The bottom 3" of my 20 years old orange tree trunk has been striped of bark. And something, maybe a mole or gopher, has dug around the tree base right up against the trunk. The tree feels stable, not wobbly. How can I help the tree and replace the bark?
Another possibility for citrus bark damage is sunburn. But it is usually on the side of the tree trunk that is exposed to the afternoon sun, if the foliar crown has been pruned up to allow exposure. But it would not likely be all the way around.
In any case the first step would be to try and determine the cause and prevent further damage if possible.
You asked about helping the tree and replacing the bark. That depends on how deep the damage is. The area of the trunk with superficial bark damage may regenerate from the underlying growing layer. Helping the tree with good water and soil fertility management is about the only thing you can do.
If the wounding is deep, the bark cannot regenerate, but only close over with callus tissue from the undamaged edges. If there is deep wounding all the way around the circumference, then it is a dire sign and the tree may not survive.
In the case of deep wounding that "girdles" or "ring barks" the trunk, extraordinary measures to restore circulation and uptake of water and nutrients may include 'bridge grafting'. But that is a very specialized tree surgery technique and even an experienced professional may have a poor success rate.
The bark damage at the base of the orange tree may or may not be related to rodent damage. The soil disturbance may be coincidental, or could be related to the bark damage. There are other possibilities:
"Lawn mower blight" or string trimmer hitting the base of the tree is a very common problem.
There are fungal stem cankers that infect citrus tree trunks.
Crown rot (Phytophthora sp) is a common soil borne disease of the root collar at soil grade, due to over wet soil conditions, or sprinkler water hitting on the base of the tree.
Bark irregularities in the area of the graft can be related to an advanced incompatible graft condition.
Rodents, usually rats or squirrels can strip bark for food or nesting material. Do you have skunks or raccoons?
This is my first post on Gardening Know How, I'm not sure if there is a provision for attaching photos of your tree. If so, I may be able to give you a better guess.