Seasonal Dynamics of Soil Seed Bank in Honghu Wetland Withdrawn from Long-term Rice Culture

Abstract

Germination tests of two water regimes were used to evaluate traits, mainly community structure, of the soil seed bank of Honghu wetland withdrawn from long_term rice culture. One way ANOVA was employed by means of diversity, richness and evenness indices, and seed density. To evaluate the role of seed bank in restoration of wetland communities, a soil core was sampled in June 2000, December 2000, March 2001 and May 2001. Furthermore, the delamination of the seed bank was conducted by comparing seed densities at different depths in the soil in the March 2001 sample. The results showed that: 1) seed density in different seasons varied a lot, from 2.90×10~(4) ind.·m~(-2) in. June 2000 to 2.61×10~(5)ind.·m~(-2) in December 2000. The size of the seed bank in Honghu wetland is the largest among all the types of seed banks. The seed bank belonged to the Ⅳ type of the Thompson and Grime model of soil seed banks of different habitats. 2) For the community of the soil seed bank of Honghu wetland, Simpson and Shannon Wiener diversity indices, and Shannon evenness index were maximal in June 2000, and minimal in December 2000. 3) The number of species had no significant difference between soil depths of 0 5 cm and 5 10 an. The seed density in the upper layer accounted for 78% of the total seed number of the two layers, which indicated that it was creditable to study only the upper level(0.5cm) in this kind of research. 4) Seed germination was affected by water depths in both number of species and number of individuals of seedlings. 5) Degrees of similarity between species composition of soil seed banks and that of the wetland vegetation during December, March and May were 33.3%, 20.8% and 15.4%, respectively. They were considerably high compared to those of some other types of habitats. 6) Seeds of typical wetland species were scarce in all sampling periods, suggesting that in order to restore the vegetation of the disturbed wetland more quickly, external seed banks with abundant wetland species need to be introduced rather than only depending on the original ones.