The seed-bank of a lakeshore wetland in Lake Honghu: implications for restoration

The abundance and species composition in the seed-bank and extant vegetation were investigated in a lakeshore wetland. The seed-bank in different layers at 5 cm intervals was also studied by using the seedling-emergence method with waterlogged and submerged greenhouse treatments. Thirty-four species and 1788 seedlings germinated in the seed-bank, with a mean density of 1227 seedlings m(-2) (40-2600). Thirty-one species and 22261 individuals were obtained in the extant vegetation with a mean density of 1436 seedlings m(-2) (368-12632). The Margalef species richness index was 4.41 in the seed-bank and 2.99 in the extant vegetation. Little overlap (14 taxa, 43%) was found between the seed-bank and the extant vegetation. The total number of species and seedlings that germinated in different layers was significantly different. The number of species that germinated in the surface layer (21 taxa) was not significantly different from that in the second layer (27 taxa). Only 39.2% of the total number of seedlings appeared in the surface layer. Our results indicated that a lakeshore wetland seed-bank with viable seeds and high species richness can be used as a macrophyte pool in degraded wetland restoration. Vegetation produced from such a seed-bank will have species similar to the pre-disturbance assemblage. The large number of viable seeds that we found conserved in deeper layers suggests that the most valuable macrophyte pools are conserved at depth. With disturbance, these seeds could be brought back to the surface, and serve as a reserve in recruiting the extant vegetation. We suggest using the sediment containing rich viable propagules in the actual reconstruction project.