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~~3 Forest Service Research Note , . Southern Forest

Experiment Station

Water Tupelo in the Atchafalaya Basin

Does Not Benefit from Thinning

SO-298

August, 1983

Harvey E. Kennedy, Jr.

SUMMARY

Water tupelo occurs on about 4 million acres in

the South and Southeast. Its wood is exceptionally

clear and defect-free and is used primarily for veneer and box lumber. Most stands are dense, stagnated, and appear to need thinning or some other

type stand improvement work. But in a typical stand

in the Atchafalaya Basin residual trees showed no

significant growth response to thinning. Reasons

could be age of stand, small live crown ratio, and

yearly defoliation by the forest tent caterpillar.

Greatest benefit from thinning is probably salvage

of trees that would otherwise be lost through mortality.

Additional keywords: Nyssa aquatica, wetlands,

flooding, growth, volume.

INTRODUCTION

Water tupelo (Nyssa aquatica L.) grows most commonly in swamplands and bottomlands along watercourses in the South and Southeast. It normally

grows in even-aged dense stands with or without

cypress (Taxodium distichum (L.) Rich) and other

tupelos. The wood is exceptionally clear and defectfree and is used primarily for veneer and box lumber. Small dimension trees are used for cros.$ies

and pulpwood.

Water tupelo typically has a long, clean bole

strongly buttressed at the base. Trees are cut near

the top of the butt swell, which may be as much as

8 feet aboveground, or they are felled and bucked

to leave the basal wood. Laundrie and McKnight

(1969) reported that bleached kraft and neutral sulfite semichemical pulps made from butt swells of

water tupelo were well suited for manufacture of

greaseproof papers and a good quality corrugating

medium.

There are about 4 million acres of water tupelo

in the South and Southeast. Most of this acreage is

dense, stagnated, and appears to need thinning or

some type of stand improvement work. Growth rates

are usually low. This paper reports on the growth

response of water tupelo to four thinning intensities

in a typical stand in the Atchafalaya Basin. The results are probably applicable over most of the area

where water tupelo is found.

METHODS

The stand was fairly uniform and well stocked

except for remnants of some old pullboat roads

used in logging the virgin cypress and tupelo. It is

typical of forests found on thousands of acres of

swampland in the South and Southeast (fig. 1).

When the study was started in 1967, stand basal

area was about 250 square feet per acre; trees

averaged about 13 inches in diameter above the butt

swell and 65 feet in height. Two crown classes,

codominant and suppressed, were represented although most trees were codominant.

The individual crop-tree approach was used. Forty

codominant trees, which normally should be left as

crop trees during thinning, were randomly selected.

One of the following treatments was randomly

assigned to each:

Southern Forest Experiment StationTT-10210 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

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1. Check-no thinning.

2. Light thinning-measure out 10 feet on each

side from center of sample tree and cut all

trees within the 20- X 20-foot square.

3. Medium thinning-same as light thinning, except measure out 15 feet from center of

sample tree.

4. Heavy thinning-same as light thinning, except

measure out 20 feet from center of sample tree.

These thinnings would leave about 109, 48, and

27 trees per acre, respectively. Individual tree thinning treatments appear open to question by some,

but our data are sound and similar to those reported

by McGarity (1979).

After treatments were assigned, trees to be removed were marked and diameter of each measured

at a point above the butt swell. This was considered

to be where diameter of merchantable stem would

be measured-about 6-7 feet above ground line.

These were used to calculate basal area removed

around each tree. Stand age was determined by

representative ring counts.

Study trees were marked so diameter measurements could be made at the same location each

time. Measurements of diameter above the butt swell,

total height, merchantable height, crown width, and

live crown ratio were made when the study was installed, and at the end of 5 and 12 growing seasons.

Diameter measurements were made on 30 cut

trees at 1 and 4 feet above groundline, then up every

4 feet to a 4-inch outside bark diameter. Total tree

height and length of butt swell were also measured.

Cubic-foot volumes in butt swell, merchantable stem,

and total tree were calculated using Smalian’s formula. Percent volume in butt swell in each tree was

computed using the ratio of volume in butt swell to

volume in total tree.

A completely randomized design with 10 replications of each treatment was used for the study.

Analysis of variance using a completely randomized

design was used to test differences between treatments at the 0.05 level of significance.

RESULTS AND DISCUSSION

Ring counts on cut trees showed the stand to be

about 55 years old (table 1). An average of four trees

and 2 square feet of basal area was removed around

each tree in the light thinning treatment, nine trees

and 5.6 square feet of basal area in the medium

thinning, and 16 trees and 10 square feet of basal

area in the heavy thinning.

