APES Notes 2.7 - Ecological Succession
Summary
TLDRIn this educational video, Mr. Smeeds explores ecological succession, a process of change in forest ecosystems. He distinguishes between primary and secondary succession, detailing how pioneer species like moss and lichen initiate growth on bare rock in primary succession, while grasses and wildflowers take the lead in secondary succession where soil already exists. The video progresses through the stages of succession, from early to late, explaining how soil depth and nutrient richness develop over time, allowing for larger, slower-growing trees like maples and oaks to eventually dominate. The video concludes with a data analysis exercise, challenging viewers to determine the successional stage of spruce trees based on a graph showing their population changes post-glacial retreat.
Takeaways
- πΏ Ecological succession is a series of predictable changes that occur in a forest ecosystem, involving the gradual replacement of one community of plants and animals by another over time.
- π There are two types of succession: primary and secondary. Primary succession starts on bare rock with no soil, while secondary succession begins in areas where soil is already present but the existing plant community has been removed by a disturbance.
- π± In primary succession, pioneer species like moss and lichen colonize the area, breaking down rocks and initiating soil formation through the secretion of acids.
- πΌ Secondary succession starts with pioneer species like grasses, sedges, and wildflowers, which are quick to grow and tolerant of full sunlight, colonizing areas where the previous plant community has been disturbed.
- π² The process of succession is marked by different stages, each dominated by species adapted to the conditions of that stage, progressing from early to mid to late successional species.
- π³ Pioneer species are characterized by wind or animal dispersal, rapid growth, and the ability to grow in nutrient-poor conditions, such as bare rock or recently disturbed soil.
- π³ Mid-successional species, like shrubs and fast-growing trees, require deeper, more nutrient-rich soil and can tolerate full sunlight but take longer to grow and establish.
- π³ Late successional or climax community species are large, slow-growing trees that are tolerant of shade and require deep, nutrient-rich soil to anchor their roots, often taking hundreds of years to reach maturity.
- π The video emphasizes the importance of understanding the characteristics of different successional stages and species to predict and manage ecological changes.
- π The practice task involves analyzing data, such as a graph showing the number of spruce trees over time, to determine whether a species is early, middle, or late successional based on its population trends.
Q & A
What is ecological succession?
-Ecological succession is a series of predictable changes that occur in an ecosystem over time, involving the gradual replacement of one community of plants and animals by another.
What are the two types of ecological succession?
-The two types of ecological succession are primary succession and secondary succession.
How does primary succession begin?
-Primary succession begins on bare exposed rock where no soil exists. It starts with pioneer species like moss and lichen that can grow directly on rocks and break them down to form soil.
What role do moss and lichen play in primary succession?
-Moss and lichen play a crucial role in primary succession by secreting acids that break down rocks, releasing nutrients needed for their growth and eventually leading to soil formation.
What is secondary succession and how does it differ from primary succession?
-Secondary succession occurs in an area that already has established soil but has lost its plant community due to a disturbance. It differs from primary succession in that it starts with grasses, sedges, and wildflowers rather than moss and lichen.
What are pioneer species and why are they important in succession?
-Pioneer species are the first species to colonize an area during succession. They are important because they can grow in harsh conditions, help break down rocks or enrich soil, and create conditions for other species to grow.
What are mid-successional species and what characteristics do they have?
-Mid-successional species appear after pioneer species have built up the soil. They are typically faster-growing, larger plants like shrubs and small trees that can tolerate full sunlight and require deeper, more nutrient-rich soil.
How do late successional or climax community species differ from pioneer and mid-successional species?
-Late successional or climax community species are the last to colonize an area. They are large, slow-growing trees that can tolerate shade and require deep, nutrient-rich soil. They indicate the end of the succession process.
Why does secondary succession occur faster than primary succession?
-Secondary succession occurs faster than primary succession because it starts with established soil, which already contains nutrients and organic matter, speeding up the process of plant colonization and growth.
What is the role of disturbances in ecological succession?
-Disturbances, such as wildfires, storms, or human activities, can initiate secondary succession by clearing away existing vegetation and creating space for pioneer species to colonize and start the succession process anew.
How can data analysis skills be applied to understand ecological succession?
