GEOG5839.02. What are tree rings?
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September 6 What are tree rings?
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Tree rings are a powerful natural archive of past environments. But how do trees form rings? And what are the major types of cells that make up rings in conifers and deciduous trees?
Transcript of GEOG5839.02. What are tree rings?
September 6
What are tree rings?
Source: dylancantwell
MAJOR TOPICSWhat are trees?Tour of basic anatomy The cambium
GEOG5839WHAT ARE TREES?
Tree at Chancellorsville
Source: Andy Frasse!o
Trees are not limited to a single order or even division of plants.
“Tree-ness” is defined by a specific
GROWTH FORM.
Trees are perennial plants, which are plants that live for more than two years.
Trees have a single main stem (or trunk).
Shrubs have multiple stems (and are not trees).
Plants are o!en required to a"ain a minimum height at maturity to qualify as trees (usually between 3 and 6 meters tall).
Trees are woody plants (a category that also includes shrubs and some vines).
Woody plants are capable of secondary thickening, adding new yearly growth layers of cells onto the accumulated growth of previous years.
Oldest wood
Most recentgrowth
Cross-sectional plane
Radial plane
Source: Hoadley, Identifying Wood
Cross-sectional (or transverse) plane
Tangential plane
Photograph: Dave_Gray
GEOG5839TOUR OF BASIC ANATOMY
Heartwood
SapwoodCambium
Bark
The vascular cambium is a lateral meristem in the vascular tissue of plants.
tissue containing plant ‘stem’ cells
The vascular cambium is also the source of both the secondary xylem (inwards, towards the pith) and the secondary phloem (outwards), and is located between these tissues in the stem and root.
Photograph: easagor
BarkPith
Cambium
The pith is the small core of so! spongey tissue that forms the central longitudinal axis of a tree stem, branch or twig.
Scots pinePinus sylvestris
Source: Fritz Schweingruber
Common beechFagus sylvestris
Source: Fritz Schweingruber
Sapwood
Photosynthetic wastes
Heartwood
VS.GYMNOSPERMS
ANGIOSPERMS
Gymnosperms(coniferous)
Gymnosperms like this Douglas-fir have encapsulated seeds.
Red pinePinus resinosa
Earlywood
Latewood
Total ring-width
Eastern hemlockTsuga canadensis
Tracheids
Scots pinePinus sylvestris
Tracheids are elongated cells that function in food conduction and structural support.
Photograph: Fritz Schweingruber
large cellsthin cell walls
small cellsthick cell walls
Scots pinePinus sylvestris
Ray
Scots pinePinus sylvestris
Rays are fla"ened bands of tissue that extend horizontally in a radial plane through the tree stem.
Angiosperms(deciduous)
White oakQuercus alba
Angiosperms like this oak have exposed seeds.
Bur oakQuercus macrocarpa
Earlywood vessels
English oakQuercus robur
Latewood vessels
English oakQuercus robur
Vessel elements are a type of hardwood cell that has a relatively large diameter, thick cell wall and perforate (open) ends.
English oakQuercus robur
Photograph: Fritz Schweingruber
Fibre
Fibres are an elongated hardwood cell with thick walls that contributes greatly to the material strength of wood.
Photograph: Fri"s Schweingruber
English oakQuercus robur
Ray
RING POROUS DIFFUSE POROUS
Bur oakQuercus macrocarpa
Sycamore mapleAcer psudoplantanus
European beachFagus sylvatica
A growth-ring boundary in Chamaecyparis lawsoniana (Port-Orford cedar)
Source: Bu!erfield and Meylan (1980)
GEOG5839THE CAMBIUM
The vascular cambium is a lateral meristem in the vascular tissue of plants.
tissue containing plant ‘stem’ cells
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).
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Photograph: mlhradio
Bristlecone pinePinus longaeva
Resource-intensiveAs the cambium grows, it consumes scare resources that cannot be used for growth by the rest of the tree.
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CHARACTERISTICS OF THE CAMBIUM
Limber pinePinus flexilis
Limber pinePinus flexilis
FlexibleCells produced by the cambium (called ‘cambial derivatives) can be di#erentiated into the range of cells found in the xylem and phloem.
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CHARACTERISTICS OF THE CAMBIUM
Pinus spp.
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.
DORMANT CAMBIUM
1 - 10 cells
viscous protoplasmsharp cell walls
Source: Ben Cooper
xylem
phloem
cambium
DORMANT CAMBIUM ACTIVE CAMBIUM
1 - 10 cells 8 - 20 cells
viscous protoplasm fluid protoplasmsharp cell walls semi-transparent walls
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
A growth-ring boundary in Chamaecyparis lawsoniana (Port-Orford cedar)
Source: Bu!erfield and Meylan (1980)
September 6
What are tree rings?
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