That’s no problem to deal with it for either species.
If temps STAY at -10C for days, then you need a cold frame or some protection, particularly if it’s also sunny and windy at the same time: frozen soil means they can’t intake water, while wind and sun are causing transpiration, resulting in dehydration for the trees.
If what you have is “some days with night lows around -10C”, while during the day temps go close (or above) freezing point, those trees are more or less in their natural habitat and there’s nothing to worry about. Just in case try to place them in a spot where they can get light but not too much wind, if you can, but that’s about it...