Impact of Water Level Fluctuations on Soil Seed Bank along Riparian Zone in JingJiang River

Riparian seeds contained in the seed bank are the potential plant population in a riparian ecosystem, and the basis of the settlement, survival, reproduction and spread of plant population. Moreover, they play a pretty important role in the process of species occurrence, species regeneration, vegetation succession and recoveration. Therefore, it is an essentially theoretical and practical significance for human beings to learn riparian zone vegetation formation, succession, river and riparian protection and utilization by researching the riparian seed bank. Based on the water depth gradient being important in determining distinct habitat types, Applying the seedling-emergence method under waterlogged and submerged treatment, the studies focusing on impact of three water level fluctuation on riparian seed bank along the riparian zone in JingJiang river are performed to investingate the distribution of seed bank. It is intended to clarify how changes the water level fluctuations make the distributing patterns of seed bank along the riparian zone. The results showed that submerged conditions were generally not suitable for the seed germination, comparing a waterlogged treatment with a submerged treatment. From the sediment samples 25 species emerged under two treatments. A total of 18 species were recorded in the seed bank of S site (low water level site), 18 in the seed bank of D site (middle water level site), and 7 in the seed bank of C site (high water level site). The total number of species germinating under waterlogged conditions was significantly higher than under submerged conditions, while they varied significantly from site to site. Germinated seedling density was 1,198, 621 and 478 seedlings m-2 in S site, D site, and C site, respectively. Frequency of distribution and densities of the dominant species, however, varied significantly from site to site. Biennial and perennial species were significantly more in the low water level S site, while the annual species were found predominately in the high water level C site. Different species in the riparian seed bank were found to contribute to a "annual species-biennial species-perennial species" distribution pattern along the water level fluctuations, thus revealing marked zonal patterns in species distributions in the riparian seed bank.