Nature based solutions We have a couple of projects examining the potential of nature based solutions to mitigate negative impacts of climate change in natural and working lands. Both of these projects are taking place in the Hofmann Forest. In one project we are examining the potential of restoring hydrologic regimes in pocosin wetlands to decrease greenhouse gas emissions. This is a collaboration with The Nature Conservancy and builds on our previous work (Armstrong et al. 2022, Swails et al. 2022). The other project is examining the potential of using pine plantation to store water after storms. This is a collaboration with Drs. Barbara Doll, Mohamed Youseff, and Chad Poole from BAE.
Ghost forests Thanks to an NSF CAREER grant, we have been examining the resilience of forested wetlands in the coast of North Carolina. You can find a description of the project here . We measured long-term sediment, carbon, and nitrogen accumulation in forested wetlands, ghost forests, marshes, and open water. We found that forested wetlands can sequester more carbon than marshes (Gundersen et al. 2021). We have also measured greenhouse gas emissions from standing dead trees (snags) and found that they can be a source of greenhouse gases to the atmosphere (Martinez and Ardon 2021). That paper caught the attention of lots of reporters, because we called them tree farts (find one story here). We also worked with Luke Groskin from the NPR show Science Friday to make a video. As part of this project we launched a citizen science project examining the health of cypress trees along the NC coast. You can learn more here.
Salinization of inland waters With funding from NSF Coastal SEES, we have been examining the human and ecological consequences of saltwater intrusion in the Albemarle-Pamlico Peninsula of North Carolina. This is an interdisciplinary collaborative project with Ryan Emanuel (NCSU), Emily Bernhardt (Duke), Justin Wright (Duke), and Todd BenDor (UNC Chapel Hill). You can find a description of the project here. We have documented that ditches and drains facilitate the movement of saltwater deeper into the landscape (Bhattachan et al. 2018). We have also measured response of different tree species to salinity and maintained a long-term salt addition experiment to a coastal forested wetland.
Long-term patterns in tropical stream biogeochemistry
In collaboration with Drs. Cathy Pringle (UGA), Alonso Ramirez (NC State), John Duff (US Geological Survey) and Gaston Small (University of Minnesota), we are examining long-term patterns in stream biogeochemistry at La Selva Biological Station in Costa Rica. We have observed that ENSO-related changes in dry season rainfall lead to increases in stream water P and episodic pH drops (Triska et al. 2006, Small et al. 2012). The episodic pH drops are not the same in all streams through out La Selva, due to very different buffering capacity provided by interbasin groundwater inputs into some of the streams. (Ardón et al 2013). WE have been examining the sources of CO2 into these streams (Marzolf 2021) and controls on stream metabolism (Marzolf and Ardon 2021). This work is supported by an NSF-LTREB.
Consequences of saltwater intrusion on nutrient cycling in a coastal plain wetland
In collaboration with Drs. Emily Bernhardt (Duke), Geoff Poole, Clem Izurieta, Robert Payn (University of Montana), and Amy Burgin (University of Nebraska), we are examining the consequences of drought-induced saltwater intrusion on the coupled cycling of carbon, nitrogen and sulfur in the Timberlake Wetland Restoration project. Our work combines long-term field measurements, laboratory experiments of soil anaerobic metabolic pathways, mesocosms and simulation modeling. I have been conducting microcosm experiments examining the role of drought and saltwater on greenhouse gas emissions and soil solution nutrients. We documented large increases in ammonium release due to increased salinity (Ardon et al. 2013). This work was supported by NSF.
Biogeochemical tradeoffs in wetland restoration
As a postdoc I examined the water quality benefits of the Timberlake Wetland Restoration Project. We were interested in examining potential tradeoffs associated with wetland restoration, particularly: 1) is there a N benefit at a P cost for water quality? 2) is there a water quality benefit at a greenhouse gas cost? In the first two years after restoration the site functioned as a NO3sink, while being a source of NH4, DON and TP to downstream ecosystems (Ardón et al. 2010 a). To examine hydrologic control over P export, we conducted two large-scale draw-down experiments where we drained 10 ha of the site. We found 4x fold increases in P concentrations in soil solution and surface water in summer but no changes in winter (Ardón et al. 2010 b). We also found that the restored site emitted less greenhouse gases than an active agricultural field or two reference wetlands. (Morse et al. 2012). Collaborators: J.L. Morse, M.W. Doyle, E.S. Bernhardt
Carbon processing in tropical and temperate streams
I am a part of a group conducting a Meta-Analysis & SynthesiS of Leaf decomposition in StreamS (MASS-LOSS). This is in collaboration with Jennifer Follstad-Shah (Utah State University), John Kominoski (UGA) and others. This group is examining the role of temperature, litter chemistry, and biota on decomposition rates of leaf litter in streams worldwide. For my dissertation I examined how interactions between leaf litter chemistry and stream water nutrients affect leaf litter breakdown rates. I found that structural compounds were more important than secondary compounds in determining leaf breakdown rates (Ardón and Pringle 2008). My data also showed that leaf litter quality determined the magnitude of microbial response to enhanced nutrients (Ardón et al. 2006, Ardón and Pringle 2007). And, contrary to common misconceptions in the literature, leaves from temperate tree species can have more secondary compounds than leaves from tropical species (Ardón et al. 2009).