SUCCESSION

Communities change through long periods of time

Traditional Succession

• Lichens grow first (called pioneer species) and break-down rock into soil

• Then mosses, followed by ferns and flowering plants

• The rock is completely broken down over thousands of years and what results is the CLIMAX COMMUNITY

• The climax community is NOT replaced by any other community unless a disturbance or change in the climate occurs.

• The type of climax community (grassland, forest, etc.) is determined by the climate of the area

• We will look at 2 forms of succession. The first will be an orderly succession of a forest and the other will be the not so orderly succession following the eruption of Mount St. Helens.

1st year field• A field dominated by

summer and winter annuals, such as species of mustard and foxtail grass (Setaria faberii). Note the large amount of open soil and the irregular plant canopy. In the near background are approximately 20 year old fields and rising behind those is the old growth Hutcheson Memorial Forest.

5 year-old field

• A field of approximately five years old. The closed canopy is dominated by goldenrod (Solidago) species.

10 year-old field

• A field dominated by an irregular canopy of goldenrods, daisies (Chrysanthemum leucanthemum), yarrow (Achillea millefolium), asters and goldenrods. Woody invaders include eastern red cedar (Juniperus virginiana) trees. The dark green in the background is in older fields and the old growth forest.

20 year-old field

• A with additional invasion of woody species including shrubs such as multiflora rose and gray dogwood (Cornus racemosa). Trees invaders include flowering dogwood (Cornus florida) and the evergreen eastern red cedar. Red maple (Acer rubrum) and oaks (Quercus spp) are in the background. This field is slightly drier than the others pictured in this series and so supports some little bluestem (Schizachyrium scoparium).

30 year-old field

• A field dominated by a canopy of red maple near the adjacent old growth forest (behind the photographer) grading into a section of the field still dominated by shrubs and perennial field herbs.

Biologic History of Mount St. Helens

• The eruption of Mount St. Helens in 1980 changed the face of the land. Before the eruption, the area around the mountain was renowned for its pristine natural beauty.

The Eruption

• During the May 18, 1980 eruption, many events occurred that changed the landscape in various ways.

After Eruption

• Large mammals did not survive the extreme heat of the blast.

Where snow cover offered protection, patches of conifer saplings, shrubs and leafy plants survived in the scorched forest.

Forests without snow cover had few survivors

Animal Colonizers

The many dead trees provide a variety of places for insects to live.

Animal Colonist

• Frogs, toads, and salamanders which survived the hot gasses of the blast. Because there were many survivors, and the unaffected green forest is so close, it is difficult to tell the difference between the colonizers and survivors.

Other Animal Colonists

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Primary Succession Plants

Secondary Succession Plants

Un-orderly Succession

• Some scientist believed that succession in this area would be orderly while others believed it would happen by chance.

• The outcome was a combination of both: some pioneer plants did colonize and make it suitable for new species to come in; also, alter trees have become established in the middle of very desolate areas without the help of pioneer plants