Ecological succession is a basic concept in ecology. So I have a long definition, written here up on the board, of ecological succession; but it’s pretty easy to understand.
It’s the generally predictable stages an ecological system undergoes before eventually arriving at a stable climax biotic community best adapted to the prevailing climate, soil, and other conditions in an area.
The next lesson: Measuring Earthquakes, both lessons are included in Practice Tests.[divider]The following transcript is provided for your convenience.[divider]
So basically, ecological succession occurs after something devastating happened in that area. It can be a volcanic eruption, fire, logging. Basically, that area has been cleared of vegetation. Ecological succession is the process by which organisms or plants come back into that area.
And so, eventually, this area wants to get to a stable climax. So basically, they want to get to equilibrium. That way, a lot of new plants are happy to grow. It’s just kind of like business as usual. Some plants are dying. Some new plants are growing. So everything is pretty stable. Individually, these plants are going to grow in a certain way depending on the climate, the soil, and other conditions in an area so the plants are going to grow in a certain way, in a certain area, in a certain quantity to be suited to the conditions that they are in.
So first, like I said, the area is going to be cleared of vegetation by fire, logging, volcanic eruptions, or other disturbances. And then the area is first colonized by what we call pioneer organisms. This makes sense because a pioneer is the first person into the area. And so in this case, it’s the first plants into the area. And so these are mainly grasses and herbaceous plants. These are organisms that can pop-up really quickly.
And from there, shrubs and small, rapidly growing trees begin to grow. These rapidly growing trees are ones that require light. And so these trees are going to begin to mature, and they are going to get bigger. Eventually, they start blocking out the sunlight to the plants below it. So what’s going to happen then is, as those trees mature, more and more shade-tolerant species appear.
And so the plants that go come in after the trees have matured must be shade-tolerant, meaning they’re okay with shade. And then from there, those shade-tolerant species are going to appear until the climax community is attained. So once that climax community is attained, ecological succession has basically come to an end for that area.
Now, many biological communities undergo such rapid man-made or other disturbances that they cannot achieve their climax state. Nevertheless, the concept remains a valid description of older growth or mature ecosystems. So maybe there’s a certain area that’s continually being harvested for lumber. It’s going to have trouble coming back fully, or maybe there’s an area totally wiped out by a volcano. And then as it starts to grow again, another volcano eruption occurs. And so since there are such rapid disturbances in that area, then it’s going to be hard for the plants to go back. But under normal circumstances, this is how ecological succession works.
The next lesson: Measuring Earthquakes, both lessons are included in Practice Tests.