Total tree and product weight of beetle-killed loblolly pines in northeast Georgia / by W. Henry McNab

-
?l
A GEORGIA FOREST RESEARCH PAPER

42
March, 1983

TOTAL TREE AND PRODUCT WEIGHT OF BEETLE-KILLED LOBLOLLY

PINES IN NORTHEAST GEORGIA
BY

Received

W. HENRY Mc NAB

DOCUMENTS

J

RESEARCH DIVISION
GEORGIA FORESTRY COMMISSION

COVER
These loblolly pines were recently killed by southern pine beetles and are still merchantable for a variety of products, including saw logs, pulpwood, and total tree fuel-
wood chips. Note particularly the low-value understory hardwoods, which have been released from competition and may soon dominate this pine site.

WILLIAM H. McNAB is a Research
Forester with the Southeastern Forest Experiment Station at Athens, Geor-
gia. He has a BS degree in Forest Man-
agement and MS in Silviculture, both
from the University of Florida. He is a member of the Utilization of Southern Timber Research Work Unit, where he works mainly on problems related to the effects of silvicultural practices on biomass yields and utilization of forest
residues.

ACKNOWLEDGMENT

Received
OCT 4683
DOCUMENTS UGA LIBRARIES

The author gratefully acknowledges the financial support and assistance given by the Georgia Forestry Commission for making this research possible. Special thanks are given to B. F. Young, Superintendent, Hard Labor Creek State Park, and Roswell P. Goolsby, Assistant Ranger, Oconee National Forest, for assistance in locating the trees sampled in
this study.

TOTAL TREE AND PRODUCT WEIGHT
OF BEETLE-KILLED LOBLOLLY PINES IN NORTHEAST GEORGIA
BY
W. HENRY Mc NAB

INTRODUCTION

Utilization of beetle-killed trees not only helps control the spread of southern
pine beetles, but is a good management
practice to increase profits. Recently killed trees are usually merchantable with little loss of quality and lower stumpage value. However, during severe outbreaks of southern pine beetles, immediate utili-
zation of dead trees may not be possible
because of oversupply at the mill. Standing dead trees will deteriorate
rapidly in the warm, humid climate of

the South. Barron (1971) found that within several months of their death,
beetle-killed trees lose little wood sub-
stance but over half of their moisture content. Since half of the total weight of live loblolly pines consists of water (Taras and Clark 1975), this loss of water results in a major reduction of tree weight, especially if beetle-killed trees are
marketed on a weight basis. The yield of harvested southern pine
timber is commonly measured on a

weight basis for convenience and, with proper factors, is converted to conventional volume units by the buyer. Conversion factors are available for live pine sawlog and pulpwood timber (Saucier and others 1981) but they should not be applied to beetle-killed trees because of the lower moisture content of dead trees. Reported here are the results of a study to develop prediction equations and tables for estimating the weight of trees killed by southern pine beetles.

PROCEDURE
Loblolly pine trees killed by southern pine beetles during 1980 and 1981 were selected from natural upland stands at four locations in northeast Georgia (Figure 1). Sixty trees, ranging from 5 to 18 inches d.b.h., were sampled and grouped in two classes according to crown ap-
pearance (Table 1). Trees in class A were
estimated to have been dead from 5 to 7 months, and still had fine twigs attached to the larger branches (Figure 2). Those in class B had lost some of their small branches and had been dead from 10 to more than 18 months (Figure 3).
The amount of bark remaining on the trees varied widely, particularly between classes. Levi (1981) found that the pres-
ence or absence of bark is not a reliable
indicator of wood quality. Generally, all
stem bark was still attached on trees in
class A and was present on the lower half
of trees in class B. All trees sampled had bark present at 4.5 feet. The 13 sawtim-
A ber-size trees sampled in class averaged
12.9 inches d.b.h. and contained an average of 2.5 to 3.0 saw logs 16.3 feet in
length.
Trees were felled with a chain saw, limbed, and the main stem was bucked into major products of saw logs and pulpwood, depending on tree class and size. In class A, saw logs to a 7-inch d.o.b. or merchantable top were cut from trees greater than 9 inches d.b.h. Pulpwood was cut to a 4-inch d.o.b. top from the stem above the saw-log top, and from smaller trees.
No saw logs were cut from trees in class B
because of probable low grade and loss of strength resulting from blue stain, decay, or insect damage ( Levi 1 981 ).
The crown, consisting of stem wood
above the 4-inch top and all branches, was weighed separately to the nearest pound. Broken branches and topwood
were included in the weighing when they could be found and identified according
to the proper tree. Samples of stem and
branch wood were collected and returned
to the laboratory for determination of moisture content.

Figure 3.

-Class B beetle-killed loblolly pines have broken branches and lack fine branch twigs.

SAMPLING LOCATIONS
Figure 1. -Sampling locations of beetle-killed loblolly pines in northeast Georgia.

A Figure 2. -Class beetle-killed loblolly pines still have fine twigs attached to
the main branches.

