Transcript Secondary succession

Lecture #2
Ecological Succession
Unit 7: Ecology
Ecological successionthe regular progression
of species replacement
over time in a new or
disturbed community.
Succession shows some general trends that
include:
1) Biomass increases
over time.
2) An increase in the
number & proportion
of longer-lived
species.
3) Increased
species diversity.
Succession on Mt. St. Helens
There are two types of terrestrial
succession
1) Primary Succession
2) Secondary Succession
Primary succession: The establishment
and development of an ecosystem in an
area that was previously uninhabited
This colonization of new sites by
communities of organisms takes place on
bare rock
New bare rock comes from 2 sources
1. A volcanic lava flow cools
and forms rock
– This is how the Galapagos
islands and the Hawaiian
islands formed!
New bare rock comes from 2 sources
2. Glaciers retreat and expose
rock
How does the process
begin?
Pioneer organisms- the first
organisms
to colonize a new site
– Ex: lichens are the first to
colonize lava rocks
These guys are
TOUGH! They
thrive where no
other species
can.
What do they do and what
happens next ?
– As lichens add organic matter and form soil,
mosses and other plants can colonize and
grow.
– As organic matter continues to
accumulate, other species move in and
change the environment further. First fast
growing plants, then slower growing
plants.
– Over time, more and more species can
find suitable niches and survive.
Primary succession-
Is there an ‘end’ to succession?
Climax Community - a stable, mature
community that undergoes little or no
succession.
** This is not necessarily a ‘permanent’
community however. What would cause
it to change?
Answer: A changing environment!
Secondary successionDefinition: Sequence of community
changes that takes place when a
community is disrupted by natural
disaster or human actions
• This type of succession occurs in
areas where there HAD been
previous growth. Because of this,
the process is much faster than
primary succession.
What can cause
secondary succession to
occur?
1) Forest fire
• The regrowth
that happens
after a fire
levels a
portion of a
forest.
What can cause
secondary succession to
2. Abandonedoccur?
Agricultural
Field
• Native plant life from
the areas
surrounding the
agricultural field
reinvade the area.
Secondary succession-
Case StudyYellowstone
National
Park
1988 – Park map
showing areas
(1.6 million acres)
burned by the
series of fires.
Yellowstone National Park
1988 fires – The immediate aftermath.
Photo: National Parks Service
Yellowstone
National Park
• One year after the
fires
• Note the appearance
of fireweed
Photo: National Parks Service
Yellowstone National Park
• Ten years after the fires (1998)
Photo: National Parks Service
Yellowstone National Park
• Twenty years after the fires (2008)
Is the Yellowstone Case study an example
of primary or secondary succession?
Case Study - Chernobyl
• In April, 1986, a
nuclear power plant in
the former USSR
experienced a core
meltdown and a
catastrophic release
of radioactivity into
the environment.
Chernobyl
• Surrounding
towns and
villages had to
be immediately,
permanently
abandoned.
Chernobyl – Twenty Years Later
Chernobyl – Twenty Years Later
Pripyat town square.
Chernobyl – Twenty Years Later
Chernobyl – Twenty Years Later
A local highway.
Is the Chernobyl Case Study an example of
Primary or Secondary Succession?
Take 2 minutes to describe what succession is,
and to identify the similarities and
differences that exist between primary and
secondary succession.