Primary succession and secondary succession are two processes through which ecosystems develop and change over time, but they differ significantly in their starting conditions.
Primary succession begins in lifeless areas where there is no soil, such as after a volcanic eruption or a retreating glacier. The first organisms to populate these areas are usually lichens or mosses, which can tolerate harsh conditions and contribute to soil formation over time. As these pioneer species die and decompose, they create organic material that allows soil to develop, enabling other plants to grow.
On the other hand, secondary succession occurs in areas where a disturbance has destroyed an existing community but left the soil intact. This can happen after events like forest fires, floods, or human activities such as farming. Because the soil and some organisms are already present, secondary succession typically happens more quickly than primary succession.
In summary, the key difference is that primary succession starts from bare rock or inorganic material with no soil, while secondary succession begins in areas where soil is already found. This fundamental difference leads to varying timescales and starting conditions for the development of the ecosystem.