Warming experiments underpredict plant phenological responses to

climate change

Elizabeth M. WolkovichUniversity of British Columbia

Ben Cook & collaborators:J. AllenT. AultJ. BetancourtK BolmgrenE. ClelandT. Crimmins J. DaviesN. KraftS. MazerG. McCabeB. McGillC. ParmesanS. PauJ. RegetzM. SchwartzS. Travers

Warming experiments underpredict plant phenological responses to

climate change

Elizabeth M. WolkovichUniversity of British Columbia

Warming by 2099

Changes relative to last 20th century A2 scenario, IPCC, WG1 summary, 2007

How will species respond?

Changes relative to last 20th century A2 scenario, IPCC, WG1 summary, 2007

How will species respond?

Changes relative to last 20th century A2 scenario, IPCC, WG1 summary, 2007

Extinctions

How will species respond?

Changes relative to last 20th century A2 scenario, IPCC, WG1 summary, 2007

Spatial shifts Temporal shifts

Extinctions

Critical predictor & trait:

Critical predictor & trait:

Ties to plant species:

Critical predictor & trait:

Ties to plant species:- Performance

Cleland et. al., in press, Ecology

Critical predictor & trait:

Ties to plant species:- Performance

Cleland et. al., in press, Ecology

- Extinctions

Critical predictor & trait:

Ties to plant species:- Performance

Cleland et. al., in press, Ecology

- Extinctions

- Ranges

Critical predictor & trait:

Ties to plant species:- Performance

Cleland et. al., in press, Ecology

- Extinctions

- Ranges

Controls:- Trophic webs

- Ecosystem functioning

Plant phenology most reported biotic response to climate change

Plant phenology most reported biotic response to climate change

Plant phenology most reported biotic response to climate change

Experiments used for over 20 years

Do experiments and observations predict the same responses to

warming?

Experiments Observations

vs.

Global synthesis of warming effects on plant phenology

Global synthesis of warming effects on plant phenology

Chinnor, UK

Global synthesis of warming effects on plant phenology

Chinnor, UK

Washington, DC

Harvard Forest

Global synthesis of warming effects on plant phenology

experimentsobservations

Common metric for both data types

- Calculated change in days per °C

- Hierarchical mixed-effects models- Accounts for non-

independence among sites and species

Long-term records consistent with other large analyses

mixed-effects model means +/- SE

Long-term records consistent with other large analyses

mixed-effects model means +/- SE

Experiments show smaller effects

Wolkovich et. al., in press, Natureflowering: F1,34 = 9.7, p = 0.004leafing: F1,18 = 2.8, p = 0.1

Experiments show smaller effects

Wolkovich et. al., in press, Nature

1,634 species

flowering: F1,34 = 9.7, p = 0.004leafing: F1,18 = 2.8, p = 0.1

Experiments show smaller effects

Wolkovich et. al., in press, Nature

1,634 species matching species

flowering: F1,34 = 9.7, p = 0.004leafing: F1,18 = 2.8, p = 0.1

Experiments show smaller effects

Wolkovich et. al., in press, Nature

1,634 species matching species

Experiments show smaller effects

1,634 species matching species

binomial tests: flowering & leafing: p = 0.02

Why do experiments underpredict long-term responses?

Difference not due to:

• Species-sampling

• Timescales & genotypic change

• Degree of warming

• Habitat, latitude. . .

Why do experiments underpredict long-term responses?

Why do experiments underpredict long-term responses?

flowering: F2,22 = 7.2; p = 0.004

Species diversity in responses to temperature

Wolkovich et. al., in press, Nature

Species diversity in responses to temperature

Poa annua

Acer saccharum

Wolkovich et. al., in press, Nature

Predicting species’ variation

Predicting species’ variation

• Early-season species

• Annuals vs. perennials

Predicting species’ variation

• Early-season species

• Annuals vs. perennials

Predicting species’ variation

• Early-season species

• Annuals vs. perennials

• Functional traits: Leaf-tissue density

Predicting species’ variation

• Early-season species

• Annuals vs. perennials

• Functional traits: Leaf-tissue density

• No variation with functional groups

Predicting species’ variation

• Early-season species

• Annuals vs. perennials

• Functional traits: Leaf-tissue density

• No variation with functional groups

• Phylogenetic approach

Experiments underpredict phenological responses

to climate change

Experiments Observations

vs.

Conclusions

•Consistent mean response of 5-6 days/˚C

•Warming experiments underpredict 4-8X vs. observations

•Models based on warming experiments should be re-evaluated

AcknowledgementsData managers: David Inouye and George Aldridge (Gothic), Paul Huth, Shanan Smiley, and John Thompson (Mohonk Preserve), John O'Keefe (Harvard), Elisabeth Koch, Wolfgang Lipa and all those who contributed to PEP725 Pan European Phenology Data, Tim Sparks (Marsham), Richard Primack and Abe Miller-Rushing (Concord), F. Stuart Chapin, Niels M. Schmidt, Melissa Martin, Jennifer Dunne, Rebecca Sherry, Xavier Morin, Dustin Bronson and K. Dunnell, Ethel & Gunnar Johansson

Trait data: W. Wen

Photo credits: C. Chen, J. Dukes, C. Kopp, R. Montgomery, N. Sanders

Degree of warming

Davies, et al., in review

Most studies based on long-term records

Marsham

ConcordHarvard Forest

Mohonk

Most studies based on long-term records

Marsham

Most studies based on long-term records

Marsham

Most studies based on long-term records

Marsham

Mohonk

Most studies based on long-term records

Marsham

Concord

Mohonk

Most studies based on long-term records

Marsham

ConcordHarvard Forest

Mohonk