In a large bowl, gently toss the turkey, celery, celery leaves, apple, grapes, and pecans until combined. In a small bowl, whisk together the yogurt, mayonnaise, honey, and 1/4 teaspoon salt until well combined. Put the celery root in a small bowl, add 2 tablespoons of the dressing, and toss to coat completely. Add the remaining dressing to the turkey mixture, season with salt and pepper, and toss gently to evenly dress the salad.
To serve, spread the celery root evenly onto a serving platter, top with the dressed salad, garnish with celery leaves and serve immediately.