The Lumberjack outfit requires 44 woodcutting to wear and you can get it as a drop in pieces from undead lumberjacks during the Temple Trekking and Burg de Rott Ramble minigame. Undead lumberjacks come out of the water during the bridge event where you must kill them to get planks to rebuild the bridge, sometimes they wont appear but only if theres trees nearby. You can only get 1 piece of the lumberjack outfit during the event. Wearing the full set gives 5% bonus xp to woodcutting (1.05 xp).
[1]Lumberjack hat = 0.8% [2]Lumberjack top = 1.6% [3]Lumberjack legs = 1.2% [4]Lumberjack boots = 0.4% Sub-total = 4.0% Set Bonus = 1.0% Total= 5.0%