Department of Silviculture and Forest Ecology of the Temperate Zones, Faculty of Forest Sciences and Forest Ecology, University of Göttingen, Büsgenweg 1, 37077, Göttingen, Germany.
Albrecht von Haller Institute for Plant Sciences, Plant Ecology and Ecosystem Research, University of Göttingen, Grisebachstraße 1 and 1a, 37077, Göttingen, Germany.
Glob Chang Biol. 2016 Feb;22(2):903-20. doi: 10.1111/gcb.13113. Epub 2016 Jan 6.
Some forest-related studies on possible effects of climate change conclude that growth potential of European beech (Fagus sylvatica L.) might be impaired by the predicted increase in future serious drought events during the growing season. Other recent research suggests that not only multiyear increment rates but also growth resistance and recovery of beech during, respectively, after dry years may differ between pure and mixed stands. Thus, we combined dendrochronological investigations and wood stable isotope measurements to further investigate the impact of neighborhood diversity on long-term performance, short-term drought response and soil water availability of European beech in three major geographic regions of Germany. During the last four decades, target trees whose competitive neighborhood consisted of co-occurring species exhibited a superior growth performance compared to beeches in pure stands of the same investigation area. This general pattern was also found in exceptional dry years. Although the summer droughts of 1976 and 2003 predominantly caused stronger relative growth declines if target trees were exposed to interspecific competition, with few exceptions they still formed wider annual rings than beeches growing in close-by monocultures. Within the same study region, recovery of standardized beech target tree radial growth was consistently slower in monospecific stands than in the neighborhood of other competitor species. These findings suggest an improved water availability of beech in mixtures what is in line with the results of the stable isotope analysis. Apparently, the magnitude of competitive complementarity determines the growth response of target beech trees in mixtures. Our investigation strongly suggest that the sensitivity of European beech to environmental constrains depends on neighborhood identity. Therefore, the systematic formation of mixed stands tends to be an appropriate silvicultural measure to mitigate the effects of global warming and droughts on growth patterns of Fagus sylvatica.
一些与森林相关的研究得出结论，未来生长季节严重干旱事件的预测增加可能会损害欧洲山毛榉（Fagus sylvatica L.）的生长潜力。其他最近的研究表明，不仅多年增量率，而且山毛榉在干旱年份期间和之后的生长阻力和恢复能力在纯林和混交林中可能不同。因此，我们结合树木年代学研究和木材稳定同位素测量，进一步研究了林分多样性对德国三个主要地理区域欧洲山毛榉长期表现、短期干旱响应和土壤水分可用性的影响。在过去的四十年中，与共存物种竞争的目标树木表现出比同一调查区域纯林的山毛榉更好的生长性能。在异常干旱的年份也发现了这种普遍模式。尽管 1976 年和 2003 年的夏季干旱主要导致目标树木暴露于种间竞争时相对生长下降幅度更大，但除了少数例外，它们仍然形成了比附近单一种群中生长的山毛榉更宽的年轮。在同一研究区域内，与其他竞争物种林分相邻的山毛榉目标树木径向生长的恢复速度始终比单一种群中慢。这些发现表明，在混交林中，山毛榉的水分可用性得到了改善，这与稳定同位素分析的结果一致。显然，竞争互补性的大小决定了目标山毛榉树木在混交林中的生长响应。我们的研究强烈表明，欧洲山毛榉对环境限制的敏感性取决于林分的身份。因此，系统地形成混交林倾向于成为一种适当的造林措施，以减轻全球变暖和干旱对欧洲山毛榉生长模式的影响。
