Ch. 20 - Succession

Ecological Succession

Change in animal, plant, and microbial community in an area following disturbance or creation of new substrate.

Pioneer community

First organisms to colonize in a successional sequence.

Climax community

Late successional community that persists until disturbance.

Primary succession

Occurs on newly exposed geologic structures or formed surfaces.

Examples of primary succession events:

• glacial retreat

• volcanic eruptions

• severe flooding

• severe soil erosion

Glacier Bay succession

• Primary succession began after glaciers retreated and exposed new geological surfaces, creating space for new communities to develop.

  • Lichens and mosses were the first to colonize these surfaces and allowed for the formation of soil. As soil quality improved, vascular herbaceous plants were able to establish, furthering the development of soil and allowing intermediate species such as shrubs and various perennial and annual plants to establish. Over time, trees began growing, and the plant community gradually transitioned into a forest ecosystem.

Secondary Succession

Occurs in areas where disturbance destroys terrestrial community without destroying soil.

Examples of secondary succession events:

• Wildfires

• clear cutting

• tornadoes

• land use changes

Secondary succession in old-fields of Piedmont Plateau 

The Piedmont Plateau experienced disturbance for centuries from forest clearing and human influence leaving the region cleared of trees and vegetation. Eventually species of terrestrial plants began to colonize this region which started as weeds and eventually developed into shrubs, annuals, perennials, and even began developing trees.

Three mechanisms of succession (Connell & Slatyer 1977)

• facilitation

• tolerance

• inhibition

Facilitation

Environment becomes less suitable for pioneer species and more suitable for late successional species.

• early species modify environment in a way that makes it easier for later species to establish

Tolerance

The environment becomes less suitable for pioneer species but neither less nor more suitable for later successional species

• early species don’t facilitate or inhibit, they just coexist temporarily until late successional species dominate. 

Inhibition

Environment becomes unsuitable for both pioneer and later successional species.

• Pioneer species modify the environment in a way that makes the area less suitable for both

Ecological restoration

restoration of damaged ecosystems to acceptable levels of biodiversity, physical structure, and ecosystem functioning. 

How can ecological succession inform restoration efforts?

Understanding how succession works can guide restoration efforts by helping us identify which species are likely to establish naturally and which pioneer species should be introduced to support the recovery of a damaged ecosystem. This knowledge also allows us to create conditions that encourage community development as well as design interventions that promote soil formation, increase ecosystem stability, and ultimately allow for long-term ecological resilience.

Restoring tropical forests in mining tailings

Addition of forest floor litter and seedlings promoted faster succession.