长江口滨海湿地原生海三棱藨草种群恢复的实验研究

A trial study on revegetation of the native Scirpus mariqueter population in the coastal wetland of the Yangtze Estuary

我国滨海湿地外来物种入侵威胁较为严重。以长江口湿地为例,快速蔓延的互花米草(Spatina alterniflora)逐渐替代了中国特有的原生种—海三棱藨草(Scirpus mariqueter Ts.Tang&F.T.Wang)。基于正在实施的外来入侵种生态控制工程,开展了海三棱藨草在新生湿地的种群恢复实验。实验采用两种恢复策略,即建立种子库和植物球茎(地下繁殖体)种植,并实施了低、中、高密度种植处理以比较其成本效益。研究结果表明,海三棱藨草种子在实验室条件下有较高的出苗率,且5 cm的种植深度最佳。但由于潮滩湿地泥沙淤积的掩埋胁迫,在5 cm的种植深度下,即使采用高密度种植处理也仅有极少数种子能萌发生成植株,且不同种植密度处理间的幼苗存活率和植株密度没有显著差异。而将海三棱藨草球茎作为植被恢复的种植材料时,其出苗率和植株密度远优于种子种植策略,多数球茎能实现出苗和定居,并通过地下分蘖和地下根茎发育迅速形成密集的种群。密度处理结果表明,中密度和高密度种植处理下的生长季后期的植株密度没有显著差异,说明在滨海湿地原生植物种群重建时宜选择经济高效的中密度种植策略。据此可为大规模的长江口原生植被恢复工程提供参考。

Many coastal wetlands were invaded by the exotic species along Chinese coastline. In the Yangtze Estuary, the Chinese endemic community of Scirpus mariqueter Ts. Tang ＆ F.T. Wang has been shrunk due to the rapid expansion of exotic Spartina alterniflora. In this study, the experiments involving S. mariqueter revegetation were conducted based on an ecological engineering for controlling the invasive species, by using seed-planting and corm-planting approaches. At the same time, three levels of planting density were employed in order to assess their cost-effectiveness through the experiments. Under the condition in laboratory, the rate of seed germination was high, especially when planted in 5-cm depth. However, the rates of seed germination and seedling emergency were extremely low when planted in the field mudflat （5-cm depth）, even using the highest planting density, mainly due to the burial stress of sediment deposition during the growing season. There were not significant differences in the rate of seedling emergency and shoot density between different seed-planting densities. In contrast,the approach of corm-planting was feasible when planting in the mudflat, and the rates of seedling emergency and shoot density were significantly higher than those with seed-planting approach. The surviving seedlings sprouting from the soil substrates formed a dense shoot community quickly through underground tillering and rhizome development. Our results also indicated that a medium planting density appeared to be a cost-effective way for establishing the native species in the coastal wetland, because there were not significant differences in the rate of seedling emergency and shoot density between medium and high planting density. We suggested that this study might be helpful for planning further large-scale revegetation of the native species in the Yangtze Estuary.