UniDted States 

Department of 

Agriculture 

Growth and Crown Vigor 

of 25-Year-Old Shortleaf Pine Progenies 

Forest Service 

on a Litt eleaf Disease Site 

Southeastern Forest 

Experiment Station 

Research Paper 

SE-289 

Stanley J. Zarnoch, John L. Ruehle, 

Roger P. Belanger, Donald H. Marx, 

and W. Craig Bryan 
The Authors 

Stanley J, Zarnoch is Mathematical Statistician; John L. 

Ruehie is Plant Pathologist (retired); Roger F, Belanger is 

Principal Silviculturist (retired); Donald H, Marx is 

Director, Institute of Tree Root Biology (Emeritus 

Scientist); and W. Craig Bryan is Plant Pathologist 

(retired), a11 from Southeastern Forest Experiment Station, 

U.S. Department of Agriculture, Forest Service, Athens, 

GA 30602. 

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September 1994 

Southeastern Forest Experiment Station 

P.O. Box 2680 

Asheville, North Carolina 28802 
Growth and Crown Vigor of 25-Year-Old Shortleaf Pine 

Progenies on a Littleleaf Disease Site 

Control-pollinated progenies of shortleaf pines that appeared to be 

resistant to littleleaf disease were planted on a test site near Union, 

SC, in 1965. The planting was assessed at ages 17 and 25 to identify 

progenies with superior growth and resistance to pest problems 

associated with littleleaf disease sites. Among the 30 progenies in the 

experiment, 2 produced more than 12 cubic feet of total volume 

growth per tree and an additional 5 produced more than 11 cubic feet 

per tree. However, at age 25 even rhe best growing progeny had 

individual trees with visual crown symptoms of Iittlefeaf disease. A 

control seedlot from open-pollinated shortieaf pines ranked law in 

performance (7 @/tree) and crown vigor. All trees with crown 

densities of less than 50 percent, regardless of parents, were growing 

poorly and in accelerated decline. There was a close relationship 

between rankings in volume growth at ages 17 and 25, indicating that 

candidates for future tree improvement programs can be reliably 

selected at an early age. 

Keywords: Tree decline, forest health, tree-ring chronologies, pinlrs 

eclt inafa . 

f nt roductt ion 

Shortleaf pine {Pittus eel~ittam Mill.) has the largest 

natural range of any southern pine (fig. 1)- Although it 

is well atlaptwl to a broad range of environmental 

conditions, its growth, health, and survival can be 

severely reduced on poorly aerated soils with poor 

internal drainage. On these sites, trees often decline at 

an early age. Their crows become sparse, cone 

production is prolific, and growth is reducd. Fine 

roots are lost to infection by the soilborne fungus 

Pliytophthorn cirttlnmomi Rands and other pathogens as 

well as soil factors. Symptoms of littleleaf disease 

rarely occur before age 20. Trees expressing littleleaf 

disease symptoms often die prematurely or are at high 

risk to attack by the southem pine beetle (Detlcirocrottus 

finratis Zimermann) (Oak and Tainter 1988). 

400 MILES , 

Figure 1-Natural distribution of shortleaf pine. 
Campbell and Copeland (1954) found that even where 

disease incidence was high, not all shortleaf pines on 

the site died. Trees that remained healthy were judged 

to be resistant to the disease or better adapted to 

associated site conditions. A long-term research study 

was initiated to test the performance of selected crosses 

made between these healthy trees. 

Symptom-free trees of good form and vigor were 

selected on severely affected littleleaf disease areas at 

Hamilton, GA, and Union, SC (Zak 1955). Scions 

from selected trees were grafted onto shortleaf and 

loblolly (P, taerfa L.) rootstocks, and the clones were 

planted during the winter of 1953-54 at mitehall, GA. 

Sixteen different selections were successfully grown to 

seed-bearing size in this breeding orchard. In 1965, a 

field experiment was installed on a littleleaf disease site 

in Union, SC, to test F-1 progenies from controlled 

crosses between these selections (Bryan 1965). The 

planting was assessed at age 17 to identify progenies 

with disease resistance and siiperiolr growth (Ruehle and 

others 1984). Among the 38 progenies in the 

experiment, 6 were rated superior in height, d.b.h., and 

tree volume growth. Since few individuals showed 

symptoms of littleleaf disease at this time, it was 

concluded that the stand was too young for proper 

evaluation of disease resistance. 

In this Research Paper, we report results of 

measurements and evaluations at 25 years. We paid 

particular attention to visual crown characteristics. The 

recent interest in the effects of atmospheric deposition 

and global climate change on forest health has 

emphasized the need to document growth rates of 

important tree species and develop field methods and 

indicators of growth decline. Several crown 

characteristics have been employed in forest health 

monitoring programs to indicate the relative condition 

andfor susceptibility of a tree to specific insect and 

disease problem. In addition, dendrochronoIogy has 

been used to detect abnormal changes in radial or basal 

area growth caused by environmental factors. The 

present study planting presented a first-time opporpani ty 

to document growth rates, observe crown conditions, 

and analyze tree-ring chronologies for a wide range of 

shortleaf pine progenies growing on a Iittlefeaf disease 

site. 

