Tree Growth Rate Table: Absolute Area Increase & Annual ...

Tree Gr

owth R

ate Table:

Gro

Ra

Absolute Ar

ea Incr

ease &

Area

Increase

Ann

ual P

er

centa

ge Gr

owth

Annual

Per

ercenta

centag

Gro

by Dr. Kim D. Coder, Professor of Tree Biology & Health Care

Warnell School of Forestry & Natural Resources, University of Georgia

Trees grow in diameter every year. From the farthest reach of woody roots to tips of

twigs, trees expand in girth. This annual growth increment allows trees to respond to changing

environmental conditions and react to injuries. The ability of a tree to resist strong winds, ice

storms, and major losses of woody materials, while remaining alive and erect, is a direct

consequence of annual diameter growth.

A New Annual Sheath

Trees produce a sheath of living cells, more exterior to last year¡¯s wood, every growing

season. Much of the new growth increment is composed of longitudinal transport cells. These

cells quickly die and only then become functional in transporting water, essential elements, and

growth regulators. These functional but dead cells are held within a matrix of living cells which

regulate water pressure, help correlate growth in the rest of a tree, store food, and react to injury

or attack. Only the outer few annual increments (visible as rings in a cross-section) are reactive

to short term changes inside and outside a tree.

As you examine a tree stem farther to the inside, living cells become fewer and less

active. Depending upon environmental conditions, tree health, and usable food reserves, at some

position inside a tree an inner core of living tissues are systematically shut-down. During

senescence of this inner core of wood (xylem), valuable materials still needed for tree life are

moved outward to living cells, and waste materials are stored or manufactured within each cell as

it dies. These waste materials can make the inner dead core resistant to decay. This dead inner

core is called heartwood.

Leaf Crown Production

The amount of woody increment produced each year is dependent upon proper

functioning and productivity of leaves. All leaves together make up the living crown of a tree.

Food and growth substances ultimately generated by photosynthesis and metabolic processes in

leaves determine the amount of materials available for generating annual increments. An annual

increment of xylem produced throughout a tree is a result of crown production ¡ª crown

production is a direct result of annual increment transport efficiency and volume. A growth

increment also mechanically supports the crown against dynamic forces of gravity, wind,

precipitation and the tree¡¯s own size, shape and mass.

Because the tree¡¯s crown of leaves is provided with raw materials and growth substances

collected and generated by roots, and roots are provided with food and growth substances

generated by the crown, the physical pathway and shear distance between living crown and

absorbing root is critical to tree survival. All the cells between leaf and rootlet must store,

defend, support, transport, prevent waste, and conserve precious resources needed for tree life

and survival. Trees invest heavily in woody materials applied as an annual layer of cells over the

outside of last year¡¯s structure.

Ecological Growth Summary

The annual addition of tree growth represents an approximation of specific crown vigor,

general tree health, relative whole tree growth rates, and crown volume. The more net food

(CHO) and growth substances generated by the crown of leaves, the larger a tree grows at a faster

annual pace. Each year the total annual growth increment is an ecological integration of all

genetic, environmental, and chance occurrence factors influencing whole tree survival and

growth.

Cross-Sectional Area of Growth

One measure of annual growth increments in trees can be estimated by circular crosssections showing annual radial growth (as measured with an increment core, for example).

Annual increment values in square inches using Table 1 can be determined by first estimating

tree diameter in inches at four-and-one-half feet above the ground (DBH) as measured along the

main stem on the uphill side. For this table, an estimate of generalized annual growth rate is

determined based upon the number of annual increments present in the last (outside or most

exterior) inch of wood (xylem). This measure estimates a growth rate by diameter (DBH) class.

Table 1 provides the annual xylem increment area increase based upon growth rate per tree

diameter class in square inches. Note, DBH should be estimated inside the bark.

For example ¨C if an increment core of a 20 inch DBH tree reveals 3 annual increments

(rings) per inch, the tree is growing an estimated 21 square inches of cross section (wood) per

year. Table 1.

Percent Area Growth

A second annual growth rate percent can be estimated for a tree by measuring annual

growth increment circular cross-sections and annual radial growth. Relative annual increment

values (as a percent of last year¡¯s increment) can be determined by first estimating tree diameter

in inches at four-and-one-half feet above the ground (DBH) as measured along the main stem on

the uphill side. Table 2 provides an estimate of annual growth rate based upon the number of

annual increments present within the last (outside or most exterior) inch of wood (xylem)

generated. This percent measure estimates a growth rate by tree diameter (DBH) class. Table 2

provides a percent (in decimal form) increase per year in xylem increment area based upon

growth rate per diameter class. Note, DBH should be estimated inside the bark.

For example ¨C if an increment core of a 20 inch DBH tree reveals 3 annual increments

(rings) per inch, the tree is growing at an annual rate of roughly 7%. Table 2.

Dr. Kim D. Coder, Warnell School, University of Georgia

2

Table 1: Tree area increase measured in cross-sectional

inches (square inches) for each single growth

increment by tree diameter.

Growth rate estimator ranges from 1.0 growth increment (ring) per

inch (R1) to 20 growth increments (rings) per inch (R20).

Diameter (D) ranges from 6 inches DBH to 100 inches DBH.

(D = DBH = diameter of tree in inches at 4.5 feet above ground).

