Nonlinear response of soil microbial necromass nitrogen to nitrogen addition gradient in an alpine grassland

doi:10.1093/jpe/rtag132

J Plant Ecol ›› 2026, Vol. 19 ›› Issue (4): rtag132.DOI: 10.1093/jpe/rtag132

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Nonlinear response of soil microbial necromass nitrogen to nitrogen addition gradient in an alpine grassland

Quan-Cheng Wang¹, Jinsong Wang^{2, *}, Yang Li³, Houkun Chu², Ronglei Zhou², Ning Liu², Mengjie Liu², Fangfang Ma⁴, Chen Chen², Jingjing Shi⁴, Huichen Zhang⁵, Ruifa Wang⁶, Shuli Niu²

1 National Field Observation and Research Station (Sichuan Zoige) for Alpine Wetland Ecosystem, Southwest Minzu University, Chengdu 610041, China;
2 Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China;
3 CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610213, China;
4 School of Ecology and Nature Conservation, Beijing Forestry University, Beijing 100083, China;
5 State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, College of Soil and Water Conservation Science and Engineering, Northwest A&F University, Yangling 353001, China;
6 School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China
^*Corresponding author. E-mail: wangjinsong@igsnrr.ac.cn

Received:2025-09-21 Revised:2025-12-10 Accepted:2026-05-18 Published:2026-08-01
Supported by:
This study was supported by the National Natural Science Foundation of China (32401384, 32588202, 32241035), and the Open Project Program of National Field Observation and Research Station (Sichuan Zoige) for Alpine Wetland Ecosystem, Southwest Minzu University (NFORSREMF202601, NFORSREMF202605). Jinsong Wang acknowledges the support from 'Kezhen-Bingwei' Young Talents (2022RC004). Quan-Cheng Wang and Houkun Chu receive the support from the China Postdoctoral Science Foundation (GZC20232624, 2023M733472, GZC241692).

高寒草甸土壤微生物残体氮对不同氮水平的非线性响应

Abstract

Abstract: Microbial necromass nitrogen (N) constitutes a major component of soil N pools, and elucidating its response to N enrichment is essential for optimizing fertilizer management in grassland ecosystems. However, the effects of varying N addition levels on microbial necromass N and the underlying mechanisms remain elusive. Here, we leveraged a decade-long field experiment in an alpine meadow on the Qinghai-Tibetan Plateau (QTP), applying six N addition levels (0, 2, 4, 8, 16, 32 g N m^-2 yr^-1) to investigate the response of microbial necromass N and its key drivers. Microbial necromass N exhibited a nonlinear response to N enrichment, remaining stable under low N inputs (2, 4 and 8 g N m^-2 yr^-1) but increasing significantly at higher N addition levels (16 and 32 g N m^-2 yr^-1). Across all treatments, microbial necromass N accounted for 67%–76% of total soil N. Nitrogen-induced changes in plant, soil and microbial factors collectively explained 60% of the variation in microbial necromass N. Among these, soil factors were the dominant predictors, accounting for 34% of the total variance, with mineral protection (Fe_o + Al_o) and soil inorganic nitrogen (SIN) identified as the primary drivers. These findings highlight the pivotal role of microbial necromass N in soil N storage and its nonlinear response to N enrichment, underscoring the importance of effective N management for enhancing soil N retention and stability in alpine grasslands.

Microbial necromass nitrogen (N) comprises a major fraction of soil N pools, yet the effects of varying N addition levels on its accumulation and the underlying mechanisms remain unclear. Our results show that microbial necromass N increases nonlinearly with N addition gradients, comprising 67–76% of total N in alpine grassland soils. Mineral protection and soil inorganic N content were identified as the primary drivers of this response. These findings provide a robust scientific basis for optimizing N fertilization in grassland ecosystems.

Key words: microbial necromass nitrogen, nitrogen addition gradient, nonlinear response, alpine grasslands, mineral protection

摘要：
微生物残体氮是土壤氮库的重要组成部分，明确其对氮富集的响应对于优化草地养分管理至关重要。然而，学术界尚不清楚微生物残体氮沿不同氮水平的变化及其机制。本研究基于青藏高原高寒草甸持续十年的野外控制试验，设置6个氮添加水平(0、 2、4、8、16和32 g N m^-2 yr^-1)，探究微生物残体氮对不同氮水平的响应及其驱动因素。结果表明：在所有处理中，微生物残体氮占土壤总氮的67%-76%。微生物残体氮对氮添加呈现非线性响应，在低氮输入水平(2、4和8 g N m^-2 yr^-1)下保持稳定，而在较高氮添加水平(16和32 g N m^-2 yr^-1)下显著增加。氮添加引起的植物、土壤和微生物属性变化共同解释了微生物残体氮变异的60%。其中，土壤因素—主要包括矿物保护(Fe_o + Al_o)和土壤无机氮—是最重要的预测因子，解释了总变异的34%。上述发现揭示了微生物残体氮在土壤氮储存中的关键作用及其对氮富集的非线性响应特征，强调了优化氮素管理对提升土壤氮固持能力、维持氮库稳定性的重要意义。

关键词: 微生物残体氮, 氮添加梯度, 非线性响应, 高寒草甸, 矿物保护

Quan-Cheng Wang, Jinsong Wang, Yang Li, Houkun Chu, Ronglei Zhou, Ning Liu, Mengjie Liu, Fangfang Ma, Chen Chen, Jingjing Shi, Huichen Zhang, Ruifa Wang, Shuli Niu. Nonlinear response of soil microbial necromass nitrogen to nitrogen addition gradient in an alpine grassland[J]. J Plant Ecol, 2026, 19(4): 0-.

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Nonlinear response of soil microbial necromass nitrogen to nitrogen addition gradient in an alpine grassland

高寒草甸土壤微生物残体氮对不同氮水平的非线性响应

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