As the last major glaciers retreated, lodgepole pines, spruce, alder, willow, and other trees, shrubs, and herbs revegetated the areas that had been scraped bare by ice.
(the last major glaciers; retreated; ) (lodgepole pines, spruce, alder, willow, and other trees, shrubs, and herbs; revegetated; the areas that had been scraped bare by ice; T:As the last major glaciers retreated) (the areas; had been scraped; bare; by ice)
the last major glaciers lodgepole pines, spruce, alder, willow, and other trees, shrubs, and herbs the areas
retreated revegetated had been scraped
the areas that had been scraped bare by ice T:As the last major glaciers retreated
bare by ice