R

2

R

2.5

R

3

R

4

R

5

R

7.5

R

10

R

R

12.5 15

R

R

17.5 20

6in 16in2 11

8.6

7.0

5.9

4.5

3.6

2.5

1.9

1.5

1.2

1.1

0.9

7

19

13

10

8.3

7.0

5.3

4.3

2.9

2.2

1.7

1.4

1.2

1.1

8

22

15

12

9.6

8.0

6.1

4.9

3.3

2.5

2.0

1.6

1.4

1.2

9

25

17

13

11

9.1

6.9

5.5

3.7

2.8

2.2

1.9

1.6

1.4

10

28

20

15

12

10

7.7

6.2

4.1

3.1

2.5

2.1

1.8

1.6

11

31

22

17

13

11

8.4

6.8

4.5

3.4

2.7

2.3

2.0

1.7

12

35

24

18

15

12

9.2

7.4

5.0

3.7

3.0

2.5

2.1

1.7

13

38

26

20

16

13

10

8.0

5.4

4.1

3.2

2.7

2.3

2.0

14

41

28

21

17

14

11

8.7

5.8

4.4

3.5

2.9

2.5

2.2

15

44

30

23

18

15

12

9.3

6.2

4.7

3.7

3.1

2.7

2.3

16

47

32

24

20

16

12

9.9

6.6

5.0

4.0

3.3

2.9

2.5

17

50

34

26

21

17

13

11

7.0

5.3

4.3

3.5

3.0

2.7

18

53

36

28

22

19

13

11

7.5

5.6

4.5

3.7

3.2

2.8

19

57

38

29

23

20

15

12

7.9

5.9

4.8

3.9

3.4

3.0

20

60

41

31

25

21

16

12

8.3

6.3

5.0

4.1

3.6

3.1

D

R

1

R

1.5

Dr. Kim D. Coder, Warnell School, University of Georgia

3

Table 1 (CONTINUED): Tree area increase measured in

cross-sectional inches (square inches) for each

single growth increment by tree diameter.

R

2

R

2.5

R

3

R

4

R

5

R

7.5

R

10

R

R

12.5 15

R

R

17.5 20

21in 63in2 43

32

26

22

16

13

8.7

6.6

5.3

4.3

3.8

3.3

22

66

45

34

27

23

17

14

9.1

6.9

5.5

4.5

3.9

3.4

23

69

47

35

28

24

18

14

9.6

7.2

5.8

4.8

4.1

3.6

24

72

49

37

30

25

19

15

10

7.5

6.0

5.0

4.3

3.8

25

75

51

39

31

26

19.

16

10

7.8

6.3

5.2

4.5

3.9

26

79

53

40

32

27

20

16

11

8.1

6.5

5.4

4.7

4.1

27

82

55

42

33

28

21

17

11

8.5

6.8

5.6

4.8

4.2

28

85

57

43

35

29

22

18

12

8.8

7.0

5.8

5.0

4.4

29

88

59

45

36

30

23

18

12

9.1

7.3

6.0

5.2

4.5

30

91

61

46

37

31

23

19

13

9.4

7.5

6.2

5.4

4.7

31

94

64

48

39

32

24

19

13

9.7

7.8

6.4

5.6

4.9

32

97

66

50

40

33

25

20

13

10

8.0

6.6

5.7

5.0

33

101

68

51

41

34

26

21

14

10

8.3

6.8

5.9

5.2

34

104

70

53

42

35

27

21

14

11

8.5

7.0

6.1

5.3

35

107

72

54

44

36

27

22

15

11

8.8

7.2

6.3

5.5

D

R

1

R

1.5

Dr. Kim D. Coder, Warnell School, University of Georgia

4

Table 1 (CONTINUED): Tree area increase measured in

cross-sectional inches (square inches) for each

single growth increment by tree diameter.

R

1

R

2

R

2.5

R

3

R

4

R

5

R

7.5

R

10

R

R

12.5 15

R

R

17.5 20

36in 110in2 74

56

45

37

28

23

15

11

9.0

7.5

6.4

5.6

37

113

76

57

46

38

29

23

15

12

9.3

7.7

6.6

5.8

38

116

78

59

47

39

30

24

16

12

9.5

7.9

6.8

6.0

39

119

80

61

49

41

30

24

16

12

9.8

8.1

7.0

6.1

40

123

82

62

50

42

31

25

17

13

10

8.3

7.2

6.3

45

138

93

70

56

47

35

28

19

14

11

9.3

8.1

7.1

50

154

103

78

62

52

39

31

21

16

13

10

9.0

7.8

55

170

114

86

69

57

43

34

23

17

14

11

9.9

8.6

60

185

124

94

75

62

47

38

25

19

15

12

11

9.4

65

201

135

101

81

68

51

41

27

20

16

14

12

10

70

217

145

109

88

73

55

44

29

22

18

15

13

11

75

233

156

117

94

78

59

47

31

24

19

16

13

12

80

248

166

125

100

83

63

50

33

25

20

17

14

13

85

264

177

133

106

89

67

53

36

27

21

18

15

13

90

280

187

141

113

94

71

56

38

28

23

19

16

14

95

295

197

148

119

99

74

60

40

30

24

20

17

15

100 311

208

156

125

104

78

63

42

31

25

21

18

16

D

R

1.5

Dr. Kim D. Coder, Warnell School, University of Georgia

5

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