Specific crbjwtivrts of this research were: 

* To evaluate height, d. b. h., volume, and crown 

vigor of shortleaf pine progenies on a littleleaf disease 

site at age 25 years. 

* To evaluate the periodic growth of these progenies 

from age 17 to age 25. 

* To evaluate the relationships between growth from 

ages 17 to 25 and crown characteristics at age 25. 

* To evaluate annual growth rates using tree-ring 

chronologies for the best, intermediate, and worst 

progenies based on total volume at age 25. 

Study Description 

Parent Selections and Progenies 

The families selected for this study were crosses 

between five Georgia parents (27, 213, 214, 215, and 

2117) and eight South Carolina parents (Y 1, Y2, Y3, 

Y4, Y5, Y6, Y8, and Y9). In all, there were 27 F-1 

progenies and 2 selfed progenies. Table 1 shows these 

progenies and their parents. An open-pollinated, mixed 

seedlot collected in Georgia served as the check. Seeds 

were sown in flats in June 1964. Three months later, 

seedlings were transplanted into 6-inch clay pots filled 

with forest soil. These were grown in a greenhouse 

until April 1965 when they were planted in the field. 

Study Site 

An area in the Sumter National Forest approximately 10 

miles south of Union, SC, was selected for planting. 

This area had supported 25- to 30-year-old shortleaf 

pines with moderate littleleaf disease symptoms. The 

area had been cut and cleared in 1959. The cleared 

area, about 10 acres, extends lengthwise in an east-west 

direction along a ridge with elevation ranging from 500 

to 510 feet. The soil type is HeIenalVance sandy loam; 

years of erosion have removed 50 to 75 percent of the 

topsoil, Soil samples collected from 15 random 

locations over the 10 acres were assayed for soil 

characteristics and the presence of PI~ytophtl?orn 

cirittnmomi. The apple technique (Campbell and 

Copeland 1954) revealed the presence of P. cirltrnrnomi 

in over 65 percent of the samples. Sampling also 

showed that the fungus was uniformly distributed over 

the area. The soil contained 1.7 percent organic matter 

and had a pH of 5.9. See Ruehle and others (1984) for 

further site information. 
Table I-Average bole dimensions and crown vigor ratings of shortleaf pine prtrgenlicls at age 17 on a llittfeleaf 

disme site in Union, SC (1982 data from Ruehle and others (1984))' 