-Data analysis skills can be applied to ecological succession by examining trends in species populations over time, such as the graph showing the number of spruce trees per hectare after a glacial retreat, to determine the successional stage of a species.
Outlines
πΏ Ecological Succession Overview
Mr. Smeeds introduces the concept of ecological succession, focusing on its definition and impact on ecosystem structure. He explains the two types of succession: primary and secondary. Primary succession begins on bare rock with no soil, where moss and lichen pioneer the ecosystem by breaking down rocks and initiating soil formation. Secondary succession occurs in areas with established soil but where the plant community has been removed by a disturbance like wildfire or human activity. Here, pioneer species such as grasses, sedges, and wildflowers quickly colonize the area. The video aims to develop data analysis skills by examining trends in ecological data.
π± Successional Stages and Species Characteristics
The paragraph delves into the stages of ecological succession, detailing the characteristics of pioneer, mid-successional, and late successional species. Pioneer species, like moss and lichen in primary succession or grasses and wildflowers in secondary succession, are the first to colonize an area. They are wind or animal-dispersed and can grow in harsh conditions. Mid-successional species, such as shrubs and fast-growing trees like pines and cherries, arrive after the soil has been enriched by the pioneer species. Late successional or climax community species, including large, slow-growing, and shade-tolerant trees like maples and oaks, require deep, nutrient-rich soil and take the longest to establish. The paragraph emphasizes the importance of soil development over time, which is crucial for supporting the growth of these large trees.
π Analyzing Data on Spruce Trees in Succession
In the final paragraph, the focus shifts to practicing data analysis skills. A graph is presented showing the number of spruce trees per hectare over time following a glacial retreat. The audience is prompted to determine whether spruce trees are early, middle, or late successional species based on the graph. The analysis should consider the typical characteristics of each successional stage to make an informed conclusion about the spruce trees' role in the ecosystem's development.
Mindmap
Keywords
π‘Ecological Succession
π‘Primary Succession
π‘Secondary Succession
π‘Pioneer Species
π‘Soil Formation
π‘Mid-Successional Species
π‘Late Successional Species
π‘Disturbance
π‘Chemical Weathering
π‘Data Analysis Skill
Highlights
Ecological succession is a series of predictable changes in a forest ecosystem.
There are two types of succession: primary and secondary.
Primary succession begins on bare exposed rock with no previously formed soil.
Moss and lichen are pioneer species in primary succession, growing directly on rocks.
Moss and lichen secrete acids to break down rocks and release nutrients.
Secondary succession starts in an area with established soil but cleared of plants by a disturbance.
Pioneer species in secondary succession include grasses, sedges, and wildflowers.
Succession is marked by the types of plant species that dominate each stage.
Pioneer species are followed by mid-successional species that require deeper, richer soil.
Mid-successional species include shrubs, bushes, and fast-growing trees like pine and cherry.
Late successional or climax community species are large, slow-growing trees tolerant of shade.
Maples and oaks are examples of late successional species.
Soil depth and richness are critical for the establishment of climax community species.
Primary succession can occur after volcanic eruptions or glacial retreats.
Secondary succession is faster than primary succession but can still take over 150 years.
The process of secondary succession is jump-started by disturbances like forest fires that enrich the soil.
Data analysis skill involves drawing conclusions from trends in data, such as the number of spruce trees over time.
