Andes to Amazonia: What we think we know and what we don’t.

Mark BushFlorida Instituteof Technology

&

Miles SilmanWake Forest University

Some of the big questions before us:To what extent can Andean records inform us about Amazonia?How much climatic variation was there within ice age Amazonia?How robust are the data for a 5oC cooling in the terrestrial Neotropics?How dry was Amazonia during the last ice-age?

Refugia

• Raised on modern biogeographic data but no reliable paeleocological data.

• Most recent manifestation is untestable as it has no time or habitat constraints (Haffer and Prance Amazoniana 2002).

Brown (1991)

Dry Forest Arcs

• Modern biogeographic data used to suggest the presence of a past habitat bridge of dry forests.

• Assumed to be ice-age• But there is no basis for

this assumption.• Nor a real difference from

modern required to allow movement of species.

Pennington et al. ( J. Biogeogr. 2000)

Different ideas about Arcs

Pennington et al. (J. Biogeogr. 2000)Wüster et al. (Molec. Ecol. 2005)

Miles et al. (GEB, 2004)

Sites that we’ll discuss

Amazon fan

ConsueloTiticaca

Negra

Pata &Verde Maicuru

Carajas

TRMM data and paleo locations

• Not surprising that the different paleoecological records are providing a different story

Late Glacial and Holocene Vegetation from Lake Titicaca

Paduano et al. (Palaeo3 2003)

The Glad 800 drill rig (NSF/ODP) was hauled to Titicaca in 2001 and three cores were raised from deep water under the supervision of Paul Baker, Geoff Seltzer and Sheri Fritz.

Long record from core LTO1-2B,

Titicaca Probably four, full glacial

cycles.

Pollen concentration is a proxy for productivity, and indicator of near Holocene temperatures.

MIS 5

MIS 7

MIS 9

MIS 11

Long record from core LTO1-2B,

Titicaca

MIS 5e

MIS 7

MIS 9

MIS 11

Isoetes may be important for glacial temperature.

Too cold for pollen or Isoetes

D-O cycles in Titicaca

Work in progress

Work in progress

GISPTiticaca pollenconcentration

D-O cycles in Titicaca

Lake level and insolation

• Lake Titicaca and the Salar de Uyuni, Bolivia, respond to DJF insolation.

• Lake level at Titicaca varies synchronously with Pata for the last 70,000 years.

20 40K yr BP

Baker et al. (Science 2001)

Hill of Six Lakes

Lake level fluctuation in Amazonia

• Lakes Pata and Verde show continuous forest cover through last two glacial periods.

• Periods of low lake level correlate with periods of high K+ concentrations in sediment in Pata.

• Low lake level due to reduced precipitation.

Lake level and orbital forcing

• Peak low-lake level corresponds to 11 K BP and 33 K BP with 22 K BP wet (matches Titicaca).

• Aligns to orbital rhythm of variation in insolation.

• Continuous forest cover suggests decrease in precipitation in the wet season rather than dry season.

Bush et al. (J. Paleolimn. 2002)

Bush et al. (Palaeo3 2004)

Lake Pata, Brazil

10, 000

18,00022,00034,000

48,000

Cal BP

Colinvaux et al. (Science 1996)

Fusing modern ecology and paleoecology

• Linking Amazon and Andean forests– Single system– Space and Time

• Fully vouchered 1 ha plots lowlands to treeline (17 to date)

