SO-254

Coppice Sycamore Yields Through 9 Years

Harvey E. Kennedy, Jr.

SUMMARY

Cutting cycle and spacing did not significantly

affect sycamore dry-weight yields from ages 5-9

years (1974-l 978). Longer cutting cycles usually

did give higher yields. Dry-weight yields ranged

from 2886 lb per acre (3233 kg/ha) per year in the

1 year, 4 x 5 ft (1.2 x 1.5 m) spacing to 4541 lb (5088

kg/ha) in the 4-year, 4 x 5 ft s,pacing. Survival

averaged 67 percent in the 2 x 5 ft (0.6 x 1.5 m)

spacings and 79 percent in the 4 x 5 ft spacings.

Ratio of dry weight to fresh weight averaged 49

percent, and the stem accounted for 85 percent of

the dry weight of the trees.

Additional keywords: Platanus occidentalis,

sprouting, “silage concept”

INTRODUCTION

As demand for cellulose fiber grows, industrial

needs will exceed the ability of natural and planted

forests to supply it for pulp and fuel. Forest

Industries must find new methods to increase

production rapidly. Intensive culture of hardwoods

under short rotation cycles may help supplement

conventional pulpwood and fuelwood sources.

This technique is sometimes referred to as the

“silage concept” because the cut wood resembles

crops harvested for silage. This note reports how

various cutting cycles and spacings affect growth

and yield of coppice sycamore through nine

growing seasons.

METHODS

In March 1970, nonrooted sycamore cuttings

were planted vertically In subsoiled trenches at

Huntington Point, near Greenville, Mississippi.

The soil was Commerce silt loam, a good sycamore

site.

Plots were eight rows wide (40 ft or 12.3 m) by 1

chain (66 ft or 20.3 m) long and were divided into

two subplots, each four rows wide. Two spacings

were randomly assigned on the subplots-2 x 5

(0.6 x 1.5 m) and 4 x 5 ft (1 .2 x 1 .5 m). Early in the

first growing season, all blanks in the 4 x 5 ft

spacings and consecutive blanks (two or more) in

the 2 x 5 ft spacings were replanted with extra 16.

Inch (40 cm) cuttings established when the study

was tnstalled. Plots were weeded during the first

growing season.

Southern Forest Experiment Station/T-10210 U S Postal Services Bldg 701 Loyola Avenue, New Orleans. La 701 13

Forest Servtce. U S Department of Agrtculture

Serving Alabama. Arkansas. LouIslana. MISSISSIPPI. Eastern Oklahoma, Tennessee, Eastern Texas
A randomized block split-plot design was used for

this study. Cutting cycles were 1, 2,3, and 4years.

Eachcombination of cutting cycle andspacing had

four replications. The 1 -year cycle has received

eight cuttings; the 2-year cycle, four cuttings; the

3-year cycle, three cuttings; and the 4-year cycle,

two cuttings. Cutting was done in January or

February each year except 1974, when

floodwaters delayed cutting until March.

For each subplot, growth and yield were

measured on the central 50 ft (15.4 m) of the two

center rows; the rest of the plot formed a border.

When trees were cut, stems plus branches of all

trees within each measurement area were weighed on a balance at the study site (fig. 1). Freshweight yields per acre were calculated from this

data.

Figure 1 .-Weighing freshly cut green trees at the plantation

site.

Fresh and dry weights of stems and branches

separately, stump diameter at the point of cut, and

stem length were measured on three trees (the

northernmost trees on the west row) from each

subplot. Dry weights were determined after plants

were dried 48 hours in a forced-air oven at 105OC.

Total aboveground weights were obtained, and

ratios of total dry to fresh weight and of stems to

branches (fresh and dry) were determined.

I calculated dry-weight yield per acre per year for

each subplot by multiplying the fresh weight per

acre by the ratio of dry weight to fresh weight in the

sample. Data were analyzed with analysis of

variance and Duncan’s multiple range test at the

0.05 level of probability.

RESULTS AND DISCUSSION

Results through 4 years (1970-1973) were

reported in Kennedy (1975). At that time the 2-, 3-,

and 4-year cutting cycles yielded significantly

more dry weight (slightly more than 7,000 lb) than

the 1 -year cutting cycle yielded (slightly more than

4,000 lb). The 2 x 5 ft spacing yielded significantly

more than the 4 x 5 ft yielded. Interaction between

spacing and cutting cycle was not significant. Ratio

of dry weight to fresh weight averaged 43 percent,

and the proportion of dry weight in the stem

averaged 81 percent in the 1 -year cutting cycle and

95 percent in the 4-year cutting cycle. Survival

averaged 90 percent.

In the fifth through eighth growing seasons

(1974-l 977; I-, 2-, and 4-year cutting cycle) and

for the fifth through ninth growing seasons

(1974-I 978; 3-year cutting cycle), survival in the 2

x 5 ft spacing dropped to 67 percent, a reduction of

20-25 percent since the fourth growing season.

The 4 x 5 ft spacing had 79 percent survival, a

reduction of 5-l 0 percent. Other researchers have

reported that stands planted at close spacings, 1 x

1 (0.3 x 0.3 m) to 4 x 4 ft (1.2x 1.2 m), will gradually

thin themselves to about 4 x 6 (1 .2 x 1.9 m) to 5 x 5

ft (1.5 x 1.5 m) spacing. This self-thinning seems to

be happening in the Huntington Point plantation;

the original 2 x 5 ft spacing is now about 3 x 5 (1 .0x

1.5 m) and the 4 x 5 spacing is now about 5 x 5 ft.

