amqua teaching workshop, aug. 10-11, 2010 fossil pollen, vegetation, no-analogue plant communities,...

AmQua Teaching Workshop, Aug. 10-11, 2010AmQua Teaching Workshop, Aug. 10-11, 2010

Fossil pollen, vegetation, no-analogue plant communities, and species niches

Jack WilliamsDepartment of GeographyCenter for Climatic Research (CCR)University of Wisconsin - Madison

Support (Funding & Infrastructure)

Neotoma DB

Outline1. A Pollen Primer2. Exercise & Discussion: Species Migration3. No-Analogue Communities4. Niche Theory and Novel Climates

AmQua Teaching Workshop, Aug. 10-11, 2010

Key Points1. Fossil pollen grains preserved in lakes and mires are a

primary source of information about past vegetation

2. Migration was a primary ecological response to the Quaternary ice ages, with species range shifts measuring hundreds to thousands of kilometers.

3. These migrations were highly individualistic – no two species behaved alike.

4. As a result novel communities emerged, with no modern counterpart.

5. Individualistic species dynamics and novel communities are consistent with species having unique fundamental niches and novel climates in the past.

6. Novel future climates likely to emerge this century… will novel communities also emerge?


1. Fossil pollen: a paleovegetation proxy

Lake Coring at Silver Pond, OH

1m sediment core section from Anderson Pond, TN

PollenEmission

Transport

Deposition

Mud

Sample Pollen Grains Lake

Advantages• Quantitative measures of

plant abundance

• Continuous sedimentation

• Precise radiocarbon ages: <100 yr precision

• Many sites

• Multiple proxies (charcoal, isotopes, biomarkers, etc.)

Limitations• Labor intensive

• Variable taxonomic resolution (species – family)

• ~Decadal resolution (1 cm3 mud ~ 10 years)

• Incomplete census of vegetation


Pollen Diagram: Appleman Lake, IN

Gill et al., 2010 Science

(Spr

uce)

(Pine

)(O

ak) (A

sh)

(Hop

horn

beam

/

Ironw

ood) (R

agwee

d)

(Gra

ss)

No-Analog Communities: Composed of extant species, in combinations not found at present

Time


2. Migration was a primary ecological response to the Quaternary ice ages

3. These migrations were highly individualistic – no two species behaved alike.


When climates change, species have four choices

• Sit tight and hang on• Migrate• Evolve• Die


Pollen Viewer

21,000 11,000 Modern15,000 7,000

%

Vegetational Responses: Range and Abundance Shifts

%

%

%

No Data

Williams et al. (2004) Ecological Monographs

SprucePollen

Ice IceIce

http://www.ncdc.noaa.gov/paleo/pollen/viewer/webviewer.html

(or, Google “Pollen Viewer”)

(note: requires Java installed on your Browser)


…


4. As a result novel communities emerged, with no modern counterpart.

5. Individualistic species dynamics and novel communities are consistent with species having unique fundamental niches and novel climates in the past.


No-Analogue Communities: Species that today are mostly disjunct were closely associated in past

21,000 1,00013,00015,000

Fraxinus (Ash)

Picea (Spruce)


1,00013,00015,000




(Spr

uce)

(Pine

)(O

ak) (A

sh)

(Hop

horn

beam

/

Ironw

ood) (R

agwee

d)

(Gra

ss)

No-analogue communities prevail at Appleman Lake, IN between ca. 13,700 and 11,900 years ago

Time


We can quantify the dissimilarity between fossil and modern pollen assemblages

Squared-Chord Measure of Dissimilarity between pollen assemblages i and j

dij=dissimilarity between assemblages i and jpik=relative abundance of taxon k in assemblage i


ExampleTAXON Abund i Abund j Sqrt(i)-Sqrt(j) Running Sum

of absolute difs.

Running Sum ^2 (SCD)

Picea (spruce)

0.64 0.36 0.20 0.2 0.04

Pinus (pine) 0.30 0.30 0.00 0.2 0.04

Quercus (oak)

0.00 0.30 -0.547 0.747 0.558

Tsuga (hemlock)

0.10 0.05 0.0926 0.839 0.705

Relative abundances expressed as fractional values (between 0 and 1)


When is a fossil pollen sample a ‘no analogue’

sample?

