Dendrochronology of the Sunset Crater

Tornado

Paul Sheppard

Elizabeth (Lizzie) May

Sunset-Paricutín Crew

Sunset Crater

Erupted AD 1064• Dated dendrochronologically (Smiley

1958)

Other Processes?

•Climate: Drought, but long-term?

•Ecological: Defoliators, but non-fatal?

•Other geological: Landslide? Avalanche?

•Weather: High winds? Tornado?

Sunset Crater Tornado

•October 24, 1992

•Touched down three times near Sunset Crater

•Toppled many trees

•Snapped branches on others

•Shook hundreds of trees

Dendro-tornado research

•Long-term wind effects on ring growth

•Forest compositional responses

•Nothing about tornado effects on ring growth per se

0.0

0.5

1.0

1.5

1930 1940 1950 1960 1970 1980 1990 2000

Chr

onol

ogy

Inde

xSunset Crater VisitorControl Chronology

(n = 8)

1993

1. Ring-width release since 1993

0.0

2.0

4.0

6.0

1960 1970 1980 1990 2000

Rin

g w

idth

(m

m)

0.01.02.03.04.0

1960 1970 1980 1990 2000

Wid

th I

ndex

0.0

0.5

1.0

1.5

1960 1970 1980 1990 2000Chr

onol

ogy

Inde

x

1993

2. Reaction wood since 1993

•Some reaction-wood trees leaning

•Others appeared upright

1993

3. Reaction latewood, 1993

•Usually combined with wider rings

•Notice 2002.

19934. A few suppressed rings after 1993

0.0

1.0

2.0

1960 1970 1980 1990 2000

Rin

g W

idth

(m

m)

0.0

1.0

2.0

1960 1970 1980 1990 2000

Wid

th I

ndex

0.0

0.5

1.0

1.5

1960 1970 1980 1990 2000Chr

onol

ogy

Inde

x

5. Continuous suppression since 1993

0.0

1.0

2.0

1960 1970 1980 1990 2000

Rin

g W

idth

(m

m)

0.0

1.0

2.0

1960 1970 1980 1990 2000

Wid

th I

ndex

0.0

0.5

1.0

1.5

1960 1970 1980 1990 2000Chr

onol

ogy

Inde

x

1993

6. Thin latewood, 1993

10%

20%

30%

1989 1990 1991 1992 1993 1994 1995 1996

Visitor Center Control (n = 8)

0%

20%

40%

60%

1989 1990 1991 1992 1993 1994 1995 1996

Reduced Latewood Effect

Per

cent

La

tew

ood

of T

otal

Rin

g W

idth

Year

Tornado Conclusions

•Not every survivor shows a response

•Dominant response: ring-width release

•Most responses don’t look like AD 1064

•One lengthy suppression a la AD 1064

•AD 1064 probably not a tornado event

A Surprise

Extended suppression, but not death

Decades-Long Suppression?

•Climate? Not conventionally

•Fire? No fire scar

•Leaning? Not leaning

•Defoliation? Not typically

•Some other pest? Sawfly?