This could be a water stress problem, either not enough or poor drainage. Or there is a wire or rope left around the tree and as the tree grew the wire girdled the tree, cut off the water flowing up the tree right under the bark. Check for a wire or rope at the point where the tree is alive and dead. Newly planted trees need individual watering because the potting material around the roots drys out at a different rate than the surrounding soil. A thick mulch layer also helps. Use a long screw driver to stick into the soil root ball. It is like sticking a toothpick in a cake. The screw driver will show moisture if the soil is wet and come out dry if the soil is dry. If drainage is poor and water sits in the hole, roots start rotting. But I think the whole plant would be showing damage if this were the situation. Your choice is to replace the plant or cut off the top. Cut into live green wood. As the new growth start this spring, use a long stake and tie the stalk against the trunk and tie the new growth to the stalk to help straighten the growth. If you have other question email me or call the Tarrant County Extension office Master Gardener Help Desk,<personal data hidden>