Ecosystems Lab at USF

Kirsti Martinez

Congratulations to Kirsti Martinez! Kirsti is one of only 260 undergraduate sophomores and juniors in the United States to receive the prestigious Barry M. Goldwater Scholarship for the 2015-2016 academic year. Congratulations are especially in order because this award does not simply recognize merit. Applicants had to write a competitive, rigorous research proposal, as well. Kirsti is a member of the Lewis Lab working on her Honors thesis, which investigates how leaf litter inputs from forest trees affect soil properties in upland and wetland habitats. Additionally, she is a member of Dr. Luanna Prevost’s lab, also in our department, where Kirsti participates in biology education research that investigates how biology and ecology are taught at the undergraduate level. Read the press release.

Prairie pothole wetlands in central North America. Credit: Ducks Unlimited. Taken from the National Science Foundation website.

Wetlands come in all shapes and sizes, and one form is the “geographically isolated wetland,” or GIW. Often, GIWs occur in complexes that reach across broad expanses, such as the prairie potholes shown here, which span the central plains of North America. Vernal pools in California, cypress domes in Florida, and pocosins in the Carolinas also occur as vast numbers of small basins scattered across broad landscapes. Wetlands perform many valuable services, such as filtering sediment and pollutants, and thereby protecting lakes, rivers, and bays situated further downhill. But recently, GIWs have come under attack based on the assumption that because they are “isolated,” they do not provide these valuable services. This attack has been so sweeping that the US Supreme Court recently stripped GIWs of many protections, ruling that they don’t fall within the scope of the Clean Water Act. The Lewis Lab participated in a review article, led by John Marton of Indiana University, emphasizing that GIWs are anything but isolated, as they communicate with their surroundings through the movements of organisms and flows of nutrients and groundwater. Our article discovered that GIWs indeed provide services that should place them within the scope of the Clean Water Act. Read it here.

Kristen Langanke, Jeannie Mounger, and Sandy Voors at the USF Undergraduate Research Colloquium.

Great job to the undergraduate researchers in the Dept of Integrative Biology at USF, who presented their posters yesterday at the USF Undergraduate Research Colloquium! Members of our lab presented three posters with authors including Sandy Voors, Kirsti Martinez, Kristen Langanke, and Jeannie Mounger. Thanks to faculty members Christina Richards and Luanna Prevost, and PhD student Bert Anderson, for mentoring these works!!

Congratulations to Bert Anderson, who just passed the PhD proposal examination, and has advanced to the status of PhD candidate. Bert’s research will examine how biogenic habitat modification alters organic matter dynamics in hypersaline coastal salt pans. Now the real work begins!

Viviana…from MS on to PhD.

Congratulations to Viviana Penuela! She recently defended her Master’s degree research, and has now deposited her approved thesis, thus successfully completing her M.S. degree. Viviana’s research addressed the link between land management policy and soil biogeochemistry. In particular, she examined how soil organic matter and nutrient pools in residential lawns were affected by different lawn system management strategies. These different strategies arise from an interaction between municipal-level policies and  the yard-care behaviors of individual home residents. Distinct high-amendment and low-amendment strategy types were evident, and corresponded with the use of reclaimed water. Viviana’s work identified important implications for soil chemistry and microbiology, and contributes to understanding ecological variability in urban systems. Good work Viviana!

How do ecosystems change as they age? It’s a question we address in our most recent article – read it here! We identify how ecosystems might continue accumulating nitrogen even after they stop growing.

Oak forests in Pennsylvania. Young forest stand (about 10 years old) on the left, and older forest stand (over 100 years old) on the right. The older forest has accumulated abundant soil organic matter, and has great potential for capturing nitrogen and holding it in a stable form.

Succession, or the progressive change in ecological systems as they age, has long been an important concept in ecology that helps organize the discipline. For example, ecologists who focus on the cycling of energy and essential nutrients might investigate how these cycles change as an ecosystem ages. Ecologists know that young, growing ecosystems can increase their stockpile of nutrients (such as nitrogen) by storing it in accumulating plant matter. We also know that soils are a huge reservoir for storing nitrogen, and that even old ecosystems can continue to accumulate nitrogen in soil even after the plants have stopped growing. Our research, conducted with Jason Kaye at Penn State and Michael Castellano at Iowa State, suggests a couple mechanisms by which nitrogen can continue to accumulate in the soil of old forests. First, we show that new inputs of nitrogen are captured by soil organic matter much faster than are released, meaning the soil must accumulate nitrogen over time. Second, we found that the potential for this accumulation was greater in older forests because those forests had more soil organic matter. This research helps us understand the link between ecosystem succession and the nutrient economy of ecosystems, and highlights a significant ecosystem service—the capture of nitrogen, which can severely impair air and water quality—of mature ecosystems.

As we move into the second half of the semester, members of the lab are preparing to take important steps forward in their careers as ecologists. PhD student Bert Anderson will be defending his dissertation proposal in efforts to move forward to candidacy status. Likewise, Viviana Penuela will be defending her Master’s thesis that reports her studies of urban soil responses to the use of reclaimed water. Best wishes to them!!!

Wetland carbon and nitrogen storage detected by satellite…check it out here! Naveen Anne and his advisor Dr. Amr Abd-Elrahman at the University of Florida turned their remote sensing expertise to ecosystem services provided by the soils of coastal wetlands. Ecosystem services are the free benefits that society gets from nature, and coastal wetlands like mangrove forests and salt marshes provide them in abundance. In particular, coastal wetlands store massive amounts of carbon and nitrogen in rich deposits of soil organic matter, thereby protecting the quality of the atmosphere and ocean water. The Lewis Lab at USF collaborated with Naveen and Amr to develop spectral models of organic matter, carbon, and nitrogen storage in coastal soils. Spectral models predict features of the Earth’s surface based on light detected by remote-sensing instruments such as satellites. These technologies are particularly useful because coastal wetlands are hard to access on foot, but their important services may be sensitive to disturbances ranging from habitat destruction and oil spills to climate change and sea level rise. In this paper, we took remote sensing of soil one step further than past work, by focusing on soil attributes that are particular to the service of carbon and nitrogen storage. Namely, we developed spectral models of portions of organic matter, carbon, and nitrogen that are easily lost from soils. These models could be used to prioritize coastal areas for protection. This work was supported with funds from the US National Science Foundation.

Viviana Penuela received a McKnight Doctoral Fellowship award, for tuition and stipend support for three years. Viviana’s successful proposal described her plan to investigate how the growing use of reclaimed water alters the chemical composition of soil, and may thereby affect soil microbiology, physics, and ultimately carbon and nitrogen sequestration. The title of her project was “Influences of reclaimed water irrigation on microbial processes and aggregates formation in urban soils,” an example of basic biogeochemistry set in an urban context. Viviana will conduct a comparative study between lawn management strategies (reclaimed vs. aquifer water irrigation) in urban soils. The samples will be taken from residential lawns irrigated with reclaimed water and from those irrigated with potable water. She will compare physical and microbial properties of the soil to better understand the effect of reclaimed water irrigation soil carbon and nutrient storage.