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United States

k-3 Department of

Agriculture

0

cri,I,l Forest Service

Southern Forest

Research Note

SO-322

Experlment Station December 1985

Cottonwood Development Through 19 Years

in a Nelder’s Design

Roger M. Krinard

SUMMARY

Survival, heights, and diameters at five ages, from 2 to

19 years, over six planting densities, from 63 to 1 ,135

trees per acre, are given for cottonwood planted in a

Nelder’s design.

Additional keywords: Popu/us deltoides.

INTRODUCTION

Tree diameter and survival over time in cottonwood

(Populus deltoides Bartr. ex Marsh.) plantations are related to initial spacing. The closer the spacing, the

slower the diameter growth and the sooner mortality becomes a factor. This paper presents information on tree

development through 19 years of cottonwood planted in

a Nelder’s design, a systematic design wherein the area

per tree changes in a constant manner.

METHODS

The study was planted in February 1966 at Huntington

Point, Bolivar County, Mississippi (near Stoneville), on

land of the Chicago Mill and Lumber Company in the

Mississippi River batture. The soil was cleared Commerce silt loam, a member of the fine-silty, mixed,

nonacid, thermic family of Aeric Fluvaquents, which has

an estimated site index range for cottonwood of 105 to

125 feet in 30 years (Broadfoot 1976). Multiple cuttings

were planted at each planting spot but were reduced to

one living stem during the first growing season.

There were four “circles” or “wheels,” with each wheel

containing 22 “spokes.” Two adjoining spokes served as

border spokes, and a different clone was randomly assigned to each of 20 other spokes. The angle between

spokes, other than border spokes, was 16.63”

(Namkoong 1966) (fig. 1).

Each tree outward from the center of a wheel along a

spoke had about 76 percent more growing space than

the previous tree in the spoke. Six trees per spoke, representing 1 ,135, 637, 356, 201, 113, and 63 trees per

acre, were measured for height and diameter after years

2,4, 6, and 9; diameters of all trees and heights of trees

of one clone were taken after year 19. A closer spacing

of 2,020 trees per acre was not measured after 9 years

because of poor survival and therefore was not considered. In addition to the measurement trees, an outer and

an inner border tree were planted per spoke.

A randomized complete block design seemed reasonable for analyses, even though spacings were fixed relative to each other rather than occurring randomly. The

wheels were replications and the spacings were treatments, with clones considered only as a random sample

of the cottonwood population. Testing was at the 0.05

level of significance.

RESULTS

Survival differences among spacings first occurred in

the sixth year, with the closest spacing having the least

survival (table 1). By the ninth year, survival was inversely related to the number of trees per acre, although

the three wider spacings did not differ. At age 19, the five

Southern Forest Experiment Station/l-102lO U.S. Postal Services Bldg., 701 Loyola Avenue, New Orleans, La. 70113

Forest Service, U.S. Department of Agriculture.

Serving Alabama, Arkansas, Louisiana, Mississippi, E. Oklahoma, Tennessee, E. Texas, Puerto Rico, U.S. Virgin Islands

1
Figure 1 .-Partial layout of Nelder’s design showing three measurement spokes and the two border spokes with measurement

4) and border (0) tree locations.

Table 1 .-Survival by years and trees per acre planted1

Years

Trees/acre

2 4 8 9 1 9

. . . . . . . . . . _. . _ . _ _. percent . . . . . . . . . . . . . . . . . .

8 3 100 100 99ab 99a 72a

113 100 100 1OOa 99a 58b

201 9 9 9 9 98b 94a 38c

358 100 100 98ab 88b 22d

837 100 9 8 84c 88C 8e

1,135 100 9 4 71d 54d 8e

‘Means appearing with the same letter are not significantly different

within each column at the 0.05 level by Duncan’s new multiple range

test; where no letters appear, overall test is nonsignificant.

wider spacings all differed from each other in survival.

Average diameters differed among spacings at every

age except 19, with the largest diameter at the widest

spacing and the smallest diameter at the closest spacing

(table 2). The largest tree at age 19 was 21.4 inches

d.b.h. Average annual growth of trees at the widest

spacing was 0.86 inch per year.

Height differences among spacings occurred at each

of the first four measurements when all trees were measured (table 3). Trees in the widest spacing were shorteat at age 2 but did not differ from spacings with the

tallest trees at ages 6 and 9. As a measure of dominant

heights, the four tallest trees per spacing per replication

were also analyzed (table 4). Relationships among spacings over years were similar, with dominant heights being 2 to 3 feet taller than average heights after 2 years

and 6 to 8 feet taller after 9 years. Heights of trees at the

two closer spacings apparently suffered some suppression from trees at the next wider spacing by year 6.

