I planted a spruce tree three years...

Winter drying, winter burn, salt damage, and extreme cold can cause loss of needles. Winter drying occurs when the needles lose moisture and cannot replace it because the soil around the roots is frozen. Warm winds also dry out the buds and needles that extend above the snow cover. Winter burn occurs when the temperature changes suddenly. This is common on the south sides of trees, where exposure to the sun is greatest. Winter drying and winter burn often occur together. Salt damage occurs when road salt splashes up on the foliage or when the roots absorb salt in the soil. The damage is usually greatest on the side facing a roadway. In any of these cases, don’t be too quick to cut out the brown foliage. Wait several weeks to see which shoots green up and bud out, then prune the dead portions.