Parents 

Progeny Fe~x~nle Male Volume' Height D.b,h. Crown vigor"( 

Z15 27 

215 U8 

2515 215 

Y5 U8 

Y5 27 

Y1 Z 15 

Y2 Z 13 

Y9 27 

Y5 U5 

Y1 27 

Y2 27 

U2 214 

2515 Y4 

U9 Z 13 

215 213 

Y6 Y8 

Y9 215 

Y5 Y4 

215 Y3 

Z15 Y6 

Y2 Y6 

Check 

Y9 Y4 

217 213 

Yl Y8 

Y5 Y3 

Y9 Y8 

'91 Y6 

2 17 U3 

V9 Y6 

Cubic feet 

5.41 a 

5.09 ab 

4.87 abc 

4.74 a-d 

4.68 a-e 

4.64 a-e 

4.38 a-f 

4.29 a-f 

4.29 a-f 

4.03 b-h 

3.99 b-i 

3.86 c-j 

4.76 c-j 

3.76 c-j 

3.75 c-j 

3.75 c-j 

3.65 c-j 

3.55 d-k 

3.50 e-k 

3.49 e-k 

3.35 f-k 

3.33 f-k 

3.07 g-I 

2.99 h-I 

2.81 h-1 

2.76 i-1 

2.63 jkl 

2.42 kl 

2.14 1 

2.12 1 

Feet 

42.8 a 

42.2 ab 

42.2 ab 

40.5 a-d 

40.6 a-d 

40.0 a-e 

38.9 b-g 

41.2 abc 

353.8 a-e 

44.04 a-d 

40.3 a-d 

40.0 a-e 

40.4 a-d 

39.0 b-f 

38.3 c-g 

40.3 a-d 

38.9 b-g 

38.3 c-g 

38.4 c-g 

38.9 b-g 

39.0 b-f 

38.1. c-g 

38.8 b-g 

37.2 d-g 

36.8 efg 

36.2 fg 

37.6 d-g 

37.2 d-g 

35.6 g 

36.3 g 

8.0 a 

7.9 ab 

7.7 a-e 

7.8 abc 

7.8 a-d 

7.8 a-d 

7.7 a-e 

7.5 a-g 

7.4 a-f 

7.3 a-g 

7.3 a-h 

7.2 b-h 

7.1. c-i 

7.2 b-h 

7.3 a-h 

7.1 c-i 

7.1 b-i 

7.1 b-i 

7.1 c-i 

7.0 d-i 

6.9 f-j 

7.0 e-j 

6.7 g-k 

6.8 g-k 

6.6 h-1 

6.7 h-1 

6.4 i-1 

6.3 jkl 

6.1 kl 

6.0 1 

5.94 abc 

6-00 a 

5.92 abc 

6.00 a 

5.96 abc 

5.96 abc 

5.90 abc 

6.00 a 

6.00 a 

5.98 ab 

5.90 abc 

5.66 bed 

5.92 abc 

5.96 abc 

5.96 abc 

6.00 a 

5.94 abc 

5.88 abc 

5.88 abc 

5.86 abc 

5.96 abe 

5.44 d 

6.00 a 

5.64 cd 

5.92 abc 

5.68 a-d 

5.90 be 

5.88 abc 

5.42 d 

5-66 bcd 

Mans in the same colum followed by the same letter are not significantly different at the 8.05 level. Progenies 

are ranked by voiurne. 

V = -0.98284 i- 0.00230 (Il2W) where t" = volume to 4-inch d.o.b, top, D = d,b.h, in inches, H -f total height 

in feet, 

Most of these are included in the 25-year remeasurement: however, n~ortality did eliminate some. 

The value 4.04 is a typographical error tn Ruehle and others (1984). 
Study Installation 

In the spring of 1964, a year before study installation, 

the site was intensively prepared and the large pieces of 

slash and brush were raked into piles and burned. On 

the cleared site, a 2.4-acre area was selected and 

divided into five irregularly shaped blocks. Seedlings 

were planted in April 1965 on a 12- by 12-foot spacing 

(302 treesfacre). Within each block, four seedlings of 

each progeny were randody assigned to planting spots. 

Amitrol -T @-amino- 1,2,4 triazole) was sprayed for 

weed control, For initial control of pales weevils and 

tip moths, 1 teaspoon of 5-percent granular aldrin and 1 

teaspoon of 10-percent granular Thimet were spread on 

the soil around the base of each tree. In addition, the 

trees were sprayed with 0.5-percent water emulsion of 

aldrin. A double border row of ordinary shortleaf 

planting stock from the North Carolina State Forestry 

Cornrnission Nursery at Norganton was planted around 

the five blocks. 

In September 1982 at plantation age 17, progeny 

performance was evaluated. The d. b.h. and height of 

all surviving trees were measured and crown 

characteristics were rated. Since very few trees were 

showing typical littleleaf symptoms, a crown vigor 

rating was used instead of a disease rating because few 

trees had littleleaf symptoms. Crowns were assigned a 

rating of 1 through 6: 

Rating Definition 

1 Tree dead; root disease rather than 

injury or suppression probable cause 

of death. 

2 Poor vigor; extensive twig mortality, 

obvious decline, foliage tufted and 

yellow. 

Fair vigor; thin crown, some twig 

mortality, lower branches dying, 

foliage yellow-green. 

Medium vigor; growth reduction 

evident, yellow-green foliage in lower 

half of crown. 

Good vigor; appearance good, but 

foliage in crown thin, green foliage. 

Excellent vigor; foliage and crown 

dense, good foliage growth, foliage 

dark-green. 

Tree volume was calculated using equations developed 

by Saucier and others (1 98 1 j. Breeding values of each 

parent (2 x the general combining ability vaIue (GGA) 

+ the general mean) were calculated for all growth 

parameters to gain an indication of the performance 

expected from the offspring of a selected parent when it 

is crossed with other parents of equal genetic quality. 

These preliminary results were reported by Ruehle and 

others (1984 and are shown in table I). Generally, 

only a few trees showed symptoms of littleleaf disease. 

Six progenies exhibited superior growth in height, 

d.b.h., and volume. Based on stem volume of the 

progenies, two Georgia parents (27 and Z15) and two 

South Carolina parents (Y5 and Y8) were identified as 

good candidates for future tree-improvement programs. 

At age 25, the variables observed at age 17 plus several 

others were measured. Total height (ft) and d. b. h. (in) 

of each tree were measured. Individual-tree basal area 

(ft') was calculated in the typical manner, and volume 

(ft" to a 4-inch top d.0.b. was computed using the 

volume equation of Saucier and others (1981). The 

percentage growth in height, d.b.h., volume, and basal 

area between ages 17 and 25 was computed. The 

crown vigor rating already described (1 = tree dead,. . . , 

6=excellent vigor) was applied to each tree. In 

addition, four crown measures currently used in forest 

health monitoring (Belanger and Anderson 1992) were 

obtained by averaging estimates from four observers. 

These were: 

1. Crown Density. Estimated to the nearest 5 percent 

(Belanger and Anderson 1992 j. 

2. Needle Retention. The Longer a tree retains its 

needles, the more vlgorous growth is expected. 

Recorded as 1, 2, or 3 years. 

3, Ijwarfing. The reduction in the average length of 

all needles in relation to lengths on nearby healthy 

shortleaf pines. Estimated to the nearest 5 percent. 

4. Discoloration. Degree of yellowing. Estimated to 

the nearest 5 percent. 

