Primary and Secondary Succession

Wow! Look at this beautiful waterfall! All the wonderful, green, healthy plants around it. How long has it existed? Was it always there? How was it formed? In this presentation, I will present the differences between primary and secondary succession which will explain how ecosystems are created both from scratch and from other existing ecosystems. First, we will begin with succession. Succession is the gradual growth of new organisms in an ecosystem.

Every ecosystem that you see was developed over time. Primary succession is the process by which the structure of a new ecosystem develops where there was no existing ecosystem. Primary succession can take up to 1,000 years to develop and it occurs on barren land that does not have any life forms. Primary succession begins with lichen which attaches itself to rock. Some of these lichen secrete weak acids which break down the rocks that ultimately become soil. Primary succession does not have humus present in the soil. In addition, primary succession has many intermediate communities that take a long time to reach the climax stage. In primary succession the pioneer communities come from outside of the area because there are no reproductive structures, as the ecosystem is beginning from barren land.The picture below is an example of primary succession beginning with solid rock.

Secondary succession is an ecosystem that begins where there was a previous ecosystem present. In the case of secondary succession, an event such as a fire, tornado, volcanic eruption, flood, or other type of catastrophic event took place, destroying the existing ecosystem.Unlike primary succession, secondary succession takes anywhere from 200-500 years. In addition, in secondary succession there is soil and humus present at the beginning. In secondary succession, there are only a few intermediate communities as compared to primary succession which has many intermediate communities. Finally, because there are reproductive structures present in secondary succession, the pioneer communities develop from existing previous reproductive structures. Below is an example of secondary succession following a wildfire.

Below is a real life example of secondary succession. This succession took place at Mt. Saint Helen in Washington state.

In conclusion, all ecosystems go through changes. These changes can occur as a result of human intervention or nature itself. These changes in ecology are called succession. There are two types of succession; primary and secondary. The main differences between the two are that primary succession begins with barren land while secondary succession begins where there was a previous ecosystem.

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