Lecture 33+34- Biotic Changes Flashcards
What do community distributions depend on?
Varying spatial and temporal scales
What two factors cause changes in biomass composition over temporal scales (in communities)?
Extrinsic and intrinsic factors
What is the difference between extrinsic and intrinsic factors?
Extrinsic factors are those that operate outside the community but impact it. Whereas intrinsic factors are changes that act from within the community and are often the result of interactions
Give an example of extrinsic factors(there’s four on the card)
- Climate
- Geomorphology
- Edaphic factors
- Anthropogenic influences
Give examples of intrinsic influences of communities
- Invasion
- Competition
- Predation
- Parasitism
- Disease
What are edaphic factors?
The chemical physical and biological properties of soils, all of which affect the soils ability to sustain diversity and plant support.
What are the three main types of change in communities?
- Regeneration
- Fluctuation
- Successional
Which form of change relates to the processes experienced by an individual within a population?
Regeneration
Which form of change has no impact on overall biomass?
Regeneration also
Which time of change involved a deviation from but ultimate return to mean conditions?
Fluctuation/ reversible change
Which type of change is the change from one biomass community to another over time, and is irreversible?
Successional
What do fluctuation all changes result from?
Phenological changes associated with season climatic regimes(warm/cold). These phenological changes in total biomass and different occur from different species exploiting different resources and times of year
What is short term environmental variation dependant on?
Dependant on intensity and duration of deviation from mean conditions
How do fluctional changes impact overall species composition?
They cause changes in growth of community components due to different species exploiting different environmental conditions.
What is successional change?
A sequential change in form and composition of overall biomass over time
What is succession controlled by?
Succession is biotically controlled
What are the two biotic factors that primarily control succession?
- Progressive habitat modification (eg. Adding OM to soils and changes in microclimate)
- Interspecific competition. This causes the principle of competitive exclusion
What is the principle of competitive exclusion?
Those who annoy successfully compete for resources will not progress in the successive sequence
What is the climax stage of succession dominated by?
The largest and tallest plants that have the greatest access to light
What is the difference between primary and secondary succession?
Primary succession, which occurs in areas officially devoid of life( eg. Volcanic) where there is no soil
Secondary succession: occurs after less dramatic disturbances where soils are present but degraded and seeds that are present in the soil can germinate.
What is convergence in succession?
Irrespective of initial substrate, the process of succession results in the same vegetation communities for a set of given climatic conditions
What is the final stage of Clements model?
Climatic climax
What are subclimaxes in the Clements model.
Local physical conditions slow succession , but once this is overcome the community will eventually reach climatic climax
What is plagioclimax?
When extreme human activities deflect succession from its natural course, into this new plagioclimax stage
