Research

I am improving our understanding of how wild nature and humans coexist and interact in human-dominated aquatic ecosystems.

I research what agriculture can do about its large negative contribution to water quality. My dissertation focused on the environmental science of artificial aquatic systems, especially ditches. Broadly, I am interested in how water connects and sustains socio-ecological systems.

New paper!

"North Carolina Coastal Plain Ditch Types Support Distinct Hydrophytic Communities"

We surveyed agricultural, forested, and freeway ditches throughout the Coastal Plain of North Carolina for wetland characteristics- plants, soil, & hydrology. All of the ditches had at least some. 29/32 had hydrophytic (wetland) plant communities. The ditches didn't just have the same few plants everywhere. Each ditch type (agricultural, forested, freeway) had a distinct plant palette, which suggests construction/management influences (especially mowing). National geospatial databases generally do not include these ditches, or if they do, only as part of a larger wetland. We thought the problem might be spotting ditches under tree canopy, but ditches under trees (in acknowledged wetlands) actually appeared more. So, lack of mapping is a choice of priorities. There are likely a lot of these ditches, unrecognized wetlands in plain sight, already managed. The North Carolina Coastal Plain has upwards of 2,711 km of freeway and 93,502 km of roads (USGS 2014) alone, most w/ ditches on both sides. Perhaps we should pay them more attention?

Ditch Integrating Transdisciplinary Collaboration Hub

I've founded a group of ditch researchers, practitioners, and other enthusiasts who collaborate on ditches as socio-ecosystems. Most of our materials are inward-facing for now (stay tuned!), but meanwhile you can:

Iowa agricultural drainage water management

I'm working with Dr. Matthew Helmers's lab at Iowa State University Agricultural & Biosystems Engineering to better understand what controls the water quality of drainage from agricultural fields. The expanse of corn and soybean fields that now comprises most of the U.S. Midwest helps launch cultural eutrophication from its tile drain headwaters, through the Mississippi, to the Gulf of Mexico. Similar problems occur and expand around the world, including where I've worked and lived longest, the Coastal Plain of the U.S. Southeast. Climate change and agricultural intensification make the future of an already sprawling problem perilously uncertain. Our projects, at sites around Iowa, reveal what agricultural management practices actually improve and/or exacerbate export of fertilizer-derived excess nitrogen, by how much, how reliably, for what change in crop yield, and under what conditions, including through changes in more natural factors, like weather and soil properties.

I'm focusing on disentangling the relative influences of all these drivers on primarily nitrogen export in data from our 30-year-old field plot experiment, the Agricultural Drainage and Water Quality Research site (ADW).
With undergraduate interns I mentor, we study nutrient exports after storm events and drainage response over time to plantings ranging from perennial prairie to continuous corn at our Comparison of Biofuel Systems (COBS) site, flashiness of drainage water management systems at the Southeast Research and Demonstration Farm (SERF), and wood chip bioreactor response to temperature at the Northeast Research and Demonstration Farm (NERF).
Additionally, I help monitor and maintain projects on bioreactors on farms in Story County, Prairie STRIPS, and Northwest Research Farm, in addition to ADW and COBS.
On the side, I think downstream, about the relationship between tile drainage, ditches, natural surface waters, and towns, including through an ongoing analysis of flashiness in the US Midwest Regional Stream Quality Assessment.

Corn yields increased under constant fertilizer without reducing nitrate export

I presented this poster about some of my research at the Agricultural Drainage and Water Quality Research site from the Iowa Water Conference in April 2021. The virtual format means I can now easily share this presentation with you too.

Dissertation:

Ecological Limitations and Potentials of Artificial Aquatic Systems: There’s a lot more to artificial aquatic systems than scientists currently know, and management can be improved with additional knowledge. Successfully defended, but publications still in progress. This research was conducted with PhD advisor Dr. James Heffernan at the Duke University Nicholas School of the Environment Grainger River Center.

Artificial aquatic systems

Clifford, C.C. Heffernan, J.B. “Artificial Aquatic Systems.” MDPI. Water 2018, 10(8), 1096; https://doi.org/10.3390/w10081096.

A variety of waterbodies may count as artificial in different contexts. Artificiality is an insufficient explanation for their ecological condition; instead we should test process-based alternatives such as setting, design, and age. Better knowledge of these drivers could improve management potential over a potentially large expanse of ecosystems, known to sometimes provide ecosystem services and disservices of concern. Policy based on our current perception of these systems may reinforce negative expectations.

Urban ditches and natural creeks house similar invertebrate communities in a minimally developed California watershed

Irrigation-style ditches in network with a natural creek fresh from the Sierra Nevada Mountains in small Bishop, California, have statistically undifferentiable benthic macroinvertebrate communities from natural creek communities, given similar substrate and same season. Communities do decline in sensitive taxa (mayflies, stoneflies, and caddisflies) and biodiversity downstream across town, presumably as the influence of urban and agricultural land use increases. Communities in creeks that are close together are more similar than communities in ditches that are close together, suggesting some difference in community assembly.

North Carolina Coastal Plain ditch types support distinct hydrophytic communities

Across 32 agricultural, forested, and freeway roadside ditch reaches in the North Carolina Coastal Plain, all supported predominantly wetland plants, and had at least some soil carbon and signs of wetness. Plant communities differed across site types, however, in response to landscape variables like development in the vicinity and local variables like apparent mowing (on freeway roadsides). Forested sites were more easterly and swampy. Agricultural sites had greater plant cover, including of taxa of driest and wettest wetland indicator groups.

Clifford, C.C.; Heffernan, J.B. “North Carolina Coastal Plain ditch types support distinct hydrophytic communities.” Wetlands 2023, 43, 56. https://doi.org/10.1007/s13157-023-01703-5
(Read only view here.)

Similar processes, different water quality in U.S. natural and artificial lakes

The U.S. National Lakes Assessment, executed by the USEPA, examined over 1000 lakes in 2007 and again in 2012, about half natural and half artificial reservoirs both times. They found differences in the conditions of these two categories, but they did not explore their underlying data to see why the differences occurred. Our structural equations model suggests that algal blooms form through similar processes in both systems, with statistically significant differences, with manmade lakes being less predictable.