Key message

In mixed combinations, the negative impact of water reduction and N addition is mitigated for F. sylvatica, but not for conifers.

Insight into the responses of trees in mixed and monospecific cultivation to water scarcity and nitrogen (N) excess is necessary to recommend suitable tree mixtures for future European forests. Our aim was to investigate the impact of water reduction, N addition or water reduction + N addition in comparison with control (well-watered, no excess N) on mycorrhizal roots and biomass of three temperate forest species (Fagus sylvatica Fs, Picea abies Pa, and Pseudotsuga menziesii Pm) grown in monospecific (FsFs, PaPa, PmPm) and mixed combinations (PaFs, PmFs). We predicted the probability of the responses with a Bayesian approach. Mycorrhizal colonization declined marginally for P. menziesii in PmFs under water reduction. Under water reduction and N addition combined, we found a decline in root tip vitality of F. sylvatica in PaFs and of P. abies in PaPa. F. sylvatica shoot biomass declined under water reduction + N addition in the monospecific combination. P. abies and P. menziesii had lower root biomass in mixture with F. sylvatica under water reduction + N addition and under water reduction as single factor, respectively. With water reduction and N addition, P. menziesii performed better than P. abies in terms of biomass production. F. sylvatica had a growth advantage in mixture with conifers instead of conspecifics. These findings suggest that young trees show rapid and interspecific responses to species mixing and water + N availability. The selection of suitable tree species should, therefore, consider their interactive responses to changing abiotic factors.

中文翻译：

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减水增氮条件下水青冈、冷杉和黄杉单种和混合组合的菌根、根尖活力和生物量

关键信息

在混合组合中，减少水和添加氮的负面影响对F. sylvatica有所缓解，但对针叶树则不然。

深入了解混合和单一种植的树木对缺水和氮 (N) 过量的反应对于为未来的欧洲森林推荐合适的树木混合物是必要的。我们的目的是调查与对照（浇水良好、无过量氮）相比，减水、添加氮或减水+添加氮对三种温带森林物种（水青冈 Fs、云杉Pa ）的菌根和生物量的影响和Pseudotsuga menziesii Pm）以单特异性（FsFs、PaPa、PmPm）和混合组合（PaFs、PmFs）生长。我们用贝叶斯方法预测了响应的概率。在减水条件下，PmF 中P. menziesii的菌根定殖略有下降。在减水和添加氮相结合的情况下，我们发现PaFs 中的F. sylvatica和 PaPa 中的P. abies的根尖活力下降。在单特异性组合中，在减水+添加氮的情况下，F. sylvatica地上部生物量下降。在减水+施氮和减水作为单因素的情况下，冷杉和孟氏松与森林狼的混合物的根生物量分别较低。通过减水和添加氮，孟氏松在生物量生产方面表现优于冷杉。 F. sylvatica在与针叶树混交中比同种植物具有生长优势。这些发现表明，幼树对物种混合和水+氮可用性表现出快速和种间的反应。因此，选择合适的树种应考虑它们对不断变化的非生物因素的相互作用反应。