In addition, tree-ring chronologies were developed to 

illustrate the growth rates of the five best, five 

intermediate, and five worst progenies. The progenies 

were ranked based on total volume at age 25. 

Generally, two trees were randomly selected from each 
block from each of these progenies for tree coring, 

Results were contrastd with those for the check 

progeny (13 trees) and other trees with crown density 

ratings less than 50 percent (21 trees). Tree cores were 

read on both sides of the pith where possible; mean ring 

widths were computed from 1975 to 1990 and annual 

basal area increments were calculated. 

Statistical Analysis 

The randomized block design consisted of 30 progenies 

replicated in 5 blocks. There were 27 F-1 progenies, 2 

selfed progenies, and a check. Originally there were 

four additional progenies installed in the field design but 

since they were identical to other crosses already in the 

study except that the seed was crossed a year later, they 

were eliminated from this study. Each progeny was 

originally represented by four trees in each block. Of 

the 600 trees planted in 1965, 544 survived to age 25. 

Of these, 14 were suppressed, 16 had ice damage, 1 

was suppressed and had ice damage, and 1 was 

inadvertently bypassed during crown observations. 

These atypical trees were excluded from the statistical 

analysis, leaving a sample size of 512. 

In the statistical analysis, the block mean for each 

progeny was used as the variate. Thus, each mean was 

usually based on four trees. Overall F-tests were 

performed with PROC GLM; Tukey's test was used for 

painvise comparisons at the 0.05 level (SAS Institute, 

Inc. 1988). Relationships between growth and crown 

characteristics were analyzed with PROC STEPWISE. 

Results 

Perfomance at 25 years. Growth and crown vigor of 

individual progenies at age 25 are shown in table 2, 

where the progenies are ranked in order by volume. 

Volume of progenies averaged 9.24 cubic feet and 

ranged from 13.65 cubic feet for progeny 15 to 5.21 

cubic feet for progeny 22. Although volume growth for 

the check was low (7.02 ft3 = 26 in ranking), only two 

progenies produced significantly greater volume than 

the check. Both these progenies had Z15 as one parent, 

The four progenies that grew less than the check had 

selections from South Carolina for both parents. The 

rankings in volume growth at age 25 are quite similar 

to those at age 17 (table 1) reported by Ruehle and 

others (1984). The 10 progenies with the greatest total 

volume at age 17 were also the top 10 performers at 

age 25, The largest change in ranking was for progeny 

21, which fell frorn third at age 17 to eighth at age 25, 

Similarly, 8 of the 10 poorest performers at age 17 

continued to grow sIowIy through age 25. 

The most significant distinctions in progeny 

performance were for total height growth (see table 2). 

Tree height averaged 54.0 feet and ranged from 57.5 

feet for progeny 10 to 49.4 feet for the check. A total 

of 10 progenies were significantly taller than the check. 

The rankings for d. b. h. at age 25 are quite similar to 

those for volume growth. This result was expected 

because tree diameter is the most heavily weighted 

component of volume growth. There were few 

differences in the crown vigor ratings among progenies. 

Performance frorn age 17 to age 25. Since the effects 

of littleleaf disease on tree growth are usually more 

pronounced after age 20, we were particularly 

interested in performance since age 17. Table 3 gives 

percentage growth in height, d.b.h., volume, and basal 

area from age 17 through age 25. It also gives the four 

crown characteristics. Except for the check, there was 

no significant difference among progenies in percentage 

growth in height, d.b.h., volume, or basal area. Also, 

there was little association between these growth 

variables and crown characteristics at age 25. Average 

values for crown characteristics showed that the general 

visual appearance of the progenies was excellent. The 

crown density was 59 percent or better for all 

progenies. Average needle retention was at least 2 

years. Dwarfing was less than 20 percent and 

discoloration was minimal. The exception was the 

check trees, which had relatively sparse crowns, poor 

needle retention, short needles, and a high degree of 

discoloration. 

Individual-Tree Perfomance 

ReIationship between growth and crown 

characteristics. STEPWISE regression was used to 

model percentage growth in height, d. b.h., basal area, 

and volume from ages 17 to 25 as tiinctions of the 

crown variables at age 25. Good crowns should reflect 

high growth rates, while poor crowns should show 

declining growth. The results are shown in table 4. 
"fable 2-Average bole dimensions and crotvn vigor ratings of sktortkaf pine progenie at age 25 on a littleleaf 

