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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

Low or moderate combinations of stress and disturbance can support vegetation … … but extreme combinations of stress and disturbance cannot

There are other ways of describing stress and disturbance Habitat productivity (= resource level) Stress Disturbance Habitat duration

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-tolerator where S is high but D is low S Stress Ruderal where S is low but D is high Competitor where both S and D are low C R Disturbance … plant life has evolved strategies for dealing with the different combinations

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)

Now we rearrange this shape a little … C R

S C R

S C R

S C R

S C R

S C R

S C R

C S R

C S R

C S R

C R S

C R S

C R S

An intermediate type exists … C CSR R S

… with further intermediates here C CR CS CSR R SR S

… and yet more intermediates here C CR CS CSR R SR S

To recreate these C-S-R plant functional types within the self-assembling model … … we changed the specifications controlling morphology, physiology and reproductive behaviour …

We use one morphological trait, one physiological and one reproductive to distinguish between the seven types. However, these are really super-traits, e.g. longevity in the absence of resource uptake is entrained with relative growth rate, specific leaf area, palatability and decomposability. With three levels possible within each of three traits, 27 different types could be constructed. However, we model only seven types; the other twenty would include ‘Darwinian demons’ that do not respect evolutionary tradeoffs.

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