Answer: In a quick search I learned that Prunus africanus is a hardwood tree native to cool moist highlands in several parts of Africa eg Kenya and Cameroun. These highlands are somewhat like a rainforest environment in that they do not experience cold winter weather. Unfortunately, I have not found a minimum temperature tolerance listed for this tree, but I strongly suspect it will not survive frosts or freezing weather due to its provenance. For this reason I am not sure you will be able to keep the trees growing outdoors -- unless you build a greenhouse around them.
The bark of this tree is sometimes harvested for medicinal use, and in fact overharvesting has contributed in part to the decline of this species in its native habitat. However, a single vertical strip an inch wide would probably not kill the tree. If the strips go all the way around the trunk and have girdled the tree, then it may die. So protecting it from deer and rodents would be a good idea. The only way to help it heal is to keep the tree healthy and growing vigorously. (Wound paint and other topical products are not helpful.)
The deer can be deterred by encircling the trunk with a cylinder of wire mesh fencing up as high as they can reach. The rodents can be deterred by using a smaller mesh such as hardware cloth to enclose the lower part of the trunk. It should extend least 18 ninches higher than your anticipated deepest snow. It should also extend outward from the tree along the ground to deter digging in under it. Cover the bottom portion of wire with gravel, again to deter digging, especially by voles. You could also use the commercially formulated repellent sprays sold at garden centers, apply and reapply per the label directions, but in my experience the fencing is the most reliable long term measure.
I am sorry I can't find more specific information for you ina quick search. Perhaps if you contact the horticulture department at your closest botanical garden, or a botany department at a nearby university, they would have more extensive resources to check on tropical and semitropical plants and could give you a more specific temperature expectation as far as cold tolerance. Best of luck with your trees!
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