disease site in Unian, SC 

Parents 

Progeny3 Fema te Mate Volume Height D.b.h. Crown vigor 

2 15 27 

Yl Z15 

Y5 27 

215 Y8 

Y5 Y8 

U1 27 

U9 27 

Z1 5 215 

Y5 Y5 

U2 213 

Y2 27 

Z15 2 13 

U2 Z14 

U9 Z 15 

U5 Y4 

Y9 213 

Z15 U4 

Z15 Y6 

2 17 Zt3 

Y2 Y6 

Y6 Y8 

Z 15 V3 

U5 Y3 

U9 Y4 

217 Y3 

Check 

YI Ye3 

V9 V8 

Y% k"6 

V9 V6 

Cubic feet 

13.65 a 

12.57 ab 

11.48 abc 

11.35 abc 

11.26 a-d 

11.12 a-e 

11.06 a-e 

10.76 a-f 

10.67 a,-f 

10.56 a-f 

18.43 a-f 

10.16 a-f 

9.46 a-g 

9.18 a-g 

8.93 b-g 

8.80 b-g 

8.76 b-g 

8.68 b-g 

8.44 b-g 

8.34 b-g 

8.26 b-g 

8.16 b-g 

7.93 c-g 

7.76 c-g 

7.56 c-g 

7.02 c-g 

6.77 d-g 

6.66 efg 

4.19 fg 

5.21 g 

Feet 

57.3 a 

56.8 ab 

56.0 abc 

56.2 abc 

57.0 ab 

54.9 a-e 

57.5 a 

56.2 abc 

56.0 abc 

55.5 a-d 

56.7 abc 

53.1 a-e 

55.3 a-e 

52.9 a-e 

52.9 a-e 

52.6 a-e 

54.0 a-e 

53.9 a-e 

53.2 a-e 

53.4 a-t: 

53.8 a-e 

53.7 a-e 

51.9 a-e 

53.2 a-e 

52.8 a-e 

49.4 e 

51.0 b-e 

51.5 a-e 

50.8 cde 

49.6 de 

10.3 a 

10.1 ab 

9.7 abc 

9.7 abc 

9.6 abc 

9.7 abc 

9.5 a-d 

9.4 a-cl 

9.4 a-d 

9.4 a-d 

9.2 a-e 

9.4 a-d 

8.8 a-f 

9.0 a-e 

8.h-e 

8.8 a-f 

8.6 b-f 

8.7 a-f 

8.6 b-f 

8.6 b-f 

8.5 b-f 

8.5 b-f 

8.5 b-f 

8.3 c-f 

8.2 C-f 

8.3 c-f 

8.8 clef 

7.9 def 

'7-7 ef 

7.2 f 

5.95 ab 

6.00 a 

5.95 ab 

6.00 a 

6.00 a 

6.00 a 

6.00 a 

5.93 abc 

6.00 a 

5.90 abc 

5.98 abc 

5.95 aab 

5.55 e 

5.93 abc 

6.00 a 

6.00 ;;a 

5.90 abc 

5.95 ab 

5.95 ab 

5.93 abc 

6.00 a 

5.82 abc 

5.85 abc 

6.00 a 

5.83 abc 

5.73 abc 

5.90 abc 

6,00 a 

5'88 abc 

5-63 bc 

"The means for these characteristics for a given progeny were based on the mean of the five block means since ths 

block means were used as the variatss in the statistical analyses. Generafly, the hdocks contained four trees but 

occasionally less due lo rnortali ty . "ltaeans in the same column followed by the same letter are not significantly different at the 0.05 level using 

Tukey's test. 

Progenies 24, 26, 28, and 34 %ere tdentical to other progenies and were deleted from this study, Progeny 30 was 

not a shortleaf cross and, thus, was never used. 

The p-value obtained from an analysis of variance. 
Table 3-Growth and crown cLharacteristia under early iitteleaf disease complex' 

BasaI Crown Needle 

IgrogenyVeight D, b.h. Volume area density retention Dwarfing Discoloration 

Feet Cubic feet Sqnnre feet 

62 hcd 

77 ab 

'97 ab 

76 ab 

76 abc 

77 tib 

82 a 

59 cd 

84 a 

78 ab 

78 ab 

69 abcd 

72 abe 

75 abc 

77 ab 

78 ab 

74 abc 

75 abc 

75 abc 

81 a 

80 a 

61 bed 

71 abcd 

82 a 

69 abcd 

55 d 

76 ab 

77 ab 

76 abc 

75 ahc 

16 abcd 

13 bcd 

22 bcd 

1 1 bed 

5 d 

1 1 bed 

10 bcd 

17 abcd 

6 cd 

12 bed 

13 bed 

22 ab 

14 bcd 

1 1 bcd 

12 bed 

7 cd 

17 abcd 

IS bed 

7 cd 

13 bcd 

8 cd 

19 abc 

14 bed 

8 cd 

15 bed 

30 a 

8 bcd 

6 cd 

7 cd 

6 ed 

"he mcans for these characteristics for a given progeny were based on the meat1 of the five block means since the 

block means were used as the variates in the statistical analyses. Grnerafty, the blocks contained bur trees but 

occasionally less due to mortality. 

hfeans in the same column followed by the same letter are not significantly different at the 0.05 Its-vet, using Tukey's 

test, 

Percent growth of a characteristic is defined as IOO(X, - XI7)/X,, where X,, and X, are the values of the characteristic 

at age 17 and 25 years, respectively, based only an the trees alive at both times. 

