I've tracked down three threads for this puzzle on AB - one of them is very detailed/generous and will spoil things if you're trying to solve it for real.
However, there was a preamble attached to the original puzzle, so it is only fair that you have a rough translation of that -
Solve the clues normally, look for a set of consecutive letters for a tree. There are 25 theme words, 3 are used twice.
The puzzle's title was REAFFORESTATION, I believe.