Remove any large rocks from the area to be cleared for easier use of the dozer. You can, of course, use the dozer to help push the rocks out of the way. Doing so helps the dozer drive on a straighter path without interruption.
Make a cut into the tree's trunk with the chainsaw that is equal to roughly half the height of the dozer's blade; this provides enough of a "target" for the dozer to push against. Make the cut on the side of the trunk opposite to the path of the dozer.
Evacuate the area of any bystanders. Cut into the tree at an upward angle. Stand to the side of the tree once you're about three-quarters of the way through the trunk and finish the cut. The angled cut should allow the tree to fall safely away from the dozer.
Cut the fallen tree into smaller, more manageable sections for removal. You can cut the trunk into even smaller pieces to used or sold as firewood if desired. Start the dozer's ignition and lower the blade until there's about one foot of clearance from the ground.
Drive the dozer forward until the blade makes contact with the trunk. Slowly release the brake to allow the dozer to inch forward and begin pushing the trunk and root system from the ground. You may have to back up and adjust the blade if necessary to get a better angle on the trunk. Cut and remove the root system once it's free from the ground.