Can I correct girdled roots myself?
Girdling of the roots of a tree comes from planting the tree too deep. The roots will not spread out in search of nutrients, but will cicle around the trunk. As the tree grows, the roots get bigger and cut off circulation and cause the eventual death of the tree. You can tell girdling by following the roots from the trunk. You may need to hose off the soil with some pressure, but the tree is already dead. There are exprensive techniques that can correct the problem if caught early.
At this time of the year it is not unusual for a tree to drop leaves in late summer. Scratch the bark to see if there are signs of life, like a green color below the bark. If so, wait until next year as it may leaf out normally. However, if branchs start falling off, it is propbably dead and should be removed.