Paleo-perspectives on climate sensitivity

• What are the patterns of climate variation and ecosystem response?

• What are the most important climate drivers?• What is the role of disturbance in moderating ecosystem response to climate variation?

• How does sensitivity to climate variation differ among species?

• How do boreal ecosystems respond to climatic conditions outside the range of observed variability?

What are the patterns of climate variation and ecosystem response?

030006000900012000Years B.P.

`Dry Increasing

moisturemoist dry moist

Cool warm cooling modern

Cooldry

warmdry

warm<dry

warmmoist

Coolingmoist

(based on Edwards et al. 2001, Mann et al. 2002, Hu et al. 2001)

What are the patterns of climate variation and ecosystem response?

Populus zone

P.glauca zone

Alnus expansion

P. Mariana expansion“modern” boreal forest

What are the patterns of climate variation and ecosystem response?

What are the patterns of climate variation and ecosystem response?

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

(From Bigelow and Edwards 2001)

Paleo-perspectives on climate sensitivity

• What are the patterns of climate variation and ecosystem response? – Substantial climate variation during Holocene– Three major vegetation transitions– Unknowns: rate of transitions, significance of high-frequency variation.

What are the most important climatic drivers?

Transition time Hypothesized climate driver

Shrub tundra --> deciduous forest

11,500 Warming

Deciduous forest --> white spruce expansion

9,500 Increased moisture

White spruce--> black spruce

5,500 Increased moisture

What are the most important climatic drivers?

0

1

2

3

1800 1825 1850 1875 1900 1925 1950 1975 2000

year

ring-width index

Paleo-perspectives on climate sensitivity

• What are the patterns of climate variation and ecosystem response?

• What are the most important climate drivers?– Moisture

What is the role of disturbance?

0

0.1

0.2

0.3

0.4

0.5

0.6

0 2500 5000 7500 10000

Calibrated Years before present

Charcoal influx

Black spruce forests White spruce foreststransition

Paleo-perspectives on climate sensitivity

• What are the patterns of climate variation and ecosystem response?

• What are the most important climate drivers?

• What is the role of disturbance in moderating ecosystem response to climate variation?– Few studies with enough resolution to disentangle climate/veg/disturbance but…

– Preliminary evidence suggests climate --> veg --> fire

How does sensitivity to climate vary among species?

How does sensitivity to climate vary among species?

Paleo-perspectives on climate sensitivity

• What are the patterns of climate variation and ecosystem response?

• What are the most important climate drivers?

• What is the role of disturbance in moderating ecosystem response to climate variation?

• How does sensitivity to climate variation differ among species?– Black spruce: low sensitivity?– White spruce: high sensitivity?

How do boreal ecosystems respond to climatic conditions outside the range of observed

variability?

(From Edwards et al. 2005)

Paleo-perspectives on climate sensitivity

• What are the patterns of climate variation and ecosystem response?

• What are the most important climate drivers?• What is the role of disturbance in moderating ecosystem response to climate variation?

• How does sensitivity to climate variation differ among species?

• How do boreal ecosystems respond to climatic conditions outside the range of observed variability?– Non-analog ecosystems

Future directions…

• Examine time slices with large changes in climate: what, if any, was the vegetation response?– 9000 BP increase in moisture– Early Holocene rapid warming

• Examine time slices with ‘abrupt’ vegetation change.

• Explore fine-scale variation in abundance as it relates to climate variation