Effects of flooding on seed viability and nutrient composition in three riparian shrubs and implications for restoration

Constructions of large reservoirs (all over the world) have resulted in the degradation of riparian vegetation. The coverage and species biodiversity of riparian communities in the Three Gorges Reservoir area have dramatically decreased since the completion of the Three Gorges Project. The responses of three shrub seeds to flooding time were examined to investigate the potential use of soil seed banks for the ecological restoration of the drawdown zone in the Three Gorges Reservoir Area. The effects of flooding time on seed viability and seed nutrient composition for the riparian shrubs Buxus ichangensis, Cornus paucinervis and Distylium chinense were tested by simulating 0, 5, 6, 7, 8 and 9 month flooding periods under a controlled experiment. Results showed that seed viability decreased with the length of flooding treatment. Seeds of all three shrubs displayed relatively high viability and remained viable after six months of flooding. However, seed viability significantly decreased after seven months of flooding. After nine months of flooding, the seed viability of B. ichangensis, C. paucinervis and D. chinense decreased by 86.14%, 24.03% and 43.43%, respectively, compared with a non-flooded control. The protein, starch and soluble sugar content of seeds from the three shrubs decreased with flooding time. The seed bank samples of D. chinense and B. ichangensis showed the highest tolerance against short-term flooding, while the seeds of C. paucinervis exhibited the strongest tolerance against long-term flooding