Fundamentally, I practice teaching and research as one, not as a separate entity. My research feeds all my teaching activities, and vice versa. My general research interests include ecological functions of freshwater wetlands, wetland creation and restoration, soil physicochemistry, wetland mitigation, design elements for wetland ecosystem development, treatment wetlands (nitrogen and phosphorus), system ecology and ecological modeling, ecological sustainability, large river and floodplain system, vegetation response to river hydrology, experimental mesocosms, fate of pollutants (nutrients and trace elements) in soil and water systems, undergraduate research and scholarship, EcoScience + Art collaboration, ecological science communication, and STEAM education. The following explains the major research activities by Ahn Wetland Ecosystem Lab at GMU.
Design elements for creating wetlands to restore ecosystem functions (i.e., N cycling in wetlands and plant community productivity)
This is my lab’s major research agenda. By establishing a collaboration with local mitigation bankers and environmental firms specializing in wetland mitigation banks, Ahn Wetland Ecosystem Laboratory has been studying design elements that can be incorporated in creating and restoring wetlands to develop and restore ecological functions, respectively. The part of the research involves three major design elements so far, microtopography (MT), hydrologic connectivity (HC), and planting diversity (PD). Our team has been studying plant community development, biogeochemistry in a number of created wetlands for the past several years, particularly in the Piedmont region of Virginia. The following publications show the trajectory of the research. Currently we are conducting a study for its fourth (last) year with the design element of planting diversity on ecosystem function and resilience of created wetlands. During the study, our team has also come up with a suit of simple soil properties that can be used to evaluate the functional development of created mitigation wetlands (see Dee and Ahn, 2012; Ahn and Peralta, 2012). We are currently investigating complex relationships among the number of variables relating to three major design elements along with “age (time)” factor to tease out what mechanisms supported by which design elements and/or their interactions can lead to better developments of functionality in created/restored wetlands.
Ecological modeling and system ecology
Understanding the dynamics of an ecological system being studied plays a pivotal role in elucidating mechanisms for functioning and services being provided by the ecological system. I have developed a course through which I can teach system-thinking and building an ecological model. Building an ecological model (conceptual, dynamics and spatial) contributes greatly to our understanding of the ecological dynamics of a system we study and provides necessary feedbacks in our knowledge about the system. Moreover, understanding the relationships between system dynamics and services to society supplied by the ecological system is an important research theme. At GMU, I developed a class titled ‘Ecological Modeling and Analysis’ and taught it a few times so far, especially in more recent years. A dynamic model of floodplain woody species as affected by flooding regime, sponsored by NSF fund, was published in Ecological Modeling (Ahn et al., 2007), and a DRAINMOD modeling approach was developed to simulate wetland hydrology being altered by soil physical properties siginificantly altered during the construction to predict a type of wetland habitat to be developed to guide nation-wide wetland mitigation practice. Currently we are building a water quality model for stormwater wet retention modeling design and management.
Microbial community indicators for ecological functions in wetlands
Upon my arrival at George Mason University I made great efforts to establish a collaboration with other faculty members for interdisciplinary research. With Dr.Patrick Gillevet, molecular microbiologist in my department, I have developed a new area of study that focuses on soil microbial communities and their dynamics over varying environmental conditions in wetlands. A preliminary study I conducted in a greenhouse setting as a starter resulted in a publication (see Ecological Indicators, 2007). In addition, we collaborated to study soil bacterial community dynamics in a palustrine forested wetland in the Bay watershed as affected by hydrologic regime (i.e., wetland vs. upland), which eventually obtained a research funding from the school for a further investigation. The outcome of the study has published in Wetland Ecology and Management. Furthermore, I collaborated with Dr. Mary Voytek at USGS (Reston, VA) to study denitrifying bacteria community and their relations to key soil physicochemical properties indicative of maturation of created/restored wetlands. Currently, I am collaborating with Dr. Stephanie Yarwood, a soil molecular ecologist at University of Maryland, to study the impacts of planted macrophyte community diversity in soil microbial community structure of which changes might provide a clue for our better understanding on the relationship between productivity and diversity of macrophytes in freshwater wetlands.
River-floodplain ecology and restoration
My research experience includes developing a master plan for a large-river floodplain ecosystem restoration, with a focus on a specific vegetation community (i.e., moist-soil plants) as a food source for migrating birds. I developed a dynamic model with field data collection, which would simulate the responses of vegetation to potential river hydrologic manipulations being designed for the restoration. The project was for a strategic renewal of large floodplain rivers as part of NSF-sponsored interdisciplinary research. My achievement in this project include: (1) successful development of a new computer simulation model for a key plant community in floodplains (the moist soil plant community) and verification of the model using historical vegetation survey data; (2) development of a new biologically meaningful hydrologic measure, the lowest successful elevation parameter; and (3) application of both the new model and new measure to the practical problem of restoring a large floodplain river. This research started when I was a postdoctoral researcher. I am still interested in doing research with this subject matter.