1) It must have a high dissimilarity to all modern pollen samples

2) Requires setting a ‘no-analogue’ threshold of dissimilarity

North American Pollen Database(Whitmore et al. 2005)


We can map the minimum dissimarity as an indicator of no-analogue communities

Minimum Dissimilarity from Present (pollen)


Niche Theory: Four Fundamental Concepts

Climate Variable 1

Clim

ate

Var

iab

le 2

1. Fundamental Species Niche: the set of all environments in which a species can grow and reproduce

2. Realized Environmental Space: The set of environments existing at a moment in time.

3. Potential Niche: The set of environments available to a species at a moment in time (i.e. the intersection of fundamental niche and realized environmental space)

4. Realized Niche: The set of environments occupied by a species

Fundamental Niche

Realized Environmental Space

Potential Niche

Realized Niche

redrawn from Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220


Niche theory predicts that no-analog communities can form in response to novel environments

Climate Variable 1

Clim

ate

Var

iab

le 2

1. Species’ fundamental niches may extend and overlap outside the current realized climate space

2. Past climates may differ substantially from modern climates.

3. Novel climates: climatic conditions that do not exist today.

4. No-analogue associations of species may form under climates unlike any at present.

redrawn from Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220

Species 2

Species 1

Novel climate

No-analogue speciesassociation

Past climate

Climate today


We can use the contemporary range of species to estimate their climatic niche

Jan

ua

ry T

em

pe

ratu

re

Thompson et al. 1999

(White spruce)

Jan

ua

ry P

reci

pita

tion

(m

m)


Web Resources – Niche Visualizations1) Atlas of Relations Between Climatic Parameters and

Distributions of Important Trees and Shrubs in North America– http://pubs.usgs.gov/pp/p1650-b/– GOOGLE: Thompson tree atlas

2) North American Modern Pollen Atlas– http://www.ncdc.noaa.gov/paleo/pubs/williams2

006/williams2006.html– GOOGLE: modern pollen atlas

Extra credit exercise on handout: Map your own niche!


The no-analog communities are linked to highly seasonal insolation and temperature, wet conditions, and the decline of North American megafauna

Jackson and Williams 2004 AREPSKutzbach et al. 1998 QSR

North American Climates: Modern vs. 14,000 yr BP

Evidence for high temperature seasonality

Fraxinus presentFraxinus absent

Moreseasonal

Lessseasonal

Modern Geographic and Climatic Range of Fraxinus (Ash)

Thompson et al. 1999, USGS Atlas


6. Novel future climates likely to emerge this century… will novel communities also emerge?


No-Analogue Climates: Past, Present, Future

2050

Modern15 ka

(°C)

(°C

)

Climate simulations from CCSM climate model (Liu et al. 2009)

Veloz et al. unpub.


Novel Climates Most Common in Tropics

A2 (CO2atm=850ppm by 2100AD)

B1(CO2atm=540ppm by 2100AD)

• Novel climates projected to emerge in tropics and subtropics– Logical outcome of warming

world

• Combined with many other anthropogenic drivers – Land use, invasive species,

nutrient cycling…

• We should expect the unexpected

Williams et al. (2007) PNAS

Projected Distributions of Novel Climates by 2100AD

Low Climatic Dissimilarity High


The closest future climatic analogs don’t always come from modern climate!

Veloz et al. unpub.

Climate simulations from CCSM climate model (Liu et al. 2009)


Sporormiella, a ‘megafauna proxy’

Burney et al. 2003 PNAS

•Sporormiella, a dung fungus found in many species, including mammoths (van Geel et al. 2008)

•Spores found in high abundances (>2%) in Pleistocene sediments (Davis & Shafer 2006)

•A proxy for mammalian dung loadings and mammalian herbivore biomass

•Also preserved in lakes & mires allows precise sequencing of vegetation change and megafaunal decline

Jacquelyn Gill




(Spr

uce)

(Pine

)(O

ak) (A

sh)

(Hop

horn

beam

/

Ironw

ood) (R

agwee

d)

