Biogeographical and ecological processes 2, Lecture 34 Flashcards
Case study for change in vegetation linked to topographic change
- Sierra Nevada, Spain
- mountain building region
- large difference between sea level & mountain altitude which are very close
Other than availability of environmental resources, what determines species distribution of plants?
ability to tolerate periods and levels of environmental stress
Environmental stresses
4
Deficiency of: - light - moisture - nutrients and - temperature (which limits photosynthetic production)
Common adaptive strategies to severe stress:
(of vegetation)
5
- a small hard-leaved perennial habit,
- conservative use of resources,
- slow growth and turnover of materials,
- sequestration / accumulation of food reserves above and/or below ground.
- flowering + seed production intermittent but vegetative repro. common
Niche concept
presence or absence of a species in a habitat depends on availability of a suitable niche
Potential range of a plant species
Range of tolerance to abiotic conditions is the physiological or potential range of a plant
Actual range of a plant species
no organism exists in isolation so it’s ecological or actual range depends on suitability of biotic environment as well as the abiotic
Biotic interactions can be
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Direct or indirect
Exclusively or mutually antagonistic
Depressive or beneficial
Preclude or essential
Two main types of biotic interactions
Negative and positive
Negative biotic interactions
2 types
- competition, both species suffer
2. herbivory, predation and parasitism, one species benefits at the expense of the other
Positive biotic interactions
2 types
- Mutualism, both species benefit
2. Commensalism, one species is benefitted, other is unaffected
Two definitions of competition
Struggle of two or more organisms to exploit same limited resource
Or
When interactions between two or more individuals or populations adversely affects growth, fitness or population size of other
Competitive exclusion
“when two species are grown in the same environment one either wholly or partially displaces the other”
Why is there limited evidence of competitive exclusion in the field?
existing distributions result from past competition
Example of obvious competition in disturbed habits
between crops and weeds
Most intense (intra-specific) competition
between young individuals of same species, very similar resource requirements
Direct form of competition in plants
Allelopathy
Most competition in plants is indirect or direct?
indirect
Example of allelopathy
plants exude chemicals which inhibit growth if other species
eg: rhododendrons
Chemical inhibition can occur…
between species or between seedlings of the same species
Intra and inter - specific competition more complex in plants or animals?
and why?
animals,
more mobile, diverse behaviours etc.
Competition for what in animals
3
living space
food
breeding partners
Animal competition
Interference
aggression/ territorial behaviour
Animal competition
predation
but depresses abundance of food (prey or host)
Mutualism
Both species benefit
Example of mutualism
lichen
Lichens- associate between a fungus and algae
Example of mutualism
nitrogen-fixing bacteria
Symbiotic nitrogen-fixing bacteria living within root nodules of legumes
Example of mutualism
mycorrhizal fungi
Mycorrhizal fungi in roots of trees and shrubs
Commensalism
one species benefitted, other unaffected