Succession

Ecological Succession  Is studied by ecologist.  An ecologist is a scientist that studies the interactions among organisms and their environment.

Ecological Succession  Is a series of more or less predictable changes that occur in a community over time.  Occurs because every organism changes the environment it lives in.  There are two types –Primary –Secondary

Primary Succession  Begins in an area with no remnants of an older community.  Pioneer species change these barren areas. –An example is a lichen (a fungus and alga)

Primary Succession  A lichen converts atmospheric nitrogen into useful forms that other organisms can utilize to break down rock and dead organic material to from soil. Lichen

Primary Succession: Sand Dune to Forest Dune grassess  cottonwoods and shrubs  evergreens  oaks  beeches maples

Secondary Succession  Occurs after a disturbance (wildfire or hurricane) effects a community without destroying it completely.  Proceeds faster than primary succession because the soil survives a disturbance.

Secondary Succession In the image below, a former bog in Maine has almost completely filled

Secondary Succession  Soil already present.

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.

Climax Communities  Is the final stage of ecological succession in which a relatively constant environment and species composition is reached.  Can be seen as a community that has developed in response to the prevailing climatic conditions

Climax Communities  Are not always uniform and stable because they do not always follow the same path.  May be destabilized by human-caused disturbances.

Figure Spruce and hemlock forest