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Satellite radar
imagery provides scientists with regional wetland waterlevel patterns. Using satellitebased remote sensing technology, Duke University Wetland Center researchers are building detailed computer models to predict hydrologic changes and habitat distribution in regionalscaled wetland systems. Wearing mosquito netting, Kevin Smith, left , of the Environmental Research Institute of Michigan and a Nicholas School of the Environment and Earth Sciences alumnus, and hydrology Robert Sobscak of the Big Cypress National Preserve, prepare to measure soil temperature. |
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The images, assembled from satellite based radar calibrated with measurements from groundbased field monitors, allow researchers to view a broader area of largescale wetlands and provide information on sites that were previously inaccessible due to dangerous terrain or expense, said Edwin A. Romanowicz, Assistant Research Professor.
"One of the advantages of remote sensing is that it allows us to take a real broad regional perspective," Romanowicz said in an interview. "A lot of big environmental problems that people are working on pertain to regional scales, such as the construction of a new roadway or the impacts of agriculture."
DUWC is collaborating on the remote sensing project with the Environmental Research Institute of Michigan. The team is studying the effects Florida state highway 41, known as the Tamiami Trail, is having on the surface hydrology of the 600,000acre Big Cypress National Preserve.
Traditional fieldbased data collection methods have limited researchers in their ability to apply hydrologic models over broad areas of a wetland. Remote sensing techniques are used with groundbased water monitors that take actual measurements on the ground.
"The highway effects are going to be over a regional scale," Romanowicz said. "It’s very difficult to use simple point data. The conventional way to do this is to go out, put up a station and measure water depths. But that’s all you have — a point of data in one specific location. It’s hard to take that data and go two kilometers away and figure out what’s happening there. The radar gives us a way of linking everything to a regional scale."
In a radar wetland hydrology study, the satellite "shoots" the earth’s surface with a radar signal that reflects off plant stems and tree trunks down toward standing water and then back to the satellite, he said. Monitors onboard the satellite then use the signals to produce digital images of the wetlands.
A number of factors, including the depth of standing water and the types and densities of vegetation, determine how radar is reflected back to the satellite from any given point in the wetland.
To properly interpret images, researchers monitor selected sites in the field and then use the data to calibrate the radar imagery for water depth and vegetation. Using the calibrations as a key, researchers can then use the images to estimate water depths across the entire wetland.
"With radar, you don’t need to worry about daylight – it can be done at night, it can be done in cloud cover, and it can even penetrate some tree canopies," he said. "If you have some standing water, you get a reflection off the water and off the vegetation. That will vary as a function of what type of vegetation you have and how dense the vegetation is and how deep the water is relative to the vegetation. That’s why it’s really important to calibrate on the ground."
Each digital satellite image costs close to $1,500, about the cost of one groundbased recorder. However, one satellite can shoot the entire Big Cypress area while ground monitors can only pinpoint small areas.
"It would be almost impossible to do this type of study at this scale just using groundbased monitors," Romanowicz said. "If we were to do this without satellite technology we would have to locate hundreds of ground monitors all over the place measuring water depths. Many would have to be in remote areas that are difficult or dangerous to get to and expensive because of helicopter access. It would drive up the cost significantly."
The new technology is a nice fit with traditional field techniques, he said. "We have used ground data to show problem areas we really need to look at with radar, and we’ve used radar to show problem areas on the ground where we really need to increase our ground monitoring," he said.
The satellite models also appear to have multiple uses.
"It’s going far beyond hydrology," he said. "Remote sensing is allowing us to come up with much better ecological models. Wildlife biologists are now using the models to look at panther habitats and wading bird habitats and using the models to impose various management scenarios."
Researchers hope to apply the technology in Minnesota’s Lake Agassiz peatland where wetlands have been impacted by agriculture and new roads.
From the Director
New millennium brings new wetland concerns
The Duke University Wetland Center prepares to celebrate its 10th anniversary as we reach the end of this decade and the beginning of a new millennium.
