1. Heat 2 tablespoons butter in a large saucepan over medium heat; swirl to coat. Add leek, thyme, and 1/2 teaspoon salt; sauté 8 minutes, stirring occasionally. Add 3 cups water, chicken broth, and wild rice; cover. Increase heat to high; bring to a boil. Reduce heat, and simmer 30 minutes. Stir in brown rice; cover and simmer 30 minutes. Remove from heat.
2. Preheat oven to 400°.
3. Heat remaining 2 tablespoons butter over high heat in a large skillet; swirl to coat. Add turnip, celery, carrot, and remaining 1/2 teaspoon salt; saute 1 minute. Reduce heat to medium; cook 4 minutes, stirring occasionally. Remove from heat.
4. Combine rice mixture, turnip mixture, pecans, cherries, and onions in a large bowl. Spoon stuffing into a 13 x 9-inch glass or ceramic baking dish. Cover with foil; bake at 400° for 20 minutes or until liquid is absorbed. Let stand 5 minutes before serving.