• Series of lakes along transects

• Peru and Bolivia

Andes Biodiversity Consortium

L

LLL

L

L

LLL

LL

L

LLLLLL

LLL

L

L

L

LLL

Modern Ecology: 77 ha (Peru) -17 Montane, 60 Lowland

w3 tropicos databasePaleoecology: 24 Lakes

0 1000 2000 3000 4000 5000Piper

0.0000

0.0004

0.0008

0.0012

0 1000 2000 3000 4000 5000Weinmannia

0.0000

0.0004

0.0008

0.0012

0 1000 2000 3000 4000 5000Clethra

0.0000

0.0004

0.0008

0.0012

0 1000 2000 3000 4000 5000Polylepis

0.0000

0.0004

0.0008

0.0012

Collection data for 4 genera

0 1000 2000 3000 4000 5000Piper

0.0000

0.0004

0.0008

0.0012

0 1000 2000 3000 4000 5000Weinmannia

0.0000

0.0004

0.0008

0.0012

0 1000 2000 3000 4000 5000Clethra

0.0000

0.0004

0.0008

0.0012

0 1000 2000 3000 4000 5000Polylepis

0.0000

0.0004

0.0008

0.0012

Representation of pollen taxa

Continuous wet forest taxa for 50,000 yrs

Gradual change in community composition

Bush et al. (Science 2004)

Consuelo Ordination

Two basic states(1) 30 kyr

(2) 11 kyr

Evidence of cycles

DCA Axis 1

0 50 100 150 200

Age (cal y

r bp)

0

10000

20000

30000

40000

50000

DCA Axis 1 vs. Time

• Two major forest types

• Periodic changes– ENSO, drought

cycles, D-O events

• Gradual ~8-10 ky transition

• Non-equilibrium?

0 1000 2000 3000 4000 5000

Predicted elevation (m)

0.000

0.005

0.010

0.015

0.020

0.025LG

M (21K

cal y

r B

P) Post

eri

or

Densi

ty~1200m

0.0055 °C m-1

~6.6 °C cooler

Elevation for taxa found 21,000 years ago (500 cm pollen assemblage)

Q: What does time course look like?

If taxa were found co-occurring today, most likely elevation

would be 2400m

Laguna Negra waveletsLake at 3300 m elev, 7oS.

Dry event

Bush et al. (JQS In press)

Consuelo and Pata

Pata

Pata

Maicuru

0

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

504200

405160

409070

6012960

601568024029550

28038890

>40000

C-14 (

years

BP)

Depth (

cm)

Litholo

gy

20% 40% 60% 80%

Arbore

al low

land for

est

20

Arbore

al fores

t (coo

l-ada

pted)

20 40

Terre

strial

herbs

20 40

Aqua

tic he

rbs

20

Unide

ntifie

d po

llen g

rains

100 200 300

Spore

s

2000 4000 6000 8000

Algae

Zone

MAI-

MAI-2

MAI-2

MAI-3

MAI-3

Percentage Sum

15-30K

hiatus

Colinvaux et al. (Amazoniana 2001)

15,000

25,000

31,000

>50,000

Carajas, eastern Amazonia

15-25Khiatus

Absy et al. (Compt Rendus 1991)

Amazon Fan data (S. Haberle 1999)

Fan deposits reflect pollen from entire basin

Ice age does not have more grass pollen than modern

Modern Grass

Ice age Grass

Amazon fan reconsidered

Discharge source and Fan data

What is cooling? All these sites provide evidence of a 5-7oC cooling at the LGM

13oC

8oC

Plants probably respond to minimum temperatures, and absolute modern minima are very different across the basin.Were absolute minima in the north reduced while monthly minima were reduced in the south?

Extract sub-region for training and recognition

One way forward: Improving pollen recognition

Using SEM and vector-based computer modeling we aim to improve identification of key taxa to species or species group.More precise taxonomy = more precise bioclimatic envelope modeling

What we think we know: Strong decline in species diversity with elevation. Species migrate individualistically in response to climate change. Strong cooling signature in all Pleistocene records with some

species’ ranges typically moving 1000 m -1500 m downslope. Lowland taxa are adapted to Pleistocene cooling. Amazonian paleoclimates were temporally and spatially

heterogeneous. Refugia and savanna corridors are not grounded in reality.

What we don’t know:Do we have to reconcile the terrestrial record with the marine record?Difference in temperature could be absolute minima (NH) or mean temperature (SH)? To what extent forest structure changed.Fine-resolution climate change from the lowlands.The full impact of Holocene human activities.

The Coring Gang

Andrea Gomez

Alex CorreaDunia Urrego

Jen Hanselman

Dr. Will Gosling