Your tree was girdled, most likely by a rabbit. Vascular plants like trees have tissues called xylem (the wood) and phloem (the inner layer of bark). Sugars produced in the leaves through photosynthesis are moved from the leaves to the roots via the phloem. This process supports the transport of water and nutrients from the roots through the xylem to the rest of the tree. Sometimes animals such as rabbits will “girdle” a tree by eating through the bark and removing the phloem tissues, interrupting the ability of the phloem to transport sugars. The xylem may continue short-term transporting water and nutrients; however tree health is compromised and will result in decline and ultimately death. If you decide to replace the tree place a plastic sleeve or chicken wire around the bottom 2-3 feet of the trunk to prevent damage from rabbits.