ECOLOGICAL SUCCESSION

Ecological Succession Change of environment involving a series of species replacements in a community. Two types: Primary Secondary

Primary succession — occurs where there is no soil, e. g Primary succession — occurs where there is no soil, e.g. after a volcanic eruption or a glacial retreat “pioneer organisms” Simple plants first – no or shallow roots. Gradual influx of more complicated and larger plants as the habitat changes. Ends with a “climax community” – ecosystem stays constant, provided there are no changes in abiotic influences.

Primary Succession: Sand Dune to Forest Dune grassescottonwoods+shrubsevergreensoaksbeeches maples

Bare rock bare rock→lichens→mosses→grasses→shrubs→trees

Glacial retreat

Man-made structures

Secondary succession — begins in an area where soil is already present, (e.g. a once cultivated field or after a forest fire.) Old field succession: grasses + weeds taller grasses + golden rod small trees (cherries, dogwood, sumac)  mature climax forest (oak, beech-maple, hickory)

Secondary Succession Soil already present.

Pond Succession Abandoned field succession

Pond→marsh→dry land/grasses →shrubs→forest

Pioneer species—first species to begin a succession. Climax community—the final stage in a succession.

Primary vs. Secondary No soil Pioneer species Weathering & decomposition Humus and sand increase over time End = climax community Soil already exists Seeds have suitable soil conditions. Occurs much faster Climax community.

Secondary Succession After a forest fire

Hurricane

Table 53.2 The Pattern of Succession on Moraines in Glacier Bay

Figure 53.20 Alders and cottonwoods covering the hillsides

Figure 53.20 Spruce coming into the alder and cottonwood forest

Figure 53.20 Spruce and hemlock forest

Figure 53.18x1 Large-scale disturbance: Mount St. Helens

Figure 53.18x2 Forest fire

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