Research areas
Biogeochemistry of restored streams and riversHealthy streams are ecological hot spots, but these characteristics are rarely replicated following restoration. Our research focuses on creating transferable knowledge that allows experimental, data-driven approaches to scale from small streams to large rivers. My team’s research in agricultural and urban streams has demonstrated the capacity for restoration features in the channel to improve water quality by generating diverse flowpaths between stream water and the sediments where microbes flourish, but that construction practices can shut down this exchange reducing effectiveness (McMillan et al 2014, Welsh et al. 2017). We have also showed how these structures can amplify riparian processes by raising local groundwater tables, increasing residence times thereby promoting nitrogen removal (Welsh et al. 2020). This research was part of multiple restorations completed in collaboration with restoration partners and governmental agencies. Current efforts are aimed at connecting land-based conservation and riparian/edge-of-field practices with channel restoration to better quantify possible synergies and efficiencies of implementation.
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Floodplain reconnection to restore hydrologic connectivityFloodplains are key locations for pollutant removal and flood storage, but many have been disconnected from the river through levee creation and stream channelization. Our work established the role of hydrologic connectivity in floodplain restoration and the importance of place-based solutions that are transferable but also focused on localized problems and assets (McMillan and Noe 2017). In agricultural landscapes, my team’s research shows that creating floodplains via two-stage ditches and restoring floodplains along large river corridors promotes water quality improvements by enhancing denitrification and organic matter accumulation (Hanrahan et al 2019). However, nitrogen reductions often come at the expense of phosphorus release and greenhouse gas emissions under prolonged flooding (Welsh et al 2021). Ongoing research funded by the NSF, is testing this model showing the importance of watershed position and vegetation patterns in addition to connectivity and future efforts will continue this throughout the Midwest where strategies to improve water quality and ecosystem health are critically needed.
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Wetland Biogeochemistry
Wetlands remove nitrogen and are among the largest carbon sinks per area, yet fluxes are highly variable and there is potential for significant release of phosphorus and methane – a potent greenhouse gas. My current work in wetlands has built off many of our findings in riverine floodplains on the environmental controls of these tradeoffs. Our current research is funded by USDA-NIFA and shows that plant residue from native grasses can amplify denitrification, but that invasive species, particularly reed canary grass, further increase methane release. Future projects are aimed at molecular controls and microbial response using isotope labeling and probing techniques to trace metabolic products through model wetland ecosystems. I anticipate that future efforts will include similar research into the role of vegetation and hydroperiod on the balance between full denitrification and other nitrogen transformation pathways. Our goals is to better understand these governing relationships so that we can generate wetland restoration designs to achieve agronomic and environmental goals – reduced nutrient export, storage of water for possible irrigation, and carbon sequestration.
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Watershed scale stormwater managementMore frequent and intense storms resulting from climate change coupled with land use changes are resulting in more frequent algal blooms, catastrophic floods, and reduced biodiversity. Understanding outcomes of successful restoration at watershed scales is at the heart of my work to mitigate these negative impacts. My team has shown the localized positive impacts of green infrastructure on hydrology (Jefferson et al. 2014), and water quality (Rivers et al. 2018, Scarlett et al. 2018) but despite intense efforts to implement these practices, they have been insufficient in reducing impacts at watershed scales (Bell et al. 2016, Liu et al. 2017). In a well-cited review, our interdisciplinary team showed that placement and watershed context can mediate the persistent effects of urbanization but that flow reductions are key to reducing pollutant loads (Jefferson et al 2017). We are extending this work internationally with urban communities in Arequipa, Peru to further demonstrates how historic land use and current land management influence water availability, soil health, and plant disease, findings that have applicability for water-limited regions across the world (Rodriguez-Sanchez et al. 2021).
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Together with interdisciplinary collaborators, we are showing the disproportionate impact of stormwater hazards on socially and economically vulnerable communities and uncovering an important link between environmental concern and higher rates of volunteerism, which can better guide engagement (Scarlett et al. 2021). Current research and extension funding from NOAA is helping us support community centers in the Chicago metro area to build tools and capacity for climate resilience and sustainable urban farming. Future efforts are aimed at co-production with Great Lakes communities focused on climate resilience through generation of transferable knowledge and co-creation of decision support tools. I anticipate my future work will connect research and engagement in small to medium sized communities throughout the Midwest where local impacts of flooding and impaired water quality are often under-resourced and strong partnerships can create multiple benefits through green stormwater infrastructure projects.