In the center’s 10 years we have confronted many key wetland issues. Our research on constructed wetlands and on wetland functions and values addresses central concerns of the wetlands scientific community — as does our work on biogeochemical cycling, nutrient, and water quality issues — in the Everglades and in North Carolina’s wetlands.
The new century will bring new issues to address. We must begin the restoration of major wetland systems damaged by man’s activity over the last 200 years. Increasing our knowledge of hydrology and nutrient quality is essential to better manage wetland ecosystems. The role wetlands may play in global climate change must be investigated. And we must integrate our understanding, valuation and appreciation of wetland ecosystems with the economic, social, and legal costs of maintaining and reconstructing these systems.
Moreover, the focus of our concern needs to stretch beyond the United States and other industrialized nations to developing countries where the mass destruction of wetlands proceeds at an alarming pace. While wetland issues will become more and more central among the 21st century’s ecological concerns, the fact is that national interest level and research funding remains fairly low.
As we enter the next decade, the Wetland Center will try to develop a more integrated program where members of the Duke community representing other disciplines — from engineering and law to the social and economic sciences — can explore the ways that wetland issues will effect 21st century society.
We plan to start this process in the coming year with a program of multidisciplinary symposia addressing legal, social, and economic factors of wetland management as well as the integration of engineering and ecological principles in the construction and restoration of wetland ecosystems. We will work to raise public awareness of wetland issues both by cooperating with state agencies as they develop wetland educational programs and by including interactive educational material on our own website.
We must wisely plan the stewardship of our restored and natural wetland resources as we face the challenges of the coming century.
- — Curtis J. Richardson,
- Director, Duke Wetland Center
Distinguished Speaker Series
The Duke University Wetland Center 199899 Distinguished Seminar Series concluded March 8 with a lecture by Scott Bridgham, Assistant Professor in the Department of Biological Sciences at the University of Notre Dame.
Bridgham, who earned his Ph.D. from Duke in 1991, presented research on the first three years of fen and bog ecosystem responses to elevated temperatures and altered water levels.
Surprisingly, methane production did not increase, but carbon dioxide respiration did, Bridgham said. In addition, he found shifts in belowground shrub biomass and aboveground sphagnum growth.
This project will provide important insights into peatland responses to global warming, he said.
Research News
Effects of hydrologic management decisions on marsh structure and function in Water Conservation Area-2A of the Everglades, Florida
A project funded by the Duke University Wetland Center and Everglades Agricultural Area Environmental Protection District, May 1998 — May 1999 • Principal Investigators: Kirsten Hofmockel, Curtis J. Richardson and Patrick N. Halpin
Monitoring the effects of management decisions in the remnant northern Everglades of south Florida is logistically challenging due to the scale of the region. One means of evaluating the impacts of past management decisions is through assessing changes in landscape pattern over time.
A spatial time series of tree island patterns was created to quantify landscape level impacts of water impoundment in the Everglades of Water Conservation Area2A (WCA-2A). Tree islands are indicative of both microscale processes (i.e., peat accretion, sediment transport) and macroscale processes (flow direction and velocity, dispersal). They are an important habitat in this otherwise homogeneous landscape, providing diversity of vegetation and indices of hydrologic conditions.
Changes in the landscape pattern of WCA-2A were evaluated using panchromatic aerial photos from winter scenes in 1953, 1980, and 1995 and TM satellite imagery from 1995. Tree island landforms were extracted from the imagery, and spatial characteristics were calculated.
The total number of tree island structures decreased by 87 percent between 1953 and 1995. Small tree islands were impacted most, with nearly complete destruction. Loss of tree island area was the most severe between 1953, when a flow through system still remained, and 1980, after complete impoundment. Tree island loss rate continued to be significant after 15 years of impoundment and water regulation.
The nearest neighbor distance has increased almost three fold since impoundment, while density of tree islands decreased by more than 80 percent. More than 70 percent of the total tree island perimeter has been removed, resulting in a reduction of habitat diversity and hydrologic variability.
