Sub-topic 2.4 Biomes Zonation and Succession

Biome

a collection of ecosystems sharing similar climatic conditions, grouped into 5 major classes: aquatic, forest, grassland, desert, tundra.

Succession

Succession is the process of change over time in an ecosystem involving pioneer, intermediate and climax communities.

Zonation

Zonation refers to changes in a community along an environmental gradient due to factors such as changes in altitude, latitude, tidal level or distance from shore (coverage by water).

insolation

the amount of solar radiation reaching a given area

precipitation

Rain, snow, sleet or hail - water that moves from a gaseous state, condenses and falls to the ground

tricellular model

the model which describes 3 large convection cells moving air from the equator towards the poles in each hemisphere of the earth that explains the distribution of precipitation and temperature that influence structure and relative productivity of different terrestrial biomes

terrestrial

relating to the earth i.e. ecosystems occurring on land

aquatic

relating to water i.e. ecosystems dominated by water

r-strategist

r-strategist species are those that produce large numbers of offspring so they can colonize new habitats quickly and make use of short-lived resources

K-strategist

K-strategist species tend to produce a small number of offspring, which increases their survival rate and enables them to survive in long-term climax communities.

climax community

There is no one climax community, but rather a set of alternative stable states for a given ecosystem. These depend on the climatic factors, the properties of the local soil and a range of random events that can occur over time.
Historically it is thought of as the community of organisms at the end point of succession but succession never really ends!

community respiration

The total respiration rate for all the populations within that system.

Productivity:Respiration Ratio

The ratio between how productive a system is and how much respiration is happening. As a system approaches its climax community, gross productivity equals respiration rates and so P:N approaches 1.

P:R>1

biomass accumulates

P:R<1

biomass depletion

P:R=1

steady state community in equilibrium

nutrient and energy pathways

The ways that nutrients/minerals and energy move through an ecosystem. These tend to become more complex as a system undergoes succession. Often represented by a food web.

alternative stable state

A stable state that is the result of a series of feedback loops and random events which give rise to a particular set of biotic and abiotic conditions. A particular system may be able to exist under several alternative stable states but will be the result of the random events and feedback.

stochastic

having a random probability distribution

climate

the average of the weather over a relatively longer period of time, usually about 30 years of data is required to give the climate of an area.

weather

the conditions is a given place at any one time. It is measured by the temperature, air pressure, precipitation (rain/snow etc.), wind speed, humidity.

steps of succession

colonization, establishment, competition, stabilization, and climax

primary succession

colonization of bare inorganic surfaces

secondary succession

when an already established community is destroyed