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This is a presentation by Titles A model involving self-assembling modular plants Roderick Hunt, Ric Colasanti & Andrew Askew University of Sheffield It is all about SAM

Community image This is what a community of virtual plants looks like Contrasting tones show patches of resource depletion

CSR type, frame 1 This is a single propagule of a virtual plant It is about to grow in a resource-rich above- and below-ground environment

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ditto f. 20 The plant has produced abundant growth above- and below-ground and zones of resource depletion have appeared

Binary tree diagram Above-ground binary tree base module Below-ground binary tree base module Above-ground array Below-ground array Above-ground binary tree ( = shoot system) Below-ground binary tree ( = root system) A branching module An end module Each plant is structured like this This is only a diagram, not a painting !

Water and nutrients from below-ground The branching (parent) modules can pass resources to any adjoining modules Explanation The end-modules capture resources: Light and carbon dioxide from above-ground In this way whole plants can grow

The virtual plants interact with their environment (and with their neighbours) just like real ones do They possess most of the properties of real individuals and populations Explanation For example …

S-shaped growth curves

Older plant, low nutrient Partitioning towards the resource-poorer half of the environment

Allometric coefficients Maintaining a functional equilibrium above-and below-ground

Older plant, asymmetric nutrients Foraging towards resources in a heterogeneous environment

Dense population And when many plants are grown together in a dense population …

Self-thinning … they exhibit self-thinning but as the plants are 2-dimensional the thinning slope is not –3/2

All of these plants have the same specification ( modular rulebase ) But this specification can easily be changed if we want the plants to behave differently… Explanation

For example, we can recreate J P Grime’s system of C-S-R plant functional types For this, the specifications we need to change are those controlling morphology, physiology and reproductive behaviour … Explanation

Modular rulebase

With three levels possible in each of three traits, 27 simple functional types could be constructed However, we model only 7 types ; the other 20 include Darwinian Demons that do not respect evolutionary tradeoffs Explanation

Let us see some competition between different types of plant Initially we will use only two types … Explanation

R-CSR-R, frame 1 Small size, rapid growth and fast reproduction Medium size, moderately fast in growth and reproduction

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Now let us see if white always wins This time, its competitor is rather different … Explanation

CSR-C-CSR, frame 1 Medium size, moderately fast in growth and reproduction Large size, very fast growing, slow reproduction

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The huge blue type has out-competed both of the white plants, both above- and below-ground And the simulation has run out of space … Explanation

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So competition can be demonstrated realistically … … but most real communities involve more than two types of plant Explanation

We need seven functional types to cover the entire range of variation shown by herbaceous plant life To a first approximation, these seven types can simulate complex community processes very realistically Explanation

For example, an equal mixture of all seven types can be grown together … … in an environment which has high levels of resource, both above- and below-ground Explanation

7 types, high nutrient, f.1

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The blue type has eliminated almost everything except white and green types And the simulation has almost run out of space again … Explanation

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Now we grow the equal mixture of all seven types again … … but this time the environment has low levels of mineral nutrient resource, as indicated by the many grey cells Explanation

7 types, low nutrient, f.1

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White, green and yellow finally predominate … … blue is nowhere to be seen … Explanation … and total biomass is much reduced

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Environmental gradients can be simulated by increasing resource levels in steps Explanation Whittaker-type niches then appear for contrasting plant types within these gradients

Whittaker-type gradient (types)

Next we grow the equal mixture of all seven types again … … but this time under an environmental gradient of increasing mineral nutrient resource Explanation

Stress-driven hump Greatest biodiversity is at intermediate stress

Now, environmental disturbance can be defined as ‘removal of biomass after it has been created’ Explanation For example, grazing, cutting, burning and trampling are all forms of disturbance

In our model, ‘trampling’ can be applied simply by removing shoot material from certain sizes of patch at certain intervals of time and in a certain number of places Explanation Other forms of disturbance can be simulated by varying each of these factors

So we grow the equal mixture of all seven types again … … but this time under an environmental gradient of increasing ‘trampling’ disturbance Explanation

Disturbance-driven hump Greatest biodiversity is at intermediate disturbance … … but the final number of types is low

Environmental stress and disturbance can, of course, be applied together Explanation This can be done in all forms and combinations

Again we grow the equal mixture of all seven types … … but with one of seven levels of stress and seven levels of disturbance in all factorial combinations Explanation

Productivity-driven hump Greatest biodiversity is at intermediate productivity

The biomass-driven humpbacked relationship is one of the highest-level properties that real plant communities possess Yet it emerges from the model solely because of the resource-capturing activity of modules in the self-assembling plants Explanation

Productivity-driven hump

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