1. Disturbance: This refers to any event that disrupts the existing community and creates opportunities for new species to colonize. Examples of disturbances include:
* Natural disasters: Fires, floods, volcanic eruptions, and storms can drastically alter the environment, removing existing vegetation and creating bare ground.
* Human activities: Deforestation, agriculture, mining, and urbanization can all cause significant disturbances, leading to changes in species composition.
* Disease outbreaks: Epidemics can wipe out entire populations, leaving space for new species to take over.
2. Species interactions: The interactions between different species can also drive succession. These interactions can be:
* Competition: Species may compete for resources like sunlight, water, nutrients, and space. This competition can lead to the dominance of certain species and the exclusion of others.
* Facilitation: Some species can create conditions that favor the establishment of other species. For example, nitrogen-fixing plants can increase soil fertility, making it easier for other species to grow.
* Inhibition: Some species can inhibit the growth of other species. For example, a species that produces toxins might prevent other species from growing nearby.
It's important to note that these two causes often work together. For example, a fire (disturbance) might create bare ground, allowing for the colonization of pioneer species (facilitation), which might then be replaced by other species due to competition.
