Increased nitrogen (N) input can potentially lead to secondary phosphorus (P) limitation; however, it remains unclear whether differences in the plant's ability to cope with this P deficiency are related to their growth responses. Using a long-term experiment of N addition in a boreal forest, we explored the potential role of plant nutrient resorption efficiency and its stoichiometry in mediating plant growth responses to increased N input. We recorded the cover and measured the concentration and resorption efficiency of leaf N and P as well as the photosynthesis of a grass Deyeuxia angustifolia and a shrub Vaccinium vitis-idaea. The cover of the grass D. angustifolia increased with increasing N addition, while that of the shrub V. vitis-idaea decreased with N addition rate and almost disappeared from the high-level N addition over time. P resorption efficiency (PRE) increased in D. angustifolia but decreased in V. vitis-idaea with increasing leaf N:P which was increased by N addition for both species. In addition, photosynthesis increased linearly with N resorption efficiency (NRE) and PRE but was better explained by NRE:PRE, changing nonlinearly with the ratio in a hump-shaped trend. Furthermore, the variance (CV) of NRE:PRE for V. vitis-idaea (123%) was considerably higher than that for D. angustifolia (29%), indicating a more stable nutrient resorption stoichiometry of the grass. Taken together, these results highlight that efficient P acquisition and use strategy through nutrient resorption processes could be a pivotal underlying mechanism driving plant growth and community composition shifts under N enrichment.

中文翻译：

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将养分再吸收化学计量与长期氮添加下的植物生长联系起来


氮 （N） 输入增加可能导致次级磷 （P） 限制;然而，目前尚不清楚植物应对这种 P 缺陷的能力差异是否与它们的生长反应有关。利用北方森林中氮添加的长期实验，我们探索了植物养分吸收效率及其化学计量在介导植物生长对增加的氮输入的反应中的潜在作用。我们记录了覆盖度，并测量了叶 N 和 P 的浓度和再吸收效率，以及草 Deyeuxia angustifolia 和灌木 Vaccinium vitis-idaea 的光合作用。草 D. angustifolia 的覆盖率随着 N 添加量的增加而增加，而灌木 V. vitis-idaea 的覆盖率随着 N 添加量的增加而降低，随着时间的推移，几乎从高水平的 N 添加中消失。随着叶片 N：P 的增加，D. angustifolia 的 P 再吸收效率 （PRE） 增加，但 V. vitis-idaea 的 P 吸收效率 （PRE） 降低，两个物种的 N 添加都会增加。此外，光合作用随氮吸收效率 （NRE） 和 PRE 线性增加，但用 NRE：PRE 更好地解释，随比值呈驼峰形趋势非线性变化。此外，V. vitis-idaea 的 NRE：PRE 方差 （CV） （123%） 远高于 D. angustifolia （29%），表明草的养分吸收化学计量更稳定。综上所述，这些结果强调，通过养分再吸收过程实现高效的 P 获取和利用策略可能是在 N 富集下驱动植物生长和群落组成变化的关键潜在机制。