Hi. It's Mr. Andersen and in this podcast I'm going to talk about ecological
succession. Succession is simply a series of events by which life comes back. And so
what am I talking about? Well, look here. We've got a picture of a forest. But this
is a year after there was a forest fire. And so you can see a lot of the charred burnt
trunks. And so basically a photographer came here. And he came here once a year to the
same place and took pictures. And so this would be year one. This would be year two.
This would be year three. Year four. And year five. And so basically what you see is life
coming back and changes taking place. And that is called succession. And it tends to
occur at a predictable rate. And using a number of predictable species. And so basically succession
we could break into two different parts. The first one is called primary succession. Primary
succession occurs when you have bare rock. In other words when there's no soil left.
And so if you look at this lava flow, basically the lava flowed down here. You can see they
kind of cut a foot path here. But basically life is starting to come back. Life can't
grow out here for the most part because there's not soil there. We can't have plants that
start to grow there. And so we have to have erosion. We have to have wind and rain and
eventually we have soil. And then we can start to have plants come back. Another example
of primary succession is right here. This is a picture of Mount St. Helens the day before
it exploded. After it exploded it looked just like this. And so here in Montana we had about
that much ash. Everywhere. And that just came from the top of this mountain as it exploded.
Well this would be primary succession because there's no soil left. It's all gone. It's
in Montana, not in Washington. And so basically life has to reestablish itself. And so this
is a picture of Mount St. Helens now, a few years ago. And so this is kind of on this
rim up here. And so basically what's had to happen, a series of events by which life has
come back. Now if you compare this to that estonian forest, you can see that it's coming
back slower. And that's because we had to go all the way down to the rock. Great example
of this the Island of Surtsey. And so I think this was in 1962. All of the sudden of the
coast of Iceland there's a huge volcano and a brand new island shows up. They name it
Surtsey which is some Norsk god. And so basically what scientists decided to do is to not go
there. A few scientists will go there every year just basically to study how life comes
back. And so you can see all this vegetation on this island. And there's been weathering
going on. You would just think this is a just a regular island and it's really not that
old. And so the cool thing is they can see what species are showing up first. It didn't
take long for vascular plants to show up. And you might think, how did they get there?
Well a lot of them are blown by the wind or carried by birds. Or float there. And so it's
pretty cool. But all of that again is primary succession. Secondary succession, and this
is a gorgeous picture that was taken here in Montana during a forest fire. Secondary
succession occurs when we have some kind of a disturbance but the soil still remains.
And actually the burning of fire is something that's really common in the mountains. And
so you can see this elk here after the fires in Yellowstone Park. And there's no vegetation.
But what you should know is that the soil is sitting there. And life is ready to come
back. And so basically this is what Yellowstone Park looked like a few years later. And then
looks like now. And so what were some of the first organisms to come in? Well we tend to
call these things pioneer organisms. And pioneer organisms are going to be organisms that tend
to make their living by coming into an area after there is a disturbance. And so two examples
in Montana, one would be lupine. Lupine is going to be a flower that's actually a legume.
So it's related to a pea. And what's nice about lupine is that it can fix nitrogen.
It has bacteria that live on its roots and they can actually take nitrogen in the air
and return it to the soil. And then another example would be Lodge Pole Pines. Lodge Pole
Pines are really skinny and long conifer trees that we have here in Montana. And basically
what they do is they have two different cones. They have certain cones that they use year
to year to reproduce. But they also have these really waxy, what are called serotinous and
they're just filled with wax. And they never open. Unless there's a fire. And if there's
a fire then they'll open up and then their seeds will come back. And so basically lodge
pole pine have evolved this niche. The way to be a pioneer species. To come in. Now eventually
as that forest starts to develop, it's going to be replaced by more climax species. And
so that's another term that I just threw in there. That's called the climax. Climax is
basically what's going to happen after successions. So on this side we'll have a disturbance.
So we're going to have a disturbance on this side. So what are some disturbances? We could
have fire or human disturbances or like a tsunami. A really cool disturbance is after
Chernobyl, the meltdown there, all humans had to leave. And so it's a wild kind of a
land. But basically life can come back and how does it come back? Well let's look at
this chart which is great. So if we look at bare rock, bare rock is going to be the first
thing that you have. And the amount of bare rock is going to drop off as vegetation of
course starts to come in. What's next? Well then we're going to have mosses and grasses
come. Why don't they come right away? Well lot's of times there's no soil there. And
so we have to have weathering, rain, wind. And then we start to get soil. And then they
can come back. Now you might think well why don't they just stay forever? Why don't they
just have a huge amount of these grasses? Well if you think about it, as the other species
start to take off they're going to be taller than those grasses. They're going to start
to take the sunlight. And so they're going to be replaced by other species which is eventually
we're going to have some small wooded plants. And then we're going to have some tress. This
would be like the lodge pole pine. And eventually we have some trees that come back like that.
And so what happens eventually, everything kind of levels off. And then we have these
climax species at the end. Does it stay like that forever? Well, it depends on your size.
So if you're like a redwood tree, you're big enough that fire sweeping through an area
is not going to effect you. But most species are going to be killed by a disturbance and
then that whole process starts over again. And so what is succession? It's the series
of steps by which life comes back. Remember there's primary, secondary. Primary no soils.
Secondary soil. And I hope that's helpful.