He, Q. (email@example.com) & An, Y. (corresponding author, firstname.lastname@example.org): School of Agriculture and Biology, MOA Key Laboratory of Urban Agriculture (South), Shanghai Jiao Tong University, Shanghai 200240, China Cui, B. (email@example.com): State Key Laboratory of Water Environmental Simulation, School of Environment, Beijing Normal University, Beijing 100875, China
The importance of facilitation in the zonation of shrubs along a coastal salinity gradient
Article first published online: 4 MAY 2011
© 2011 International Association for Vegetation Science
Journal of Vegetation Science
Volume 22, Issue 5, pages 828–836, October 2011
How to Cite
He, Q., Cui, B. and An, Y. (2011), The importance of facilitation in the zonation of shrubs along a coastal salinity gradient. Journal of Vegetation Science, 22: 828–836. doi: 10.1111/j.1654-1103.2011.01300.x
Co-ordinating Editor: Hans Henrik Bruun
- Issue published online: 1 SEP 2011
- Article first published online: 4 MAY 2011
- Received 3 January 2011, Accepted 5 April 2011
- Positive interactions;
- Salt marsh;
- Stress-gradient hypothesis (SGH);
- Yellow River Delta
Question: What are the interactive roles of abiotic stress and plant interactions in mediating the zonation of the shrub Tamarix chinensis along a salinity gradient?
Location: Yellow River estuary (37°46′N, 119°09′E), northeast China.
Methods: We surveyed the zonation of T. chinensis along a salinity gradient and quantified its salt tolerance using a pot experiment. In two field experiments, we transplanted T. chinensis seedlings into salt marsh, transitional zone and upland habitats, manipulated neighbours and quantified survivorship and biomass to examine neighbour effects. We also quantified vegetation effects on abiotic conditions in each zone.
Results: Tamarix chinensis dominated the transitional zone, but was absent in upland and salt marsh habitats. In the pot experiment, T. chinensis grew well in freshwater treatments, but was inhibited by increasing salinity. Field experiments revealed that competition from neighbours limited T. chinensis growth in the uplands, while T. chinensis transplants were limited, with or without neighbours, in the salt marsh by high soil salinity. In the transitional zone, however, T. chinensis transplants performed better with than without neighbours. Vegetation removal significantly elevated soil salinity in the transitional zone, but not in other zones.
Conclusions: Competition, facilitation and abiotic stress are all important in mediating the zonation of T. chinensis. Within its physiological stress tolerance range, or fundamental niche, it is limited by plant competition in low salinity habitats, and facilitated by neighbours in high salt stress habitats, but cannot survive in salt marshes having salinities above its salt stress tolerance limit. Our results have implications for understanding the relationships between facilitation and stress gradients.