Differentiate between autogenic and allogenic succession.

Autogenic and allogenic succession are two types of ecological succession that occur in natural ecosystems. They differ in terms of the driving forces or mechanisms that initiate and guide the succession process. Here's a differentiation between autogenic and allogenic succession:

Autogenic Succession:
Autogenic succession refers to the type of succession where the changes in the environment are primarily driven by the interactions among the organisms within the community. The key factors that influence autogenic succession include competition, predation, herbivory, and mutualistic relationships between species. As the community develops and evolves, the interactions among the organisms lead to changes in the physical environment, such as nutrient availability, soil structure, and light penetration. These changes then further influence the composition and abundance of species in the community. Autogenic succession is often characterized by a gradual and predictable pattern of change.
Example: In a forest ecosystem, autogenic succession can occur when early successional species, such as pioneer plants, modify the soil conditions and microclimate, enabling the establishment of later successional species like shade-tolerant trees.

Allogenic Succession:
Allogenic succession refers to the type of succession where the changes in the environment are primarily driven by external factors or disturbances, such as natural disasters or human activities. These external forces create abrupt changes in the physical environment, disrupting the existing community structure and initiating a sequence of ecological changes. Allogenic succession is often characterized by a more rapid and unpredictable pattern of change compared to autogenic succession.
Example: Following a volcanic eruption, allogenic succession can occur as the lava flow destroys the existing vegetation, and the subsequent deposition of volcanic ash and the availability of new nutrients create opportunities for the establishment of pioneer species, eventually leading to the formation of a new community.

In summary, autogenic succession is driven by interactions among organisms within a community, leading to gradual changes in the environment, while allogenic succession is driven by external factors or disturbances, causing abrupt changes in the physical environment, which then influences the development of a new community.