The standing dead yellow cedars last a really really long time. I have watched this for at least 40 years, and noted the rust red foliage of  recently dead yellow cedars. The long dead spiketops that have been deceased so long that their branches have rotted and fallen far outnumber the recent dead. I think this would be a non issue if they rotted and fell in less than a decade like hemlocks instead of continuing to stand for a hundred years.