Forest Succession

Two types of changes occur in the forest, seasonal changes and succession.

Seasonal changes are the short-term changes that occur over a 12-month cycle. These changes include loss of leaves in the fall, accumulation of snow and ice on the forest floor in the winter, internal and external changes in plants and animals, varying temperatures, and changes in the length of day light.

Succession occurs over a long time two types, primary and secondary.

Primary Succession

Primary Succession begins with a barren area that does not support vegetation like sand or rock.

Primary Succession On rock, succession begins when soil-building organisms such as lichen break down the rock to build pockets of soil that will support larger vegetation.

Primary Succession As soil accumulates, new plants germinate, grow and reproduce, and begin a new stage of succession

Secondary Succession occurs when vegetation is destroyed or removed by a disturbance

Vast areas of lodgepole pine and other forest types were killed.

Similar area, two years following harvest, showing that grass has covered the site.

Pioneer Species: Used to describe species that are intolerant to very intolerant to shade. The first tree species to inhabit a site after a stand-replacing event. They are typically fast-growing, are characterized by open or low density crowns, and have a relatively short life span.

Climax Species: Used to describe the most shade tolerant tree species that are native to a particular region.

Microclimates Succession is also responsible for changes in the abiotic features of the forest such as microclimate, soil characteristics and water table.

Canopy Openings Older trees in the forest are always dying and new ones are ready to take advantage of canopy openings and replace the dead trees

It may take 70 years for a forest to recover after a fire or 300 years for a rocky hill top to become a forest.

Forest Fires - POSITIVE EFFECTS a natural event for the boreal forest

Forest Fires - POSITIVE EFFECTS creates the conditions for regenerating the forest (e.g. creates large openings, destroys stands of old/unhealthy trees, prepares soils)

Forest Fires - POSITIVE EFFECTS the regeneration of black spruce is enhanced by fire

Forest Fires - Negative consumes twice as much forest as is harvested each year.

Forest Fires - Negative may eliminate a preferred species for harvesting or may change the age and species mix of a forest

Forest Fires - Negative poses a threat to human communities

Forest Fires - Negative may have negative affects on fish and wildlife

Disturbance

Forbes/Shrub Stage

Mature Forest

Climax Forest

The End