Due to the ia1cula;ion method (footnote 1) ar,d the sample of trees (footnote 31, the percent growth characteristics 

cannot be computed exactly from tables 1 and 2. 

Progenies 24, 26: 28, and 34 were identical to other progenies and were delektf from this study. Progeny 30 was not 

a shortleaf crass and, thus, was never used, 

"This high value Tor volume is due ro one tree that had a very low vntume (0.23 ft3) at age 17 and grew considerably to 

a moderately high voEume (13.14 ft3), which resulred in a very high percent growth (5500%) due to the very low volume 

used in the decsminator of the percent growth calculation (footnote 3). 

7T11e p-value obt2tinaI froin an il11alysis of variance. 

7 
Table &Models developed to describe the relationship betwen several grotvth variables 

and the crown variable1 

Eight-Year Periodic Growth h%odels (17-25 years) 

HTPG = 21.5 + 0.19 CDR - 0.07 DWAF + 0.07 DCOL R2 I- 0.09 

DBHPG = 13.6 - 0.20 DWAF + 0.17 DCOL + 0.13 CDR R2 = 0.10 

BAPC = 34.1 - 0.58 DWAF + 0.51 DCOL + 0.25 CDR R2 = 0.07 

VPC = 146.6 - 2.18 DWAF + 2.54 DCOL R2 = 0.02 

Previous-hr Periodic Growth Models (24-25 years) 

DBHI = -0.00651 - 0.00192 DWAF + 0.00196 CDR + 0.000900 DCOL R2 = 0.35 

DBHPG = 0.705 - 0.0198 DWAF + 0.0154 CDR R2 = 0.32 

BAT = -0.00441 - 0.000193 DWAF + 0.000223 CDR + 0.000125 DCOL R2 = 0.33 

BAPG = 1.42 - 0.0403 DWAF + 0.0312 CDR R2 = 0.31 

* HTPG = Percent height growth 

DBWPG = Percent d.b.h. growth 

BAPG = Percent basal area growth 

VPG = Percent volume growth 

CI)R = Crown density rating (%) at age 25 years 

DWAF = Dwarfing (5%) at age 25 years 

DCOL = Discoloration (%) at age 25 years 

DBHI = Diameter increment (in) 

BAI = Basal area increment (ft') 

"Tinhe variables entered the stepwise regression models in the order in which they 

are in the equation. 

The associations between crown characteristics and 

percentage growth from age 17 to age 25 were poor; R2 

values were less than or equal to 0.10. Radial growth 

at age 24 was obtained from the tree-ring chronologies 

and regressed on the crown variables at age 25. These 

relationships had higher R2 'S (0.3 1 to 0.35) for 

diameter and basal area increment and percent growth. 

Therefore, current crown conditions such as those 

observed in this study cannot be used to predict the 

previous 8-year periodic growth rate, but may be useful 

in explaining the previous year's growth. 

randomly selected from each of these progenies. 

Generally two trees were selected per progeny from 

each of the five blocks. All 13 check trees were also 

cored, 

In order to examine trees in obvious decline, trees with 

a crown density rating of less than 50 were also 

selected. These 21 trees were in the foIlowing 

progenies (the number in parentheses indicates the 

number of trees in that progeny): lfl), 5(1), 6(1), 

85(3), 21(4), 23(1), 29(1), 32(3), 33(2), and check(4). 

Tree-ring chronologies, Dendrochronologies permitted Mean annual basal area increment from age 10 through 

us to study long-term annual growth in a representative 25 years averaged 0.022 square foot for the Best, 0.016 

sample of the progenies. When the progenies were square foot for the Intermediate, and 0.012 square foot 

ranked based on individual tree total volume at age 25, for the Worst progenies (table 5). These vaIues 

the Best progenies were 6, 11, 15, 25, and 3 1; the corroborate the rankings of the progenies into these 

Intermediate were 5, 7, 9, 16, 19; and the Worst were groups based on total volume at age 25. The check had 

2, 4, 17, 22, and 23, The trees to be cored were a growth rate of 0.014 square foot, which was between 
Table 5-Basal area increment (BAI) for the Best, Intemediate, Worst, Check, and CDR 

< 50 progenies based on tree-ring chronologies 

Progeny Number of Mean annual 6-yr periodic 

group trees Progenies BAI (1975-90) BAI (1985-90) 

Best 33 

Intermediate 50 

Worst 350 

Check 13 

CDR < 50 21 

Means in the same column followed by the same letter are not significantly different at the 0.05 

level using Tukey's test. 

Since the CDR <50 progeny group contained trees from each of the other progeny groups, it was not 

included in any statistical tests. 

Progeny 15 had 13 trees cored. 

Progeny 17 had 9 trees cared, and progeny 23 had 11 frees cord, 

the Intermediate and Worst. Trees with poor crowns 

(crown density rating < 50) had a similar low growth 

rate of 0.015 square foot. 

We examined 6-year periodic growth from age 20 to 

age 25 to determine the effeet of early littleleaf disease. 