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A

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V *"m jfjp

/^3

^_J_i A
J

.,.,,_
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j j/F
k^*<*js&j$ ^^^N

f$kl

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RESULTS AND DISCUSSION

Preliminary analysis of the weight data showed no practical difference in total tree or product weight between the two
tree classes. Wood moisture content was
also similar between the two classes of
trees:

Tree Class
A
B

Main Stem Branches

Percent- -

62

24

45

26

Except for the saw-log weights, total tree and pulpwood weight data from both classes were combined into a single group for further analysis.

Total Tree Weight

The relationship of average total tree green weight by d.b.h. class is shown in
Figure 4. Results are presented for tree
wood content only, and do not include bark. Even though bark was present on most of the bole on trees in class A, it was loosely attached and would probably
be lost during felling and skidding opera-
tions.

8

10

12

14

D.B.H. CLASS (INCHES)

Figure 4. --Relationship of total-tree green weight to d.b.h. class of beetle-killed loblolly pines in northeast Georgia.

I00r-

CROWN

PULPWOOD mi SAW LOGS

80

A considerable amount of crown ma-
terial was often broken from trees in class
B during felling. On the average, about 15
percent of the total tree weight in
branches and top wood was broken and probably would not be recovered for
utilization. Larger trees appeared to lose a
higher proportion of crown wood than
small trees.

Product Weight

60
Q: 40
20

8

10

12

14

16

D.B.H. CLASS (INCHES)

The distribution of pulpwood and sawlog product weight as a percentage of
A total tree weight is shown in Figure 5.
large proporation of total tree weight consists of pulpwood in the bole to a 4inch d.o.b. top, indicating that recover-
A able crown weight is relatively small.
similar trend occurs between the bole weight to a 4-inch top and saw-log weight. The proportion of weight in saw logs increased until tree d.b.h. reached 14 inches, where it leveled off at about 83
percent.
Figure 5. -Proportion of total-tree green weight in crown, pulpwood, and saw logs for beetle-killed
loblolly pines.

Predicition Equations
Prediction equations were developed
from common cruise variables to estimate A total tree and product weight. predic-
tion equation for pulpwood weight was developed by using d.b.h. and height to a 4-inch d.o.b. top. Total tree weight was estimated by developing a prediction equation for the crown separately, and adding it to the predicted weight of pulpwood. An equation using d.b.h. and merchantable height was developed to allow
estimation of saw-log weight. All equations were sufficiently accurate to ac-
count for over 95 percent of the variation associated with total tree or product
weight.
Weight Scale Factors
Factors for converting weight to units of volume were calculated from field weights and published volume tables (Knight and McClure 1974 Mesavage and
Girard 1956). An average of 2,996 pounds of wood from 8-inch d.b.h.,
beetle-killed trees was required for a stacked cord containing 68 cubic feet of wood. For sawtimber in our study, the average weight per thousand board feet (Scribner log rule, form class 78) was about 10,600 pounds. Saw-log conversion factors were also calculated from d.b.h. class and estimated weights (Table
2).
Weight Tables
Prediction equations were used to construct Tables 3, 4, and 5 for estimating saw-log, pulpwood, and total tree green
weight. Other components may also be estimated by using values from these tables. For example, pulpwood above the
saw-log merchantable top can be determined by subtracting saw-log weight from weight to a 4-inch top. Likewise, crown weight can be estimated by subtracting pulpwood weight from total tree weight. As with any table of this type, predicted weights are most accurate near the center of the "blocked-in" area and, where possible, predicted weights should be verified for accuracy.

branch wood moisture content of live
loblolly pines is slightly over 100 percent (Taras and Clark 1974), almost double the amount measured in beetle-killed trees. Tables for estimating the weight of the total tree and products, and

weight-scaling factors were developed for
beetle-killed loblolly pines.
If markets are not available or if excessive deterioration lowers qood quality for conventional products, beetle-killed trees can be harvested for fuelwood
chips.

-- Table 1. Means and ranges in dimensions of beetle-killed
loblolly pines sampled in northeast Georgia

Tree Trees class sampled

Number

A

26

B

34

All 60

D.b.h.

Height to 4-inch top

Mean

Range

Mean

Range

- - -Inches- - -

-Feet

9.8 11.6

5.1-15.3

46

5.2-18.8

56

14-72 14-82

10.8

5.1-18.8

52

14-82

-- Table 2. Estimated green weight of pulpwood and saw logs
per unit volume for beetle-killed loblolly pines in northeast Georgia

D.b.h. class (inches)

Pulpwood 1/

Saw

2/ log

Merchantable

height

Weight

Lb /cord

Feet

Lh/MBF

2,745

3,064

10

3,290

12

3,452

14

3,573

16

3,672

18

3,748

1.5

12,700

2.0

11,200

2.5

10,300

3.0

9,600

3/

9,100

SUMMARY AND CONCLUSIONS
Pines killed by beetles are merchantable for various products if harvested soon after attack. In the South, however, significant weight loss occurs quickly, especially during the summer months, and will affect accurate conversion of weight to volumes if factors for live trees are used. For example, the main stem and

-- Cubic feet of wood per cord from Knight and
McClure 19 74. Average field weight of wood and bark per cubic foot of wood was about 45 pounds for the main stem.
2/ Scribner log rule; form class 78.
3/ No trees measured in this d.b.h. class weight extrapolated.

