Vegetative zonation patterns in depression and riparian wetlands of the Sanjiang Plain, Northeastern China
The vegetation of depressional and riparian wetlands in the Sanjiang Plain of Northeastern China was studied to describe their vegetation composition and to quantify community differences. Reciprocal transplants were performed to test the importance of biotic factors in governing zonation. One hundred and seventy-two (172) sampling plots in depression and riparian wetland was used. Samples were classified in 9 groups at the fourth level using two-way indicator species analysis (TWINSPAN): Four marsh communities, one meadow marsh community, one wet meadow community, two swamp communities and one island forest community. The TWINSPAN groups could be recognized in the detrended correspondence analysis (DCA) graph. DCA ordination indicated a wetness gradient associated with altitude. The species turnover between communities were rather high (similarity index less than 0.40), and this indicated that the corresponding habitats heterogeneity increased gradually. Three transplanted species showed different effects of biomass production among vegetation zones. The greatest transplant effect occurred for Carex lasiocarpa, followed by Calamagrostis angustifolia, with the least effect for Carex appendiculata. This study provides evidence that hydrologic gradients and biotic factors commonly determine the spatial pattern of wetland plant communities. This should therefore be considered in future management and protection under the circumstance of climate change and human activities.
Key words: Vegetation classification, ordination, community similarity, depression and riparian wetlands, Sanjiang Plain.