Tree species rather than type of mycorrhizal association drives inorganic and organic nitrogen acquisition in tree-tree interactions

A field study was conducted to evaluate the effects of associated mycorrhization type on tree-tree interactions using the framework of the MyDiv tree diversity experiment established at the Bad Lauchstädt Experimental Research Station of the Helmholtz Centre for Environmental Research (UFZ) (Saxony-Anhalt, Germany). Inorganic and organic net N uptake capacity was quantified in fine roots of AM (i.e. Acer pseudoplatanus L., Fraxinus excelsior L., and Prunus avium L.) as well as EM associated tree species (i.e. Carpinus betulus L., Fagus sylvatica L., and Tilia platyphyllos Scop.) using 15N/13C isotopes. Trees grew either in monocultures or 2-species mixtures, either only ectomycorrhizal, only arbuscular mycorrhizal, or in combination. Generally, ammonium was preferred over glutamine and glutamine over nitrate. Inorganic and organic N sources were not used complementarily depending on a species´ mycorrhizal association, but their uptake rather depended on the competitor indicating species...本研究依托赫尔姆霍茨环境研究中心（Helmholtz Centre for Environmental Research, UFZ）设于德国萨克森-安哈尔特州巴德劳赫斯塔特（Bad Lauchstädt）实验研究站的MyDiv树木多样性实验框架，开展野外实地研究以探究菌根共生类型对树木间相互作用的影响。本研究采用15N/13C同位素标记法，量化了丛枝菌根（Arbuscular Mycorrhizal, AM）树种（即槭树Acer pseudoplatanus L.、欧洲白蜡Fraxinus excelsior L.以及欧洲甜樱桃Prunus avium L.）与外生菌根（Ectomycorrhizal, EM）树种（即欧洲鹅耳枥Carpinus betulus L.、欧洲山毛榉Fagus sylvatica L.以及阔叶椴Tilia platyphyllos Scop.）的细根对无机态与有机态氮的净吸收能力。试验设置单优林与两物种混交林两种种植模式，混交林又分为仅外生菌根树种混交、仅丛枝菌根树种混交，以及二者混合混交三种类型。整体而言，受试树种对铵态氮的偏好性强于谷氨酰胺，对谷氨酰胺的偏好性又强于硝态氮。研究未发现受试树种对无机态与有机态氮源的吸收存在互补性，该特性并不受树种所属菌根共生类型的影响，反而其氮源吸收主要取决于竞争伙伴，该结果提示……