Activity 6: Inquiring Further
1. Primary succession
A rock can be broken by lichens and plants that produce acids. The acid dissolves the rock minerals. After the rock is transformed into soil by the pioneers or soil builders, the next groups of plants that are usually taller succeed. Several seral stages occur that are eventually followed by the climax community.
2. Hydrach succession
The pioneer community in hydrarch succession are submerged aquatic plants. Seral communities may consist of cattails and bulrushes, which take root in shallow water’s mud. Willow thickets found along the banks constitute another seral community. The climax community, eventually, is a mature forest that may be in the form of a conifer forest.
3. Succession and Mt. St. Helens
Two groups of scientists made predictions as to the recovery of Mount St. Helens. One group predicted that pioneer plants would start and that succession would end in a mature forest. The other group thought that succession would occur by chance where a seed borne by the wind would take root and influence the kinds
of plants that would grow next. This is in contrast to the earlier thought of an orderly process. Recovery is occurring as predicted by the two groups. A typical colonizer started as one of the first plants. When this colonizer died, its stalk and leaves collected particles of sand and dust. This allowed the perennials to grow resulting in an orderly succession. In the other barren areas, trees, which were usually alder, grew. Alders can survive even in poor soil that is deficient in nutrients because of its symbiotic relationship with nitrogen-fixing bacteria.
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