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

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

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 -- 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 ? 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 ? 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

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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

R R

RR R R

R R

R R R R

D 1 1.5 2 2.5 3 4 5 7.5 10 12.5 15 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

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

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Table 1 (CONTINUED): Tree area increase measured in cross-sectional inches (square inches) for each single growth increment by tree diameter.

R

R R

RR R R

R R

R R R R

D 1 1.5 2 2.5 3 4 5 7.5 10 12.5 15 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

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

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Table 1 (CONTINUED): Tree area increase measured in cross-sectional inches (square inches) for each single growth increment by tree diameter.

R

R R

RR R R

R R

R R R R

D 1 1.5 2 2.5 3 4 5 7.5 10 12.5 15 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

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

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