COMPARTMENTALIZATION 

OF 

DECAY 

IN 

TREES 

Forest Service 

U.S. Department of Agriculture 

Agriculture Information 

Bulletin No. 405 

July 1977 
Watercolor illustrations by David M. Carroll, Warner, New Hampshire. 

* u.s. GOVERNM ENT PRINTING OFFICE, 19n 0-231-254 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

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COMPARTMENTALIZATION 

OF DECAY IN TREES 

Alex L. Shiga 

Plant Pathologist, U,S, Department of Agriculture, 

Forest Service, Northeastern Forest Experiment Station, 

Durham, New Hampshire 

and 

Harold G, Marx 

Research Applications Staff Assistant, U,S, Department of Agriculture, 

Forest Service, Washington, D,C, 

Forest Service 

U.S. Department of Agriculture 

Agriculture Information 

Bulletin No. 405 

July 1977 
INTRODUCTION 

The science of tree pathology 

emerged from studies on decay 

almost a century ago. Many of 

the concepts developed then 

have changed little over the 

years. But, in the last few decades some additional information 

on the decay process in trees 

has been developed. This new 

information has added to the 

basic story of decay without 

subtracting anything important 

from it The new expanded 

concept of decay is simply more 

complete. And this new, more 

complete concept gives us a 

better opportunity to regulate and 

control decay. 

Dr. George H. Hepting made 

the first sound observations on 

compartmentalization of decay in 

trees in 1935. His ideas acted 

as a trigger for the work that 

followed. The work presented 

here is an expansion of his 

ideas. 

The information in this publication is based on 16 yea rs of 

research by Dr. Shiga that involved complete dissections of 

approximately 10,000 trees -

mostly deciduous hardwoods, at 

least 1,000 conifers, and 17 

tropical species. Details of these 

stUdies have been published 

elsewhere. 

The purpose of this publication 

is to show how most columns of 

discolored and decayed wood 

associated with trunk wounds in 

trees are compartmentalized . A 

great number of confusing 

terms are given to a wide variety 

of defects caused by discolorations and decays in trees. This 

book describes a system that 

makes it possible for forest 

managers to understand how 

most of these defects develop. 

To understand the system, the 

2 

report must be studied very carefully. The system is called 

CODIT 

Compartmentalization Of Decay 

In Trees 

When the system is learned, it 

will act as the code for understanding a wide variety of 

defects on most tree species. 

The CODIT system is based on 

two major points. First, a tree is 

a highly compartmented plant 

Second, after a tree is wounded, 

the resulting defects are 

compartmentalized. 

To apply the CODIT system 

it is necessary to understand that 

the new expanded decay concept 

developed in the last few decades 

includes: 1) Successions of 

microorganisms associated with 

discoloration and decay, and 2) 

Compartmentalization of dis· 

colored and decayed wood 

associated with trunk wounds. 

To begi n with , decay of wood 

is a natural process caused by 

microorganisms, mainly fun gi, 

that enter trees through wounds. 

Tree wounds are usually inflicted 

by fire, weather, insects, birds, 

small or large animals, or man 

and his activities. These wounds 

start the processes that can lead 

to decay, and decay is a major 

cause of damage to trees. While 

wood decay is most often caused 

by decay-causing fungi, these 

fungi are often intimately asso· 

ciated with bacteria and nondecay fungi in the process. 

Decay is the breakdown or decomposition of dead organic 

matter. It is also essential to 

new life. 

To understand how trees react 

to wounding and the associated 

defects by compartmentalizing 

the defects, it is necessary to 

reevaluate our concept of how 

a tree is constructed. A tree is 

considered here as a highly 

compartmented plant In a sense, 

a tree is made up of many trees; 

each growth ring is a "tree." 