(Gra

ss)


Time


Other sites confirm linkage between Sporormiella

decline, no-analog plant communities, and fire

regime shift

Gill et al., in press, Science

Red=charcoal (inverted scale)Black=Minimum SCDBlue=Sporormiella

Time


EXTRA CREDIT EXERCISE: Visualizing Niches

AmQua Teaching Workshop, Aug. 10-11, 2010IPCC 2007 WG1 Ch6 Fig. 6.3

Gre

en

lan

d

Te

mp

era

ture

Age (103 years before 2005)

The Quaternary is an excellent model system for studying biotic responses to climate change

1. Frequent, large, and rapid climate variations

2. Data-rich – in both climatic and ecological data

Ice Cores

Tree Rings

Loess

Ocean Sediments

Speleothems

LAKES


– C:\Jack\Figures\OthersFIgs\GISPtempLGM-0.JPG

(Grootes et al. 1993 Nature)

The Last 20,000 yrs

Temperature Variations Since the Last Glacial Maximum

GISP2 Ice Core (Greenland)

PLEISTOCENE || HOLOCENE

Bølling-Allerød

• Global temperature: rose ~5°C

• Ice sheets melted• Sea level: rose by

120m• CO2atm: rose from

190 to 280 ppm

Diff

ere

nce

fro

m p

rese

nt (

°C)

TimeAge (years before present [BP])


Dramatic Biotic Responses21,000 11,000 Modern15,000 7,000

%

Spruce Pollen Distributions: 21000 years ago to present

%

%

%

No Data


SprucePollen

Ice IceIce

Google: Pollen Viewer

• Species ranges shift 102-103km• Humans enter the Americas• 34 genera of vertebrates go

extinct• Species reshuffle, new

communities emerge

http://www.jqjacobs.net/anthro/paleoamericans.html



Gill et al., in press, Science

(Spr

uce)

(Pine

)(O

ak) (A

sh)

(Hop

horn

beam

/

Ironw

ood) (R

agwee

d)

(Gra

ss)


Time


Species that today are mostly disjunct were closely associated in past

Percent Pollen

No Data

Fraxinus (Ash)

Picea (Spruce)


1,000 years ago15,000 years ago


No-analog communities most common between 17,000 and 12,000 years BP

Minimum Dissimilarity from Present (pollen)

Squared-Chord Measure of dissimilarity between pollen assemblages i and j

Modern Pollen Samples

pik=relative abundance of taxon k in assemblage i


The No-Analog Problem: How do we study ecosystems we’ve never seen?

1. Why were past communities unlike any today?

– Will novel communities develop in response to 21st-century climate change?

2. Are the no-analog communities and the megafaunal extinction linked?

– What are the ecological consequences of the current wave of extinctions?


Thesis: The late-glacial no-analog plant communities caused by novel climates and altered disturbance regimes.

Vegetation

Fire Mammals

Climate HumansKey Drivers:Climate1. High temperature seasonality

2.High precipitation

Humans(?)3. Megafaunal extinction and enhanced fire regime


Niche Theory: no-analog communities arise in response to novel environments

Jackson and Overpeck (2000) Paleobiology 26 (supp) 194-220Williams and Jackson (2007) Frontiers in Ecology and Evolution

Climate Variable 1

Clim

ate

Var

iab

le 2

Species 1

Species 2

‘No-analog’ or ‘novel’climate

No-analog species association

Present climate domain“Climate Space”

Species fundamental niche

Past climate domain


The no-analog communities are linked to higher-than-present temperature seasonality

Jackson and Williams 2004 AREPSKutzbach et al. 1998 QSR

North American Climates: Modern vs. 14,000 yr BP

Evidence:1.Global Climate Models: late-glacial climates were more seasonal than present2.Apparent truncation of potential species niches by the seasonal edge of the modern climate envelope


Moreseasonal

Lessseasonal

Modern Geographic and Climatic Range of Fraxinus (Ash)



Last 21,000 years: Temperature seasonality correlates well to no-analog communities

No-Analog Communities (Min. SCD)

TemperatureSeasonality

Williams and Jackson 2007 Time


Implication: species distributional models that are based on observed species-climate relationships should perform poorly

for novel climates… surprises are likely


Climate Variable 1

Clim

ate

Var

iab

le 2

Species 1

Present climate domain“Climate Space”

Species fundamental niche

Past climate domain

Species realized niche


But wait: what about that megafaunal extinction?

