Diane,
Second growth redwoods often grow in very tight groups around the old growth stumps.
In select cut logging practices in the second growth stands the forester marks the trees to thin the stand for uniformity. So the remaining trees have close, or equal, to the same amount of room to grow. It sounds good in theory alright, but thinning the clumps by ripping the co dominate trees apart can present many problems. Way more problems than there is room here to be specific on. In minor degrees often not, but with major rips certainly so.
It's only my opinion that the thinning of redwood sucker clumps not be practiced through ripping the co dominant trees in the group. From my experience it's not good for the leave trees.