Each "tree" is divided into many 

compartments. A compartment 

can be thought of as a "room," 

with side walls made up of rays 

and front and back walls made 

up of cells that are the last to 

form in each growth ring. The 

top and bottom of the compartment is formed after wounding 

when the elements that transport 

liquids plug up. The compartment is the least common denominator of the tree. All the 

types of cells found in the woody 

stem of a tree will be found in 

each compartment 

When microorganisms invade 

tree stems through wounds, they 

do so in successions. Bacteria, 

nondecay fungi , and decay fungi 

are often intimately associated 

in this invasion process. When 

microorganisms invade, they first 

su rmount the chemical protec· 

tive barriers set up by the tree 

and then move into the tree from 

compartment to compartment 

The weakest walls of a compartment are the tops and bottoms, 

and the inner walls. The side 

walls are fairly strong. When all 

these walls fa ll to the invading 

microorganisms, there is another 

wall that begins to form. The 

wall formed by the cambium 

after wounding is the barrier 

zone. This wall confines the in· 

vasion to the wood present at the 

time of wounding. The new 

"trees" or rings that continue 

to form are then protected from 

invasion unless new wounds are 

inflicted. When new wounds are 

inflicted at later times, multiple 

columns of defect develop. 

An understanding of CODIT 

will help to clarify many misconceptions about decay. 
Decay is a natural process. 

The breakdown of dead organic 

matter is essential for new 

life. 

Fungi are the major group of 

microorganisms that decay wood. 

In many cases fungi accomplish 

this only in association with 

other organisms, especially 

bacteria. 

- "" -

/ 

3 
Wood -inhabiting microorganisms enter trees through wounds. 

Wounds start the processes that 

can lead to decay. And decay is 

a major cause of damage to 

trees. 

4 

Decay 

1,p.,.ci,jU()US hardwoods and 

tinJoical trees 

Small animals 

Insects 

~ I , 

8 
Fire 

Large animals 

9 
10 

But, before explaining how 

• start the decay process, 

necessary to understand 

a tree is constructed. A 

highly compartmented p.laij1!i~ 

<i'~,'Vr P.< do not replace i 

as animals do. 

A tree is a 

compartmented plant 
"15 ", ee 

,...' . 

Diagrammatic 

drawing 

of a tree. 

In a sense, a tree is made up 

of many trees. Each growth ring 

can be thought of as a separate 

tree, 

\ 

\ 

" 

11 
12 

Pith 

Ray cells form side walls of 

In a diagrammatic way, here 

is how a tree is constructed. 

(The drawings are designed to 

give a general impression of 

compartments in trees and they 

are not intended as technical 

anatomical descriptions of cell 

types and arrangements.) 

The rays define the side walls 

of the compartments. The last 

few series of cells in the growth 

ring define the inner walls. The 

compartment has holes in the 

top and bottom walls because 

the flow of materials is maintained in a vertical direction. 

But, one of the first events that 

happens after wounding is a 

plugging of this system above 

and below the injury. Complete 

tops and bottoms then begin to 

develop on the compartments. 

(The term "walls" is used here 

in a very loose sense only to 

give the mental impression of 

"rooms" or compartments in 

the tree.) 

compartments. 3 -----;--------.11 ~tH-+-_ 

Last cells to form in growth ring 

form inner walls of compartment. 

2 

Top and bottom of compartment 

form when vertical elements plug 

after wounding. 1 ------ ll~fSt;-: l::tJ=::_-\~ 

Compartment 

I 

.l 
In wood present at the time of 

wounding, the tops and bottoms 

of the compartments are the 

weakest walls. These we will call 

Wall 1. The inner walls are the 

second in weakness-Wall 2. The 

side walls are fairly strongWall 3. The strongest wall is the 

one formed by the cambium 

after wounding-Wall 4. 

Wall 1 is incomplete in living 

sapwood because the conducting elements-vessels, tracheids 

-conduct liquids in a vertical 

direction. But as heartwood 

forms, or after wounds are 

inflicted , pits close or the conducting elements are plugged. 

The rate and degree of pit closure 

and element plugging depend on 

many factors. Completion of 

Wall 1 is the result of a dynamic 

process. The plugging will then 

set the limits for the vertical 

extension of each compartment. 

