Chin J Plant Ecol ›› 2008, Vol. 32 ›› Issue (2): 392-401.DOI: 10.3773/j.issn.1005-264x.2008.02.017

• Research Articles • Previous Articles     Next Articles


ZHAO Cong-Jiao1, DENG Zi-Fa1,2, ZHOU Chang-Fang1, GUAN Bao-Hua1, AN Shu-Qing1,*(), CHEN Lin1, LU Xia-Mei1   

  1. 1Institute of Wetland Ecology, School of Life Science, Nanjing University, Nanjing 210093, China
    2School of Life Sciences, Nantong University, Nantong, Jiangsu 226007, China
  • Received:2007-01-24 Accepted:2007-07-05 Online:2008-01-24 Published:2008-03-30
  • Contact: AN Shu-Qing


Aims Spartina alterniflora, originating from North America, has become an invasive species in Europe and China. Meanwhile, Phragmites australis, a species experiencing 'die-back' in Europe, has invaded coastal ecosystems in North America. Each species is invading the other's native habitat. We studied changes of leaf characters for the two species under different nitrogen and planting densities in the greenhouse to 1) compare the relative competitiveness and invasive capacity of the two species and 2) reveal potential mechanisms that determine successful invasion in different regions.
Methods We grew artificial populations of Spartina alterniflora (S) and Phragmites australis (P) at three different densities in monoculture (S, SS, SSS and P, PP, PPP) and mixed-culture (SP, SPP and PSS), and under three levels of nitrogen (0, 60 and 120 mg·kg-1). Plants were harvested after 15 weeks, and their leaf characteristics, including area, length, width, thickness and number were measured.
Important findings Nitrogen addition increased leaf area in both species whether in monoculture or mixed-culture (p<0.05), but the change in leaf area of P. australis in mixed-culture decreased with high nitrogen level, which may be due to greater interspecific competition from S. alterniflora. In monoculture, the effects of nitrogen addition on leaf number were greater than on the other leaf traits (p<0.01), while the effects on leaf number (S. alterniflora) or leaf width (P. australis) were greatest (p<0.05) in mixed-culture. Plant densities decreased leaf area of the two species in all treatments (p<0.05). In monoculture, the effects of plant densities on leaf number were greatest (p<0.05). However, in mixed-culture, P. australis mainly reduced leaf width and leaf number of S. alterniflora (p<0.05), while S. alterniflora reduced all the parameters of P. australis (p<0.05). The intensity of competition which S. alterniflora imposed on P. australis was greater than the reverse with low and high nitrogen levels, but this outcome was reversed with medium nitrogen level. At high nitrogen levels, S. alterniflora dominated interspecific competition, with its increased leaf area restraining the leaf growth and reducing the leaf area of P. australis; this may be a mechanism for the successful invasion of S. alterniflora into P. australis populations.

Key words: nitrogen level, plant density, competition, Spartina alterniflora, Phragmites australis, leaf morphology