Pleistocene Epoch & Biological Dynamics

Transcription

1 Pleistocene Epoch & Biological Dynamics Lomolino et al. (2010) Chapter Pleistos most Keinos - new

2 Pleistocene CondiEons Wisconsin glaciaeon Blue indicates ice extent during the last glacial maximum

3 Models of Change over Earth s History Predictable rules govern climate change (direceonal change, stable climate) Random, abrupt, catastrophic events cause climate change (e.g. asteroid impacts) The climate alternates between alternate stable states (e.g. glacial/interglacial periods) (From last Eme) Models of Change over Earth s History Predictable rules govern climate change (direceonal change, stable climate) Random, abrupt, catastrophic events cause climate change (e.g. asteroid impacts) The climate alternates between alternate stable states (e.g. glacial/interglacial periods) (From last Eme)

4 What Drives Change? Changing Solar output Tectonic & Volcanic AcEvity Asteroid Impacts Methane Clathrate Releases Orbital Pa\erns Milankovitch Cycles Changing Ocean CirculaEon Changing sea levels Homo sapiens What Drives Change? Changing Solar output Tectonic & Volcanic AcEvity Asteroid Impacts Methane Clathrate Releases Orbital Pa\erns Milankovitch Cycles Changing Ocean CirculaEon Changing sea levels Homo sapiens Pleistocene Epoch

5 What Drives Change? Changing Solar output Tectonic & Volcanic AcEvity Asteroid Impacts Methane Clathrate Releases Orbital Pa\erns Milankovitch Cycles Changing Ocean CirculaEon Changing sea levels Homo sapiens? Pleistocene Epoch Over the Earth s history, decreasing atmospheric CO 2 has counteracted the increasing solar luminosity, preveneng the Earth from overheaeng. Mackenzie

6 Fig Lomolino et al Pleistocene climate forcing factors Earth s orbital geometry (Milankovitch Cycles) VariaEon in solar insolaeon Atmospheric absorpevity/reflecevity Earth surface albedo (snow, water, soil, vegetaeon) Feedback effects (interaceons)

7 Milankovitch Cycles Eccentricity egg- shaped orbit Obliquity Elt Precession - wobble Milu%n Milanković

8

9 Precession Precession

10 Milankovitch Cycles InsolaEon Oxygen isotopes (temperature proxy) Pleistocene climate forcing factors Earth s orbital geometry (Milankovitch Cycles) VariaEon in solar insolaeon Atmospheric absorpevity/reflecevity Earth surface albedo (snow, water, soil, vegetaeon) Feedback effects (interaceons)

11 Massive Ice Dams at the end of the Pleistocene Changing Ocean CirculaEon Thermohaline circulation in the North Atlantic Broecker s Hypothesis: The drainage of Lake Agassiz suddenly switched off the Atlantic thermohaline circulation and plunged the North Atlantic back into a short ice age known as the Younger Dryas Stadial Source: Locthe, (Rahmstorf 2001) 11

12 Younger Dryas a brief return of the ice age to the North AtlanEc region Younger Dryas h\p://en.wikipedia.org/wiki/younger_dryas How do we reconstruct past climates?

13 ReconstrucEon using proxies Tree Rings (climate: moisture & temperature) Sediment Pollen (plant distribueon) Foraminifera (phytoplankton & chemical composieon) Dust (aridity) Ice cores (e.g. Vostok, EPICA) Gas concentraeons Stable isotopes (e.g. deuterium, oxygen temperature) h\p://en.wikipedia.org/wiki/pleistocene 13

14 Ice core showing layers h\p://en.wikipedia.org/wiki/pleistocene h\p://en.wikipedia.org/wiki/pleistocene 14

15 Pleistocene Climate Drier Climate During Glacial Periods

16 Remnant pluvial lake landscape (Mojave Desert near Barstow, California) h\p://en.wikipedia.org/wiki/pluvial_lake Pluvial Lakes landlocked, rain- fed lakes common during Pleistocene

17 ElevaEonal shils in plant community distribueon aler the Pleistocene Pleistocene Temperatures RelaEve to Today

18 Sea Level Change Pleistocene land bridges

19 Refugia and range contraceons Refugia Coastal refugia may have allowed migraeon

20 Filters restriceng dispersal Dispersal across Wallace s Line EustaEc & IsostaEc Changes Sea- level (EustaEc) ElevaEon (relaeve) ConEnental crust level (IsostaEc) Time since last ice age

21 ArcEc landscape near Churchill, Manitoba sell undergoing isostaec rebound Recent vicariance Cakile edentula

22 HypotheEcal range dynamics Glacial periods allowed dispersal across hemispheres North American Terrestrial Plant CommuniEes

23 Did communiees migrate together? à Did all species move at the same rate? à Did they move in the same direc:on?

24 Pollen in sediments - can be used to analyze changes in plant populaeons over long Eme spans, - can be used to infer rates of plant dispersal Molles 2008, Chapter Tree migraeon aler the last ice age ended (about 12,000 years ago). Davis et al, cited in Molles (2008)

25 Dispersal in maple & hemlock Maple samaras Hemlock cone h\p://en.wikipedia.org/wiki/maple h\p://en.wikipedia.org/wiki/ Tsuga_canadensis ß Lodgepole pine (Pinus contorta) White spruce (Picea glauca)

26 Predicted Climate Change Velocity Diffenbaugh & Field (2013) Science 341: Will species be able to keep up with these rapid rates of climate change?

27 Dicrostonyx sp. h\p://en.wikipedia.org/ wiki/collared_lemming Lemmus sp. h\p://en.wikipedia.org/ wiki/lemming

28 Tamias striatus h\p://en.wikipedia.org/ wiki/eastern_chipmunk Thomomys talpoides h\p://en.wikipedia.org/wiki/ Northern_Pocket_Gopher

29 Species Range Shils Bog lemmings, chipmunks & prairie dogs

30 Shrews & pocket mice Pack rats & bog lemmings

31 Mammalian range shils do not fit simple prediceons of simple southern and northern movement with glaciaeon, deglaciaeon What do these range shils tell us about community successional concepts? à Clements vs. Gleason?

32 CommuniEes AssociaEons of species in a parecular place and Eme. F. Clements ( ) likened the community to a superorganism (obligate associaeons) H.A. Gleason ( ) preferred an individualisec view of community structure & composieon