Different roles of three emergent macrophytes in promoting sedimentation in Dongting Lake, China

摘要

Aquatic macrophytes play an important role in promoting sediment deposition. However, compared to submerged macrophytes, the influence of emergent macrophytes on sedimentation dynamics have been studied less often. In this study, a field experiment was conducted to compare the influence of three typical emergent macrophytes (Miscanthus sacchariflorus, Carex brevicuspis, and Phalaris arundinacea) on sedimentation characteristics in Dongting Lake. In addition, the factors that determine sediment characteristics were also investigated. Both vegetation type and vegetation removal treatments had significant effects on sedimentation depth. Compared to the non-vegetated treatment, sedimentation depths were much greater in the vegetated treatments in all three communities. The order of sediment-trapping ability, from highest to lowest was P. arundinacea > M. sacchariflorus > C. brevicuspis; sedimentation rate was much higher in the P. arundinacea community than that in the other two communities, especially in the Tuanzhou and Chapanzhou lakeshores. In the vegetated treatment, clay and fine sand contents were significantly influenced by both vegetation type and vegetation removal treatment, whereas fine silt, coarse silt, and coarse sand contents were significantly affected only by vegetation type. Sand content was higher, but clay and silt contents were lower in the M. sacchariflorus community compared to the other two communities. Median particle size in the M. sacchariflorus community was much higher than that in the other two communities in both non-vegetated and vegetated treatments. Organic matter content, total N, and sediment pH were influenced by vegetation type alone. Sediment in the M. sacchariflorus community had a lower pH but higher organic matter and total N content compared to the other two communities. Multiple linear regression indicated that sediment characteristics were significantly correlated with vegetation characteristics (e.g. plant density, height, and biomass), elevation, and flooding time. The data indicate that the roles of these three emergent macrophytes in promoting sedimentation vary significantly, which is mainly due to their different structural properties and distribution patterns. Our results provide experimental information on the role of emergent macrophytes in promoting sedimentation and may assist in the effective management of Dongting Lake.