Only one clone had all trees survive at the four widest

spacings through 19 years. Data from these trees were

used to compare growth over the 19 years, where mortality was not a factor. Total heights did not differ among

spacings at the five ages. Also, height mean annual

increment (m.a.i.) by growth periods never differed

(table 5). Diameters between adjacent spacings did not

differ at age 2 but were different among all spacings at

ages 4 and 6. The diameter of the widest spacing for

ages 9 and 19 was greater than that of the next widest

spacing, which in turn was greater than the two closest

spacings. Diameter m.a.i. did not differ among spacings

over the fifth and sixth years or over the last 10 years.

During the other three periods, diameter m.a.i. of the

widest spacing was greater than that of the two closest

spacings (table 5).

Mean annual cubic-foot volume growth in cottonwood

,plantations usually peaks at 7 to 10 years for pulpwood

spacings. A relative assessment of cubic volume production for the Nelder’s spacings was made by using

(trees per acre)-(survival)-(average d.b.h.)*-(average

height at age 9). Relative productivity expressed as a

ratio to the lowest value (by planting density) was as

follows: 1 (63), 1.4 (113) 1.5 (637 and 1,135), 1.7 (201),

and 1.8 (358). Thus, the maximum yield in 9 years, in this

case, would have been at an equivalent 1 1 - by 11 -foot

spacing.

Only two of the spacings in 19 years, based on average d.b.h., could be considered for sawtimber. Using a

form class of 78 and an average d.b.h. to a lo-inch top,

the average tree of the two wider spacings had 60 and

133 board feet (Doyle) in 19 years.

Table P.-Average diameter by years and trees per acre Planted’

Years

Trees/acre

2 4 8 9 19 (range)

. . . . . . . . . . . ..w...... inches.........-..........

8 3 4.la 8.8a 10.8a 13.0a 18.4a (10.7-21.4)

113 4.0b 7.9b 9.76 11.4b 14.0b (7.8-18.7)

201 3.8c 7.Oc 8.4c 9.8c 12.9bc (8.7-l 8.9)

358 3.8d 8.od 7.Od 8.ld 11.8cd (8.8-18.1)

837 3.18 4.8e 5.88 8.8e 10.3d (8.3-13.4)

1,135 2.8f 4.Of 4.8f 5.8f 8.8e (5.2-12.1)

‘Means appearing with the same letter are not Significantly different

within each column at the 0.05 level by Duncan’s new muftiPte range

test.

Roger M. Krinard is Mensurationist at the Southern Hardwoods Laboratory, maintained at Stoneville, Mississippi, by the Southern Forest Experiment

Station, Forest Service--USDA, in cooperation with the Mississippi Agricultural and Forestry Experiment Station and the Southern Hardwood Forest

Research Group.

2
Table 3.-Average height by years and trees per acre planted’

Years

Trees/acre

2 4 6 9 192

6 3

113

201

356

637

1,135

---------------------feet ____________________

25.6~ 49.4b 67.3a 76.7a 100.0

26.7b 51 .Oa 67.la 76.4a 105.2

27.4ab 52.0a 67.2a 74.6b 104.6

26.0a 51.4a 63.6b 70.4c 101.2

26.la 48.7b 59.7c 63.4d . .

27.6a 44.7c 54.6d 56.26 . . , .

Weans appearing with the same letter are not significantly different

within each column at the 0.05 level by Duncan’s new multiple range

test; where no letters appear, overall test is nonsignificant.

2Based on trees of one clone that survived in all four repiications.

Table 4.-Height of four tallest trees per replication per spacing by

years and trees per acre planted1

Trees/acre

2

Years

4 6 9

__________________. feet ___________-______

6 3 29.0 54.2b 72.8a 82.2a

113 30.1 56.5a 72.la 83.4a

201 30.5 57.la 72.la 81 .Oa

358 30.9 56.7a 69.5b 78.lb

637 30.6 54.2b 65.9c 70.9c

1,135 29.8 50.4c 60.5d 65.84

l Means appearing with the same letter are not significantly different

within each column at the 0.05 level by Duncan’s new multiple range

test; where no letters appear, overall test is nonsignificant.

Tree development by spacings in Nelder’s design may

be compared to run-of-the-bar trees in a spacing study at

Fitler, Mississippi (Krinard and Johnson 1984). The trees

at Fitler were on similar soils-mainly Commercewhere trees per acre were 151 (16 by 18 feet), 302 (12

by 12 feet), 605 (8 by 9 feet), and 1,210 (4 by 9 feet).