The orde~g for periodic growth (see table 5) was 

similar to that found for mean mua1 basal area 

increment. Analysis of variance and Tukey's test 

showed significant differences between the Best, 

Intemediate, and Worst. Only the Best was 

significantly different from the check. 

The annual basal area growth increments are shown in 

figure 2. The Best progenies have always been the 

fastest growers, the Worst have always been the 

slowest, and the Intermediate in between. No evidence 

of littleleaf disease was found in selected progenies, and 

growth did not taper off unexpectedly for any group 

around age 20 as it would if the disease was 

progressing. In contrast, however, performance of the 

check was similar to that of the Intermediate at early 

ages but began to slow down and approach the Worst 

starting at age 19. The check trees may be reflecting 

susceptibility to littleleaf disease or an inability to grow 

well on littleleaf disease sites. A quadratic equation 

was fitted to each of these sets to smooth out the annual 

fluctuations (fig. 3). 

The results from the 21 poor-crown trees are shown in 

figure 2, while the quadratic equation smoothing results 

are in figure 3. In these trees, annual basal area 

growth started to decrease drasticalIy at age 115. Before 

that, growth of trees with poor crowns was similar to 

that of the Intermediates. Oak and Tainter (1988) noted 

similar growth responses for loblolly pine with light and 

severe littleleaf disease symptoms. It is noteworthy that 

four of the shortleaf pine trees in decline belonged to 

the Best progeny group, while only one came from the 

Intermediate and one from the Worst groups. Thus, it 

seems that progenies with generally excellent growth 

have certain individuals with poor crowns and slow 

growth. The average 6-year periodic basal area 

growth of these four trees was 0.066 square foot, which 

is between the Tntemediate and Worst groups. Thus, 

progenies that exhibit excellent growth do have 

individuals that are susceptible to growth decline, 

possibly from littleleaf disease. Of further interest is 

the genetic composition of trees with poor crown 

density ratings. Of these 21 trees, 17 had known 

genetic composition, of which 14 (82 percent) had at 

least one 215 parent. Generally, in the population of 

progenies shtdied here, only 9 of 29 had at least one 

Zl5 parent (3 1 percent). This is ironic since it was 

fomerly believed that Z15 was resistant to littleleaf 

direase (Zak 1955). If 215 is resistant, then the poor 

crown density ratings may well be genetically controlled 

and do not reflect littleleaf disease symptoms. 
- - Intermediate 

0.000 

Year 1974 1976 1978 1980 1982 1984 1986 1988 1990 

Age 10 12 14 76 18 20 22 24 

Figure 2-Annual basal area growth (ft2/tre) for the Best, htemdiate, and Worst 

progenies based on tree-ring chronologies. The check progeny and the GDR < 50 

trees from certain progenies are included for comparison. 

Figure 3-A quadratic model fit to the annual basal area growth (ft2/tree) for 

the Best, Intermediate, and Worst progenies based on tree-ring chronologies. 

The check progeny and individual CDR < 50 trees from certain progenies are 

included for comparison. 
Discussion 

The wide range in average volume growth among 

progenies indicates that selective brding can improve 

growth of shortleaf pine on littleleaf disease sites. Only 

two progenies grew significantly better than an ordinary 

check, but the general vigor and recent growth of the 

check were poor. Urrhealthy crowns and a reduction in 

periodic volume growth indicate that growth of the 

check will continue to decline. We therefore expect 

some of the selected progenies to perform much better 

than the check in the next few years. 

The most significant differences among progenies were 

in height growth. A total of 10 progenies were 

significantly taller than the check. The check ranked 

last of 30 in total height at age 25 and in periodic height 

growth between ages 17 and 25. Height growth of 

individual trees may be the most sensitive growth 

variable affected by site conditions conducive to 

littleleaf disease. Once crown position in the stand 

canopy is lowered, a reduction in crown vigor, d.b.h., 

and volume growth may follow. Alternatively, height 

growth rate may simply be an inherited characteristic. 

Height growth and crown position need to be examined 

more closely in assessing stand and individual-tree 

health. 

The average vigor rating of all the progenies was high, 

indicating that stand health in general was good. The 

high vigor ratings were substantiated by favorable 

values for crown density, needle retention, dwarfing, 

and discoloration. The high vigor ratings may reflect 

the initial selection of parents that performed well on 

severe littleleaf disease sites. Again, the ordinary 

nursery-selected check had the poorest visual crown 

ratings. Thus, choosing trees that perform well on 

littleleaf disease sites may be an effective form of 

selection. 

There was a close association between rankings for totaI 

volume, height, and d.b.h. growth at ages 17 and 25 

years. Tfie 10 progenies that produced the most total 

volume at age 17 were also the top performers at age 

25. That finding suggests that performance could be 

assessed at age 17, lowering the time and administrative 

expense associatd with a 25-year progeny test. The 

tree-core chronologies show that current annual basal 

area growth of the Best, Intermediate, and Worst 

progenies is closely related to past volume growth. 

Growth curves for selected progeny show no evidence 

of a decline due to littleleaf disease. However, in the 

check-which was originally intermediate in annual 

basal growth rate-there has been a recent decline. 