Reduction in the number and total area of tree islands has changed the structure of the remaining Everglades landscape resulting in ecosystem functional changes. Loss of total tree island area reduces the habitat for terrestrial dwelling organisms including deer, small mammals, and especially birds. Loss of island perimeter has resulted in severe reduction of important nesting and foraging habitat for wading birds during early season draw down. In the absence of tree islands, the landscape has become more homogeneous, particularly in terms of diversity of hydrologic conditions created by the increased topographic elevation of tree islands. In addition, connectivity of the landscape has been reduced, and distance required for dispersal of drier site Everglades species has increased significantly.
Impoundment of the remnant northern Everglades has eliminated the natural hydrologic flux and increased water storage of the system. The significant ecosystem changes caused by the impoundment can be detected by reductions in tree island landscape pattern. Disappearance of tree islands causes loss of landscape heterogeneity and reduces vegetative and hydrologic diversity. Restoring ecosystem health requires a flow through system similar to preimpoundment conditions.
The US Army Corps of Engineers has recently proposed eliminating some of the impoundments as part of the 25year restoration plan in which levees will be removed and water will flow more naturally through part of the system. This study shows that water impoundment and loss of natural flow cause serious changes in tree island density in the Everglades.
- — Kirsten Hofmockel
- MEM Student
Meet The Durham Staff
The Durham staff at the Duke University Wetland Center is involved in the center’s current North Carolina projects, including research on wetland restoration and a study of how highway construction effects the state’s coastal wetlands. The staff also helps evaluate the effects of nutrient loadings and hydroperiod alterations on vegetation, community structure, and nutrient retention in the Water Conservation Areas of south Florida. The center is housed on the main campus at Duke University in the 300,000 square-foot Levine Science Research Center. DUWC has chemical analysis labs, an ultraclean room, microbial labs with two laminar flow hoods, and dedicated radioisotope facilities.
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Blumenthal oversees the administration of the Wetland Center’s operations in Durham and Florida, including personnel and budget matters. She serves as the liaison for academicians, students, conservationists, and corporate and government officials to coordinate research on critical wetlands issues. She also manages the center’s public relations activities, including publications such as the annual report and newsletters. Her prior experience includes directing scientific conferences for public and private organizations, managing a comprehensive program to foster an understanding of the acid rain issue in North Carolina, and researching and writing on environmental issues. She is the author of The Guide to Environmental Organizations in North Carolina. |
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Laboratory Administrator since 1989, Heine is responsible for overseeing all aspects of lab operation, including employee supervision, student training, instrument maintenance, data review, expenditures, purchases, alterations, and inventories. He is experienced in methods of total elemental analysis in soils and plants, atomic absorption spectrophotometry, and protocols related to quality assurance and quality control. Heine previously worked at the School of Natural Resources and University Hospitals at the University of Michigan. He was a Peace Corps volunteer working in Guatemala from 1979 to 1981, and in 1987 was a Research Fellow of the Organization of American States. His publications include articles in Oecologia and Ecology. |
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Ho returns to Duke from Harvard University, where he was a Statistical Data Analyst for the School of Public Health. Prior to that he was a Research Associate at Dartmouth College’s Environmental Studies Program, conducting comparative research on desert ecosystems in New Mexico and Antarctica. In addition to being the Wetland Center’s main liaison with the NSOE programming personnel, he provides statistical and graphical analyses in support of the center’s research as well as technical guidance to faculty, staff, and students. Ho’s publications have appeared in Antarctic Journal of the United States, Arctic and Alpine Research, and Southwestern Naturalist. |
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The only nonscientist on the Wetland Center staff, Neighbarger is an organist, harpsichordist, and chorister in his off hours. In addition to serving as Associate Editor of WetlandWire, he assists in the DUWC’s administrative functions, maintains the center’s library, and participates in the preparation of manuscripts for publication. His own publications include a book on Restoration theater music as well as articles on American opera and 20th century organ music. |
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Julie Rice has been at the Wetland Center since 1991. She prepares plant and soil samples for analysis and analyzes samples for phosphorus and nitrogen. In addition, she helps maintain and troubleshoot laboratory instruments. Before coming to Duke, Rice was a lab technician at Compuchem Laboratories, Inc. |