Transcripts
hey everybody it's mr smeeds and today
we'll be covering topic 2.7
which is ecological succession our
objective for today's video is to be
able to describe what ecological
succession is
but also to describe the different
effects that ecological succession has
on an ecosystems
structure the skill that we'll be
practicing at the end of today's video
is a data analysis skill
and it will involve looking at a set of
data and trying to draw conclusions
based on the trends we see in those data
so ecological succession refers to a
series of predictable changes
that occurs in a forest ecosystem
there's two different types
and the first type is referred to as
primary succession
in primary succession the area has only
bare exposed
rock so there's no previously formed
soil
the process involves moss and lichen
which are species of plants that have
their seeds or their spores dispersed by
the wind
so the wind carries in those seeds and
moss and lichen are actually uniquely
adapted to grow directly on
rocks they're able to break the rocks
down by secreting acids
which releases the nutrients that they
need to grow and so if we look at a
diagram what we'll see here
is that we start with this bare rock
then as the wind carries in those seeds
the moss and the lichen are able to
colonize or start going on the rock
that breaks the rock down into smaller
bits and eventually forms soil
over time in secondary succession on the
other hand
we're starting in an area that already
has previously established soil
but the plants in that ecosystem have
been cleared away by some sort of large
disturbance
so that could be a wildfire could be a
wind storm
or even a human disturbance like
clearing an area of land
to use for agriculture we're also going
to see
some pioneer species or some initial
species move in
similar to in primary succession but the
big difference
is that these first species to arrive
are going to be grasses
sedges and wildflowers and these are
species that are quick growing
and they have their seeds dispersed by
the wind or by animals
so if we look at a diagram of secondary
succession you'll notice the big
difference
is that there is established soil
already existing
it's just that a disturbance has cleared
out the existing plant community
and that leaves the soil open for these
pioneer species to come in
and start to take up root now we'll talk
about the basic steps of succession
which are common to both primary and
secondary so really the only difference
between those two
is the starting stage whether or not
there's already established soil
after that it's relatively the same
process so it's important to understand
that these stages of succession or this
process is marked
by which types of plant species dominate
the ecosystem during each stage
and that's because different species are
adapted to the different conditions
that occur in each phase or each stage
of succession
so we always start with pioneer or early
successional species
these are the first species to appear in
the area
and they are able to become established
either on the bare rock
if we're talking about primary
succession or in the recently disturbed
soil if we're talking about secondary
succession
they share some characteristics which is
that they are dispersed by the wind
meaning that their seeds are often
carried by the wind to the area
or by animals who may eat the seeds and
then disperse them
in their waste or the seeds may get
stuck to the animal's fur so we have a
picture here of the wind blowing seeds
to help us remember
that pioneer species need to be able to
be dispersed by the wind
or by animals some examples would be
moss and lichen
if we're talking about bare rock that
occurs in primary succession
or wildflowers plants that produce
berries like raspberries or grasses and
sedges if we're talking about secondary
succession
pioneer species are always followed by
mid-successional species
mid-successional species appear after a
couple years where the pioneer species
have built up the soil
so it's a little bit deeper and a little
bit more nutrient-rich
and so what happens is those pioneer
species as they grow and die
grow and die their biomass or their
organic matter gets added to the soil
and that increases the richness of the
soil and increases the depth over time
which eventually enables the mid
successional species to come in
those mid-successional species share
some characteristics as well
they're going to be fast growing they're
going to be a little bit larger than the
pioneer species
so they're going to grow a little bit
slower they're typically going to need a
little bit deeper soil with more
nutrients
than those pioneer species were able to
tolerate but they're also
able to be tolerant of full sunlight and
that's because there's no shade in the
ecosystem yet
if we look at a diagram we can see here
that it takes some time for the shrubs
and the smaller trees which are
mid-successional species to arrive
because those pioneers have to build up
that soil depth for them
and they're also just species that grow
a little bit more slowly so these
trees you know take years to start to
develop and so they're not going to be
seen
right you know the first or second year
after a disturbance
if we want some examples to remember we
can think of shrubs
and bushes you know things that take a
couple of years to start developing
same thing with trees that are fast
growing so pine
and cherry are two great examples of
mid-successional species
and then we have late successional
species which as their name implies
are the last species to colonize or to
start going in an area
we also sometimes call these members of
a climax community
because a climax is at the end of the
transition and so it takes them quite a
while to arrive
so they are going to be able to start
growing after the soil has been deepened
and enriched further by this process of
the early and mid successional species
dying
and having their biomass and their
nutrients added to the soil
all of these late successional species
share some characteristics
those would be that they are large slow
growing trees
