Transcript Forest Succession - CHS Science Department: Jay Mull

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
The End