When plugging occurs rapidly, 

short compartments form, but 

when plugging is slow, long 

compartments form. 

Wall 2 is continuous around 

every growth ring, and from the 

top to bottom of the tree. 

Wall 3 is discontinuous because sheets of ray cells are not 

continuous radially and longitudinally throughout the tree. 

Wall 4 is a much stronger, 

more localized version of Wall 2. 

The area-longitudinal, tangential 

-covered by Wall 4 will depend 

on many factors: Wound size, 

type, position, severity, time of 

year when wounding occurs, 

and intrinsic genetic potential 

to respond to wounds. 

Wall 2 is continuous around growth~ ~~ ~;~~~i~:~~5~~~~i ~~:~:~~j ring and from top to bottom of the 

tree. 

Side Walls 3 are the strongest walls. 

Present at time of wounding. ---....;f.-------.;;:§ 

Inner Walls 2 are the next weakest 

walls. ------------.!j-- l----!j--

Wall 1 is incomplete until heartwood 

forms or after wounding. It is not 

planar. ----------....:.L.._ 

Top and bottom Walls 1 are the 

weakest walls. 

Wall 3 is discontinuous. 

Sheets of ray cells may end abruptly 

both radially and 10ngitUdinaIlY.·:::::::==~~ ~~ ~::==::;~l ~~1 

Each growth ring is made up of 

many compartments. 13 
14 

Walls rings and 2 are 

from continuous top to bottom. arou ndi~t~h:e ~~~i~~~i~:~~~;~;~;~.~ 

A compartment _;;.---'-;----

Wa ll 3 ,...,.... ........ -r-__ ~ 

Wa ll 2 +'+it-....... "-.r-F-S-,... 

Wall 1 is in complete until after 

wounding. _________ ,.....I;j.:. 

Wa lls 3 are discontinuous inwa rd and 

up and down. 

A compartment 

Vascular elements plug after 

wou nding and complete Wall 1. 
Each growth ring is made up of 

many compartments. 

A tree is a highly compartmented 

plant. 

Discontinuous Walls 3 

Discontinuous Walls 3 Continuous Walls 2 

Continuous Walls 2 

15 
16 

.u.Ii+4lill. Section B 

lO·year·old wound on maple 

Barrier zone Wall 4 formed atter 

illlli.lL wou 11d in g 

B 

Barrier zone 

After wounding, the cambium 

forms Wall 4. Thi s wall is called 

a barrier zone. It sepa rates wood 

formed before wounding from 

wood that forms after wounding. 

Color key to all drawings 

RED-Host response to wounding, 

chemical reactions to STOP 

invasion. 

GREEN-Invasion processes by 

microorganisms GO through the 

barriers set up by the tree. 

BLUE-Infection of dead and dying 

tissues on wound surface. 

BROWN-Decay processes. 
_____ Bark 

1-Top and bottom walls are weakest walls 

4-Barrier zone equals strongest wall 

Section A 

2-lnner wall 3-Raywall 

17 
Deep 

experimental 

i wound 

Host 

response 

Maple 

After wounding, the tree 

reacts. Chemical barriers de· 

velop around the injured tissues. 

Some wood·inhabiting micro· 

organisms surmount these 

barri ers and begin to interact 

with the tree. The tree exerts a 

living protective force to keep the 

invaders out, and the invaders 

exert a strong force to get into 

the tree through the wound. 