No-Analog Communities (Min. SCD)

TemperatureSeasonality

Williams and Jackson 2007

Hypotheses:1.No relationship2.Habitat loss megafaunal extinction3.Megafaunal extinction altered herbivory vegetation change

Pleistocene megafauna

http://www.jqjacobs.net/anthro/paleoamericans.html

Problem: The temporal sequence of vegetation change and megafaunal extinction is imprecisely known.1.Pollen collected from lakes & mires2.Bones collected from caves, digs, etc.

Time


Appleman Lake: the Sporormiella decline precedes the no-analog communities

Gill et al., in press, Science•Sporormiella decline: 14.8 to 13.7 kyr•First charcoal peak: 14.1 kyr

(Spr

uce)

(Pine

)(O

ak) (A

sh)

(Hop

horn

beam

/

Ironw

ood) (R

agwee

d)

(Gra

ss)

Time


Implications for the Future

A2 (CO2atm=850ppm by 2100AD)

B1(CO2atm=540ppm by 2100AD)

• Novel climates projected to emerge in tropics and subtropics– Logical outcome of warming

world

• Combined with many other anthropogenic drivers – Land use, invasive species,

nutrient cycling…

• Expect the unexpected – ecological surprises may be the new normal.

Williams et al. (2007) PNAS

Projected Distributions of Novel Climates by 2100AD


Summary1. Both global-change ecologists and paleoecologists

face the ‘no-analog’ problem

2. No-analog communities linked in past to:– Novel climates (higher-than-present temperature

seasonality, high precipitation)

– Megafaunal extinction and altered disturbance regime

3. Novel climate states pose a major challenge for observationally based species distribution models

4. We are pushing the climate system to a geologically novel state: we should expect surprises.


Some of these surprises may be faster than we think

“Beetles are the bullet that killed the pines, but drought pulled the trigger”


Species Responses to Quaternary Climate Change

PatternsSpecies migrate. Ranges are highly dynamic.

This migration is individualistic – i.e. communities do not move as intact units.

Implications: Co-evolutionary relationships among many species must be fairly weak.

Species must be able to survive some range of climate variability.


1) Species ranges are highly dynamic

21,000 11,000 Modern15,000 7,000

%

Vegetational Responses: Range and Abundance Shifts

%

%

%

No Data


SprucePollen

Ice IceIce

Google: Pollen Viewer


OUTLINE

I. Setting the Stage: Climate Variations and Quaternary Ice Ages

II. Species Migration

III. No-Analog Communities and Climates

IV. Genetic Legacies

V. Extinction


Plant taxa that rarely co-occur today…(Spruce) (Ash)

Thompson et al. (1999a,b) Atlas of Woody Plant Distributions…


… are closely associated in the past ‘no-analog’

communities

21,000

Percent

1,00013,00015,000

No Data

Fraxinus (Ash)

Picea (Spruce)


21,000 1,00013,00015,000


No-analog communities most common during the last deglaciation

(Williams et al. in press Ecological Monographs)


Niche theory predicts that no-analog communities should occur in response to novel environmental conditions.


Climate Variable 1

Clim

ate

Var

iab

le 2 Species 4

Species 2

Species 3

Species 1

‘No-analog’ or ‘novel’climate

No-analog association

Disappearing climate‘Realized’ climates

Time tPresent


Late-glacial no-analog communities linked to no-analog (highly seasonal) climates


Moreseasonal

Lessseasonal

Williams and Jackson 2004 AREPSKutzbach et al. 1998 QSR

Modern Range Modern Climate SpaceClimate Simulations: Modern, 14,000 yr BP


Williams and Jackson (2007) Frontiers in Ecology and the Environment

amqua teaching workshop, aug. 10-11, 2010 fossil pollen, vegetation, no-analogue plant communities,...

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