Belowground carbon transfer from plant to plant has been extensively described, but such transfer for nitrogen has been less thoroughly investigated when the donor is a non-N2-fixing species. This study, applied to forest regeneration, aimed to determine whether tree seedlings facilitated neighbouring grass growth through nitrogen transfer at an early stage of development, thus facilitating nitrogen acquisition by understory species. Quercus petraea seedlings were planted in pots either sole-grown or mixed-grown with Molinia caerulea tufts or another oak seedling. 15N-urea pulse-chase labelling (cotton wick method) was performed in oak shoots and the fate of 15N in each soil and plant compartment was tracked for one year. N transfer pathways were investigated using two degrees of physical separation between root systems. Molinia dry weight was higher when mixed-grown with oak seedlings than when sole-grown. Increase in grass dry weight correlated with N transfer from donor oak to receiver Molinia. Interestingly, the presence of Molinia increased N rhizodeposition of oak. N allocation in donor oak towards root in winter and shoot in spring was enhanced. Oak seedlings facilitated Molinia growth through rapid N transfer, underlining the ability of non-N2-fixing species to supply N to neighbours. 15N allocation within donor oak and its rhizodeposition depended on neighbour identity.

中文翻译：

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橡树幼苗的地下氮转移促进 Molinia 生长：15N 脉冲追踪标记

从植物到植物的地下碳转移已被广泛描述，但当供体是非 N2 固定物种时，这种氮转移的研究较少。本研究应用于森林更新，旨在确定树苗是否在发育早期通过氮转移促进邻近草的生长，从而促进林下物种获取氮。Quercus petraea 幼苗种植在单独种植或与 Molinia caerulea 簇绒或其他橡树幼苗混合种植的盆中。15N-尿素脉冲追踪标记（棉芯法）在橡树芽中进行，15N 在每个土壤和植物隔间中的命运被跟踪一年。使用根系之间的两个物理分离度来研究氮转移途径。Molinia 与橡树苗混合种植时的干重高于单独种植时。草干重的增加与从供体橡树到受体 Molinia 的氮转移相关。有趣的是，Molinia 的存在增加了橡木的氮根沉积。供体橡树冬季向根部和春季地上部的氮分配增加。橡树幼苗通过快速 N 转移促进了 Molinia 的生长，强调了非 N2 固定物种向邻居提供 N 的能力。供体橡树内的 15N 分配及其根系沉积取决于邻居身份。供体橡树冬季向根部和春季地上部的氮分配增加。橡树幼苗通过快速 N 转移促进了 Molinia 的生长，强调了非 N2 固定物种向邻居提供 N 的能力。供体橡树内的 15N 分配及其根系沉积取决于邻居身份。供体橡树冬季向根部和春季地上部的氮分配增加。橡树幼苗通过快速 N 转移促进了 Molinia 的生长，强调了非 N2 固定物种向邻居提供 N 的能力。供体橡树内的 15N 分配及其根系沉积取决于邻居身份。