Dry-weight yields did not differ significantly

among treatments during 1974-1978 (table 1),

probably because yields within replications

differed greatly. Yields were much smaller than

1970-l 973 yields (11 percent in the 1 -year, 2 x 5 ft

Kennedy IS Prlnclpal Sllvlculturlst at the Southern Hardwoods Laboratory maIntaIned at Stonevllle, Mlsstssippl, by the Southern

Forest Experiment Statlon. Forest Service-USDA. In cooperation with the Mlsslssippl Agricultural and Forestry Experiment Statlon

and the Southern Hardwood Forest Research Group

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spacing to 42 percent in the 3-year, 4 x 5 ft

spacing). During the second 4 years, longer cutting

cycles still usually produced higher yields.

Yields during 1974-l 978 were lower than ones

reported by other researchers (Belanger and

Saucier 1975, White and Hook 1975). Yet, even

though yields in this study were lower, the highest

yields were still in the longer cutting cycles.

Trees were significantly shorter in the

1974-l 978 period than in the 1970-I 973 period;

diameters were not significantly smaller (table 2).

A significant interaction among treatments for

heights and diameters was caused by varying

degrees of growth differences.

Trees were smaller and yields lower during

1974-1978 than during 1970-I 973 for several

reasons. Reduced survival could have led to lower

yields because fewer trees were available. But the

remaining trees should have grown more because

of more growing space per tree. Climatic and insect

conditions at the site might also have lessened

yields. The Mississippi River flooded the plantation

for several weeks early in the 1974 and 1975

growing seasons. Then the 1976 growing season

was dry, and the 1977 growing season was

extremely dry. Also, the sycamore tussock moth

(Nalisidota harrisii Walsh) completely defoliated

plantation trees during July and August in 1976

and 1977. Results over the next 4 years should

answer whether the reduction was caused by

climatic and insect conditions at the study site or by

the imposed treatments or by a combination of all

these factors.

Ratios of dry weight to fresh weight and

proportion of dry weight in stems were not affected

by cutting cycle and spacing (table 1). Dry to fresh

weight ratios average 49 percent, a gain of about 5

percentage points from the average after four

growing seasons. These percentages are similar to

the 50 percent dry to wet weight ratios reported by

Steinbeck and May (1971). The proportion of dry

weight in stems was probably not affected much by

treatments. Over all treatments, proportion of dry

weight in stems averaged 85 percent. This

proportion is about 5 percent smaller than it was in

1970-l 974, probably because the trees had more

branches, as each tree had more growing space.

If forest managers are considering using short

rotations and close spacings for sycamore, they

should probably plant at 4 x 6 ft to 5 x 5 ft spacings

and use cutting cycles of 4 to 5 years to maximize

yields.

Table 1 .-Average annual dry weight, ratio of dry to fresh weight, and dry weight percentages of

stems by spacing and cutting cycle for 1970-1973 and 1974-1978

Spacing (feet) Dry weight Ratio dry to Proportion of dry

and cutting fresh weight weight in stem

cycle (years) 1970-73 1974-78 1970-73 1974-78 1970-73 1974-78

2x5

1

2

3

4

4x5

1

2

3

4

------lb/ecre/yr. (kg/ha/yr.)------ .----------.---percent.----..------

4349 (4875) 3702 (4149) 44 4 9 81 8 3

7001 (7847) 4260 (4775) 4 5 4 9 90 8 7

7210 (8081) 4164 (4667) 41 4 7 9 2 8 3

7161 (8026) 4448 (4986) 4 6 5 1 9 5 9 2

3229 (3619) 2886 (3235) 4 6 4 7 8 5 8 4

5167 (5791) 3347 (3752) 41 48 8 6 8 3

6175 (6921) 4278 (4795) 43 5 0 91 7 9

6441 (7219) 4541 (5090) 4 2 49 9 5 8 8

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Table P.-Diameters and heights by spacing and cutting cycle for 1970-1973 and 1974-1978

Spacing (feet)

and cutting

cycle (years)

Diameters Heights

.____

1970-73 1974-78 1970-73 1974-78

--------inches(cm)-------- ---------feet(m) ---------

2x5

1 1.0 (2.54) 0.9 (2.29) 9.4 (2.87) 9.3 (2.84)

2 1.8 (4.57) 1.3 (3.30) 17.0 (5.18) 12.6 (3.84)

3 2.1 (5.33) 1.5 (3.81) 20.4 (6:22) 13.2 (4.02)

4 2.0 (5.08) 1.8 (4.57) 23.6 (7.19) 17.7 (5.40)

4x5

1 0.9 (2.29) 1 .O (2.54) 8.7 (2.65) 9.5 (2.90)

2 1 .8 (4.57) 1.3 (3.30) 16.6 (5.06) 12.8 (3.90)

3 2.4 (6.10) 1.7 (4.32) 23.1 (7.04) 11.4 (3.47)

4 2.4 (6.10) 2.7 (6.86) 23.6 (7.19) 22.8 (6.95)

LITERATURE CITED

Belanger, Roger P., and Joseph R. Saucier.

1975. intensive culture of hardwoods in the

South. Iowa State J. Res. 49: 339-344.

Kennedy, Harvey E., Jr.

1975. Influence of cutting cycle and spacing on

coppice sycamore yield. U.S. Dep. Agric. For.

Serv. Res. Note SO-l 93, 3 p. South. For. Exp.

Stn., New Orleans, La. *

Steinbeck, K., and J. T. May.

1971. Productivity of very young Platanus

occidentalis L. plantings grown at various

spacings. ln Forest Biomass Studies, Maine

Agric. Exp. Stn. Misc. Rep. 132, p. 153-162.

Life Sci. and Agric. Exp. Stn., Univ. Maine,

Orono.

White, Edwin H., and Donal D. Hook.

1975. Establishment and regeneration, of

silage plantings. Iowa State J. Res. 49:

287-296.

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