Key message

On calcareous soil, European beech roots prefer organic nitrogen, but only arginine and not glutamine or inorganic nitrogen.

Abstract

Nitrogen (N) acquisition is a major factor determining the processes and mechanisms involved in tree productivity, development, and competitiveness. However, only few studies have investigated changes in N capturing with tree age. We conducted ¹⁵N incubation experiments to quantify inorganic (i.e. ammonium and nitrate) and organic (i.e. glutamine-N and arginine-N) net N acquisition capacity of beech trees of five age classes. Our results showed no general pattern, but that net N uptake capacity was rather N source-specific. Inorganic and glutamine-N uptake did not differ between age classes at all. Arginine-N uptake was highest in the youngest and oldest stands reflecting a high N demand by seedlings for root foraging and biomass production despite low internal N storage capacities and by older trees for storage and reproduction. Organic N was preferred over inorganic N regardless of tree age. Overall, our study shows the high significance of organic N sources for N acquisition in beech trees.

中文翻译：

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欧洲山毛榉 (Fagus sylvatica L.) 的氮吸收能力仅部分取决于树龄

关键信息

在石灰质土壤上，欧洲山毛榉根更喜欢有机氮，但只喜欢精氨酸，而不喜欢谷氨酰胺或无机氮。

抽象的

氮 (N) 获取是决定树木生产力、发展和竞争力所涉及的过程和机制的主要因素。然而，只有少数研究调查了 N 捕获随树龄的变化。我们进行了¹⁵N 孵化实验以量化五个年龄等级的山毛榉树的无机（即铵和硝酸盐）和有机（即谷氨酰胺-N 和精氨酸-N）净 N 获取能力。我们的结果没有显示出一般模式，但净氮吸收能力是特定于氮源的。无机和谷氨酰胺-N 的吸收在不同年龄段之间完全没有差异。最年轻和最老林分的精氨酸-N 吸收量最高，这反映了幼苗对根系觅食和生物量生产的高氮需求，尽管内部氮储存能力低，而老树则用于储存和繁殖。无论树龄如何，有机氮均优于无机氮。总体而言，我们的研究表明有机氮源对山毛榉树中氮的获取具有重要意义。