Day 3

Day 3Driving Questions1. Why do we need to study past climate?2. How can we reconstruct past climate?

AgendaMorning 1. Observing tree cookies.2. Tree rings: How can trees tell us about climate?3. Tree coring (10 oak trees)4. Tree as proxy data: Tree core analysis and finding correlations with climate.Afternoon 5. Classroom Activities for teaching climate using tree rings6. Presentation (Emi Ito): Climate change in Earth history and Human history7. Manoomin Project (Holly Pellerin)8. Medicine Wheel (Daiana, Dwight, Younkyeong)

Telling time and climate using tree rings

Tree cookies?

Observation of a tree cookie – What did you find about the tree?

In order to move water and nutrients efficiently within themselves, woody plants had to develop a plumbing system.  Just underneath the bark is a layer of plant tissues that serves this function.  This is actually the only part of the trunk that is alive.  It is called the Cambial Layer (red arrow).   Within the cambial layer, one kind of tissue transports liquids from the roots to the leaves.  This is called the Xylem.  Another transports liquids from the leaves to the roots and also laterally above ground.  This is called the Phloem.   As the plant grows it constantly renews both of these.  Only the new xylem and phloem transport water and nutrients.  The old xylem tissue becomes the wood and the old phloem tissue becomes the bark. 

How do trees grow?

What is a tree ring?• A tree ring is really an expression of the

seasonality of climateEarly Wood(Spring Wood)

Late Wood(Summer Wood)

Annual Ring

WidthChemical/Isotopic

Composition(Climate change,

pollution tracking, precipitation sources,

tropical dendro)

Tree-ring Density(X-Ray Densitometry;

temperature variability)

Oak Maple

Bark

Center

Tree coring and making tree cores

How do scientist study trees?

Biological Growth Curve: The average radial growth of as tree as measured over time.

Standardization: The process by which the biologicalgrowth curve is removed from the individual raw ring width measurements producing a new time series of index values(indices).

The Principle of Crossdating• Ring counting ≠ crossdating.• Crossdating: The procedure of matching

ring-width variations among many trees from nearby areas allowing the identification of the precise year in which each ring was formed (Fritts 1976).– Absolutely essential in applications that make

comparisons with time-dependent phenomena (e.g., interannual climate variability).

Crossdating: Temporal Control and Chronology Extension

Chronology Extension

Living TreeDead TreeVery Old Dwelling

The Importance of Chronology Extension

Living trees only extend to 1675

Remnant materials extend chronology to 1197

>470 year difference!

Living Trees

Remnants

Cross-dating in Practice: Skeleton PlottingThe narrowest ring is connected (blue line) with the longest skeleton mark. The widest ring is connected (green line) with a "b" mark.Note the red line: 1.Points to a ring of average width, but it seems narrow compared to the preceding ring 2.Perhaps it merits a small mark because of the large year-to-year difference

Dendrochronologists can make skeleton plots to standardise scales:

Note the three skeleton plots of the figure above: Have the same relative scale making themeasy to compare to one another whileclearly showing the same pattern of ring width variation in each sample

18951898

19011904

19071910

19131916

19191922

19251928

19311934

19371940

19431946

19491952

19551958

19611964

19671970

19731976

19791982

0

5

10

15

20

25

30

Mud River Tree rings and Precipitation (Minnesota)

Tree Ring width(mm) *10 Precipitation (inch)

Full ring

False ring

Morrison Lake, Beaverhead Mountains, MT

About 25cm

Published by AAAS

U. Siegenthaler et al., Science 310, 1313 -1317 (2005)

Fig. 4. A composite CO2 record over six and a half ice age cycles, back to 650,000 years B.P. The record results from the combination of CO2 data from three Antarctic ice cores: Dome C (black), 0 to 22 kyr B.P. (9, 11) and 390 to 650 kyr B.P.; Vostok (blue), 0 to 420 kyr B.P. (5, 7), and Taylor Dome (light green), 20 to 62 yr B.P.

Karner et al. Paleoceanography, 2002

Varia

tion

rela

tive

to a

nom

inal

mea

n va

lue

per c

ore

1.5‰

~70% of variation continental ice volume

Col

d

War

m

Thousands of years ago Lüthi et al. 2008, Nature

Antarctic Dome C ice core record

warmer

2010

2008

2009

20

15

10

5

0

Steel Lake core image(scale in cm; this section represents ~100 years)

spruce

pine

pine savanna

oak savanna

Pra

irie

Per

iod

pine/birch/aspen

470510550590630670710750790830870910950990

1030107011101150119012301270

Depth (c

m)

1620±120

1350±30

2510±35

3770±40

12000±290* rejected(8000- Steel L.)

10550±35

14C D

ates un

cal. B

P

40 80Trees+Shrubs/Herbs

AP/NAP

20 40 60

Picea (

Spruce)

20 40 60%Pollen Sum=AP+NAP

Pinus (Pine

)

20 40 60 80

Betula

(Birc

h)

50

Quercus

(Oak

)

20

Cypera

ceae (

Sedges)

20 40 60

Poace

ae (G

rasse

s)

20 40 60

Artemisi

a (W

ormwoo

d)

20

Ambrosia

(Rag

weed)

Prairie period

Moody Lake C, Cental CorePollen Diadram of Selected TaxaAnalisys: Jacqueline van Leeuwen