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Rogers is the most recent addition to the DUWC lab staff. He conducts phosphorus, iron, and aluminum analyses of wetland water, soil, and plant samples from the Everglades Nutrient Removal project. He is also responsible for lab data and statistical analyses, technical data transfer, and file management protocols. Rogers came to Duke from positions as supervisor and chemist at various labs in Maine and Massachusetts. |
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Willis is in his sixth year at the Wetland Center. Before coming to Duke he was a research scientist at Sadtler Research Labs and RhonePoulenc for over 20 years. His current activities for the Wetland Center lab include nutrient analysis in soil, water, and plant tissue; highsensitivity P analysis; and instrumentation for supporting wetland research. The topics of his published papers include forensic methodologies for drugs of abuse and techniques in microscale digestion. |
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Faculty Notes
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Curtis J. Richardson presented "Phosphorus Assimilative Capacity in Freshwater Wetlands: A New Paradigm for Maintaining Ecosystem Structure and Function" at the annual meeting of the American Society of Limnology and Oceanography (ASLO) in Santa Fe, N.M., in February. An abstract was provided by Richardson and Song S. Qian. Formerly a post doc at the Duke University Wetland Center, Qian is an assistant research professor at Portland State University. |
Sherri Cooper presented "Diatoms and Paleoecology: Water Quality History of the Neuse and Pamlico Estuaries" at "North Carolina Resources: Water Quality Trends and Enhancement," the Annual North Carolina Water Resources Research Conference. The conference was sponsored by the Water Resources Research Institute of The University of North Carolina at Chapel Hill. |
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Craig Stow gave the talk "Recent Historical Nutrient Loading in the Neuse River" at "North Carolina Resources: Water Quality Trends and Enhancement," the Annual North Carolina Water Resources Research Conference. The conference was sponsored by the Water Resources Research Institute of The University of North Carolina at Chapel Hill. |
| Ram Oren presented "Effects of Fertilization on Transpiration and Canopy Stomatal Conductance in Pine and Spruce Plantations" this winter at an agrophysics conference in Havana sponsored by the Cuban Society of Physics. He was the lead author of "Sap-flux-scaled transpiration responses to light, vapor pressure deficit, and leaf area reduction in a flooded Taxodium distichum L. forest" in Tree Physiology. |  |
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Student News
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Lee Barber, Ph.D. candidate, B.S., Biology, Georgia Southern College; M.S., Marine Biology, The University of Miami. Barber joined the Wetland Center in 1992. He is currently in the final stages of his doctoral work studying the effects of agricultural runoff on the biogeochemistry of mercury in the Everglades. His interests include the biogeochemical transformations of nutrients and metals in wetland systems, the impacts of agricultural activities on water quality, and alternative methods of wastewater treatment based on ecological processes. He has presented his work at the 1997 Soil Science Society of America Annual Meeting and at the 1996 International Conference on Mercury as a Global Pollutant in Hamburg, Germany. |
Publication: Bloom, N.S., J.A. Colman and L. Barber. 1997. Artifact formation of methyl mercury during aqueous distillation and alternative techniques for extraction of methyl mercury from environmental samples. Fresenius Journal of Analytical Chemistry 358: 371-377.
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Paul Benzing, Ph.D. candidate, B.S., Biochemistry and Biology, Virginia Polytechnic Institute. Benzing is in the last year of his Ph.D. work at DUWC, where his research has focused on phosphorus chemistry in soil and water. His interests include the chemical partitioning of P in soil and water and the effect of flooding, draining, and redox status on that partitioning. In pursuit of these interests, Benzing has constructed a computer-controlled bench-top microcosm system for analyzing soil and water under different redox conditions. He has also done extensive analysis of soils from south Florida investigating the variability of P partitioning under different field conditions. During the past three summers Benzing has taught a class in Appalachian Mountain Ecology for gifted high school seniors at the Mountain Lake Biological Station in the Allegheny Mountains of southwestern Virginia. He has also been a Durham Summer Institute mentor for high school students interested in science. Benzing served as a teaching assistant for Nicholas School of the Environment and Earth Science’s class in Applied Ecology. |
Publication: Atkinson, R.B., J. Cairns, Jr. and P.R. Benzing. 1993. Constructed wetland potential for performing wetland functions dependent on anaerobic soil conditions. In: F.J. Webb (ed.) Proceedings of the Twentieth Annual Conference on Wetlands Restoration and Creation, Hillsborough Community College, Tampa, FL. 1993.
