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, eastern North America

Pollen diagram, Kirchner Marsh, Minnesota. from: Webb (1980) J. Interdisciplinary History, 10,

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 Climate PhaseDominants TemperatureMoisture Upper Cryptomeria, Sciadopitys TemperateWet Middle Cyclobalanopsis,WarmWet Castanopsis LowerFagus, LepidobalanusCoolWet from: Miyoshi et al., (1999) Rev. Palaeobot. Palynol, 104,

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,

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,

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

Heinrich events recorded at Lake Tulane, FLA.

Present (potential) vegetation of North America Biome maps from:

LGM vegetation (18 ka 14 C yrs BP): North America

Present (potential) vegetation of Europe

LGM vegetation (22-14 ka 14 C yrs BP): Europe

LGM (a) and present (b) pollen and vegetation (c,d) patterns in East Asia from: Harrison et al. (2001) Nature 413, NB continental shelf extent

Reconstructing LGM refuges and post- glacial migrations: isopoll data from: Davis and Shaw (2001) Science 292,

LGM refuges (R) and post-glacial isochrons in eastern North America. Where there separate Atlantic and Gulf refuges? R? White pine E. hemlock Oaks 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 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 seed wt. (mg) oaks white pine spruce larch elm hemlock hickory maple fir 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, 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 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 high from: Cwynar and MacDonald (1988) Amer. Nat. 129, Colonization date 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 LGM coastal refuges from: Davis and Shaw (2001) Science 292,

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,

Post-glacial colonization routes of tree species based on DNA variation Fagus sylvatica Quercus sp. Taberlet et al., (1998) Molecular Ecology 7,

Post-glacial colonization routes of tree species based on DNA variation Taberlet et al., (1998) Mol. Ecol. 7, ; Scottii et al. (2000) Mol. Ecol. 9, Abies alba Picea abies

Post-glacial colonization routes of animals based on DNA variation from: Hewitt (2000) Nature, 405,

Post-glacial colonization routes of animals and subsequent hybrid contact zones from: Hewitt (2000) Nature, 405,

From: Jackson and Weng (1999) Proc. Nat. Acad. Sci. US, 96, Extinction: Picea critchfeldii was a dominant tree in eastern North America in LGM; it died out about 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 AmEuropeE Asia XXX XFX XXX XFX 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?