J Plant Ecol ›› 2023, Vol. 16 ›› Issue (3): rtac078.DOI: 10.1093/jpe/rtac078

• Research Articles •    

Increasing nitrogen addition rates suppressed long-term litter decomposition in a temperate meadow steppe

Pei Zheng1,2,*,†, Ruonan Zhao1,2,†, Liangchao Jiang1,2, Guojiao Yang3, Yinliu Wang1,2, Ruzhen Wang4,5, Xingguo Han1,2, Qiushi Ning1,6,*   

  1. 1State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;
    2University of Chinese Academy of Sciences, Beijing 100049, China;
    3College of Ecology and Environment, Hainan University, Haikou 570228, China;
    4Erguna Forest-Steppe Ecotone Ecosystem Research Station, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China;
    5School of Life Sciences, Hebei University, Baoding 071002, China;
    6State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China


Abstract: Plant litter decomposition is critical for the carbon (C) balance and nutrient turnover in terrestrial ecosystems, and is sensitive to the ongoing anthropogenic biologically nitrogen (N) input. Previous studies evaluating the N effect on litter decomposition relied mostly on short-term experiments (<2 years), which may mask the real N effect on litter decomposition. Therefore, long-lasting experiments are imperative for the overall evaluation of the litter decomposition dynamics under N enrichment. We conducted a relative long-term (4-year) N-addition experiment with N levels ranging from 0 to 50 g N m-2 yr-1 to identify the potential abiotic and biotic factors in regulating the decomposition process of litterfall from the dominant species Leymus chinensis. The results showed a consistent decrease of decomposition rate with increasing N-addition rates, providing strong evidence in support of the inhibitory effect of N addition on decomposition. The N-induced alterations in soil environment (acidification and nutrient stoichiometry), microbial activity (microbial biomass and enzyme activity), changes of litter quality (residual lignin and nutrient content) and plant community (aboveground productivity and species richness) jointly contributed to the lowered decomposition. During the whole decomposition process, the changes of litter quality, including accumulation of lignin and the concentrations of nutrient, were mainly driven by the soil and microbial activity in this N-enriched environment. The findings help clarify how increasing N input rates affect long-term litter decomposition, and advance the mechanistic understanding of the linkages between ecosystem N enrichment and terrestrial C cycling.

Key words: nitrogen addition, litter carbon and nitrogen loss, lignin, species richness, enzyme activity

植物凋落物分解是陆地生态系统碳平衡和养分周转的关键,对持续的人为氮输入增加十分敏感。氮素增加影响凋落物分解的研究大多依赖于短期实验,这可能掩盖氮素增加对凋落物分解的真实影响。因此,长期实验对于全面评价凋落物分解对氮素增加的响应是非常必要的。本研究基于氮添加实验(0-50 g N m-2 yr-1),对羊草(Leymus chinensis)凋落物分解进行了长达4年的研究,探讨了影响凋落物分解的非生物和生物因子。研究结果表明,随着氮添加速率的增加,凋落物分解速率呈持续下降趋势,为氮添加抑制凋落物分解提供了可靠的证据。氮添加条件下土壤环境(酸化和养分化学计量学)、微生物活性(微生物生物量和酶活性)、凋落物质量(残余木质素和养分含量)和植物群落(地上生产力和物种丰富度)的变化共同导致了凋落物分解速率的降低。在分解过程中,凋落物质量的变化,包括木质素的积累和养分的残留,主要受土壤环境和微生物活性的影响。该研究有助于阐明不同氮添加速率对凋落物分解的长期影响,并有助于理解生态系统氮素增加与碳循环之间的关系及相关机理。

关键词: 氮添加, 凋落物碳氮损失, 木质素, 物种丰富度, 酶活性