Chin J Plant Ecol ›› 2020, Vol. 44 ›› Issue (1): 33-43.DOI: 10.17521/cjpe.2019.0283

• Research Articles • Previous Articles     Next Articles

Effects of Caragana microphylla encroachment on community structure and ecosystem function of a typical steppe

DING Wei1,WANG Yu-Bing2,3,XIANG Guan-Hai2,3,CHI Yong-Gang4,LU Shun-Bao1,*(),ZHENG Shu-Xia2,*()   

  1. 1College of Life Sciences, Jiangxi Normal University, Nanchang 330022, China
    2State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China
    3University of Chinese Academy of Sciences, Beijing 100049, China
    4College of Geography and Environmental Sciences, Zhejiang Normal University, Jinhua, Zhejiang 321004, China
  • Received:2019-10-22 Revised:2020-01-14 Online:2020-01-20 Published:2020-03-26
  • Contact: LU Shun-Bao,ZHENG Shu-Xia
  • Supported by:
    National Key R&D Program of China(2016YFC0500801);National Natural Science Foundation of China(41671046);National Natural Science Foundation of China(31400393)


Aims Shrub encroachment is a critical ecological problem in arid and semi-arid ecosystems worldwide. The effects of shrub encroachment on ecosystem structure and function of grasslands are complicated and need to be explored in future studies. Our objective is to examine the effects and pathways of shrub encroachment on ecosystem structure and function in a typical steppe of the Inner Mongolia grassland.
Methods Three grassland sites with different degrees of shrub encroachment (i.e. light, moderate, heavy) were selected in the Xilingol Nei Mongol, of which Caragana microphylla was the dominant shrub. Species richness and composition, aboveground net primary productivity (ANPP), soil property, and plant functional traits of dominant species were determined in this study. In addition, species diversity, functional attribute diversity, community-weighted mean traits, and vegetation leaf and soil carbon and nitrogen pools were further calculated.
Important findings 1) The species richness, functional attribute diversity and community-weighted mean traits differed significantly among three grassland sites, and species diversity and functional diversity were relatively higher in the moderate shrub-encroachment site, indicating moderate shrub-encroachment favors biodiversity maintenance. 2) The aboveground net primary productivity of heavy shrub-encroachment grassland was significantly higher than those of light and moderate shrub-encroachment grasslands, which was mainly due to a shift in functional group composition, that is, the proportion of annuals and biennials to perennial grasses and forbs increased greatly with intensifying shrub encroachment. The vegetation leaf and soil carbon and nitrogen pools differed little among three sites. 3) Shrub encroachment did not directly affect ecosystem function, including ANPP, vegetation and soil nutrient pools, but it indirectly affected them through pathways of the shift in functional group composition and changes in soil property and functional diversity. Particularly, the shift in functional group composition and intensified soil drought and basification was separately important biotic and abiotic factors for variations in ecosystem function.

Key words: shrub encroachment, species diversity, functional diversity, plant functional trait, functional group composition, ecosystem function