Chin J Plant Ecol ›› 2023, Vol. 47 ›› Issue (1): 1-24.DOI: 10.17521/cjpe.2022.0107

Special Issue: 青藏高原植物生态学:生态系统生态学

• Reviews •     Next Articles

Nonlinear responses of community diversity, carbon and nitrogen cycles of grassland ecosystems to external nitrogen input

YANG Yuan-He1,2,*(), ZHANG Dian-Ye1, WEI Bin1,2, LIU Yang1,3, FENG Xue-Hui1,2, MAO Chao1,4, XU Wei-Jie1,2, HE Mei1, WANG Lu1,2, ZHENG Zhi-Hu1,2, WANG Yuan-Yuan1, CHEN Lei-Yi1, PENG Yun-Feng1   

  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 Resources and Environmental Science, Hebei Province Key Laboratory for Farmland Eco-Environment, Agricultural University of Hebei, Baoding, Hebei 071000, China
    4School of Geographical Sciences, Fujian Normal University, Fuzhou 350117, China
  • Received:2022-03-26 Accepted:2022-06-27 Online:2023-01-20 Published:2022-10-25
  • Contact: *YANG Yuan-He,
  • Supported by:
    National Natural Science Foundation of China(31825006)


Understanding the response patterns and potential mechanisms of structure and function in grassland ecosystems to nitrogen (N) enrichment is essential to evaluate ecological impacts of external N input. The muti-level N manipulative experiment offers the possibility to explore the nonlinear response patterns and associated mechanisms of structure and function in grassland ecosystems to additional N input. In this review, we summarized the impacts of additional N inputs on community diversity, carbon (C) and N cycling in grassland ecosystems around the world. Numerous studies illustrated that N enrichment induced the decline of plant species diversity, plant functional diversity and soil bacteria richness in grassland ecosystems, yet the change of fungal diversity was not significant. Above- and below-ground plant productivity showed different responses to N input: aboveground plant productivity exhibited initial increasing and subsequent saturation trends, but root productivity and root:shoot ratio showed downward patterns, and root turnover rate appeared a single-peak pattern of first increasing and then decreasing with the continuous increase of N addition rate. Meanwhile, different C decomposition processes responded variously to N enrichment. Specifically, litter decomposition rates exhibited multiple response of “exponential decrease, liner increase or insignificant change with N addition level”. However, the relationship of soil respiration and CH4 consumption with N addition was dominated by a single peak trend of increasing at low to medium N levels but declining at high N levels. Likewise, different soil C fractions showed multiple response patterns to N input. N addition generally stimulated soil C storage and particulate organic C accumulation, while the mineral-associated organic C exhibited divergent responses of “increase, unaltered, and decrease” along the N addition gradient. In addition, plant N uptake exhibited initial increasing and subsequent situation trends along N addition gradients, while different soil N transformation processes showed differentiated responses along N addition gradients and the relationship between N2O emission and N addition rate varied among various grassland ecosystems. An exponential increase of N2O fluxes with N addition rate was observed in temperate grasslands, while the patterns of first increase and then saturation or linear increase of the N-induced changes in N2O emissions had been discovered in alpine grasslands. Future studies should focus on the nonlinear responses of rhizosphere processes and phosphorus (P) cycle to external N input, and also explore potential mechanisms from the aspect of multi-dimensional biodiversity changes.

Key words: grassland ecosystem, species diversity, functional diversity, ecosystem productivity, litter decomposition, soil respiration, soil nitrogen transformation process, greenhouse gas flux