How does primary succession typically begin?

Primary succession typically begins on bare rock after a volcanic eruption because this process initiates the establishment of biotic communities in areas devoid of soil and organic material. When a volcanic eruption occurs, it can completely clear the land, exposing bare rock that lacks any existing life forms. The first organisms to colonize these harsh conditions are often lichens and mosses, which can adhere to rock surfaces and help to weather the rock, contributing to soil formation over time. As these pioneer species die and decompose, they create organic matter that enriches the developing soil, allowing for a broader range of plant species to establish, therefore facilitating the further stages of ecological succession.

In contrast, previously cultivated land may have some soil and plant life present, which signifies secondary succession rather than primary. Areas disturbed by fire often have surviving seeds and root systems in the soil, leading to secondary succession as well. Similarly, regions where human activity has ceased might still have underlying soil and remnants of previous ecosystems, also indicating a secondary succession scenario. Therefore, the correct understanding of primary succession centers on the initial colonization of barren surfaces, such as those found on bare rock after volcanic activity.