BIO205 Chapter 13/15

Community

A group of interacting species in the same location.

Climax community

A predictable and permanent group of species that occurs in a location after a long period of succession.

Chronosequence

When scientists compare different sites that are the same in every way except age to see how an ecosystem changes over time. (waiting 50–200 years to watch a forest grow is impossible for one researcher. instead they look at:

• a very young forest (5 years old)

• a middle-aged forest (50 years old)

• an older forest (100 years old)

and pretend these sites represent different stages of the same timeline.)

Succession

The series of changes in a community through time at a particular location that occur in a fairly predictable way.

Sere

A plant community at a particular point in the process of succession.

Primary succession

The temporal sequence of changing communities that begins on substrates containing no organisms and no organic material. (starts from NOTHING. Soil must be made from scratch by pioneer species (like lichens and mosses) Because of this, it takes a very long time.)

Secondary succession

The temporal sequence of changing communities that occurs on already established soils following a disturbance. (starts from something, soil and seeds are already present, so recovery is much faster.)

R-selected species

Species that tend to be small in body size, have high rates of reproduction and dispersal, low rates of survival, short generation times, rapid development, and early maturity.

Facilitation model of succession

A conceptual model positing that earlier arriving species alter the environment in ways that enhance the establishment and growth of later successional species. (early species = helpers)

Inhibition model of succession

A conceptual model positing that early successional species actively inhibit and prevent the establishment and growth of species that arrive later. (early species make it harder for later species)

Allelopathy

A biological phenomenon in which a plant releases toxins that impede the growth or reproduction of other plants.

Tolerance model of succession

A conceptual model positing that early successional species have little to no effect on later-arriving species. (early species do nothing/have no effect on later species)

Priority effect

An ecological phenomenon in which the order of species' arrivals influences the final community membership.

Assembly rules

a "rule" for how the timing of species arrival or the composition of the initial suite of colonizing species determines the success of subsequent colonizations and the final species composition of a community

Disturbance

Includes the factors that cause change, the change themselves, and the processes associated with such changes.

Disturbance regime

An overview of disturbance in a location that includes a description or quantification of multiple factors.

Distribution

The size and spatial extent of the disturbed area, including the relationship to geographic and environmental gradients.

Magnitude

The intensity and severity of the disruptive force.

Frequency

The mean number of disturbances per unit time.

Predictability

The regularity of the disturbance event through time.

Return interval

The mean time between disturbances, or the inverse of the frequency.

Synergism

The effects of the disturbance on the occurrence of other disturbances.

Characteristic flow regime

The seasonal water flow pattern for a lotic system in a given region.

Exogenous disturbances

A disturbance event that comes from outside the system. (e.g., asteroid impacts or volcanic eruptions)

Endogenous disturbances

A disturbance event that has a historical or evolutionary presence in the system and produce change from within (e.g., successional forces or predation)

Intermediate disturbance hypothesis

Suggests that the highest levels of species diversity are found in ecosystems that have intermediate levels of disturbance.

Equilibrium view

A historical idea about the natural world that suggests all communities eventually settle into an equilibrium or steady state.

Defaunation

the loss of animals from the biosphere

Alternative stable state

a novel equilibrium state for any dynamic system. In community dynamics this may refer to succession that does not lead to climax community

Anthromes

the anthropogenic version of a biome (e.g., a village)