-- Table 3. Predicted green weight of wood to a saw-log merchantable
height for beetle-killed loblolly pines in northeast Georgia

D.b.h. class (inches) 1.0

9

288

10

359

11

437

12

523

13

617

14

719

15

16

17

18

19

20

Merchantable

saw-log

top

(16-foot

L/
logs) J

1.5

2.0

2.5

3.0

3.5

- - -Pounds-- - - -

379 472 5 74 688 811 946 1091 1247

461 573 698 836 987 1150 1326 1516 1718 1934

537 668 813 973 1149 1339 1544 1765 2000 2252 2518 2800

608 756 921 1102 1301 1516 1749 1999 2266 2550 2852 3171

1023 1225 1446 1685 1943 2221 2518 2833 3169 3523

1/ Blocked-in area indicates range of data,

y

y=

o^ocdV-^V)

- 68894
.

where:

Y = saw-log weight in pounds, D = d.b.h. in inches, Mh = saw-log merchantable height in 16-foot logs

:
3 2106 DMSSM 5M75

Table 4.- -Predicted green weight of wood to a 4 -inch d .o.b. top for beetle--killed loblolly pines in northeast Geo rgia

D.b.h.

Heigh t to 4-inch top (feet)-7

class

(inches)

10

20

30

40

50

60

70

80

- - Pounds-- - -

5

37

70

103

134

166

197

6

52

99

144

189

233

277

7

69

132

193

253

311

369

427

8

88

169

248

324

400

475

548

9

110

211

309

405

499

592

684

755

10

134

257

377

49 3

608

721

833

944

11

308

450

590

727

862

996

1129

12

362

530

694

856

1015

1173

1329

13

616

806

994

1180

1363

1545

14

708

927

1142

1355

1566

1775

15

1055

1300

1543

1782

2020

16

1190

1467

1741

2012

2280

17

1644

1951

2254

2555

18

1830

2171

2509

2844

19

2403

2777

3147

20

2646

305 7

3465

1/ Blocked-in area indicates range of data.

y2

93763

Y - 0.20679(D H4)-

.

where

Y = stem weight to 4-inch d.o.b. top, D = d.b.h. in inches, H4 = height to 4-inch top.

:

'

-- Table 5. Predicted green weight of total tree wood for beetle-killed
loblolly pines in northeast Georgia

D.b.h.

Hei ght

to

4 -inch

top

1/ (feet)

class

(inches)

10

20

30

40

50

60

70

80

- - Pounds2--/- -

5

56

97

135

172

208

242

6

74

131

184

234

283

331

7

95

169

238

305

370

433

495

8

119

212

299

384

466

547

626

9

144

259

367

471

573

673

771

869

10

172

310

441

567

690

811

930

1048

11

366

521

671

817

961 1103 1243

12

425

607

782

954

1123

1289

1453

13

699

902

1101

1296

1488

1678

14

797

1029

1257

1480

1701

1919

15

1164

1422

1676

1926

2174

16

1307

1598

1883

2165

2444

17

1782

2102

2417

2728

18

1976

2331

2681

3027

19

2571

2958

3341

20

2822

3248

3668

1/
Blocked-in area indicates range of data.

-'

Y

=

2
0.20679(D H4)

' 93763

2

4866

+ 1. 30503(D H4)

where

Y = total tree weight in pounds, D = d.b.h. in inches, H4 = height to 4-inch top.

10

LITERATURE CITED
Barron, Edwin H. 1971 . Deterioration of southern pine beetle-killed trees. For. Prod. J. 21(3): 57-59. Knight, H. A.; McClure, J. P. 1974. Georgia's timber, 1972. Resour. Bull. SE-27. Asheville, NC: U.S. Department of
Agriculture, Forest Service, Southeastern Forest Experiment Station; 19 p.
Levi, Michael P. 1981. A guide for using beetle-killed southern pine based on tree appearance. Agric. Handb. 572. Wash-
ington, DC: U.S. Department of Agriculture; 19 p. Mesavage, Clement; Girard, J. W. 1956. Tables for estimating board-foot volume of timber. Washington, DC: U. S. De-
partment of Agriculture, Forest Service; 94 p. Saucier, J. R.; Phillips, D. R.; Williams, J. G. 1981. Green weight, volume, board-foot, and cord tables for the major
southern pine species. Ga. For. Res. Pap. 19. Macon, GA: Georgia Forestry Commission; 63 p. Taras, M. A.; Clark, A. 1975. Aboveground biomass of loblolly pine in a natural uneven-aged sawtimber stand in central
Alabama. Tappi 58(2): 103-105.

GEORGIA
FORESTRY,
\er>
#*\%*J
John W. Mixon, Director
J. Fred Allen, Chief of Forest Research