Recognition of wetland ecosystem services has led to substantial investment in wetland restoration in recent decades. Wetland restorations can be designed to meet numerous goals, among which reestablishing a diverse native wetland plant community is a common aim. In agricultural areas, where previously drained wetland basins can fill with eroded sediment from the surrounding landscape, restoration often includes excavation to expose buried seed banks. The extent to which excavation improves the diversity of wetland plant communities is unclear, particularly in terms of longer-term outcomes. We examined plant species diversity and community composition in 24 restored agricultural wetlands across west-central Minnesota, U.S.A. In all study wetlands, hydrology was restored by removing subsurface drainage and plugging drainage ditches, thus reestablishing groundwater connectivity and hydroperiod (“business as usual” treatment). In half of the wetlands, accumulated sediment was removed from the basin and redeposited on the surrounding landscape (“excavated” treatment). Initially, sediment removal significantly decreased invasive species cover, particularly of hybrid cattail (Typha × glauca) and reed canary grass (Phalaris arundinacea), and increased community diversity and evenness. Over time, the effects of sediment removal diminished, and eventually disappeared by approximately 6 years after restoration. While our results demonstrate that sediment removal improves initial restoration outcomes for plant communities, longer-term benefits require sustained management, such as invasive species control or resetting of basins through additional excavation.
Bibliographical noteFunding Information:
Acknowledgements—The authors would like to thank the ICIPE Cereal Stemborer project Coordinator Dr W.A. Overholt for arranging financial support from the Netherlands Government. We thank Dr R. Link (Tanzania-Germany IPM Project) for logistical support. We are also indebted to Dr J. C. Mbapila, Officer-in-Charge Katrin, Ifakara, Morogoro for his advice on potential areas for cereal stemborer survey in Kilombero District, and Dr J. M. Katundu (Senior Entomologist, ARI, Kibaha) for his advice and valuable comments during the preparation of this manuscript.
© 2020 Society for Ecological Restoration
- Phalaris arundinacea
- Typha × glauca
- agricultural wetland