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Quaternary environments and N.
hemisphere temperate forests
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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
60°N
45°N
30°N
15°N
Eq.
15°S
30°S
45°S
60°S
Temperate forest
Pollen
sites,
eastern
North
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
Phase
Dominants
Upper
Cryptomeria, Sciadopitys
Middle
Cyclobalanopsis,
Castanopsis
Lower
Fagus, Lepidobalanus
Climate
Temperature
Moisture
Temperate
Wet
Warm
Wet
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.
Long cores from temperate forest areas
60°N
45°N
30°N
15°N
Eq.
15°S
30°S
45°S
60°S
> 50 ka
>100 ka
Pollen
record,
Lago di
Monticchio
(Italy)
from: PAGES website
Pollen
record,
Grande
Pile
(France)
From: Guiot (1998)
Nature 388, 25-27.
Pollen
record,
Lake Biwa
(Japan)
Pinus = cool indicator;
Cryptomeria = warm
Indicator;
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
vegetation
(18 ka 14C
yrs BP):
North
America
Present
(potential)
vegetation
of Europe
LGM
vegetation
(22-14 ka
14C yrs
BP):
Europe
NB continental
shelf extent
from: Harrison et al. (2001) Nature 413, 129-130.
LGM (a) and present (b) pollen and
vegetation (c,d) patterns in East Asia
Reconstructing LGM refuges and postglacial migrations: isopoll data
from: Davis and Shaw (2001)
Science 292, 673-679.
R?
LGM refuges (R)
and post-glacial
isochrons in
eastern North
America.
Where there
separate Atlantic and
Gulf refuges?
R?
Oaks
White pine
R?
E. hemlock
R?
Elms
How quickly did trees migrate in eastern
North America in the post-glacial?
Jack/Red pine
White pine
Spruce
Larch
Elm
Hemlock
Balsam fir
Maple
Beech
Oak
Hickory
Chestnut
0
100
200
300
m / yr
400
500
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)
(b)
(c)
(=a x b)
(=a x c)
Was the rate
of post-glacial
migration
controlled by
rates of
climatic
change or
seed size?
m / year
500
400
jack pine
red pine
white
pine
300
larch
spruce
elm
200
maple
fir
Data: see previous slide and
USDA (1974) “Seeds of Woody Plants in the
United States” Agric. Handbook No. 450.
hemlock
100
hickory
beech
oaks
chestnut
0
1
10
100
1 000
seed wt. (mg)
10 000
blue jay
passenger pigeon
Quercus macrocarpa
Are seed-caching birds the
main agents of dispersal in
post-glacial time for ‘nut
trees’?
Fagus grandiflora
see: Webb (1986) Quat. Res. 26, 367-375
for 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
Range
Source: USDA Handbook - Silvics of Forest Trees
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
Colonization
date in ka BP
from pollen data
low
from: Cwynar and MacDonald (1988) Amer. Nat. 129, 463-469.
high
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
LGM
coastal
refuges
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
Abies alba
Picea abies
Taberlet et al., (1998) Mol. Ecol. 7, 453-464; Scottii et al. (2000) Mol. Ecol. 9, 699-708.
Post-glacial colonization routes of
animals based on DNA variation
from: Hewitt (2000) Nature, 405, 907-913.
Post-glacial
colonization
routes of
animals and
subsequent
hybrid
contact
zones
from: Hewitt (2000)
Nature, 405, 907-913.
Extinction: Picea
critchfeldii was a
dominant tree in
eastern North
America in LGM;
it died out about
15 000 cal. yrs BP
Above: crosssections of needles
(E-G are P. critchfeldii).
Left: cones of P.
critchfeldii
From: Jackson and Weng (1999) Proc. Nat. Acad. Sci. US, 96, 13847-13852.
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 Asia
X
X
X
X
X
X
X
X
X
X
X
X
X
X
F
X
X
X
F
F
X
X
X
X
X
X
X
X
X
X
X = extant; F = fossil
Quaternary extinctions of
trees in the Netherlands
loss of
sub-tropical
genera
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?