Measurement plots were 144 feet squared. In annual

height growth, dominant trees at Fitler averaged about

12 feet a year for the first 4 years, 8 feet a year for the

next 4 years, 3 feet a year for the following 7 years (83

feet in 9 years vs. about 81 to 83 feet for the tallest trees

i n Nelder’s), and 1 foot a year for the next 5 years (106

feet in 20 years vs. 103 feet in 19 years in Nelder’s).

Diameter growth differed, probably due in part to clonal

variation between the two tests, with better growth

through age 9 for the Nelder’s trees. Individual regression equations of diameter over spacings by years between sites, where d.b.h. = b,, + b, log (ft2/tree), had significantly different intercepts and slopes at ages 4 and 19

and different intercepts at ages 6 and 9 (fig. 2). Greater

competition from better survival at younger ages and

from wider spaced trees with increasing age may have

l AGE 19

1 6 -

1 4 -

AGE 9

I* -

AGE 6

AGE 4

1,s 2.2 2.9

LOG (FT2/TREEl

Figure 2.-Average d.6.h. by spacing for Nelder 6) and Fitler (0) trees

after 4. 6, 9, and 19 years where regression lines calculated from d.6.h. = b O + b, log (ft?tree).

Table 5.-Average annual growth in diameter (D) and height (H) of one c/one by age group periods and trees per acre

planted’

Years

Trees/acre l&2 3&4 5&6 7-9 10-19

D H D H D H D H D H

by2 WY3 W fPY iw fPY iPY fPY iw fPY

8 3 2.6a 14.6 2.5a 13.9 1.1 7.9 1 .Oa 3.3 0.5 1.7

113 2.4ab 14.8 2.2b 14.2 1.1 8.2 0.7ab 3.3 0.5 2.0

201 2.2bc 15.2 1.7c 13.9 1.0 7.6 0.6b 3.1 0.4 2.2

358 2.oc 15.2 1.5c 13.4 0.8 7.1 0.6b 2.7 0.5 2.2

‘Means appearing with the same letter are not significantly different within each column at the 0.05 level by Duncan’s

new multiple range test; where no letters appear, overall test is nonsignificant.

21nches per year.

3Feet per year.

3
been a factor in subsequent lower survival and smaller

average diameter by age 19 for the four closer spacings

in Nelder’s design compared to the Fitler plots.

Nelder’s design is rather unique and has been of interest to a number of visitors to Stoneville over the years.

But, because of increasing mortality and a thick understory of sugarberry (Celtis laevigata Willd.) and boxelder

(Acer negundo L.), the wheels are no longer very apparent. The remaining cottonwood trees are not impressive

because of numerous limbs or limb stubs and general

lack of both straightness of stem and well developed

crowns. Nelder’s design, at least in this example with

cottonwood, appears to be a way to compare relative

tree development in height, d.b.h., and volume over a

number of spacings in a minimum area, which could

mean less site variation, and with a minimum number of

trees. A disadvantage of the design is that it does not

allow for mortality effects. Due to intertree competition in

the Nelder’s plots, 6 years may be the maximum time

period for comparing cottonwood trees with less than 70

square feet of growing space. For whatever reasons,

survival at the wider spacings at age 19 was lower than

what ordinarily would be expected; conversely, survival

through age 9 was unusually high. Biomass-type spacings-more than 700 trees per acre-may only have a

5 to 6-year useful life. Without thinnings, pulpwood

spacings of 200 to 700 trees per acre would not be

expected to have more than 12 to 14 years of useful life.

Additional spacings wider than those used in this study

would be desirable to follow sawtimber tree development

through 20+ years.

LITERATURE CITED

Broadfoot, Walter M. Hardwood suitability for and properties of important Midsouth soils. Res. Pap. SO-1 27.

New Orleans, LA: U.S. Department of Agriculture,

Forest Service, Southern Forest Experiment Station;

1976.84 p.

Krinard, Roger M.; Johnson, Robert L. Cottonwood plantation growth through 20 years. Res. Pap. SO-212.

New Orleans, LA: U.S. Department of Agriculture,

Forest Service, Southern Forest Experiment Station;

1984. 11 p.

Namkoong, Gene. Application of Nelder’s designs in tree

improvement research. In: Proceedings, Eighth

Southern Conference on Forest Tree Improvement;

1965 June 16-l 7; Savannah, GA. Sponsored Publication No. 24 of the Committee on Southern Forest

Tree Improvement. Macon, GA: Georgia Forest Research Council; 1966: 24-37.

srU.S.COVERNMENTPRIMINGOFFICE:1986 -659-OI30/ 40011REGl0NN0.4