Scots pinePinus sylvestris

Photograph: Fritz Schweingruber

Photograph: Paul Schulte

Populus spp.

parenchyma

Pinus spp.

Photograph: Paul Schulte

A growth-ring boundary in Chamaecyparis lawsoniana (Port-Orford cedar)

Source: Bu!erfield and Meylan (1980)

T R E E - R I N G F O R M AT I O N

CAMBIAL GROWTHCell division in the cambiumProduction of xylem and phloemTime of growth and amounts of xylem and phloem producedDi"erentiation of cambial derivativesIncrease in cell sizeCell wall thickeningLoss of protoplasts

sections to read

Why do trees form rings?

Pinus spp.

Photograph: Paul Schulte

Gymnosperms(coniferous)

1 a lateral meristem in the vascular tissue of plants.

2 the source of both the secondary xylem (inwards, towards the pith) and the secondary phloem (outwards), and located between these tissues in the stem and root.

vascular cambium

tissue containing plant ‘stem’ cells

Cambium

Scots pinePinus sylvestris

Photograph: Fritz Schweingruber

Photograph: Paul Schulte

Populus spp.

xylem

phloem

cambium

Characteristics of the cambium

Self-sustainingThe cambium is a self-sustaining system, and retains its functions for a long time (sometimes for centuries or millennia).

1

Bristlecone pinePinus longaeva

Photograph: mlhradio

Characteristics of the cambium

Resource-intensiveAs the cambium grows, it consumes scare resources that cannot be used for growth by the rest of the tree.

2

Limber pinePinus flexilis

Limber pinePinus flexilis

Characteristics of the cambium

FlexibleCells produced by the cambium (called ‘cambial derivatives) can be di!erentiated into the range of cells found in the xylem and phloem.

3

Pinus spp.

Photograph: Paul Schulte

Photograph: Steven Vance

dormant cambium

1 - 10 cells

viscous protoplasmsharp cell walls

Source: Marchand, P. J. 1996. Life in the Cold: An Introduction to Winter Ecology, 3rd ed. University Press of New England. Hanover, NH. 304 pp.

Photograph: Ben Cooper

Photograph: Paul Schulte

Populus spp.

xylem

phloem

cambium

dormant cambium active cambium

1 - 10 cells 8 - 20 cells

viscous protoplasm fluid protoplasmsharp cell walls semi-transparent walls

Cambial growth

Cambial growth

Cambial growth

Cambial growth

Cambial growth

Cambial growth

Cambial growth

Scots pinePinus sylvestris

Photograph: Fritz Schweingruber

Radial file

Latewood(prior year)

Early season

phloem

Immature earlywood

Latewood(prior year)

phloem

Immature earlywood

Mid-season

Mature earlywood

phloem

Immature latewood

Late season

Mature earlywood

How does weather affect tree-ring formation?

3main pathways

Photograph: spaka!acks

T E M P E R AT U R E

cold hotlow growth

high growth

T E M P E R AT U R E

cold hotlow growth

high growthfrozen water

low photosynthetic rate

shorter growing season

T E M P E R AT U R E

cold hotlow growth

high growthlow photosynthetic rate

higher evaporation

T E M P E R AT U R E

Photograph: circulating

WAT E R

dry wetlow growth

high growth

WAT E R

dry wetlow growth

high growthreduced cell division

reduced cell expansion

C02 starvation

WAT E R

dry wetlow growth

high growthflooding

anoxic conditions

WAT E R

Photograph: Chris Nixon

DAY L E N GT H

short longlow growth

high growth

D AY L E N G T H

short longlow growth

high growth

flowering

dormancy

germination

D AY L E N G T H

How do we know tree rings are annual?

The “pinning” methodPhotograph: Keith Weston

Band dendrometer

Band dendrometer measurements, white pine near Cloquet MN

Source: Alm and Brown, Minnesota Forestry Notes, 1964

Photograph: Baillie (1982)