Unit 1 - Land Ecology (APES) *Part 2*

Ecological succession and zonation

Climax community

A stable and mature ecosystem that has reached a steady state, where species composition remains relatively unchanged until disrupted by external factors. It represents the final stage of ecological succession.

Clumped distribution

A pattern of species distribution where individuals are grouped in patches or clusters rather than being spread evenly across an area. This distribution can occur due to resource availability or social behavior.

Ecological succession

The process by which ecosystems change and develop over time, leading to a series of progressive stages that ultimately result in a climax community. This involves changes in species composition, structure, and function, and is often a result of a natural or anthropogenic disturbance.

Edge habitat

A transitional area between different ecosystems or habitats, characterized by increased biodiversity and unique species that thrive in this environment. Edge habitats can be influenced by both natural and human activities.

Pioneer species

The first organisms to colonize a barren or disturbed area, initiating the process of ecological succession. They often prepare the environment for subsequent species by improving soil quality and stabilizing the substrate. Examples include lichens, mosses, and grasses that can survive in harsh conditions.

Primary succession

The process of ecological succession that occurs in an environment that has never been previously colonized, such as bare rock after a volcanic eruption or glacial retreat. It begins with pioneer species and gradually leads to a mature ecosystem.

Random distribution

A pattern of species distribution where individuals are positioned independently of one another, often influenced by environmental factors or random chance rather than specific attractants or repulsants.

Secondary succession

The process of ecological succession that occurs in a previously colonized area that has been disturbed or damaged, but where soil and some organisms still remain. It typically follows events like forest fires, floods, or human activities, and generally leads to a quicker restoration of the ecosystem compared to primary succession.

Seral stage

A series of stages in ecological succession (i.e. 1-2 years, 5-100 years, etc.), representing the changes in species composition and community structure over time, ultimately leading to a stable climax community. These stages include pioneer, intermediate, and climax communities, reflecting the gradual transition of the ecosystem.

Sere

A sequence of seral stages in ecological succession, representing a progression of community types leading towards a climax community. Also known as a seral community.

Simpson’s Diversity Index

A mathematical formula used to measure the biodiversity of a community, taking into account both richness and evenness of species. It ranges from 0 to 1, where 0 indicates no diversity and 1 indicates infinite diversity. The reciprocal equation provides a final value in the form of a percentage, where higher values indicate greater diversity.

Species evenness

A measure of how similar the abundances of different species are in a community, indicating the distribution of individuals among the species. High evenness occurs when species are represented by similar numbers of individuals, while low evenness indicates dominance by one or a few species.

Species richness

The total number of different species present in a given community or ecosystem. It reflects biodiversity and is a key component of ecological diversity.

Uniform distribution

A pattern of species distribution where individuals are evenly spaced across an area, often resulting from competition for resources or an even distribution of environmental factors.

Zonation

The spatial arrangement of different ecosystems or communities within a specific area, often influenced by environmental factors such as altitude, moisture, or soil type.