Transcript Ecological Succession - NserekoEnvironmentalScience

Ecological Succession
• A gradual process of
change and
replacement of some
or all of the species in
a community.
• Succession may take
100’s to 1000’s of
years
Primary Succession
• Occurs on a surface where no ecosystem
existed before. Ex. On a rock, sand dune,
retreating glacier, newly formed island,
sidewalk cracks
• It can take 1000’s of years for fertile soil to
form
• Pioneer species such as bacteria and
lichens colonize rock surfaces
What is a lichen?
• A lichen is an important pioneer
in primary succession
• It is composed of a fungi and
algae working together
• Algae photosynthesizes, fungi
absorb nutrients from rock and
holds water.
• Together they break down rock
• Soil accumulates as dust
particles trapped in cracks in
rock
• Lichens decompose providing
food for mosses
Examples of Primary Succession
Plants colonize cracks
in the sidewalk
Primary succession – plants take
over an abandoned home
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Secondary Succession
• Occurs on a surface where an ecosystem had
previously existed
• Faster than primary succession
• Occurs in ecosystems that have been disturbed
or disrupted by humans, animals or natural
processes ex. Floods, earthquakes etc.
• Pioneer species are the first to colonize the land
• Pioneers make the ground suitable for other
species
• Eventually a final and stable climax community
appears.
The Role of Fire in secondary
succession
• Fires caused by lightening and man maintain
communities in chaparral, temperate forest and
southern and western pine forests.
• Plants in these communities have adapted to fire
• Seeds of some species will not germinate till
after fire
• Minor fires help reduce dead wood that may
lead to larger fires
• Some animal species depend on fire, they feed
on new shoots after the fire
Fire on the prairie
• Prairies produce large
amounts of plant material
• Dead plants do not
decompose quickly and
form dense mats on the
ground
• This makes it hard for
new shoots to grow and
grazers to graze
• Fire releases nutrients
and lets new shoots
access sunlight
Is this an example of primary or
secondary succession?
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• http://www.history.com/content/life_after_p
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