Changes of plant species diversity and biomass with reclaimed marshes restoration

Wetland restoration had been implemented for more than two decades in Sanjiang Plain, Northeast China. To assess the restoration efficiency of wetland vegetation, we investigated plants composition of community, plant species diversity and aboveground biomass of restored sites in a chronosequence of restoration (1, 2, 3, 6, 8, 11, 15 and 25 years) in the Sanjiang Nature Reserve. As comparison, we also investigated the same factors in a cropland and a natural marsh adjacent to the restored sites. The results showed that wetland plant species can invade quickly after croplands were abandoned when there were suitable hydrology conditions. On the early stage of the restoration, weeds were main plant species in the restored sites. Wetland species appeared at the same time but differed from the dominant species from the adjacent natural marshes. Common native wetland species could dominance the community after 3-year restoration. Species richness and diversity increased on the early stage, and then decreased to the similar level of the natural marsh with the extension of restoration. Plant biomass could restore easier than the species composition and diversity. Our results indicated that plant species composition and diversity of abandoned reclaimed wetlands can restore gradually by natural succession in Sanjiang Plain. However, 25-year restoration site had similarity index of only 56% with the natural marsh, which revealed that two decades are not enough for complete restoration of vegetation.