GEOG5839.02. What are tree rings?

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?

1. September 6
What are tree rings?

2. Source: dylancantwell

4. MAJOR TOPICS
What are trees?Tour of basic anatomyThe cambium

6. GEOG5839
WHAT ARE TREES?

7. Tree at Chancellorsville
Source: Andy Frasse!o

8. Trees are not limited to a single order or even division of plants.
“Tree-ness” is defined by a specificGROWTH FORM.

9. Trees are perennial plants, which are plants
that live for more than two years.

10. Trees have a single main stem (or trunk).

11. Shrubs have multiple stems
(and are not trees).

12. Plants are o!en required to a"ain a minimum height at maturity
to qualify as trees (usually between 3 and 6 meters tall).

13. Trees are woody plants (a category that also includes shrubs
and some vines).

14. Woody plants are capable of secondary thickening,
adding new yearly growth layers of cells onto the
accumulated growth of previous years.

15. Oldest wood Most recent
growth

16. Cross-sectional plane

17. Radial plane
Source: Hoadley, Identifying Wood
Cross-sectional
(or transverse) plane
Tangential plane

18. Photograph: Dave_Gray

21. GEOG5839
TOUR OF BASIC ANATOMY

23. Heartwood
Sapwood
Cambium
Bark

24. The vascular cambium is a lateral meristem
in the vascular tissue of plants.
tissue containing plant ‘stem’ cells

25. 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.

26. Photograph: easagor

27. Bark Pith
Cambium

28. The pith is the small core of so! spongey tissue
that forms the central longitudinal axis of a tree
stem, branch or twig.

30. Scots pine
Pinus sylvestrisSource: Fritz Schweingruber

31. Common beech
Fagus sylvestrisSource: Fritz Schweingruber

32. Sapwood

33. Source: sonykus

34. Photosynthetic wastes Heartwood

35. VS.
GYMNOSPERMS
ANGIOSPERMS

36. Gymnosperms
(coniferous)

37. Gymnosperms like this Douglas-fir have encapsulated seeds.

38. Red pine
Pinus resinosa

39. Earlywood Latewood Total ring-width Eastern hemlock
Tsuga canadensis

40. Tracheids Scots pine
Pinus sylvestris

41. Tracheids are elongated cells that function
in food conduction and structural support.

42. Photograph: Fritz Schweingruber large cells
thin cell walls small cells
thick cell walls Scots pine
Pinus sylvestris

43. Ray Scots pine
Pinus sylvestris

44. Rays are fla"ened bands of tissue that extend
horizontally in a radial plane through the tree stem.

45. Angiosperms
(deciduous)

46. White oak
Quercus alba

47. Angiosperms like this oak have exposed seeds.

48. Bur oak
Quercus macrocarpa

49. Earlywood vessels English oak
Quercus robur

50. Latewood
vessels English oak
Quercus robur

51. Vessel elements are a type of hardwood cell
that has a relatively large diameter, thick cell wall
and perforate (open) ends.

52. English oak
Quercus roburPhotograph: Fritz Schweingruber Fibre

53. Fibres are an elongated hardwood cell with thick walls
that contributes greatly to the material strength of wood.

54. Photograph: Fri"s Schweingruber English oak
Quercus roburRay

55. RING POROUS DIFFUSE POROUS

56. Bur oak
Quercus macrocarpa

57. Sycamore maple
Acer psudoplantanus

58. European beach
Fagus sylvatica

59. A growth-ring boundary in Chamaecyparis lawsoniana (Port-Orford cedar)
Source: Bu!erfield and Meylan (1980)

60. GEOG5839
THE CAMBIUM

61. The vascular cambium is a lateral meristem
in the vascular tissue of plants.
tissue containing plant ‘stem’ cells

62. xylem phloem cambium

63. CHARACTERISTICS OF THE CAMBIUM
Self-sustaining
The cambium is a self-sustaining system, and retains its
functions for a long time (sometimes for centuries or millennia).1

64. Photograph: mlhradio
Bristlecone pine
Pinus longaeva

65. Resource-intensive
As the cambium grows, it consumes scare resources that cannot
be used for growth by the rest of the tree.2
CHARACTERISTICS OF THE CAMBIUM

66. Limber pine
Pinus flexilis

67. Limber pine
Pinus flexilis

68. Flexible
Cells produced by the cambium (called ‘cambial
derivatives) can be di#erentiated into the range of cells
found in the xylem and phloem.
3
CHARACTERISTICS OF THE CAMBIUM

69. Pinus spp.

70. 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.

71. DORMANT CAMBIUM
1 - 10 cells
viscous protoplasm
sharp cell walls

72. Source: Ben Cooper

73. xylem phloem cambium

74. DORMANT CAMBIUM ACTIVE CAMBIUM1 - 10 cells
8 - 20 cells viscous protoplasm
fluid protoplasmsharp cell walls
semi-transparent walls

75. CAMBIAL GROWTH

76. Scots pine
Pinus sylvestrisPhotograph: Fritz Schweingruber Radial file

77. Latewood
(prior year)
Early season
phloem
Immature earlywood

78. Latewood
(prior year)
phloem
Immature earlywood
Mid-season
Mature earlywood

79. phloem
Immature
latewood
Late season
Mature earlywood

80. A growth-ring boundary in Chamaecyparis lawsoniana (Port-Orford cedar)
Source: Bu!erfield and Meylan (1980)

83. September 6
What are tree rings?

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