Plant Community Response to Small Dam Removal in Connecticut

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Nora Hardy & Marlyse Duguid

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The Northeastern United States has one of the highest densities of extant dams in the nation. These structures are remnants of the region’s colonial-era mills, which relied on hydropower generated by small dams. Despite growing interest in dam removal as an ecological restoration strategy, very few studies explore how dewatered dam impoundments re-vegetate following dam removal. Land managers and ecologists often cite the potential dominance of invasive plant species in recently dewatered impoundments as a key management concern, but there is very limited literature focused on plant community recovery following the removal of small dams in New England. We conducted vegetation and soil surveys in dewatered impoundments at seven sites in southern Connecticut. These dam removals were conducted between the years 2012 and 2019, have dewatered impoundments 0.5 to 2.8 hectares in area, and are managed as natural areas by public and private landowners. We found that higher concentrations of soil nutrients (K, Ca, P, and Mg) were strongly correlated with lower per-plot vegetative species richness. Larger impoundment area correlated with a higher per-plot proportion of invasive species. Finally, we found a weaker but significant positive correlation between soil K concentration and per-plot proportion of invasive species. Our findings indicate that small dam removal sites in Connecticut support a high proportion of native wetland plants, and that invasive species, while present, are not dominating these areas. Individual site characteristics, including soil K concentration and impoundment size, play a role in determining the prevalence of invasive species in dewatered impoundments.

Resource Type:
Conference Presentation, SER2021

Pre-approved for CECs under SER's CERP program