Sediment excavation as a wetland restoration technique had early effects on the developing vegetation community

Abstract

Excavating agriculturally-accrued sediment from wetland basins is an increasingly common restoration technique worldwide, but the impacts on recruiting native plant communities are unknown. Multiple agencies developed a wetland monitoring protocol to document how restoring hydrology and removing excess sediment impacted hydrology and plant assemblages both before and up to 6 years after wetland restorations in North American prairie potholes. Our results indicated that the excavated basins had marginally greater probabilities of increased total standing water, habitat interspersion, and relative plant diversity, as well as lower probabilities of having invasive plants and hybrid cattails (Typha × glauca), when compared to unexcavated basins. By year 4, the excavated basins had 50% probability of extensive cattail invasion, whereas the unexcavated basins had 85% probability of cattails. However, the benefits from excavation were typically negated by invasive species and cattail encroachment within 3–6 years of post-restoration. Therefore, the vegetation communities may benefit from sediment excavations that are also coupled with targeted management within the first few years to combat invasion. This long-term monitoring program could be continued and revised to include post-restoration management activities (e.g., seeding, invasive species control techniques, and prescribed fire) using an adaptive management framework to provide prompt feedback to managers regarding the relative efficacy of alternative post-restoration management.