When microorganisms are able 

to get in, they move from com· 

partment to compartment. And 

18 

when the walls of the compart· 

ments begin to fall to the force 

of the invaders, the tops and 

bottoms (Wall 1) go first, then 

the inner walls (Wall 2), and 

then the side walls (Wall 3). But, 

most of the time the barrier zone 

(Wall 4) holds, and confines the 

invaders to the wood present at 

the time of wounding. The 

figures 1, 2, 3, and 4, in addi· 

tion to naming the wall, al so 

indicate the relative strength of 

each wall. It must be emphasized 

that the walls are not absolute 

in their compartmentalizing 

capacities and given enough 

time, even the barrier zone 

(Wall 4) will fall. 
Wood formed 

after wounding 

lO·year·old wou 

Barrier zone Wall 4 

I 

Ii 

Ii 

4 -I1HlIH 

Wall-l Weakest 

-2 

-3 

-4 Strongest 

Barrier zone 

WaIl --~~ 

19 
r

; Wood altered slightly-NOT 

\ ..--~ heartwood 

I 

Barrier zone Wall 4 

Red maple 

20 

3 

The type, severity, and posi· 

tion of the wound will affect the 

extent of compartmentalization. 

Here are some of the most 

typical examples. 

\-+-_4 

Barrier zona 

l-i'--_ Wall 4 

22 

A basal wound of moderate 

severity. The entire "group of 

trees" present at the time of 

wounding was altered slightly, 

and were confined by the 

barrier zone. The side walls, or 

rays, held here and the column 

was wedge-shaped in crosssection. The jagged vertical edge 

was due to variation in confining 

ability of compartment tops and 

bottoms in different growth 

rings. 
A slight basal wound . The 

entire column of wood present 

at the time of wounding was 

altered very little, but it was 

still confined by the barrier zone. 

The inner walls and side walls 

held firm here and on ly a 

"moon ring" formed. 

Very faint 

discoloration =:::====:====f~4~ ~~ 

Diameter of tree 

whenwounded:::::===:=~~~ ~ ___ ~ 

Slight wound 

I ~ .• " l,l I., . . 

23 
24 

In general, the same types of 

columns occur in trees that have 

a heartwood core. Discolored 

and decayed wood is compartmentalized in heartwood. When 

a mechanical wound penetrates 

the sapwood to the heartwood, 

the column develops most 

rapidly along the sapwood· 

heartwood boundary . 

f------ Heartwood Heartwood ---4111 

Sapwood Sapwood ---110, 

Wound -.+-IP 

You ng red oak 
RED-Host response to wounding 

BLUE-Surface infection 

GREEN-Discoloration 

BROWN-Decay 

YELLOW-Heartwood 

2 

Injured cambium 

-----------------Injured cambium 

Host response 

_________________ Injured cambium 

\ 

25 
26 

Heartwood -Hl~*,,~ 

Slightly 

altered 

Heartwood formation stalled near 

wound. 

Barrier zone in heartwood 

4 

4 

4 
f/J.--------Injured cambium 

_---- Large broken 

branches 

Young 

4 

4_~+-

Di scolored and decayed wood 

associated with poorly healed 

large branch stubs is compart· 

mentalized in heartwood . Central 

columns of defect in heartwood· 

forming trees are often asso· 

ciated with poorly healed 

branch stubs. 

4 

27 
28 

altered 

wood 3 

Here are the basic patterns of 

compartmentalized columns of 

discolored and decayed wood 

associated with a single wound 

and with several wounds at one 

time shown on cross section 

in nonheartwood·forming 

trees. 

r - *--4 

central core 

Slightly ....... ~ ... A/1~" 

altered 
Here are some basic patterns 

for heartwood-forming trees. 

Slightly 

altered 

heartwood ---;H~"" 

Discolored 

heartwood 

29 
30 

Injured 

cambium 

Injured 

---- cambium 

Large 

broken 

branch 

Most trees receive many 

wounds du ring their lives. Every 

tree has some branches that 

die. When the branches are 

small and the wounds close 

rapidly, very little internal defect 

foll ows. But, when large branches 

die and healing is slow, trouble 

starts for the tree. Add to this 

the injuries caused by other 

types of wounds at irregu lar 

time intervals and a pattern of 

multiple columns begins to de· 

velop. But again the tree compartmentalizes the injuries and 

each column is separated 

from the others. 
Wound 

Injured cambium, new barrier zone 

forming Injured 

cambium 

31 
1 1 

Barrier zone 

32 

4 

Old barrier 

zone Wall 4 

New barrier 

e forming 

Old barrier 
! 

