可能会导致沿海拔梯度的高度增长更加均匀。考虑到热量需求的时间变化，在大多数地块中，预计高度生长的停止延迟了 3 ± 1 天。总体而言，预计到本世纪末，身高增长持续时间将延长 4-22 天。预计史密斯冷杉高度增长的延长持续时间可以提高青藏高原东南部的初级生长、森林生产力和 CO _2封存。