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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

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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)

C

S

R

Now we rearrange this shape a little …

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C

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C S

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CSR

An intermediate type exists …

C

R S

CSRCR CS

SR

… with further intermediates here

C

R S

CSRCR CS

SR

… and yet more intermediates here

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