30-year-old branch stub wounds 

Lu-yei,,-cHo wound 

zone Wall 4 

O-vea r-old wound 

Hr.ttHtttt Barrier zone 4 

33 
34 

Diameter 

when first 

4 

Open branch stub ;(I r::J'P 

4 

~,.,..-.,. Wound 

. , 

.-

central column. 

• 

"-

Multiple columns are common 

in trees. A minor wound may set 

up a central column of discolored 

wood and later large branches 

die and heal slowly. The decay 

associated with the branch stubs 

does not penetrate the inner 

column of compartmenta lized 

discolored wood. 
A central column of compart· 

mentalized discolored wood may 

be associated with large branch 

stubs that healed slowly, but 

did close before decay set in. 

Additional columns of discolored 

and decayed wood could develop 

later, for example, from severe 

mechanical wounds on the 

trunk. 

Stub 

rl-f_IJIO barrier 

zone 4 

-,I-BarrIEi " zone 

Wall 4 

35 
4 4 4 

36 

4 4 4 

Here are some typical patterns 

of multiple colum ns found in 

nonheartwood·forming trees. 
In heartwood·forming trees the 

patterns are the same, but they 

are sometimes difficult to see 

because they are often contained 

in heartwood that is already 

dark in color. Compartmentali· 

zation explains how columns 

of discolored and decayed wood 

can be found in ring patterns 

separated by sound wood. 

4 4 4 

37 
A major obstacle in understanding multiple columns of compartmentalized decay is the 

difficulty in "seeing" them in 

three dimensions. 

Here are some examples: 

Birch-Column of discoloration 

and decay associated with 

a wound developing 

around a central column 

of discoloration associated 

with branch stubs. 

4 ---i---HtR 

Stub --+--ll..= 

4 ___ --1 

Old wound --; 

4 

38 

:-__ .... __ Barrier zone 

Central column 

1--+---;----·01 discolored wood 

1-__ -4 

~!i!t-_-4 

IIHIItfllll--- 4 
Maple-Column of discoloration 

and decay associated 

with a wound developing 

around a central column 

of discoloration. The 

entire column of wood 

present at the time of 

wounding has been 

altered slightly. When 

this wood is dried, it 

will be a different shade 

from the wood that 

formed after wounding. 

Wood altered slightly __ ~ .... ....,,,,, 

Central column of 

discolored wood ---IF-.... -fltt"t 

Wound 

Barrier zone - ...... .""Im'! 

39 
Pine-Column of discolored and 

decayed wood associated 

with a wound developing 

around a central column 

of discolored heartwood 

associated with poorly 

healed branch stubs. 

Barrier zone ---I"""" 

Wound 

4 

40 

Central column of discolored 

....;.,r-;..::;#H~-- heartwood 

,!f !I-- H ea rtwood 



Fornes pini 

44 
_ ...... ____ Heartwood 

;'-__ .J... _________ Discolored heartwood 

Sporophore of L __ ":li&:_-F'on~es pini 

White 

pine 

New column of defect not in 

sapwood 

45 
The " holding power" of columns 

of discolored wood can be shown 

by wounds that penetrate the 

columns. The new column that 

form s remains separate from 

the inner columns. When the 

second wound is severe, decay 

may develop in the new column . 

Thi s occurs in nonhea rtwood· 

forming trees. 

New barrier 

zone Wall 4 

Deep drill wound into sapwood and 

established central column 

discolored wood 

column 

Nonheartwood·forming tree 

46 

Injured 

cambium 

Individual column in each growth 

ring 

Old column 

New 

column 
1 

Decay did not penetrate discolored 

column. 

4 

47 
And in heartwood·forming trees. 

48 

Deep drill wound penetrates 

sapwood, heartwood, and central 

column of discolored heartwood. 

