Chair of Silviculture, Institute of Forest Sciences, University of Freiburg, Freiburg, Germany.
Department of Geography, University of Cambridge, Downing Place Cambridge, UK.
Glob Chang Biol. 2017 Dec;23(12):5108-5119. doi: 10.1111/gcb.13774. Epub 2017 Jun 26.
Improving our understanding of the potential of forest adaptation is an urgent task in the light of predicted climate change. Long-term alternatives for susceptible yet economically important tree species such as Norway spruce (Picea abies) are required, if the frequency and intensity of summer droughts will continue to increase. Although Silver fir (Abies alba) and Douglas fir (Pseudotsuga menziesii) have both been described as drought-tolerant species, our understanding of their growth responses to drought extremes is still limited. Here, we use a dendroecological approach to assess the resistance, resilience, and recovery of these important central Europe to conifer species the exceptional droughts in 1976 and 2003. A total of 270 trees per species were sampled in 18 managed mixed-species stands along an altitudinal gradient (400-1200 m a.s.l.) at the western slopes of the southern and central Black Forest in southwest Germany. While radial growth in all species responded similarly to the 1976 drought, Norway spruce was least resistant and resilient to the 2003 summer drought. Silver fir showed the overall highest resistance to drought, similarly to Douglas fir, which exhibited the widest growth rings. Silver fir trees from lower elevations were more drought prone than trees at higher elevations. Douglas fir and Norway spruce, however, revealed lower drought resilience at higher altitudes. Although the 1976 and 2003 drought extremes were quite different, Douglas fir maintained consistently the highest radial growth. Although our study did not examine population-level responses, it clearly indicates that Silver fir and Douglas fir are generally more resistant and resilient to previous drought extremes and are therefore suitable alternatives to Norway spruce; Silver fir more so at higher altitudes. Cultivating these species instead of Norway spruce will contribute to maintaining a high level of productivity across many Central European mountain forests under future climate change.
提高我们对森林适应潜力的理解是应对预测气候变化的紧迫任务。如果夏季干旱的频率和强度将继续增加，那么需要为挪威云杉（Picea abies）等易受影响但经济重要的树种寻找长期替代品。尽管银冷杉（Abies alba）和花旗松（Pseudotsuga menziesii）都被描述为耐旱物种，但我们对它们对极端干旱的生长反应的理解仍然有限。在这里，我们使用树木年代学方法来评估这些重要的中欧到针叶树种在 1976 年和 2003 年异常干旱中的抵抗力、弹性和恢复能力。在德国西南部的南黑森林和中黑森林的西坡，我们沿着海拔梯度（400-1200 米）在 18 个管理的混合物种林分中，对每个物种总共采集了 270 棵树。所有物种的径向生长对 1976 年的干旱都有类似的反应，但挪威云杉对 2003 年夏季干旱的抵抗力和弹性最低。银冷杉总体上对干旱的抵抗力最强，与花旗松相似，花旗松的生长年轮最宽。海拔较低的银冷杉比海拔较高的银冷杉更容易受到干旱的影响。然而，在较高的海拔，花旗松和挪威云杉的耐旱能力较低。尽管 1976 年和 2003 年的极端干旱情况截然不同，但花旗松的径向生长一直保持最高。尽管我们的研究没有考察种群水平的反应，但它清楚地表明，银冷杉和花旗松通常对以前的干旱极端情况更具抵抗力和弹性，因此是挪威云杉的合适替代品；在较高的海拔，银冷杉更是如此。在未来的气候变化下，种植这些物种而不是挪威云杉将有助于维持许多中欧山地森林的高生产力水平。
