The massive Fresh Kills landfill, where New York City has dumped its garbage for 60 years, will be shut down two years from now, and city officials are already daydreaming about making the land into a large city park. The city’s sanitation department has hired Steven Handel, a plant ecologist at Rutgers University, to study the possibilities for restoring the 3,000 acres into coastal plain woodlands and grasslands. Handel and his students are concentrating on finding out what native plants can thrive on the mounds of trash. With 6,000 landfills across the country all eventually faced with the problem of what to do after closing, Handel is in the forefront of a growing field in ecology.