[Characteristics of soil seed banks in different water level areas after returning farmland into lake in Qingshanyuan of Dongting Lake].

To study the composition and distribution of soil seed bank in the areas after returning farmland into lake is of significance in evaluating the ecological restoration effect of damaged wetlands. In this paper, the composition and diversity of seed bank in soil profile (0-2, 2-5, and 5-10 cm) and their relationships with above-ground vegetation in different water level areas in Qingshanyuan, a typical region after returning farmland into lake in Dongting Lake, were investigated. A V-type variation pattern was observed in the seed density and species richness of soil seed bank and in the similarity coefficient of soil seed bank and above-ground vegetation along a gradient of low-medium-high water level. As for the seed density, it was the highest (36943 +/- 5207 seeds x m(-2)) in frequently flooded area, followed by in heavily flooded area (30572 +/- 5329 seeds x m(-2)), and in incidentally flooded area (18618 +/- 6977 seeds x m(-2)); for the similarity coefficient, it was also in the order of frequently flooded area (0.76) > heavily flooded area (0.53) > incidentally flooded area (0.41). The seed density, species diversity, and species richness of soil seed bank decreased along soil profile, but the decrements differed in different water level areas. The regular variation patterns of the seed density and species richness of soil seed bank and of the similarity coefficient of soil seed bank and above-ground vegetation along the water level gradient were closely related to the water-level fluctuation and the life-form composition of the vegetations in study area.