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Succession & Biodiversity
Chapter 3
Succession
• What is succession?
• Succession- the process of life recolonizing after a
disturbance in an ecosystem.
– Primary succession- recolonizing an ecosystem with no soil
• Stripping an ecosystem down to its bedrock and completely
starting over or creating a brand new ecosystem that only has
a rock surface.
• Usually due to glaciers, volcanoes or new land forming
– Secondary succession- recolonizing an ecosystem that still
has its soil
• This is where the living things have been erased but the soil is
still intact.
• Fires and agriculture clearing
Primary Succession
• Primary succession- is recolonizing an ecosystem
with no soil
• 2 ways primary succession can happen
– New land can be created as in the formation of a
volcano by lava erupting and creating new rock
– Old land can be stripped down to rock when glaciers
move and bulldoze away all of the plant life and soil
• Over time in primary succession plants will colonize
the area. How do plants grow there without any
soil?
Primary Succession
• Before plant life can grow in a new area, soil must be created. How is
new soil created?
– Lichen(the colored crusty stuff on rocks) start to grow on the rocks in the
ecosystem. The lichen secrete a very weak acid that over time breaks down the
rocks into smaller and smaller bits.
– Natural wind and water erosion also takes place which breaks down the rocks
into smaller bits.
– Moss also starts to grow on the rocks which act as a sponge to trap particles
and nutrients that are important for soil. Also, once that moss dies it becomes
nutrient rich plant matter/compost that is a main component soil
• Lichen, moss and erosion help create the soil needed for future plants to grow
• This process of creating new soil could take thousands of years or longer
Primary Succession
• After lichen, erosion and moss have created soil for plants to grow
grasses start to colonize the area
– The weeds are important because it prevents the soil created from washing away
• Next come grass, flowers and other small plants. (annuals first then
perennials)
• Next come small shrubs and bushes.
• Next come conifer trees like pines and then deciduous trees like oaks
and depending on the ecosystem, it will determine which specific
trees colonize the area.
•
Lichens/moss  weeds  grass/flowers  shrubs  evergreen trees  deciduous trees
Primary Succession
• Pioneer species- the first species to inhabit an area after succession
– Usually are lichen in primary succession and grasses in secondary succession
• Climax community- the largest and last species to colonize an area
– Usually are large hardwood trees that establish after all of the other
trees have come in…lets you know that an ecosystem has completely
gone through succession
• Why are pine trees often needed for deciduous trees like oaks to grow?
– Pines grow and provide shade for the deciduous seedlings who have a
hard time growing in direct sunlight. The cover provided by the pine
trees usually provides a good environment for the seedlings to grow
below
Secondary Succession
• Secondary Succession- recolonizing an ecosystem that still has its soil
– Fires and agriculture clearing
• weeds  grass/flowers  shrubs  evergreen trees  deciduous trees
• This process can take a few hundred years, much shorter than
primary succession because soil does not need to be created from
scratch
Aquatic Succession
• Aquatic Succession- the process of changing an aquatic ecosystem into a
terrestrial ecosystem
• How does it happen?
• Streams and rivers that feed into lakes dump sediment and as soil erodes
from hillsides it gets deposited in the lakes slowing building up the bottom
soil layer until there is no water left
• Aquatic succession turns lakes  wetlands  dry land
• This process can take hundreds or thousands
of years but can be sped up by drought or
mass erosion events
• As aquatic succession occurs aquatic species
retreat and terrestrial plant species colonize
Succession Good or Bad?
• In what ways do you think succession might be bad for an
ecosystem?
– Could eliminate rare plants
– Make soil more susceptible to erosion
• In what ways do you think succession might be good for an
ecosystem?
– Reset an ecosystem to allow new plants to grow
– Can create more diversity
• How do humans contribute to succession.
– Agriculture and man made fires
• It is sometimes said that ecosystems are always going through
succession, why do you think that is?
• How do we handle succession in the Black Hills?
• Ecological upset- where one species experiences a population boom
at the expense of another
• Ecological collapse- where almost all of the species in an ecosystem
die due to events like pollution, etc
ECOLOGY TEST
• Biomes
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Know the characteristics of terrestrial and aquatic biomes.
How do humans impact aquatic biomes?
Be able to describe biotic and abiotic factors in an environment.
Be able to read a climate diagram.
• Biogeochemical Cycles
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Understand how matter flows through the water, carbon, nitrogen & phosphorus cycles.
What are the major sinks of each cycle?
Know who the key players are in each cycle, are there 1 or 2 crucial steps?
How are humans impacting each cycle?
• Species interactions
– Why do organisms want to have niches?
– What are the various types of species interactions?
– What is the principle of allocation?
• Populations
– What are limiting factors?
– Be able to draw and describe logistical population growth?
– Be able to read a predator/prey graph.
• Energy Flow
– Be able to identify the 4 trophic levels and organisms that would be in each.
– Be able to read a food web.
– What is an invasive species and how do they impact an ecosystem?
• Succession
– Be able to describe the processes of primary and secondary succession. What colonizes 1st, 2nd, 3rd.