Impacts of Shallow Lake Restoration on Vegetation and Breeding Birds in Iowa

Abstract

The Shallow Lakes Restoration Project aims to restore eutrophic shallow lakes throughout the Iowa Prairie Pothole Region (PPR). We compared the vegetation taxa richness and frequency of taxa in three vegetation groups surveyed in 2016 and 2017 across non-restored sites, younger restorations, and older restorations. We also assessed the impact of these groups on numbers of breeding marsh birds. Restored wetlands had between 2.7 (95% CI 2.3, 3.2) and 4.7 (95% CI 3.9, 5.5) more species than non-restored sites among the three vegetation groups. Typha sp. was the most abundant emergent species. Lemna minor and Ceratophyllum demersum were the most abundant floating-leaved and submersed species, respectively. The frequency of submersed aquatic vegetation increased with years since restoration, while floating-leaved vegetation and Typha sp. peaked at 7 years post-restoration. The frequency of Typha sp. positively influenced Marsh Wrens and Yellow-headed Blackbirds. Water depth negatively affected Marsh Wrens, but water depth positively influenced Yellow-headed Blackbirds. Floating-leaved vegetation positively affected Virginia Rails, while water depth had a negative effect on this species. Our results indicate that after about 7 years further management of the vegetation and water levels may need to occur and should include maintaining appropriate conditions for breeding marsh birds.

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