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Biodiversity and DGVMsI. Colin Prentice, QUEST

Silwood Park2 June 2009

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What (some) DGVMs can do (reasonably) well

• Global carbon and water cycle properties (yes), feedbacks (maybe)• Broad-scale biogeographic patterns• Global patterns of trace gas emissions (including fires)

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Carbon and water cycling in LPJ

• Photosynthesis from simplified Farquhar model with optimized Vcmax

• Stomatal conductance maintains constant ci/ca when Emax * W/Wmax not exceeded, else is adjusted to maintain this rate of ET• ET from Monteith (1995): Priestley-Taylor, modified by stomatal conductance

PN Foster et al. (work in progress)

Xu-Ri et al. (work in progress)

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Limitations of DGVMs (1)

• PFTs are too few (5-10) => “plasticity dilemma”• Attribution of generic “literature values” for traits • No fundamental explanation for niche space of each PFT• => Divergent predictions of “biome shifts” (vegetation structural changes)

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Limitations of DGVMs (2)

• Poor representation of functional diversity within communities• Life history trade-offs (e.g. leaf economics spectrum) not modelled• => Compositional responses to environmental variability and change probably wrong• => Potential for wrong biogeochemical responses as well?

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Can DGVMs reliably predict responses to climate change on decadal-centennial time scales?

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Can DGVMs reliably predict responses to climate change on decadal-centennial time scales?

• Probably not

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Can DGVMs reliably predict responses to climate change on decadal-centennial time scales?

• Probably not• Iconic example: “Amazon die-back”

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Relevant scientific advances for next generation DGVMs

• Rediscovery of functional morphology• Link between plant hydraulics and photosynthesis• Recognition of biophysical constraints and trade-offs• Application of economic approaches to plant function and co-existence• Comparative data to test hypotheses and assign functional properties to PFTs

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Next steps for DGVMs

• Define a small set of model parameters for a plant• Define a pathway from widely measured traits to fundamental variables in models

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The List (to be developed.....)

wood anatomy/density sapwood permeabilityleaf hardness wilting pointleaf size/dissection boundary-layer conductance13C ci/ca “operating point”bark thickness fire resistance..... .....

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Conclusion: including biodiversity in DGVMs

• Characterize functional variation among species in terms of processes• A longer list of PFTs: sample from a continuum of traits, allowing for trait covariation• Exploitation of quantitative trait data at species level [TRY data base]• New benchmarks for DGVMs: compositional transects, climate responses... [BBS project]