Department of Forest Resources, University of Minnesota, St. Paul, MN, USA.
Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales, Australia.
Nature. 2022 Aug;608(7923):540-545. doi: 10.1038/s41586-022-05076-3. Epub 2022 Aug 10.
The sensitivity of forests to near-term warming and associated precipitation shifts remains uncertain. 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.
森林对近期变暖及相关降水变化的敏感性仍不确定。本研究通过在南方北方森林进行为期 5 年的露天实验，展示了 9 种北美常见树种幼苗对适度气候变化的不同反应。单独升温（比环境温度高 1.6°C 或 3.1°C）或与降雨量减少相结合，增加了所有树种的幼树死亡率，特别是北方针叶树。树种对变暖的生长反应不同，从糖槭和糖枫的增强生长到白云杉、白云杉和黄松的严重生长减少。此外，光合作用和生长的处理诱导变化有助于解释处理驱动的生存变化。在物种经历的条件比其分布边缘更温暖或更干燥的处理中，对生长和存活的影响最为不利。在南部北方森林中丰富的物种由于气候操纵而导致生长和存活的最大减少。相比之下，在变暖响应中死亡率低且生长显著增强的温带物种在整个南部北方森林中很少见，不太可能迅速扩大其密度和分布。因此，预计气候变化将导致目前占主导地位的南部北方物种的再生失败，再加上它们被温带物种缓慢取代，将导致树木再生不足，对区域森林的健康、多样性和生态系统服务产生潜在不利影响。
