Date of Award:

5-2026

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Watershed Sciences

Committee Chair(s)

Karin M. Kettenring

Committee

Karin M. Kettenring

Committee

Timothy E. Walsworth

Committee

Thomas A. Monaco

Abstract

Wetlands worldwide are expected to experience more frequent and intense droughts and floods due to climate change. These shifting water conditions introduce challenges to restoring wetland plants, especially using direct seeding. Seeding is cost and labor-efficient compared to planting, but seeds and seedlings are highly vulnerable to water stress, so restoration efforts often fail when conditions are too wet or dry. Understanding how to improve seed-based revegetation under these conditions is increasingly important. Therefore, we sought to understand the response, measured by percent canopy cover or dry biomass weights, of native plants to different durations of drought in greenhouse experiments, and the outcomes of seeding wetland restorations using two restoration approaches designed for different wetland flooding and drought conditions. In the greenhouse experiments, we grew plant communities from seed and exposed them to three durations of drought that mimicked possible summer drying events. Longer droughts consistently reduced plant cover, but species varied considerably in their survival and recovery from dry soil conditions. In a field experiment at two sites, we compared a precision restoration approach—selecting species based on a site’s water conditions—to several bet-hedging approaches, which assume water conditions will vary from year to year or through a season. In the three bet-hedging approaches, we used a range of species to account for uncertain future flooding and drought conditions, and two approaches spread germination or seeding over time to provide later opportunities for plant growth. We found that site conditions strongly shaped outcomes. At Farmington Bay, standing water dried down and groundwater levels dropped rapidly after seeding, leaving soils extremely dry. As a result, few plants established. At Howard Slough, where soils remained saturated both years, the precision approach initially produced the greatest cover of native plants. By the second year, however, seeded cover was similar amongst all seeded treatments, but the multi-year sowing approach (seeding over two years) had the lowest invasive cover. This result suggests that while precision seeding may promote fast plant growth under suitable water conditions, spreading seeding effort across years can lead to increases in invasive plant reduction. These findings highlight the importance of choosing seed-based restoration strategies tailored to unpredictable water conditions and selecting species with broad water tolerances to account for multiple potential moisture scenarios.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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