In this case, the tall perennial grasses (switch grass, Panicum virgatum) are themselves a very effective screen against salt and wind.
This fact was something of an accidental discovery made when shrubs and trees along highway shoulders started showing less damage wherever ornamental grasses became part of the scene between cars and the woody verge.
Road de-icing salt goes airborne from spinning car wheels -- it can spray 200 feet from 45mph tires. It's true it could coat, dehydrate and defoliate these spruces, but it won't because it is caught first in the blades of the switch grass. Cut that grass down in late winter, cart it away and with it goes the salt that would have damaged the plants and the soil, too.
Maybe the reason the bed is burlapped is because someone has blamed road salt for current problems there. If that's the case, we're pretty sure the diagnosis is wrong.
What we see behind the screen are salt-resistant junipers and blackeye Susan (Rudbeckia fulgida variety), the latter suffering from leaf spot (more about this in What's Coming Up 51, page 2; the inset image in the photo below, right is from that newsletter issue). As for the spruces, they are weak (we noted the scrawny top growth and dull bronze cast) and have dieback that's almost certainly the result of having been planted too deep.
It's hard to help you see details among dead twigs cluttering the view, but those defoliated branches go into the soil before they join the trunk. Given that angle, we figure the root ball is probably at least 4 inches too low.
Being buried in moist soil decayed the bark on those branches. Then, pathogens entered, killed the cambium and girdled those limbs. The same thing is happening to the trunk, so the remaining limbs have off-color, undernourished, thinning foliage.
Meanwhile, the roots are struggling because four inches of extra soil means more pressure and too little oxygen is available to them. Roots can't grow up to better conditions, only outward if conditions are good. Set too deep they deteriorate and die, starving foliage so it discolors and thins, and branches die. The tree hangs on, growing little if at all, until it has too little foliage left to sustain the woody parts. Then it dies.
For a look at how trees end up too deep and a real life example of correcting this problem, see Growing Concerns 488.
If the spruces were salt-burned there would be more damage on the top and side facing the road. The Rudbeckia would emerge weakly and die, not grow, develop spots and turn black in summer.