Evaluating floodplain nutrient functioning in urban and agricultural catchments vis a vis forested catchments across broad gradients in the Chesapeake Bay Watershed
We are about to launch a new collaborative with Dr. Noe at USGS through my current Ph.D student on denitrification function of landscape-scale floodplain wetlands. Fifteen sites, with 4 plots per site, will be established near United States Geological Survey (USGS) Chesapeake Non-tidal Floodplain Network river gauge stations. In each of the Ridge and Valley, Piedmont, and Coastal Plain provinces, five sites will be located in either predominantly forested (two sites), agricultural (two sites), or mixed urban-agricultural (one site) subcatchments of various sizes. Denitrification potential will be measured using the denitrification enzyme assay, which measures the in situ denitrifying enzymes active at the time of sampling and corresponds well to environmental conditions.
Synthesizing methodologies through structural equation modeling that can guide functional no-net-loss of Clean Water Act to restore wetland ecosystem services
The proposed study will provide an opportunity to integrate and synthesize the studies previously conducted in the same mitigation wetlands by the PI on varying subjects through a structural equation modeling approach. Furthermore, the lack of the synthesized and integrated information available on ecosystem development of mitigation wetlands is an important gap in the literature this study is designed to fill. The outcomes of the study will stimulate further investigation and analysis that develops and effectively communicates reasoned and practical alternatives to select challenges in National Water Resources Policy [i.e., no-net-loss policy under Clean Water Act (Section 404)] in relation to designing and constructing mitigation bank wetlands, mitigation performance measures (e.g., planting diversity and soil metrics), and achieving functional mitigation that would restore ecosystem services. It will also stimulate the analysis of the current evaluation and assessment protocols of legal monitoring and success criteria for mitigation wetlands.
Ecological engineering and ecosystem restoration: outdoor field mesocosm project to enhance research experience for undergraduate students
This project is a strong combination of teaching and research activities, which would provide students with an opportunity for hands-on experience with ecological engineering. I built an outdoor compound named “Wetland Mesocosm Compound” on the west campus of the GMU campus. The compound has been used for teaching and research activities for my students, scholars, visitors, and K-12 student summer internships over the past several years. Especially, my relatively new course, Ecological Sustainability, used the compound to establish a long-term research mesocosms (a set of 60 wetland mesocosm, 150 gallon each). I have developed a program in my course that undergraduate students are required to present their semester-long project outcomes to local K-12 students invited at the end of the semester to improve their science communication skills. This proved to be beneficial to K-12 students as well. It is an on-going research subject as well in collaboration with the Students as Scholars program at GMU.
“The Rain Project” under EcoScience + Art Initiative = Interdisciplinary Teaching and Scholarship
I strongly believe holistic approaches in education can reinforce students’ learning experience and help them foster innovation, collaboration, and persistence. We need to make conscious efforts on creating and nurturing more interdisciplinary programs on the campus. Currently, there is a lack of an interdisciplinary student-faculty and faculty-faculty interactions outside the classroom. There is a great lack for college students in their early academic training of an opportunity to experience, learn, and actively participate in interdisciplinary works and novel ideas across the disciplinary boundaries.
I designed a special project titled “ The Rain Project” under the initiative that started fall semester in 2014 through fall 2016 to explore and showcase what the initiative can do in terms of college education, scholarship, and service. More about the rain project can be found in the EcoScience + Art Special Project sections. Publication, videos, and photobook of the project can be found there. You can watch the video of my recent talk on the Rain Project at DASER (D.C. Art Science Evening Rendezvous) by Cultural Programs of National Academy of Sciences early February, 2017. (just click the title The Rain Project).
The 100th Meridian Project
This is a unique research collaboration between art, science, and engineering at Geroge Mason University. It is sponsored by Provost Multidisciplinary Research Initiative. I'm a co-PI of the project, collaborating with CVPA and CHSS. Here's a brief description of the project: "The American West is parched. We were warned, as early as the 1870’s, when explorer John Wesley Powell explored the entirety of the Colorado River and came to a controversial conclusion. Travel with us now down a river more complex than even the Colorado – the river of American history, whose tributaries are science, policy, high finance, environmentalism, and more – in an effort to understand how Powell’s discoveries were made and, perhaps more crucially for the present day, why they were ignored. Along the way, we may be inspired to wonder whether there are any contemporary parallels to the 19th and 20th centuries’ willful rejection of sound scientific guidance. Supported by Mason’s Office of the Provost Multidisciplinary Research Initiative, and in collaboration with Fall For the Book, the College of Science, the College of Visual and Performing Arts, and a growing number of partners – academic, community and corporate, the Project proposes to discover not only new insights into how science is translated into action or condemned to oblivion, but also to create a collaborative research protocol that can be applied in an ongoing process to any number of critical issues in the contemporary world."