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Kevin T. SmithUSDA Forest ServiceNorthern Research StationDurham, New Hampshire

Cascades of Tree Response and Recovery Following Storm Injury

ktsmith@fs.fed.us

American Society of Consulting ArboristsBoston, MADecember 2, 2016

Cascade: Linked stimulus/response eventsSeparated in time/spaceVariety of scales

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Survive

Spread

The goal of the tree:

Excurrent Decurrent

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Young tree:

High dynamic massHigh redundancy

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Compartmentalization:A conceptual framework for understanding how trees grow and defendthemselvesA.L. ShigoAnnual Review of Phytopathology 1984

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Transverse

Red oak--Transverse

Red oak--Radial

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Red oak--Tangential

Events:

Mechanical breakage—Branch breaksStem snapsSplit forksBranch pullouts

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Events:

Immediate physics—CavitationAerationTylosis formation

Black Locust--Radial

Events:Rapid biology—

Infection—pioneers + ?Cambial diebackInitial column boundary-

Reaction zoneCallus pad formation

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Events:Rapid biology—

Metabolic shiftsHormone induction &

interactionStill not well understood

Hormones involved:AuxinsGibberillinsCytokininsMethyl jasmonateAbscissic acidEthylene

Arabidopsis thaliana

Gray, WM (2004). PLoS Biol 2(9): e311.

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Bore hole closed

Bore hole open

Bore hole with mushrooms!

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Red maple1998 storm2002 dissected

Red maple1998 storm2002 dissected

Red maple1998 storm2002 dissected

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Red maple1998 storm2002 dissected

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Reaction zone / CBL

Barrier zone

Events:First growing season + —

Reduced photosynthesisReduced E storageSpreading infection ?De-repression of latent

buds / new shoots

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Red spruce callus

Ponderosa pine

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CP

WW

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Starch reserves

Buds with starchreserves

Shoot tip

Axillary bud

“Pinching back” and lateral growth

Apical meristem

Axillary bud

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Auxin (IAA) —Promotes tip growth

Cytokinin (CK) —Promotes lateral

growth

Auxin: Increases CK degradationInhibits CK synthesis

Remove the tip: Decrease CK degradationPromote CK synthesis

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CK promotes lateralshoots

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SM WA YB YB, SM

Armillaria root disease

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