Duluth WRS Seminar

Wetland Plant Community Dynamics in the St. Louis River Estuary


Dustin Haines
Lake Superior National Estuarine Research Reserve

November 9, 2020


Habitat reclamation and restoration efforts within the St. Louis River Estuary are a high priority, due to historic habitat loss, St. Louis River Area of Concern delisting efforts, and to broad initiatives for restoring wild rice in the estuary. Efforts to restore native plant communities in wetlands here have been partially successful, but nearly record high Lake Superior water levels, and the presence of invasive plants such as purple loosestrife (Lythrum salicaria) and non-native cattails (Typha angustifolia and T. x glauca) may be hampering these efforts. To evaluate the relative influence of water levels and invasives on native plant success, we analyzed wetland vegetation data from 2014–2020 collected at the Lake Superior National Estuarine Research Reserve’s Sentinel Site on the Pokegama River. During this time, water depth increased rapidly as a response to increasing Lake Superior water levels. Emergent plants substantially decreased during the sampling period, but the submergent plant communities have increased in cover with rising water levels. Native and invasive emergent plants responded very differently to the increase in water levels, with native cover having no correlation with depth when overall water levels were deeper, while invasives had an increasingly negative correlation. Our data highlights two important points: 1) water levels of Lake Superior is one of the most important factors influencing wetland plant community dynamics in the estuary, and 2) invasive plants persist these high water conditions by retreating to shallower depths, which may allow them to rapidly respond when water levels decrease in the future. Coastal wetland restoration efforts should take into account the rapid potential for change in water levels and plant communities, and the presence of invasives that are poised to expand in years of lower water levels.

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Meeting ID: 956 8739 9002
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