The distributions of many high-elevation tree species have shifted as a result of recent climate change; however, there is substantial variability in the movement of alpine treelines at local to regional scales. In this study, we derive records of tree growth and establishment from nine alpine treeline ecotones in the Canadian Rocky Mountains, characterise the influence of seasonal climate variables on four tree species ( Abies lasiocarpa , Larix lyallii , Picea engelmannii , Pinus albicaulis ) and estimate the degree to which treeline movement in the twentieth century has lagged or exceeded the rate predicted by recent temperature warming. The growth and establishment records revealed a widespread increase in radial growth, establishment frequency and stand density beginning in the mid-twentieth century. Coinciding with a period of warming summer temperatures and favourable moisture availability, these changes appear to have supported upslope treeline advance at all sites (range, 0.23–2.00 m/year; mean, 0.83 + 0.67 m/year). However, relationships with seasonal climate variables varied between species, and the rates of treeline movement lagged those of temperature warming in most cases. These results indicate that future climate change impacts on treelines in the region are likely to be moderated by species composition and to occur more slowly than anticipated based on temperature warming alone.

中文翻译：

---

高山林线对气候变化响应的区域变异性

由于最近的气候变化，许多高海拔树种的分布发生了变化；然而，高山林线的移动在局部到区域尺度上存在很大差异。在这项研究中，我们从加拿大落基山脉的九个高山林线交错带中获取树木生长和建立的记录，描述季节性气候变量对四种树种（冷杉、落叶松、云杉、白松）的影响，并估计20 世纪树木线运动落后或超过最近温度变暖预测的速度的程度。生长和建立记录显示，从 20 世纪中叶开始，径向生长、建立频率和林分密度普遍增加。恰逢夏季气温升高和水分供应有利的时期，这些变化似乎支持所有地点的上坡林线前进（范围，0.23-2.00 m/年；平均，0.83 + 0.67 m/年）。然而，与季节性气候变量的关系因物种而异，并且在大多数情况下，树木线移动的速度落后于温度变暖的速度。这些结果表明，未来气候变化对该地区林木线的影响可能会受到物种组成的影响，并且发生的速度比仅基于温度变暖的预期要慢。与季节性气候变量的关系因物种而异，并且在大多数情况下，树木线移动的速度落后于温度变暖的速度。这些结果表明，未来气候变化对该地区林木线的影响可能会受到物种组成的影响，并且发生的速度比仅基于温度变暖的预期要慢。与季节性气候变量的关系因物种而异，并且在大多数情况下，树木线移动的速度落后于温度变暖的速度。这些结果表明，未来气候变化对该地区林木线的影响可能会受到物种组成的影响，并且发生的速度比仅基于温度变暖的预期要慢。