Evergreen Trees and the problem of Winterburn
Trees growing without human interference tend to drop their seed not too far from the parent tree. These seeds, if they germinate, generally grow in the shade [or at least partial shade] of taller, more mature trees, or in areas where grasses and weeds are tall enough to provide adequate protection. This isolates the seedling from both excessive wind and a double-dose of harsh winter sunshine.
We humans tend to plant trees to fill in the wide open spaces which we ourselves created in the first place. In the Spring, Summer and Fall this human environment is often just fine for young trees. But when Winter comes, the only shelter the little trees will get is from complete snowcover. If there is no snow or a young tree is poking out above the snow in an open area, it will get hit by a double-dose of sunshine: both direct sunlight from above and sunlight reflected upwards from the white snow below, adding up to literally a bad sunburn and desiccation [freeze drying] of the needles. The double-dose of sunlight bakes the moisture out of the needles, but since the ground is frozen the tree cannot replenish that lost moisture. This results in needle death, which may not become noticeable until early Spring.
Winterburn is generally not enough to kill a young tree, since the small tree will replace those lost needles with new Spring growth. An easy way to determine if a young tree is not dead but rather suffering from winterburn is to inspect the buds in the Spring. Break open one of the buds at a low point on the tree. If the bud is moist and green inside and/or seem to be swelling with warmer Spring temperatures [or especially if they break open!], the tree is alive and well...it'll just look rather ugly for a year or two until new growth hides the old bare branches and trunk.
If your trees were planted in the Spring and had good growth all summer and then suffered that first winter, they'll probably be OK...they just need time. If your trees were planted in the Fall, the possibility of death is higher because their root systems had far less time to get established in the new soil before the stresses of winter hit. The best thing to do is wait until Spring to see if the buds start swelling and/or breaking open. The best solution for Fall planting is to do so at the earliest possible time to allow for as much root development and establishment as possible.
Commercial growers install shade netting or even move entire crops of young trees into full shade to prevent winterburn. You can use any method to block sunlight, as long as your method does not completely seal off the tree from it's environment. White foam rose bush covers found at garden centers and big box stores are a good solution, as are upside down 5 gallon buckets with a brick on top and a few air holes, or large diameter white PVC pipe held down with stakes and lines. Whatever you do, make sure your shade solution is secure...Old Man Winter laughs at poorly engineered solutions. His laughter still echoes through our building.
You can also just sit back and hope for a couple of feet of snow, or just let the trees take their lumps...both of which require no work at all :)
Once the trees have reached several feet high, they are far enough away from the snow that winterburn is no longer a significant issue.