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A brief tutorial on C-S-R strategy theory
“ The external factors which limit the amount of living and dead plant material present in any habitat may be classified into two categories ”
Opening sentence from J P Grime’s 1979 book Plant Strategies and Vegetation Processes
Category 1: Stress
Phenomena which restrict plant production
e.g. shortages of light, water, mineral nutrients, or non-optimal temperature
Category 2: Disturbance
Phenomena which destroy plant production
e.g. herbivory, pathogenicity,trampling, mowing, ploughing, wind damage, frosting, droughting, soil erosion, burning
Habitats may experience stress and disturbance to any degree and in any combination
Stress
Disturbance
Low or moderate combinations of stress and disturbance can support vegetation …
Stress
Disturbance… but extreme combinations of stress and disturbance cannot
There are other ways of describing stress and disturbance
Stress
Disturbance
Habitat duration
Habitat productivity (= resource level)
So, is ozone a stress or a disturbance?
It is a stress because its physiological action is to restrict plant production
But it is also a disturbance because it can partially or wholly destroy plant production
Now, in the domain where vegetation is possible …
Stress
Disturbance
… plant life has evolved strategies for dealing with the different combinations
Competitor where both S and D are low
Stress-tolerator where S is high but D is low
Ruderal where S is low but D is high
C
S
R
C
S
R
No plant strategies occur in the ‘impossible domain’
(different parts of this domain are devoid of vegetation for different reasons, but that is another story)
To recreate these C-S-R plant functional types within the self-assembling model …
… we changed the specifications controlling morphology, physiology and reproductive behaviour …
Combinations of plant attributes for seven C-S-R functional types ————————————————————————————— Functional Module Module Propensity to type size longevity flowering ————————————————————————————— C High Low Low S Low High Low R Low Low High SC Medium Medium Low SR Low Medium Medium CR Medium Low Medium CSR Medium Medium Medium —————————————————————————————
How does SAM re-create real vegetation?
The high dimensionality of real plant life is reduced to plant functional types
“ There are many more actors on the stage than roles that can be played ”
Do just seven functional types provide enough precision?
The C-S-R system recognizes nineteen different functional types
The seven currently used by SAM are just the main ones; intermediate types could be added later
How do we know what functional types are present in real vegetation?
There is a look-up list containing 1000 European species
For any others, simple tools can allocate functional type rapidly
See the web page ‘Allocating C-S-R types’
Do SAM’s predictions come in the form of species or functional types?
As plant functional types; however, this makes the interpretation of vegetation processes much simpler and more general
What does that mean, exactly?
Functional types provide continuity when relative abundances, and even identities, of the constituent species are in flux
This makes it possible to link communities which are separate in time and space into one conceptual framework
Then effects of ozone on biodiversity, vulnerability and stability can be compared and mapped across Europe
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