Chin J Plant Ecol ›› 2020, Vol. 44 ›› Issue (6): 642-653.DOI: 10.17521/cjpe.2019.0329

• Research Articles • Previous Articles     Next Articles

Defense strategies of dominant plants under different grazing intensity in the typical temperate steppe of Nei Mongol, China

LI Ying1, GONG Ji-Rui1,*(), LIU Min1, HOU Xiang-Yang2, DING Yong2, YANG Bo1, ZHANG Zi-He1, WANG Biao1, ZHU Chen-Chen1   

  1. 1Laboratory of Earth Surface Processes and Resource Ecology, Beijing Key Laboratory of Traditional Chinese Medicine Protection and Utilization, School of Natural Resources, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China
    2Grassland Research Institute of Chinese Academy of Agricultural Science, Hohhot 010021, China
  • Received:2019-11-30 Accepted:2020-03-25 Online:2020-06-20 Published:2020-04-03
  • Contact: GONG Ji-Rui: ORCID:0000-0003-2012-2606,
  • Supported by:
    National Natural Science Foundation of China(41571048);National Key R&D Program of China(2016YFC0500502);State Key Basic R&D Plan of China(2014CB138803)


Aims Grazing is one of the main grassland using modes, which has caused certain biotic stress on pasture. In order to survive, pasture initiates defense mechanisms by regulating the primary and secondary metabolic processes. This article aims to 1) figure out the distribution of defensive substances in different organs produced by the dominant plants Stipa grandis and Leymus chinensis; 2) explore the similarities and differences of the defense mechanisms and carbon-nitrogen trade-off strategies in S. grandis and L. chinensis.
Methods We conducted a different grazing intensity experiment in the typical temperate steppe of Nei Mongol. The lignin and secondary metabolites, such as tannins, flavonoids, phenols and alkaloids, as well as the ratio of carbon and nitrogen in different organs of the dominant plants S. grandis and L. chinensis were investigated.
Important findings Our results showed that S. grandis and L. chinensis produced a large number of secondary metabolites such as tannins, flavonoids, phenols and alkaloids in the face of grazing stress. The leaves were the main synthesis and storage organs. In addition, the chemical defense mechanism of L. chinensis was well induced and expressed under moderate grazing. There was no significant increase in the lignin content in the aboveground parts of S. grandis and L. chinensis. Therefore, both of them were more inclined to chemical defense than mechanical defense in the mechanism of avoiding grazing. Because of the higher nitrogen use efficiency of L. chinensis, it could be protected by both carbon and nitrogen metabolic pathways. However, Stipa grandis did not efficiently distribute nitrogen into chemical defense in the early stages of growth. More resources still used for primary metabolism in the early stage of S. grandis and L. chinensis growth, under light grazing stress, which increased their grazing resistance. Therefore, light grazing is conducive to improving the carbon and nitrogen use efficiency of pasture, and improving ecosystem productivity and stability.

Key words: secondary metabolism, defense mechanism, carbon-nitrogen trade-off, dominant species, grazing intensity, Stipa grandis, Leymus chinensis