Underappreciated role of canopy nitrogen deposition for forest productivity

文献类型： 外文期刊

第一作者： Li, Xiaowei

作者： Li, Xiaowei;Zhang, Chenlu;Zhang, Beibei;Jiang, Li;Tang, Shengqi;Sun, Chenhui;Bai, Yulong;Wang, Yubang;Shi, Yifei;Ma, Lei;Ort, Donald;Li, Xiaowei;Zhang, Chenlu;Zhang, Beibei;Jiang, Li;Tang, Shengqi;Sun, Chenhui;Bai, Yulong;Wang, Yubang;Shi, Yifei;Ma, Lei;Ort, Donald;Li, Xiaowei;Zhang, Chenlu;Shi, Yifei;Ort, Donald;Li, Xiaowei;Zhang, Chenlu;Zhang, Wei;Ye, Qing;Yan, Junhua;Wang, Keya;Ort, Donald;Shi, Yifei;Yan, Junhua;Wang, Keya;Fu, Juemin;Du, Wenzhi;Wan, Shiqiang;Hong, Liang;Fang, Yunting;Siemann, Evan;Luo, Yiqi;Reich, Peter B.;Reich, Peter B.;Reich, Peter B.

作者机构：

关键词： nitrogen deposition; forest canopy; carbon sequestration; 15 N recovery

期刊名称：PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA （ 影响因子：9.1； 五年影响因子：10.6 ）

ISSN： 0027-8424

年卷期： 2025 年 122 卷 34 期

页码：

收录情况： SCI

摘要： Atmospheric nitrogen (N) deposition is generally expected to stimulate plant carbon (C) sequestration and promote tree growth, thereby mitigating atmospheric CO2 accumulation. Yet, the magnitude of N deposition contribution to forest productivity remains contentious. While correlative studies suggest substantial plant growth enhancement, controlled fertilization experiments typically demonstrate a limited impact. This discrepancy may arise from whether or not to consider canopy N uptake processes. Here, we conducted a 10-y field experiment comparing canopy addition of N (CAN) with understory addition of N (UAN) at the rate of 0, 25, and 50 kg N ha(-1) y(-1) in a temperate deciduous forest in central China. We show that CAN significantly enhanced net primary productivity by 37.0% over control, driven by enhanced leaf litterfall, wood and fine root production, whereas UAN effects were marginal (8%). N-15 isotopic tracing revealed that CAN, through enhanced plant N uptake and increased ecosystem N retention, yielded a 3.5-fold higher C sequestration efficiency (triangle C/triangle N) of 54.5 +/- 7.7 kg C kg(-1) N, than UAN (12.2 +/- 3.4 kg C kg(-1) N) resulted from greater N loss through leaching. Physiological measurements indicated CAN enhanced leaf photosynthetic rates, modified leaf morphology, and extended leaf lifespan via delayed senescence. These findings provide robust empirical evidence that canopy N uptake is crucial for maximizing N-induced forest productivity, thereby holding significant implications for refining global C models and urging modelers to incorporate canopy processes for more accurate projections of future C sinks and climate change mitigation strategies.

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