Download deflected succession

• Ecological Niche
– Role a species plays in a biological community
– Total set of environmental factors that determines a
species’ distribution.
– Generalists - Broad niche
– Specialists - Narrow niche
• When generalists and specialists collide, generalists
usually win.
• No two species will occupy the same niche and
compete for exactly the same resources for an
extended period of time. (G.F. Gause)
• One will either migrate, become extinct, or
partition the resource and utilize a sub-set of the
same resource.
• Given resource can only be partitioned a finite
number of times.
Gause’s Study
These two species have the same niche. In competition, one
will win out (exclude) the other.
Resource Partitioning
Placing another closely related species in with the previous “winner”
gives a different result – both species persist.
Why?
Each species occupies a different part of the environment (i.e. they
have different niches) – there’s been a partitioning of resources.
Competition
Resource Partitioning
How is Energy Moved and Utilized in Ecosystems?
Trophic levels are the “steps” in a food chain moving
from producers to different levels of consumers.
The efficiency of energy transfer between different levels
puts a limit on the number of trophic levels.
A Food Web Describes the Way Energy is Transferred Within an
Ecosystem
Celebrating Rot and Decay - Detritivores
Energy isn’t transferred only upwards between trophic levels.
Detritovores use the energy available in dead organisms and allow recycling
of essential nutrients in ecosystems.
Only a Fraction of the Energy Present in Organisms of One Trophic
Level Is Captured by Organisms of the the Next
This limits the number of trophic levels.
Ecological Succession
Ecological succession is the set of
changes in community composition that
occur over time in a new or disturbed
community.
Succession after
the Yellowstone
fires.
Succession at Mt. St.
Helens.
Terrestrial Primary Succession
Primary Succession
Primary succession involves the changes
from pioneer species which colonise an
environment through the seral stages to
the climax community.
Changes in abiotic factors lead to more
favourable conditions and increasing
species diversity
Primary Succession
Begins in a place without any soil
Sides of volcanoes
Landslides
Flooding
Starts with the arrival of living things such
as lichens that do not need soil to survive
Called PIONEER SPECIES
http://botit.botany.wisc.edu
http://www.saguaro-juniper.com/
Primary Succession
• Soil starts to form as lichens and the
forces of weather and erosion help break
down rocks into smaller pieces
• When lichens die, they decompose,
adding small amounts of organic matter
to the rock to make soil
http://www.life.uiuc.edu
Primary Succession
• Simple plants like mosses and ferns can grow
in the new soil
http://www.uncw.edu
http://uisstc.georgetown.e
du
Primary Succession
• The simple plants die, adding more organic
material
• The soil layer thickens, and grasses,
wildflowers, and other plants begin to take
over
http://www.cwrl.utexas.edu
Primary Succession
• These plants die, and they add more nutrients
to the soil
• Shrubs and tress can survive now
http://www.rowan.edu
Primary Succession
• Insects, small birds, and mammals have begun
to move in
• What was once bare rock now supports a
variety of life
http://p2-raw.greenpeace.org
Primary Succession at Glacier Bay, Alaska
A Lithosere
A Hydrosere
Other types of sere
• Xerosere – Succession in a region with lmted
water availability e.g. deserts
• Psammosere - Succession that began with
exposed sand e.g. sand dunes, beach
• Halosere – Succession which began in a
saltwater environment e.g. a saltmarsh
Secondary Succession
• Begins in a place that already has soil and was
once the home of living organisms
• Occurs faster and has different pioneer
species than primary succession
• Example: After forest fires, human activity
http://www.scienceclarified.com/images/uesc_10_img0552.jpg
http://www.ccs.k12.in.us/chsteachers/BYost/Biology%20Notes/secondarysuccession.jpg
http://www.ux1.eiu.edu
Climax Community
• A stable group of plants and animals that is the end
result of the succession process
• The climax community produced is controlled by the
climate.
• eg water present all year – generally woodland
• distinct wet and dry seasons – grassland
• wet and acidic – blanket bog
• Does not always mean big trees
– Grasses in prairies
– Cacti in deserts
– Reeds and grasses in saltmarshes
Influencing Factors
• Various factors will influence the rate and
direction of change.
These include:
• Edaphic conditions (type of soil)
• Climatic conditions
• Biotic factors (including anthropogenic)
Speed of Succession
• Changes are slower if the abiotic conditions
are less suitable for life – too hot/cold, too dry
or if the availability of plant nutrients is a
limiting factor.
• Changes are usually slower during the early
stages of succession.
• Secondary succession is usually a faster
process than primary succession, in the same
environment
General Trends in Succession
• Biomass increase over time.
• An increase in the
number and proportion
of longer-lived species.
• Increased species
diversity over time.
Succession on Mt. St.Helens
– another site of intense study.
When human activity interferes
• What happens when human activities interfere
with the natural process of succession?
• The succession process is altered, this is called
DEFLECTED SUCCESSION
• Types of activity that can interrupt succession
include: deforestation; ploughing; grazing; water
drainage; weeding/coppicing; introducing new
species.
Plagioclimax community
• Plagioclimaxes are what is produced at the
end of a deflected succession.
• Most habitats in the UK are plagioclimaxes
produced by grazing, burning, mowing or
cutting.
• Examples include grassland and heathlands
which are used of agriculture
• Coppiced woodlands