Succession occurs in a community as species replace each other over time

• Succession: the process by which the species composition of a community changes over time

• Seral stage: each stage of community change during the process of succession

• Pioneer species: the earliest species to arrive at a site

• Climax community: the final stage in the process of succession

Succession occurs in a community as species replace each other over time

Direct observations: measuring succession after a disturbance

Indirect observation: space for time approach

• Cronosequence: a sequence of communities that exist over time at a given location

Succession in terrestrial environments

• Primary succession: the development of communities in habitats that are initially devoid of plants and organic soil, such as sand dunes, lava flows, and bare rock

• Secondary succession: the development of communities in habitats that have been disturbed and include no plants but still contain an organic soil

The Complexity of Terrestrial Succession

• Complexity: communities might have a characteristic climax stage, but the stages to reach it might vary

• Glacier Bay

• Animal succession

  • mostly a respond to the plant succession

Succession in aquatic environments

• Succession in intertidal communities

• Succession in Shallow Lakes and Ponds

Succession occurs in a community as species replace each other over time

• Change in species diversity

Succession can occur through multiple mechanisms

• Early vs. late-succession species

  • trade-offs between seed mass and seedling morality under high-shade conditions

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• Facilitation: a mechanism of succession in which the presence of one species increases the probability that a second species can become established

• Inhibition: a mechanism of succession in which one species decreases the probability that a second species will become established

• Tolerance: a mechanism of succession in which the probability that a species can become established depends on its dispersal ability and its ability to persist under the physical conditions of the environment

• Tests: intertidal community

Succession does not always produce a single climax community

• Changes in climax communities over time

  • changes continue to occur

  • mature forest in Pennysylvania

• Changes in climax communities over space

  • spatial heterogeneity

• Transient climaxes:

  • vernal pools: water vs dry stages

• creating gaps in a climax community

  • gaps open spaces for non-climax species

Communities respond to disturbances with resistance, resilience, or switching between alternative stable states

• Community stability: the ability of a community to maintain a particular species composition

• Community resistance: the amount that a community changes when acted upon by some disturbance, such as the addition or removal of a species

• Community resilience: the ability of a community to return to its original state after being disturbed

• Alternative stable states: when a community is disturbed so much that the species composition and relative abundance of populations in the community change, and the new community structure is resistant to further change

• Alternative stables states in intertidal communities: brown rockweed algae is a dominant competitor, but disturbance allows other species to thrive