What's up with Elm Street Park

I went by Elm Street Park in Bethesda, MD (on the border of Chevy Chase, MD). And what to my wondering eyes should appear, but loads of fences criss-crossing the park. According to the sign, it is a "Tree Protection Area", but most of the grassy/tree area is still accessible, just not from all directions. You can see one of the fences in the picture and from the side I was on you could walk right up to it, you could also walk up to the other side if you went along the path. The park's signs were down too. Odd. The playground area was unaffected.

[where: 4600 Elm St, Bethesda, MD]