Injured 

cambium 

When new wounds penetrate old 

columns of decay, the decay 

process proceeds rapidly in the 

new col umn . 
4 --1)_ 

49 
There are some patterns of 

defects that on first inspection 

do not appear to fit the concept 

of compartmentalization. However, they do. The most notable 

are the defects associated with 

canker rots. Canker rot fungi, 

once established in a tree, keep 

the wound open by slowly killing 

some living tissues around the 

wound. This process is the same 

as re-wounding. And, when the 

new wound is made, a new 

50 

column begins to develop. An 

intricate pattern of multiple 

columns is associated with 

canker rot. 

New columns form as cambium is 

killed each year. 

Some fungi produce sterile fungus 

material. 

Diameter of trunk 

when branch died. 

Fungus kills cambium and new ---4l~ 

wounds form. 
Mass of fungus material 

Cambium killed 

Q!l7W17r1I. 'f?.z.... 

51 
4 

Ring shake zone 

Slightly altered wood 

4 

large, old open wound 

-~ .. 52 

Barrier ~ 

zone 

Another type of defect that does 

not appear to fit the concept are 

ring shakes-separation of the 

wood along the rings. The prob· 

lem here is that the barrier 

zone associated with the wounds 

often form s far beyond the 

visible column of defect. The 

barrier zone acts as a partition 

between the wood present at 

the time of wounding and the 

new wood formed after. When 

growth stresses or other stresses 

are applied, the wood sometimes 

pulls apart along the barrier 

zone. Most shakes are associated 

with wounds, but not all wounds 

result in shakes. 
Wound 

Barrier 

Wall 4 

i \ : I 

UrV~ _ ,', l,. 

4 

And, yet another type of defect 

pattern that appears not to fit 

the compartmentalization concept 

is the "island" pattern or streak 

pattern often spoken of as 

mineral streak. Wounds indeed 

start these processes. A pattern 

type that can be termed "palm 

and fingers" develops. Near the 

wound all the columns in the 

indi vidual growth ring are 

coa lesced to form the "pa lm." 

As the discolored columns develop vertical ly above and below 

the wound, Walls 1, or the tops 

and bottoms of the compartments 

in individual growth rings, react 

in different degrees to the 

wound and the invading microorganisms. When such a "palm 

and finger" column is viewed 

in cross section at increasing 

distances above and below the 

wound, islands of defect appear. 

Often, a few " fingers" will develop 

far beyond all the others. 

Wood formed 

after wounding 

53 
In sugar maple, for example, the 

"palm and finger" pattern is 

the mineral streak pattern asso· 

ciated with sugar maple borer 

wounds. This insect is a major 

cause of mineral streak in sugar 

maple. 

54 
, \ 

I 

i 

55 
The yellow-bellied sapsucker (see 

page 7) inflicts several types of 

wound patterns on many species 

of trees. In one type of wound 

pattern a large wound is the 

result, and the "palm and 

finger" defect pattern develops. 

Again, the "fingers" may extend 

great distances above and below 

the wound. And cross sections 

of trunks made through the 

"fingers" will show islands of 

defect, or mineral streaks. 

\ 

.. I 

56 

.. ~ 
, 

H 

¥ 

:; 

, 

1 )1 

;; 

, 1 ! 

1 , 

1 

I 

I 

I 

Sapsucker 

The "palm and finger" defect 

pattern is also associated with 

some other wounding patterns 

made by the sapsuckers. 

wounds--________ _ 

~per birch 

57 
Palm and finger 

58 
Sapsuckers wi ll often wound one 

area on a trunk. On paper birch 

a swollen black band will form 

at these sites. 

Not only will discolored streaks 

of the "palm and finger" pattern 

develop from such wounds, but 

the barrier zone that develops 

after wounding may pu ll apart 

from the inner rings to form a 

complete ring shake which is 

sometimes called cup shake or 

loose heart. 

