LAWRENCEVILLE, NJ -- A recently completed sabbatical has allowed Dr. Mary Allessio Leck, professor of biology at Rider University, to compare the natural and constructed wetlands of the Hamilton-Trenton marshes. The research has become a vital component of the Delaware & Raritan Greenway's marsh management plan, and has resulted in some surprising observations and conclusions drawn from Leck's four years of studying the constructed wetland on Duck Island.

The natural environment of the marshes was disturbed beginning in 1984 by the construction of the Route 29 expansion and Route 129 in south Trenton and the creation of interchanges linking the roads with Interstates 195 and 295. Since completion of this major infrastructure project in 1994, the State of New Jersey has gone to considerable effort and expense to restore vegetation.

The largest components of Dr. Leck's research were studying the soil seed bank of the area and compiling a species list identifying all types of plant life existing in the 1,250-acre wetland. To date, Dr. Leck's list has remarkably grown to nearly 800 species.

At least equally astonishing as the overall diversity of plant life is the emergence of plants and seedlings in the 94 acres of constructed wetland, where approximately 450 species of plants have been observed in just four years. Although 36 species were transplanted in the constructed area as part of the state's landscaping effort, new vegetation that wasn't previously present has appeared.

"It's amazing," said Dr. Leck, a resident of Kendall Park, NJ. "When we first went out there in 1994 just after construction was completed, the top six feet of soil had been removed and used in the building of the adjacent highway. It was a barren landscape, almost like a moonscape. So to have all of this diversity there is really remarkable."

Of the emerging plant species in the wetland, Dr. Leck has identified eight endangered plant species and another 30 species that are on the state's list of sufficiently infrequent plants. She also noted that since 1994, more than 150 species of birds, including fairly rare types such as the American bittern, bald eagle, and osprey, have maintained Duck Island's reputation as one of the state's most popular birding places.

Dr. Leck's husband, Dr. Charles Leck, has contributed to the project by compiling lists of birds, butterflies, mammals, and reptiles and amphibians, completing a comprehensive reference of wetland habitat diversity in both the natural and constructed marshes.

This work has allowed Dr. Leck to serve as a valuable consultant for the Hamilton-Trenton Marsh management plan, part of the Delaware & Raritan Greenway's land conservancy endeavors. The complex management structure involves collaboration between three municipalities -- Hamilton Township, Bordentown, and Trenton -- the New Jersey Department of Transportation and Department of Environmental Protection, Mercer and Burlington Counties, and private ownership.

As an educator, Dr. Leck's obvious interest as part of the management team lies in exploiting the educational opportunities offered by the wetlands.

"The plan involves several issues, including proposals for how to preserve and protect the marsh over the long term and how stewardship should evolve," she said. "But we've also discussed what types of educational possibilities and recreation could be developed. The ultimate effort from my standpoint is to have a nature center and education programs that are focused on the marsh."

The proposed site for such a visitor center is on Lamberton Road, south of the new Route 29 extension.

The semester-long sabbatical also enabled Dr. Leck to enhance her research by touring Australia to study the contrasts between that continent's freshwater and saltwater marshes and those common to New Jersey. She worked with Dr. Margaret Brock, a wetland botanist at New England University in Armidale, New South Wales. The two will collaborate on a presentation titled "Aquatic Plant Seed Dormancy" for a symposium at the International Botanical Congress in St. Louis this August. The discussion will focus on their experience studying many types of wetland seed banks.

This diverse research background and considerable time working in the local wetlands have allowed Dr. Leck to form preliminary conclusions that lawmakers and environmentalists alike should find useful when dealing with future constructed wetland projects, especially in tidal freshwater marshes.

"The state spent quite a lot of money on landscaping at the constructed wetland," said Dr. Leck. "If they had waited a year or two, at least two-thirds of the 36 species they planted would've come in on their own. A few are new due to the planting, but the whole area certainly would've been vegetated without spending any money. Tidal fresh water marshes appear to be unique in their ability to be restored and vegetated naturally.

"There are regulations that if wetlands are destroyed, two times the original area must be replaced," she added. "There is concern about the functions of created wetlands. In this particular case, it appears that functions such as flood water control, species diversity, and habitat for wildlife have been restored. The type of vegetation that has developed in the constructed marsh so far is not exactly like what's in the natural marsh -- that may just be a matter of time or due to soil differences. But in four years, we have seen changes that indicate the constructed wetland vegetation is becoming more like that of the adjacent natural marsh."

Dr. Leck has been teaching in Rider's department of biology since 1970. She holds a B.S. in botany from the University of Massachusetts and a Ph.D. in botany from the University of Colorado. Her primary research, which was further enhanced by her sabbatical, involves seed germination ecophysiology and the relationship of seed banks to vegetation dynamics, primarily in tidal freshwater wetlands.