Trees of hardwood varieties often do this on their own. Usually if the roots of a hardwood are still alive the tree will put up new shoots which would in decades grow back into a sizeable tree. If the roots are dead the tree will not come back. A good thing to do is to select the healthiest looking Shoot(s) and cut all the others. The tree will send up many shoots but the healthy one(s) you selected should be the only ones left uncut. This will help the tree to 're establish itself faster and grow without competition from the other shoots.
It would also help to bring the tree some water when it has been dry but don't give it too much or it could cause unwanted and potentially damaging fungal infections. Energy work and or spells could be used to help the process along. Best of luck.
This time of the year is quite promising for reviving things that may appear dead. If it is a deciduous tree, wake it by pruning back its large branches until you see green or soft white material between the bark and the core wood. Then douse the root area with a mixture of vitamin B1 root stimulator and water. The dormant buds will sprout from the bark and perhaps the tree may regrow. When you have finished, leave a small offering to Thor and the land wights. Donars Oak may have succumbed to vicious vandalism but its roots live forever.
Perhaps you could dedicate a sacrifice to the dryads(tree spirits) and ask their assistance in healing the tree. Because it is the Mycelium which connects the plants in a Forrest I would recommend plunging your fingers into the soil and meditating on your intent after making your sacrifice. The mycelium is a white layer beneath the fallen debris.
I hate to see a tree die but sometimes it is not preventable. If it is already truly dead then there's nothing to be done as one cannot revive the dead be they plant or animal. I would look as suggested into mundane ways to save the tree if it still alive, but it couldn't hurt to try to send positive energy towards the tree if it is still living as well.
In the past a similar event occurred where to make a long story short many believed a tree would die except I coudln't accept it. I recall directing energy towards the tree, trying a spell to help it gain back its lost vitality, and simply releasing my wish into the universe for it to live. Honestly, nature is very resilent so I sincerely doubt I had any effect yet thankfully the tree did pull through surviving for the past few years, though admittedly every winter I worry the leaves might not return :). All you can truly do is let nature run its course and see what is meant to be.
Thank you everybody for you're wise words of wisdom, and maybe with you're suggestions I can save this tree. If I manage to save it I'll let you know, but if I can't well you probably won't here anything.