Many of the check trees show advanced symptoms of 

littleleaf disease, In contrast, the progenies from 

parents selected for apparent resistance may be 

exhibiting a degree of resistance to problems associated 

with littleleaf disease sites. 

Trees with poor crowns (CDR < 50) exhibited a 

drastic decrease in annual basal area growth at age 18. 

It is of more interest, however, that many of these trees 

were from the Best progenies. Thus, progenies that 

generally show excellent growth include individual trees 

that have poor crowns and slow growth. 

Although trends indicate a direct relationship between 

crown vigor and tree growth, it appears that the visual 

characteristics of crowns are indicative only of growth 

in the recent past. Perhaps a stronger association would 

be found by regressing current crown conditions on 

future tree growth. The detailed tree and crown 

measures taken in this study at age 25 will allow us to 

test these relationships over extended periods of time. 

Findings may be critical for developing biological and 

statistical techniques needed to evaluate individual tree, 

stand, and forest health. 

Acknowledgment 

The authors thank James S. Cunningham, Michael D. 

Thompson, and Linda nil. White, all from the 

Southastern Forest Experiment Station, for technical 

assistance in this study. 
Literature Cited 

Belanger, R,P,; Andemon, R.L. 1992. A guide for 

visually assessing crow densities of Ioblolfy and 

shortleaf pines- Revised Res. Note SE-352. 

Asheville, NC: U.S. Department of Agriculture, 

Forest Service, Southastern Forest Experiment 

Station. 4 pp. 

Bryan, W.G. 1965. Testing shortleaf pine seedlings for 

resistance to infection by Phyropl7rhora cinrznmomi. 

Res. Note SE-50. Asheville, tdC: U.S. Department 

of Agriculture, Forest Service, Southeastern Forest 

Experiment Station. 4 pp. 

Campbell, W.A.; Copelland, Otis L., Jr. 1954. 

Littleleaf disease of shortleaf and loblolly pines. 

Circ. 940. Washington, DC: U.S. Department of 

Agriculture. 41 pp. 

Oak, S.W.; Tainter, F.H. 1988. Risk prediction of 

loblolly pine decline on littleleaf disease sites in 

South Carolina. PIant Disease. 72: 289-293. 

WuehIe, John L.; Sluder, Earl It.; Bryan, ktt. Craig. 

1984. Perfomance of control-pollinated progeny 

from selected shortleaf pine on a IittIeleaf site in 

South Carolina. Res, Note SE-325. Asheville, NC: 

U.S. Department of Agriculture, Forest Service, 

Southeastern Forest Experiment Station. 7 pp. 

Saucier, Joseph R.; Phillips, Douglas R.; Willianls, 

James G., Jr. 1981. Gren weight, voIume, boardfoot, and cord tables for the major southern pine 

species. Ca. For. Res, Pap. 19. Macon, GA: 

Georgia Forestry Co&ssion, 63 pp. 

SAS Institute, Inc. 1988. SASISTAT user's guide. 

Release 6.03 ed. Cary, NC: SAS Institute, Inc. 

1028 pp. 

Zak, Bratislav. 1955. Inheritance of resistance to 

littleleaf in shortleaf pine. Res. Notes 88. Asheville, 

NC: U.S. Department of Agriculture, Forest 

Service, Southeastern Forest Experiment Station. 

2 PP* 
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1 Zarnoch, Stanley J.; Ruehle, John L.; Belanger, Roger P.; Marx, 1 Zarnoch, Stanley J.; Ruehle, John L.; Belanger, Roger P.; Marx, I 

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Donald H.; Bryan, VV. Craig. 1994. Growth and crown vigor of I Donald H.; Bryan, W. Craig. 1994. Growth and crown vigor of I 

1 

25-year-old shortleaf pine progenies on a littleleaf disease site. Res. I 25-year-old shortleaf pine pragenies on a littleleaf disease site. Res. I I 

I Pap. SE-289. Asheville, NC: U. S. Department of Agriculture, 1 Pap. SE-289. Asheville, NC: U.S. Department of Agriculture, I 

I I Forest Service, Southeastern Forest Experiment Station. 12 pp. 

I 

Forest Service, southeastern Forest Experiment Station. 12 pp. 1 I I 

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On a littleleaf disease site in South Carolina, most of the control- 1 On a littleleaf disease site in South Carolina, most of the control- 1 

pollinated progeny of shortleaf pines that appeared to be resistant to I pollinated progeny of shortleaf pines that appeared to be resismt to I 

the disease outperfomd a check seedlot througtl age 25. Rankings I the disease outperformed a check seedlot through age 25. Rakings 1 

of progeny based on volume changed little between ages 17 and 25. I of progeny based on volume changed little hetween ages 17 and 25. I 

i I 

Keywords: Tree decline, forest health, tree-ring chronologies, Pinus 1 Keywords: Tree decline, forest health, tree-ring chronologies, Pirikus 

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echinata. echinata. I I 

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