Mark Clapp, 37, a National Park Service landscape architect who selected seasonal plantings for the popular Tulip Library near the Tidal Basin and helped shape Washington's parks and green spaces, died of cancer Nov. 23 at George Washington University Hospital. He lived in Arlington.

Mr. Clapp, a former landscape architect with the New York City parks department, joined the National Park Service in 1993 and worked in the National Capital Parks-Central division, which is in charge of the monuments, the Mall and smaller parks throughout the city.

Among his projects was the reworking of the design and construction of the Korean War Veterans Memorial, in which he laid out the plants used at the site, the lighting and walkways.

He also served on the planning and design team for the future World War II Memorial and contributed to the design and construction management of four visitor service retail and food kiosk facilities under construction on the Mall.

Part of his job involved collaboration with Washington neighborhood and civic groups to restore community parks and facilities, including the project to improve the East Potomac Golf Course.

The son of an military officer, he was born in Rantoul, Ill., and raised in and around military posts in Germany, Puerto Rico and the continental United States. He graduated from North Carolina State University with a degree in horticultural science in 1987 and a master's degree in landscape architecture in 1990.

He interned with the North Carolina Transportation Department and worked for the New York City parks department from 1990 to 1993.

He was a member of the American Society of Landscape Architects and chaired its national Tellers committee.

Survivors include his parents, retired Army Lt. Col. Max A. Clapp and Helen Clapp of Fayetteville, N.C.; two brothers, Max A. Clapp Jr. of Jacksonville, Fla., and Michael C. Clapp of Wake Forest, N.C.; and his maternal grandmother, Bonnie S. Polk of Jackson, Miss.