protecting trees from mice and such

ok I have little cherry and plum and hazelnuts  starting out and all of them are at the edge of their zones here.  I would love to mulch them but I am afraid that if I pile straw around them then the mice will figure that they have found nirvana. I don't have any access to any rocks.

I'm looking for maybe used bricks to make up some sort of heat sink but this is uncertain at best.  Any way to protect these infants for the 7 months of frigid weather here aside from prayer?

And..while I'm here..what on earth does having mole hills mean?  I am next to a garden which is rototilled  regularly, and my yard is partly trees and shrubs ( a few) part raised beds part lawnish and part driveway, and the moles have suddenly started to dig holes all over the lawnish area. I thought they showed up when land was compacted but clearly not so, they aren't in those areas at all.  Will they take out young trees if they have access to them as well? All the wildlife in the village seems to land in my small patch and most of the time that's fine but....big mounds of dirt all over the yard isn't what I was hoping for. How do I get rid of them?

What I found very effective (but not extremely beautiful) is to put plastic or metal stakes around the area to be protected and on top of those empty plastic bottles (flat bottomed ones so they turn freely). The echoes this makes underground as the bottles turn in the wind makes any underground mammal with sensitive hearing go bananas and they very quickly flee the area. For us the noise is almost imperceptible. It certainly works for keeping areas mole free (a stake + bottle every 3-4 meters or so) and probably most kinds of mice also...

neat idea!    I will try that . we get lots of wind here so hopefully it will chase them all away .  Thanks!