STOCKS MIGHT have fallen on Wall Street yesterday, but the stock for the city's public spaces and rec centers rallied big time at Mayor Nutter's announcement that Michael DiBerardinis will take over as the chief of the newly merged parks and recreation departments.

The choice of DiBerardinis is a best- case scenario for the city, its parklands and rec facilities. For the past six years, he served as secretary of the state Department of Conservation and Natural Resources, which maintains the commonwealth's 117 state parks and manages 2.1 million acres of forest land.

That clearly will be a handy background to bring to the city's 9,800 acres of open space, but his background as the city's recreation commissioner under Mayor Ed Rendell gives a better ground-level view of why he's right for the job: In order to expand hours at the city's skating rinks, he sold advertising to corporate sponsors and raised $25,000. Under his leadership, rec centers got much-needed improvements, and his work 10 years ago on the Handgun Reduction Task Force was credited with a decline in the murder rate.

He spent his early career as a community organizer in Kensington, where he still lives with his wife, Joan Reilly, a director of Philadelphia Green.

He's known for his ability to bring people together. This will be critical for the merger of the parks and recreation departments, which this page advocated as part of our "Acres of Neglect" series. The merger is a logical step, but that's not to say its execution was destined to be a slam-dunk. Widely divergent cultures, constituencies and political clout of the two departments would make it a challenge for anyone, but the choice of DiBerardinis gives us confidence that it will be done right. (We're also pleased that the mayor has given Di-Berardinis oversight of the libraries, too.)

The choice should also spur a fresh flood of applications for citizens to serve on the Parks and Recreation Commission, a newly formed body to take the place of the Fairmount Parks Commission. (Applications at www.fairmountpark.org; deadline is Monday.) Realigning the city's parkland and recreational resources has been a bumpy ride; it now looks like smooth sailing. *