Glacier Bay is blanketed by a mosaic of plant life, from a few pioneer species in recently exposed areas to intricately balanced climax communities in coastal and alpine regions. Since virtually all the vegetation in the bay has returned to the land in the past 300 years following the retreat of the glaciers, this area is one of the premier sites on the planet to study plant recolonization.
In the classic story of plant succession, spores or seeds are blown into a new area by the wind or carried in by birds or other animals. Lichen spores that land on the appropriate rocky surface will anchor themselves to the rock using root-like structures called “rhizomes.” Unlike most plants, lichens absorb essential nutrients from the air and rain rather than through roots in soil. As they grow, lichens secret an acid that dissolves the rock around them, creating soil.
As soil develops, more seeds and spores arrive, such as those of mosses, avens (Dryas), horsetail and fireweed. In time, these pioneer communities can develop into dense thickets of nitrogen-fixing alder and cottonwood that enrich the soil and provide shelter for other colonizing species such as willow.
Farthest away from the glaciers in time and space, the lowlands near the mouth of Glacier Bay have become cloaked in a spruce/hemlock rainforest and lush, spongy tracts of muskeg. In the surrounding mountains, thick mats of flowers and heath carpet the alpine hills and meadows.
This story implies that plants succession is always a neat and orderly process where each plant species prepares the environment to be more favorable for plants that follow, which often comes at the expense of its own species's survival. It is not, however, always so tidy. Keep in mind that whatever seeds or spores arrive first will try to grow if conditions allow.
Did You Know?
Sitka Spruce is the third largest coniferous tree in the world. One tree even grew to 328 feet!