The sensitivity of forests to near-term warming and associated precipitation shifts remains uncertain^{1,2,3,4,5,6,7,8,9}. Herein, using a 5-year open-air experiment in southern boreal forest, we show divergent responses to modest climate alteration among juveniles of nine co-occurring North American tree species. Warming alone (+1.6 °C or +3.1 °C above ambient temperature) or combined with reduced rainfall increased the juvenile mortality of all species, especially boreal conifers. Species differed in growth responses to warming, ranging from enhanced growth in Acer rubrum and Acer saccharum to severe growth reductions in Abies balsamea, Picea glauca and Pinus strobus. Moreover, treatment-induced changes in both photosynthesis and growth help explain treatment-driven changes in survival. Treatments in which species experienced conditions warmer or drier than at their range margins resulted in the most adverse impacts on growth and survival. Species abundant in southern boreal forests had the largest reductions in growth and survival due to climate manipulations. By contrast, temperate species that experienced little mortality and substantial growth enhancement in response to warming are rare throughout southern boreal forest and unlikely to rapidly expand their density and distribution. Therefore, projected climate change will probably cause regeneration failure of currently dominant southern boreal species and, coupled with their slow replacement by temperate species, lead to tree regeneration shortfalls with potential adverse impacts on the health, diversity and ecosystem services of regional forests.

森林对近期变暖和相关降水变化的敏感性仍然不确定^{1,2,3,4,5,6,7,8,9}。在此，通过在南部北方森林进行的为期 5 年的露天实验，我们展示了九种同时出现的北美树种的幼年对适度气候变化的不同反应。单独变暖（高于环境温度 +1.6 °C 或 +3.1 °C）或与降雨减少相结合，增加了所有物种的幼年死亡率，尤其是北方针叶树。不同物种对变暖的生长反应不同，从Acer rubrum和Acer saccharum的生长增强到Abies balsamea、Picea glauca和Pinus strobus的严重生长减少. 此外，治疗引起的光合作用和生长变化有助于解释治疗驱动的生存变化。物种经历的条件比其范围边缘更温暖或更干燥的处理导致对生长和生存的最不利影响。由于气候操纵，南部北方森林中丰富的物种的生长和存活率下降幅度最大。相比之下，因气候变暖而死亡率低且生长显着增强的温带物种在整个南方北方森林中很少见，并且不太可能迅速扩大其密度和分布。因此，预计的气候变化可能会导致目前占主导地位的南方北方物种的再生失败，再加上温带物种的缓慢替代，