Quaternary environments and N. hemisphere temperate

forests Distribution Holocene dynamics The interglacial cycle “Long core” records Last Glacial Maximum refuges Migrations (rates and agents) Genetic divergence Quaternary extinctions

Global distribution of temperate forests

Temperate forest

30°N

45°N

60°N

45°S

60°S

30°S

15°S

15°N

Eq.

Pollen sites,

easternNorth

America

Pollen diagram, Kirchner Marsh, Minnesota.

from: Webb (1980) J. Interdisciplinary History, 10, 749-772.

Reconstructing post-glacial climate change (Kirchner Marsh, MINN)

Reconstructing post-glacial vegetation change at a site

The post-glacial (Blytt-Sernander) sequence

Interglacial cycle of

vegetation and soils

(based on Iversen, 1948)

Interglacial vegetation succession, Japan

ClimatePhase Dominants Temperature Moisture

Upper Cryptomeria, Sciadopitys Temperate Wet

Middle Cyclobalanopsis, Warm Wet Castanopsis

Lower Fagus, Lepidobalanus Cool Wet

from: Miyoshi et al., (1999) Rev. Palaeobot. Palynol, 104, 267-283.

Is there a repetitive

interglacial cycle?

e.g. vegetation succession in mid to late Quaternary

interglacials in Britain

Does an increase in Pinus signal the end of an

interglacial?

Kirchner Marsh, MINN.

> 50 ka >100 ka

Long cores from temperate forest areas

30°N

45°N

60°N

45°S

60°S

30°S

15°S

15°N

Eq.

from: PAGES website

Pollen record, Lago di

Monticchio (Italy)

Pollen record, Grande

Pile (France)

From: Guiot (1998) Nature 388, 25-27.

Pollen record, Lake Biwa

(Japan)Pinus = cool indicator;

Cryptomeria = warmIndicator;

Artemisia -grass-herb (not shown)

“steppe/tundra” in full-glacial phases

Pollen record, Carp Lake, WA.

from: Whitlock and Bartlein (1997) Nature, 388, 57-61.

from: Whitlock and Grigg, in: Webb et al., (1999) Mechanisms of Global Change at Millenial Time Scales, AGU Monograph, p 227-

241.

Heinrich events

recorded at Lake Tulane,

FLA.

Present (potential)vegetation

of North America

Biome maps from: www.esd.ornl.gov/projects/qen

LGM vegetatio

n(18 ka 14C yrs BP):North

America

Present (potential

)vegetatio

n of Europe

LGM vegetatio

n(22-14 ka

14C yrs BP):

Europe

LGM (a) and present (b) pollen and vegetation (c,d) patterns in East Asia

from

: H

arr

ison e

t al. (

20

01

) N

atu

re 4

13

, 1

29

-13

0.

NB continental shelf extent

Reconstructing LGM refuges and post-glacial migrations: isopoll data

from: Davis and Shaw (2001) Science 292, 673-679.

LGM refuges (R) and post-glacial

isochrons in eastern North

America. Where there

separate Atlantic and Gulf refuges?

R?

R?

R?

R?White pine

E. hemlock

Oaks

Elms

How quickly did trees migrate in eastern North America in the post-

glacial?

0 100 200 300 400 500

Jack/Red pineWhite pine

SpruceLarch

ElmHemlock

Balsam firMapleBeech

OakHickory

Chestnut

m / yr

Data: Davis; in West et al. (1980) “Forest Succession: Concepts and Applications”. Springer-Verlag p. 153; and Delcourt and Delcourt (1987) “Quaternary Ecology” (after Webb, 1986)

(=a x b)

(a)

(b)

(c)

(=a x c)

Was the rate of post-glacial

migration controlled by

rates of climatic

change or seed size?

m /

year

Data: see previous slide and USDA (1974) “Seeds of Woody Plants in the

United States” Agric. Handbook No. 450.

500

400

300

200

100

0

seed wt. (mg)1 10 100 1 000 10 000

oaks

whitepine

sprucelarch

elm

hemlockhickory

maplefir

beech

chestnut

jack pine

red pine

Are seed-caching birds the main agents of

dispersal in post-glacial time for ‘nut trees’?

Fagus grandiflora

Quercus macrocarpa

blue jay passenger pigeon

see: Webb (1986) Quat. Res. 26, 367-375for discussion

Postglacial fossil finds:passenger

pigeon (dots)

and blue jay

(triangles )

from: Delcourt and Delcourt (1987) “Quaternary Ecology”

Were some endochorous temperate trees marooned?

(i.e. refugial relicts?)e.g. Maclura pomifera

(osage orange) fruit weighs up to 1 kg

Source: USDA Handbook - Silvics of Forest Trees

Range

Was this a product of the extinction of

potential megafaunal

vectors?

e.g. Megalonyx

jeffersoni(Jefferson’s

ground-sloth)extinct by 10ka BP

Did post-glacial migration result in reduced genetic diversity in northern

populations?Allelic diversity

low highfrom: Cwynar and MacDonald (1988) Amer. Nat. 129, 463-469.

Colonizationdate in ka BP

from pollen data

Which refugial

populations supply the migrants?

e.g.Fagus crenata

(a montane species during interglacials) recolonized northern

Honshu and Hokkaido from

northern coastal refuges after LGM

LGMcoastalrefuges

from: Davis and Shaw (2001) Science 292, 673-679.

Hypothetical refugia and migration paths of Alnus rubra

since the LGM based on genetic variation

from: Hamann et al., (1998) Can. J. Forest Res., 28, 1557-1565.

Post-glacial colonization routes of tree species based

on DNA variation

Fagus sylvatica Quercus sp.

Taberlet et al., (1998) Molecular Ecology 7, 453-464

Post-glacial colonization routes of tree species based

on DNA variation

Taberlet et al., (1998) Mol. Ecol. 7, 453-464; Scottii et al. (2000) Mol. Ecol. 9, 699-708.

Abies alba Picea abies

Post-glacial colonization routes of animals based on DNA

variation

from: Hewitt (2000) Nature, 405, 907-913.

Post-glacial colonization routes of

animals and

subsequenthybrid contact zones

from: Hewitt (2000) Nature, 405, 907-913.

From: Jackson and Weng (1999) Proc. Nat. Acad. Sci. US, 96, 13847-13852.

Extinction: Picea critchfeldii was a dominant tree

in eastern North America in LGM; it died out about 15 000 cal. yrs

BP

Above: cross-sections of needles (E-G are P. critchfeldii).

Left: cones of P. critchfeldii

Why is the European forest depauperate?

Quercus (oak)Acer (maple)

Fagus (beech)Castanea (chestnut)

Carya (hickory)Ulmus (elm)

Tilia (basswood)Juglans (walnut)

Liquidambar (sweet gum) Nyssa (sour

gum)

E N Am Europe E AsiaX X XX X XX X XX X XX F XX X XX X XX X XX F XX F X

X = extant; F = fossil

Quaternary extinctions of trees in the Netherlands

loss ofsub-tropicalgenera

Causes of Quaternary plant extinctions

1. Abrupt climate change?

2. Barriers to migration (e.g. E-W

mountain ranges)?

3. Loss of seed dispersal agents?