Figure l.- Typical water tupelo stand similar to the study area.

Thinning intensity had no significant effect on

diameter growth, total height, or merchantable

height. Diameters increased by 1.7, 1.4, 1.5, and

1.1 inches in the check, light, medium, and heavy

thinning treatments, respectively, during the 12

years of this study. Heights increased by 6, 9, 8,

and 9 feet, respectively.

Thinning intensity did significantly affect changes

in crown area. Trees in the medium thinning treatment had a significantly larger crown change than

the heavy thinning, with no difference between the

check and light thinning. This is unusual as normally

a larger increase in crown size in the heavier thinning would be expected. By treatment, 40 percent

of the trees in check plots decreased in crown area

over the 12 years, none in the light, 30 percent in

the medium, and 40 percent in the heavy. Crown

area decrease may be because of death of branches

in the lower crown.

Harvey E. Kennedy, Jr., is Principal Silviculturist 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.

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Table l.-Average diameters above butt swell, total and merchantable heights, crown widths, and percent live crown by treatment

and date

Measurement

Total height (ft.)

Diameter (in.)

Merch. height (ft.)

Crown width (ft.)

Live crown (%)

Check 10x10 15x15 20x20

1967 1972 1979 1967 1972 1979 1967 1972 1979 1967 1972 1979

6 6 72 72 6 5 7 3 7 4 6 6 7 2 7 4 6 5 7 1 7 4

13.0 14.4 14.7 13.9 14.6 15.3 13.7 14.5 15.2 13.6 14.6 14.7

5 1 57 5 7 53 5 5 5 6 53 5 6 5 6 5 1 5 6 5 9

15x17 16x18 16x15 14x17 17x19 18x18 15x17 18x19 18x19 15x16 17x19 14x16

23 2 1 2 3 2 0 2 3 2 4 2 2 2 2 22 2 2 2 0 18

Live crown ratios averaged about 20-22 percent

throughout the study period. The live crown is probably too small a proportion of the tree to respond

to thinning. A general rule is to keep at least half of

the tree in live crown for best growth.

Typically, water tupelo is cut near the top of the

butt swell, which may be as much as 8 feet above

ground, or they are cut low and bucked to leave the

butt swell portion. Measurements on cut trees in

this study showed that from 30-68 percent of the

total cubic foot volume was in the butt swell, with

an average of 47 percent of the total volume left

when the butt swell portion was not used.

SUMMARY AND CONCLUSIONS

Trees showed no significant response to thinning

in this stand. Reasons could be twofold: (1) trees

were too old and the live crown ratio (20-22 percent)

was too low before thinning, and (2) the stand was

defoliated each year of the study by the forest tent

caterpillar (Malacosoma disstria Hubner). Forest tent

caterpillar defoliation each year may be a key to the

lack of response. Morris (1975) reported that studies

in Alabama showed s-year growth losses of 70 percent or more in tupelos defoliated each year. Equal

losses were estimated for trees in Louisiana. Morris

reported that trees do not usually die when repeatedly defoliated but cannot grow. Within a month

after feeding stops, new, stunted leaves appear. But

these merely maintain life until the next season

when the cycle is repeated.

McGarity (1979) reported on IO-year results from

thinning and clearcutting in a cypress-tupelo swamp.

However, because of within-replication differences

of tree size, stocking, and species distribution, only

a simple arithmetical summary was presented. From

the IO-year growth data, it appears that McGarity’s

results are similar to this study except possibly in

the control plot.

An average of 47 percent of the total tree cubic

foot volume in this study is left in the woods if the

butt swell is not utilized. But, this wood is suitable

for manufacture of greaseproof paper and corrugating medium.

Results of this study indicate that even heavy

thinning in water tupelo may not increase growth on

the residual trees. The greatest benefit from thinning

may be the salvage of trees that might otherwise die

and the resultant increase in recoverable yield over

the rotation of the stand.

Logging problems in a tupelo swamp require that

substantial volume be removed or, more likely, clearcutting be done to justify the expense. It is possible

that thinning may not be economically feasible even

if a growth response is expected.

LITERATURE CITED

Laundrie, J. F.; McKnight, J. S. Butt swells of water

tupelo for pulp and paper. Res. Pap. FPL-119.

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Lab.; 1969. 11 p.

McGarity, R. W. Ten-year results of thinning and

clear-cutting in a muck swamp timber type. South.

J. Appl. For. 3(2): 64-67; 1979.

Morris, Robert C. Tree-eaters in the tupelo swamps.

For. and People 25 (1): 22-24; 1975.

e”.S. GOVERNMENT PRINTING OFFICE: 1983 66%085/55