Oak tree model
Exported to FBX and Obj with two materials(trunk and leaves).
Textures are 8192x8192 pixels.
Model has 493000 triangles count.
Trunk fully unwrapped, no overlaps
Leaves consist of two meshes with flipped normals places at the same position. One mesh for the outside leaves and another for the inside. You can delete inside part for reducing polycount twice. In this case material for the leaves must be doublesided for the saving density of the leaves.