Final answer:
Fire is both a natural and a human cause of ecological succession. It can lead to secondary succession where nutrients from burned vegetation foster recolonization.
Step-by-step explanation:
The question refers to processes that can lead to ecological succession, which is the observed changes in species structure of an ecological community over time. Among the options provided, fire is a factor that can be both a natural and a human cause of succession. Natural fires can be caused by lightning strikes, while human causes may include prescribed burns or accidental fires resulting from human activity.
As an example of succession, secondary succession can occur when a forest is cleared by a wildfire. Whether the fire is natural or human-induced, the nutrients returned to the soil in the form of ash from the burned vegetation provide a foundation for rapid recolonization and succession.