Effects of sediment load and water depth on the seed banks of three plant communities in the National Natural Wetland Reserve of Lake Xingkai, China

The discharge of agriculture irrigation runoff containing large amounts of suspended particles resulted in a high sediment accumulation rate (0.3–1.0 cm yr−1) in the receiving wetland upstream of Lake Xingkai, Northeast of China and may create negative ecological impacts to the wetland system, particularly the vegetation community. In this study, we conducted a germination experiment and a vegetation survey to evaluate the effects of different sediment loads on the seed banks of three wetland communities (dominated by Glyceria spiculosa, Zizania latifolia and Pycreus korshinskyi, respectively) under two hydrological regimes (0 and 10 cm water depth). Results revealed significant differences in seed germination rates among the three plant communities and significant effects of sediment load on the germination rates. Species richness and seedling emergence decreased significantly at 0.5–0.75 cm of sediment addition. Species responded differently to the addition of sediment. The number of seedlings of P. korshinskyi, Sagittaria trifolia, Alisma orientale, Monochoria vaginalis, Carpesium macrocephalum decreased gradually as the sediment addition increased from 0 to 2 cm, while the number of seedlings of Fimbristylis dichotoma, Eleocharis ovata, Bidens bipinnata decreased to zero at 0.5 cm of sediment addition. The number of species germinated under the non-flooded conditions was significantly higher than that under flooded condition. All plant communities showed a similar response to the sediment load under the two water regimes. Despite low similarity, the number of species germinated from seed banks was higher than the original number of species present in each plant community. To protect and restore the wetland vegetation community in the Sanjiang Plain, irrigation and land management strategies will need to be implemented to reduce the sediment load from the paddy fields to the wetlands.

► Species richness/seedling emergence decreased significantly with sediment addition.
► Species richness/seedling emergence decreased significantly under flooded conditions.
► Plant species responded differently to the addition of sediment.
► Knowledge gained from this study will provide insight into irrigation management.