Bur, Appleman and I went to a seminar put on by UVM at their hort farm a couple years ago. They are studying several things, one being different ground maintenance. They have two blocks of apples, one organic and one IPM. In the organic block has wood chips, the IPM sprayed w/ gly and Simozene. As I remember, the big take home message was to, wrap bases w/ window screen, spray or use mulch but also keep the area nearby mowed. Areas in the orchard close by cover had more vole and rabbit use. If there isn't a lot of over head cover critters do not feel as safe and your trees will be better off. They really like mulch to ad nutrients to soil in the future. As far as protecting roots, they didn't mention that. I have a talk in Feb., I'll try to ask that question for you.
For deer managers, you may not want to keep it perfectly mowed all the time, but keeping it somewhat mowed, burn brush piles and keep bushes nearby to a minimum may be good techniques to keep the varmints away.
Several talks I have gone to they always recommend keeping bare ground under trees will help with warmth in fall and especially spring. The possible degree or two can be the difference between crop loss or not, and maybe some die back or not. They did not mention this helping with winter loss. One talk I went to last summer, they mentioned wild weather swings in late fall can play a role in winter loss, tip die back and bud formation, not just low temps. Trees not totally hardened off are subject to loss when temps rise and then drop precipitously. They mentioned being careful not to fertilize later than the beginning of June or so to keep them from hardening off to late in the fall.