Abstract

Mycorrhizal fungi play an important role for the nitrogen (N) supply of trees. The influence of different mycorrhizal types on N acquisition in tree-tree interactions is, however, not well understood, particularly with regard to the competition for growth-limiting N. We studied the effect of competition between temperate forest tree species on their inorganic and organic N acquisition in relation to their mycorrhizal type (i.e., arbuscular mycorrhiza or ectomycorrhiza). In a field experiment, we quantified net N uptake capacity from inorganic and organic N sources using ¹⁵N/¹³C stable isotopes for arbuscular mycorrhizal tree species (i.e., Acer pseudoplatanus L., Fraxinus excelsior L., and Prunus avium L.) as well as ectomycorrhizal tree species (i.e., Carpinus betulus L., Fagus sylvatica L., and Tilia platyphyllos Scop.). All species were grown in intra- and interspecific competition (i.e., monoculture or mixture). Our results showed that N sources were not used complementarily depending on a species´ mycorrhizal association, but their uptake rather depended on the competitor indicating species-specific effects. Generally, ammonium was preferred over glutamine and glutamine over nitrate. In conclusion, our findings suggest that inorganic and organic N acquisition of the studied temperate tree species is less regulated by mycorrhizal association, but rather by the availability of specific N sources in the soil as well as the competitive environment of different tree species.

中文翻译：

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树种而不是菌根关联的类型驱动了树-树相互作用中无机和有机氮的获取

摘要

菌根真菌对树木的氮 (N) 供应起着重要作用。然而，不同菌根类型对树-树相互作用中氮获取的影响尚不清楚，特别是在限制生长的氮的竞争方面。我们研究了温带森林树种之间的竞争对其无机和有机的影响N 的获得与其菌根类型（即丛枝菌根或外生菌根）有关。在现场实验中，我们使用丛枝菌根树种（即Acer pseudoplatanus L.、Fraxinus excelsior L. 和Prunus avium ）的¹⁵ N/ ¹³ C 稳定同位素量化了无机和有机 N 源的净 N 吸收能力L.) 以及外生菌根树种（即Carpinus betulus L.、Fagus sylvatica L. 和Tilia platyphyllos范围。）。所有物种都在种内和种间竞争中生长（即单一培养或混合培养）。我们的结果表明，N 源的使用并不取决于物种的菌根关联，而是它们的吸收取决于竞争者，表明物种特异性效应。一般来说，铵盐优于谷氨酰胺，谷氨酰胺优于硝酸盐。总之，我们的研究结果表明，所研究的温带树种的无机和有机氮的获取受菌根关联的影响较小，而是受土壤中特定氮源的可用性以及不同树种的竞争环境的影响。