that are tolerant of shade now they take
a long time to grow and develop but
they're able to develop in the shade
of these mid-successional species that's
an important characteristic of them
and they need deep nutrient-rich soil to
anchor their roots because they're
oftentimes
very large trees that can grow to
hundreds of feet tall
maples and oaks are great examples as
well as other large trees that reach
heights of hundreds of feet
and if we look at this diagram here what
i like about this is it helps us
remember
that we need this soil to be built up
over time so we would not have deep
enough soil
you know a couple years or even 10 or 20
years after primary succession
it takes hundreds of years to get soil
deep enough to support the roots of
these
large shade tolerant and slow growing
trees
and so again we would call this here a
climax community because it's at the
end of succession it takes hundreds of
years for the soil to be built up
and for these trees to grow and emerge
from the canopy
of the mid-successional trees so as a
reminder
that early mid to late successional
process is common to both
primary and secondary succession
the main difference is just the starting
material of those two
and so primary succession you'll
remember starts from fair rock
this is an ecosystem that has not
previously had soil present
and this can also often occur after a
volcanic eruption
or after a glacial retreat that's
because those are both events that will
leave
bare rock without soil on top of it
and so very important to remember that
moss and lichen are the colonizers or
the pioneer species
in primary succession and that's because
their spores or their seeds
are easily blown in by the wind but then
also they're uniquely adapted to grow
on rock they have a unique adaptation
that enables them to secrete acids
into the rock those acids will actually
break down or chemically weather the
rock
so that the minerals in those rocks that
have the nutrients that the moss and
like you need will be released
and those moss and liking can then
absorb the nutrients into their bodies
so these are things like potassium
phosphorus and nitrogen
and again this is really critical to
primary succession
starting without this chemical
weathering we wouldn't have the
formation of soil
so as the rock starts to break down
there are smaller bits of rocks
that mix together with the dead biomass
or the dead organic matter from
the moss and the lichen as they
eventually die and all of that kind of
miscon
mixes together and forms this initial
rocky
shallow soil so if we look at this
picture here
we can see this is a lava flow where
there is exposed rock
after the lava has cooled and it's going
to be colonized first by these lichen
and then we have this diagram that we
did look at before but it's a great
reminder that we have this bare rock
and then eventually the rock is starting
to be broken down by the secretion of
the acid by moss and lichen
and eventually we get just the very
beginnings of really rocky shallow soil
here
and then from there the process is the
same as we've discussed we have our
pioneers
our early successional species followed
by our mid-successional species
followed by our late successional or
climax community species
and finally we'll wrap up by focusing in
a little more detail on secondary
succession
so remember this isn't an area where
there's already established soil
but most of the plant community has been
removed by some sort of disturbance
so pioneers are still going to be the
first species to arrive in this area
and they're going to be plants that have
their seeds dispersed either by the wind
or by animals and they're going to be
fast growing and sun tolerant
but they're going to be wild flowers
grasses and sedges
as opposed to the moss and lichen who
are our pioneers or colonizing species
in primary succession important to point
out
that the soil is already established
here and sometimes it's even enriched if
the disturbance was a forest fire
now that's because forest fires burned
down the previous plants that were in
the area and they return a lot of the
nutrients that those plants have been
storing
back to the soil so soil in the wake of
a forest fire is often actually very
nutrient rich
and really jump starts the process of
secondary succession
so if we look at this diagram here i
know we've seen this one before but it's
a great reminder that we do start with a
disturbance of some sort
often a forest fire but it could be a
human disturbance like clearing land for
agriculture
or even just a wind storm or a flood
anything
that dramatically reduces the plant
community and basically
enables these pioneer species to come in
and dominate so remember our pioneer
species in this case are going to be
grasses
sedges weed species that have their
seeds to source by the wind
they're also going to be very fast
growing they're going to be full sun
tolerant so they can handle that full
sunlight
they colonize the area they eventually
die and build up the soil a little bit
deeper for our mid successional species
who are faster growing trees bushes and
shrubs and then finally we have our late
succession or our climax community
species
i do want to point out that this process
of secondary succession is faster than
primary succession
but it can still take upwards of 150
years
for this climax community reform that's
because these late successional species
are very slow growing
they need deep roots with a lot of
nutrient-rich soil to
nourish those huge trees that are going
to grow and anchor them and so it
is still a relatively slow process to
reach
a climax community so for practice frq
2.7 today we're going to practice the
skill
of analyzing data and drawing
conclusions from those data
so we have here is a graph showing the
number of spruce trees per hectare
in an ecosystem as time goes on after a
glacial retreat
so based on this graph i want you to
explain whether or not you think the
spruce tree
is an early middle or late successional
species and remember that with explain
you need to justify your reasoning for
this
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