Characteristics of the soil seed banks and relationships with the vegetation in restored wetlands in Sanjiang Plain, northeast of China
三江平原恢复湿地土壤种子库特征及其与植被的关系

Aims Seed banks are an important source of regenerative material in wetlands. Our objective was to study characteristics of the soil seed banks and relationships with the vegetation in different restoration successional stages. Methods We collected soil seed banks from different depths (0–5 cm, 5–10 cm and rhizomes) from farmed wetland, restored wetland in different successional stages and natural wetland and germinated them under two water regimes (flooded and non-flooded) in a greenhouse. We used quadrats to survey vegetation structure in natural wetland and restored wetlands of different successional stages. Important findings With increased the restoration time, seed bank composition and size increased, and the vegetation community showed succession from a xerophyte-dominated community to a wetland community dominated by Calamagrostis angustifolia. Number of species germinated from the seed banks was 24, 29 and 39, while 21, 25 and 14 species were recorded in the vegetation of in 7-year restored wetland, 14-year restored wetland and natural wetland, respectively. Wetland type, water regime, depth of burial significantly influenced both the species richness and seedling emergence (p < 0.01). Seed density varied with depth so that seed density was higher in 0–5 cm than in 5–10 cm. The seed density in 0–5 cm was four times as that in 5–10 cm in natural wetland while it was just 1.3 times in restored wetland. The similarity between layers was low. More species germinated under non-flooded condition than flooded and the life forms differed. Because the restoration time was short, the similarity between seed bank and vegetation in different restoration successional stages was always <30%. Many wetland species germinated from rhizome fragments, especially C. angustifolia and other wetland species. Our research suggests that the seed bank could retain and restore several wetland species in different restoration successional stages, which can be valuable for vegetation succession and wetland restoration.