59 
On some trees, such as eastern 

hemlock, the yellow-bellied 

sapsucker inflicts many wounds 

over large areas of the trunk, 

60 

" 

....-Ik---
The barrier zones that form after 

wounding act as partitions be· 

tween wood present at the time of 

woundi ng and wood that forms 

after wounding. When growth 

stresses and other stresses 

develop over long periods, the 

wood may separate along the 

barrier zones, and multiple ring 

shakes form. 

4 

Ring shake zone 

4 

4 

-- y '----'--.,.....-_._.-

Ring shake zone 

61 
The " palm and finger" pattern 

of defect and barrier zones that 

form shake are commonly 

associated with wounds made 

by larger animal,s such as beavers 

and porcupines (see page 9 ), 

When wounds are severe, Walls 

1 and 2 may fall to invading 

microorganisms. 

62 

I 

I 

! 

I ~ , 

\ 

, 

! 

\ 

',., 

r. 

I 1\' ~l ! / C- 17 

r 

-1 

-\ 

I 

i 

-. ..) 

.; 

\. 

Ri ng 

shake 

4 
Squirrels wound young, smooth· 

barked trees in several genera 

(see page 8 ). The typical "palm 

and finger" defect pattern reo 

suits. In some species these 

defects are called mineral 

streaks. 

63 
Insects wound trees (see page 

8) and small islands of defects 

form. Each island of defect is 

a small "palm and finger" 

column. The columns usually 

penetrate only to the depth of 

the hole made by the insect. 

Insect 

hole 

I ,.=-:- ~;-~ 

Tubes from 

scale insect , ... -1fO., __ 

Scale insect that lives in old insect 

lS!it:::::t"'O;;"-fff------=:;---4- holes 

.. - --;..;;...: ...... =} 

~ -..."..., 

"-"===== 

64 

Insect 

holes 

=: :. -:-:U::-.c.? 
-

C"~~--~ I -- ._ . - - ~-- " I 

I 

I 

When many insects attack a tree 

at the same time, a barrier zone 

may develop around the entire 

tree. All the wood present at 

the time of wounding will be 

slightly altered. When dried, the 

wood present at the time of 

wounding will be a different 

shade from the wood that formed 

after wounding. 

.. ' 

•• 

65 
The cambium miner is a small 

larva of a type of fly that eats 

its way down the cambial region 

of some trees. The "tracks" of 

the larvae are compartmentalized 

as ve ry long narrow streaks of 

discolored wood within growth 

rings. 

66 
On some trees the wounds are 

not visible. This is common with 

small basal wounds, especially 

those caused by fire when the 

tree was very young and now 

the healed wound is hidden by 

forest litter. The barrier zone still 

forms around such wounds and 

often results in ring shake. Also, 

the inrolled callus serves as a 

weak spot on the tree that may 

continue to split vertically. Addi· 

tional cracks may form from 

the barrier zone outward into 

the wood that forms after wound· 

ing. When the cross section of 

a trunk with such a pattern of 

internal defect is viewed above 

the base, a star·shaped pattern 

of cracks radiating out from 

the center will be seen. 

, ~ 

67 
With some basal wounds, long 

internal cracks, called seams, 

form at right angles to the 

wounds at the points where the 

calius inrolis. 

68 

-~/ 

Seams wi ll also form from 

mechanical wounds on trunl<s. 

Once a seam begins to form, 

it will usually continue to enlarge 

throughout the life of the tree. 

70 
-'-'~{ . 

,I , J.I ' -.. 

-- . 

- ' '': 

.... ..... ,... . 

• -I _ .... 'I/'...s,.." 

':--"" ,0 

,-

.. \ 

71 
In summary, the compa rtmental· 

ization of defects in trees is a 

survival system that is effective 

most of the time-not all of the 

time! And after the tree dies, 

72 

the powerful decay processes 

continue to decompose the 

wood. The decaying wood provides nourishment for a wide 

variety of organisms. 
The decomposed wood provides 

nourishment for new trees. 

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