Good deal. Ive had double girdled beech take up to 3 years to totally die.
What is this technique all about?
Use a saw to cut a circle all the way around the tree, deep enough to cut through the xylem and phloem. Effectively cutting off water and food to the tree. Works better with some species than others. When the tree doesnt leaf out, sunlight will be able to hit the forest floor allowing food and cover to come in while the tree begins to slowly lose brances, eventually falling and decaying.