Nonlinear responses of ecosystem carbon fluxes to nitrogen deposition in an old-growth boreal forest,Ecology Letters

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Nonlinear responses of ecosystem carbon fluxes to nitrogen deposition in an old-growth boreal forest
Ecology Letters ( IF 7.6 ) Pub Date : 2021-10-25 , DOI: 10.1111/ele.13906
Aijun Xing _{1,

2} , Enzai Du ₃ , Haihua Shen _{1,

2} , Longchao Xu ₁ , Wim de Vries ₄ , Mengying Zhao _{1,

2} , Xiuyuan Liu ₁ , Jingyun Fang _{1,

5}

Affiliation

Nitrogen (N) deposition is known to increase carbon (C) sequestration in N-limited boreal forests. However, the long-term effects of N deposition on ecosystem carbon fluxes have been rarely investigated in old-growth boreal forests. Here we show that decade-long experimental N additions significantly stimulated net primary production (NPP) but the effect decreased with increasing N loads. The effect on soil heterotrophic respiration (Rh) shifted from a stimulation at low-level N additions to an inhibition at higher levels of N additions. Consequently, low-level N additions resulted in a neutral effect on net ecosystem productivity (NEP), due to a comparable stimulating effect on NPP and Rh, while NEP was increased by high-level N additions. Moreover, we found nonlinear temporal responses of NPP, Rh and NEP to low-level N additions. Our findings imply that actual N deposition in boreal forests likely exerts a minor contribution to their soil C storage.

中文翻译：

北方老林中生态系统碳通量对氮沉降的非线性响应

已知氮 (N) 沉积会增加限制氮的北方森林中的碳 (C) 固存。然而，很少在古老的北方森林中研究氮沉积对生态系统碳通量的长期影响。在这里，我们表明，长达十年的实验性氮添加显着刺激了净初级生产 (NPP)，但效果随着氮负荷的增加而下降。对土壤异养呼吸 (Rh) 的影响从低水平 N 添加的刺激转变为更高水平 N 添加的抑制。因此，由于对 NPP 和 Rh 的刺激作用类似，低水平的 N 添加对净生态系统生产力 (NEP) 产生中性影响，而 NEP 因高水平的 N 添加而增加。此外，我们发现 NPP、Rh 和 NEP 对低水平 N 添加的非线性时间响应。

更新日期：2021-12-10

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