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Gloria Ferrell, Ph.D. candidate, B.S., Chemistry, West Virginia State. Ferrell is affiliated with both the Wetland Center and Duke University's Integrated Toxicology Program. She came to Durham from Lawrence, Kan. Her research investigates the effects of nutrient availability and hydrologic regime on the phenolic content of sawgrass (Cladium jamaicense) in the Florida Everglades and aims to determine the ecological effects of changes in phenolic content. Research results to date indicate that foliar phenolic concentrations are inversely related to nutrient availability. |
Publication: Richardson, C.J., G.M. Ferrell and P. Vaithiyanathan. 1999. Effects of N and P additions on stand structure, nutrient resorption efficiency and secondary compounds of sawgrass (Cladium jamaicense Crantz) in the subtropical Everglades. Ecology (In press).
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Left: Thomas Scott of the Florida Geological Survey
takes a break from collecting samples to rescue a roseate spoonbill caught in fishing line
at Duck Key, Florida Bay. A research team, including Jacqueline Huvane, Research Associate
at the Duke University Wetland Center, and researchers from the US Geological Survey in
Reston, Va., were collecting samples from a series of USGS monitoring sites within Florida
Bay in February 1999. They are working on a project designed to quantify biotic and
chemical changes that occurred in Florida Bay over the last ca.150 years. Their data will
provide information to characterize past changes in the ecosystem, to model future
changes, and to help develop restoration plans for this region.
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Alumni News
Alan "Bo" Burns, MEM’84, is an Aquatic Specialist for SePRO Corporation.
Richard Hartwell, MEM’86, works with Collier County Public Works Engineering Department in Naples, Fla. His duties include delineating wetlands and conducting endangered species surveys. In addition, he is involved with the permitting of new road and utility line construction in Collier County, the fastest-growing county in the United States and made up of approximately 70 percent wetlands. Hartwell is also currently working on a project to remove exotics, such as melaleuca and Brazilian peppers, from the Picayune State Forest.
April Lander, MEM’90, is Technical Assistance Program Manager for the Border Environment Cooperation Commission (BECC) in Juarez, Mexico. A side agreement to NAFTA created BECC as part of an environmental protection plan for the US/Mexico border area. April administers BECC’s Project Development Assistance Program, a $10 million grant fund from the EPA, which provides resources to border communities undertaking infrastructure projects (water, wastewater, and solid waste). With this support, the communities can undertake the engineering, technical, and financial feasibility studies, transboundary environmental impact assessments, and community participation plans necessary for sustainable development.
Patrick Megonigal, Ph.D.’96 (Botany), Assistant Professor of Biology at George Mason University, is currently working on several wetland-related projects. He is collaborating with Bert Drake of the Smithsonian Institution to determine the potential of a model wetland ecosystem — a salt marsh — to sequester carbon dioxide in soils. This study, funded by the US Department of Energy, has implications for the potential of terrestrial ecosystems to act as a ‘biological brake’ on rising atmospheric carbon dioxide. He is also collaborating with Chris Craft (a former Duke University Wetland Center faculty member, now at the Joseph W. Jones Ecological Research Center in Georgia) in an EPA-funded study to test Odum’s hypothesis that net ecosystem production declines during succession. Using a unique chronosequence of created salt marsh wetlands in North Carolina, Megonigal and Craft will test the theory and seek mechanistic explanations for changes in carbon cycling through time. Megonigal is also investigating the sediment dynamics of the Mattaponi River’s tidal freshwater wetlands for The Nature Conservancy’s Ecosystem Research Program. The Mattaponi, one of Virginia’s most pristine coastal rivers, is the site of a contentious water withdrawal project under development by Newport News Waterworks. The research will provide both descriptive and process-level information for evaluating future land use changes in the basin.
