Plant introductions and community dynamics across environmental gradients in Great Lakes coastal wetlands

Great Lakes coastal wetlands provide vital ecosystem services, including water quality improvement, flood mitigation, and fish and wildlife habitat. However, many of these wetlands have been lost, and those that remain face various threats, including invasion by nonnative plants. Within coastal wetlands, the uppermost edge of the herbaceous wetland is a dynamic transitional zone influenced by lake level fluctuations and the adjacent upland; this zone may serve as a refugium for herbaceous emergent vegetation species during flooding, as well as an entry point for new invaders. While previous studies have identified contributors to plant invasions in Great Lakes coastal wetlands, these studies have been limited spatially, temporally, and by species of interest, so there is a need for a larger analysis of the wetland- and landscape-level variables that contribute to invasions across the Great Lakes basin. To address this gap, I used data from the Great Lakes Coastal Wetland Monitoring Program (CWMP), spanning 12 years across 454 wetlands, to model contributors to non-native plant prevalence and impacts to native vegetation. To improve understanding of the transitional zone, I, along with other field crews across the Great Lakes Coastal Wetland Monitoring Program, sampled vegetation at the uppermost edge of the herbaceous marsh during 2024. Across all five Great Lakes, vegetation zone was a strong predictor of non-native plant prevalence, with non-native richness being greatest in the meadow zone, while non-native relative richness and relative cover were greatest in the emergent zone. There were no clear trends in the relationships between hydrogeomorphic class and non-native plant prevalence. Higher peak lake level fluctuations were associated with decreased non-native richness and increased non-native relative cover. Damming upstream of wetlands generally predicted increased non-native prevalence, although relationships were often non-significant and varied by lake. Finally, land use and water quality disturbances were strong predictors of non-native plant prevalence, predicting increased richness, relative richness, and relative cover, primarily on the upper three Great Lakes. Native species richness, diversity, and floristic quality were negatively related to non-native species relative cover across all three vegetation zones and all five Great Lakes, although the relationships were often non-significant in the submergent zone. Native species evenness increased at higher levels of non-native relative cover, contrary to expectations. In the transitional zone field study, I found significantly lower floristic quality and higher non-native species richness in the transition zone compared to the wetland interior. Floristic quality was greatest in transition zones bordered by uplands categorized as “other.” Mean wetness coefficients were lowest (wettest) in transition zones bordered by uplands categorized as “other” and “wooded.” The species in the transition zone ranged from wetland-obligate to upland taxa, comprised of numerous functional guilds. The goal of this work was to identify the wetland characteristics that best predict non-native plant species prevalence so that conservation and restoration can be better targeted toward vulnerable wetland sites. My results provide insight into the predictors of invasion and the responses of native communities to invasion. Because results vary by lake, I recommend that wetland managers use lake-specific results for management applications. Additionally, characterizing the dynamic herbaceous wetland transition zone furthers our understanding of wetland responses to lake level fluctuations and upland influences, which may aid in wetland management.

Grantor dc:publisher

SUNY Brockport Department of Environmental Science and Ecology

Year dc:date.issued

2026

Author dc:creator

• Town, Kendalyn

Advisor dc:contributor.advisor

• Schultz, Rachel

• Great Lakes
• Wetland
• Invasive
• Vegetation
• Zonation

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/20.500.12648/83759

OAI identifier oai:identifier

oai:soar.suny.edu:20.500.12648/83759