After losing ground for years, environmentalists in the District have made major gains in 1990 toward protecting trees in older neighborhoods and getting commitments for plantings along some of the city's more barren streets.

The push has come largely from residents concerned by the deterioration of streetscapes and the loss of shade trees to development in the more wooded sections of town.

An appeal from citizens in Massachusetts Avenue Heights, for example, has spurred the city to consider new regulations to severely limit the number and size of trees developers can cut without special permission from the zoning commission.

Earlier this month, the proposed regulations were presented at a public hearing, and about 30 residents from at least five neighborhoods were there to testify in favor of what would be some of the toughest city tree restrictions in the nation.

Weeks before, a group of 20 nonprofit environmental groups formed the Urban Forest Council of Washington, D.C., to coordinate tree planting projects citywide and provide a conduit for federal money from President Bush's "Plant a Billion Trees" program.

Experts say street trees in urban areas live an average of only seven years because they usually require special care to reach maturity.

An official city plan designed years ago calls for 110,000 sites for trees along District streets. But the city loses more than 1,000 each year, and two die for every one that is planted, according to city tree experts. That has left at least 10,000 sites without trees, and city officials say they can't keep up with the cost of replanting.

Help has surfaced.

Recently, Trees for the City, an affiliate of L'Enfant Trust, a private preservation group, stepped forward with a promise to help raise money to plant trees in empty sites and train neighbors to care for new trees.

"The city has a proud tradition for urban trees," said Urban Forest Council Chairman John Nelson. "It has to be maintained or it will die."

Concern about the city's urban forest is nothing new. Thomas Jefferson worried about it two centuries ago as he watched property owners clear spans of native timber from their lots for firewood, according to local historians.

Pierre L'Enfant, the city's first designer, incorporated vast numbers of trees in his unfinished plans.

A century later, Alexander "Boss" Shepherd, the last governor of the District, led an extensive urban improvement plan that called for 60,00 new street trees.

The high price on the improvements cost Shepherd his job, but the thousands of maples, poplars, lindens, sycamores, elms and ashes he planted earned Washington the name "City of Trees."

Today, many of the trees Shepherd planted a century ago have died, leaving some streets without a canopy of foliage.

"You take trees for granted until they're not there," said Laurence J. Aurbach, director of a Trees for the City project to improve Judiciary Square. The project planted seven new trees in the downtown courthouse area last month and plans to put in at least 60 more.

The tree efforts reflect a nationwide priority growing out of concerns about the global environment.

But tree plantings also have taken on a dimension of social outreach. In Georgetown, a group of citizens this year raised $20,000 to fill 90 empty tree spaces.

School groups have become involved as well. Last spring, students at Benjamin Orr Elementary planted trees in a park across from the school in Southeast.

"It fits right into the school's philosophy," said Principal Lawrence E. Boone. "To de-emphasize the material, serve the community, preserve our environment and conserve energy."