7

United States

+A Department of

‘k!$& Argriculture

Forest Service

Southern Forest

Experiment Station

Research Note

so-305

February, 1984

Yield and Nutrient Removal by Whole-Tree Harvest of a

Young Bottomland Hardwood Stand

John K. Francis

The yield and nutrient withdrawal by whole-tree harvest of young bottomland hardwoods has heretofore

been unknown. In this study of intensive harvest, samples

of chipped whole trees and soil from 16 test plots were

analyzed for nutrient content. Eighty-two percent of the

stems and 59 percent of the dry weight were green ash.

The balance was divided among a number of other species. Dry weight yields averaged 37,114 Ibs/a in summer

and 31,964 Ibs/a in winter. The annual productivity was

1.45 dry t I a / yr, which is comparable to other stands of

similar age. Summer chipping removed 176 Ibs N, 22 Ibs

P, 115 Ibs K, 240 Ibs Ca, and 23 Ibs Mg/a. Soil reserves

of these nutrients were found to be high enough to sustain intensive harvests for man’y 11 -year rotations.

Additional keywords: Biomass, Fraxinus pennsylvanica, nutrient depletion.

INTRODUCTION

Forest stands can now be harvested at any age with

today’s chipping equipment. The choice of rotation is still

primarily economic, but environmental changes must

now be considered: Will intensive harvest on short rotations deplete forest sites of essential nutrients? This study

was undertaken to obtain composition and yield data for

a typical young stand of bottomland hardwoods and to

document the export of nutrients by whole-tree chipping

under short rotations. Then, knowing the nutrient reserve

in the soil, a minimum period that the supply will last

under intensive harvest cycles can be predicted.

Yields and nutrient withdrawal by bottomland hardwoods in plantations have been reported by several

authors. Krinard and Johnson (1981) measured 17.8 t/a

of dry biomass in a stand of 1 l-year-old direct-seeded

oaks (Quercus r-Ma//ii Palmer) with many volunteer associates. Saucier, Clark, and McAlpine (1972) and Kennedy

(1975) obtained high yields from closely spaced sycamore (/?afanus occidentalis L.) harvested on short rotations. For short-rotation sycamore, Steinbeck and Brown

(1976) reported nutrients removed by harvest, and Blackmon (1979) reported that nutrients removed equal or

exceed nutrients added by natural processes. Francis

and Baker (1982) calculated that hundreds of 1 l-year

rotations of planted sweetgum (Liquidambar stymciflua

L.) would be necessary to deplete an alluvial clay soil of

nutrients. But the relationship of short-rotation yields and

nutrient withdrawal by harvest of natural stands of bottomland hardwoods had not been addressed until the

study reported here was undertaken.

METHODS

The sampling was conducted in an 1 l-year-old stand

in the Delta Experimental Forest near Stoneville, Miss.

This stand originated after a mature stand, dominated by

bottomland oaks, was logged in the fall of 1970 and the

residue was sheared and left in place. Sixteen .Ol-acre

circular plots were laid out in a line transect across the 40-

acre tract. The plots were situated in pairs spaced on

lOO-foot centers from the next pair. Half the plots, one

randomly chosen from each pair, were harvested in

summer (late August), and the remaining plots were harvested in winter (January).

Southern Forest Experiment Station/T-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
The following information was obtained from all trees

taller than 4.5 feet on each plot: species, diameter breast

height (dbh), total height, and green weight.

The trees were severed at 2 inches above ground.

Approximately one-tenth of every tenth tree was

removed, weighed green, and dried to obtain factors for

converting green weight to dry weight. The remaining

portions of all trees were separated into groups of important species and chipped with a limb chipper. The resulting piles of chips were mixed and “grab” samples totaling about 10 Ibs each were placed in plastic bags and

refrigerated. The chip samples were passed through a

sample splitter several times until a few hundred grams

remained. The samples were then separated into wood

and other tissue (bark, leaves, and small twigs) by hand

and with a sharp knife as necessary. The separated material was dried and ground for nutrient analysis. The result

was 96 samples representing 16 plots, 2 tissues, and a

variable number of species groups.

Nitrogen was determined by the Kjeldahl method.

Phosphorus was determined calorimetrically by the molybdenum-blue method. Potassium, Ca, and Mg were

determined by atomic absorption spectroscopy.

Soil samples were collected from plots of another

experiment 100 feet away and paralleling plots of this

study. The soil type, Alligator clay, was level and uniform

across the sample area. Sixteen cores were extracted

with a soil probe, and the 0 - 12-inch and 12 -24-inch

portions were taken as paired samples. The samples

were dried, ground, fused in NaOH, and analyzed for

total P according to the method described by Smith and

Bain (1982). Potassium, Ca, and Mg were analyzed by

atomic,absorption spectroscopy from an acid-diluted solution of the fused sample prepared for P determination.

Total N was determined by the Kjeldahl method. Nutrient

levels in the first foot and second foot were compared by

the paired t test with CC = .05.

RESULTS AND CONCLUSIONS

The stand had a preponderance of green ash (Fraxinus pennsylvanica Marsh.) stems. On the 16 plots, 82.4

percent of the stems were green ash (table 1). Other

important tree species represented were American elm

(Urnus americana L.), black willow (Salix nigra Marsh.),

cottonwood (Populus deltoides Bartr. ex Marsh.), and red

maple (Acer rubrum L.). The miscellaneous species category was composed principally of swamp-privet (forestiera acurninata (Michx.) Poir.) and hawthorn (Crataegus

spp.). Only a few oaks (Quercus spp.), sweetgum, and

sugarberry (Cekis laevigafa Willd.) had grown in the

sample area. Except for ash, no single species contributed a large percentage of the total stocking.

Green ash, relatively small individuals, provided a

smaller portion of the basal area than of total stems. Ash

accounted for 63.5 percent of the basal area, elm 9.2

percent, willow 8.8 percent, cottonwood 8.6 percent,

maple 1.7 percent, and miscellaneous species 8.2 percent. Green ash provided even a smaller proportion of

dry weight. Ash made up just 58.9 percent of the plots’

dry weight. Elm contributed 12.6 percent, willow 8.2 percent, cottonwood 8.6 percent, maple 1.6 percent, miscellaneous species 9.5 percent, and dead stems of all species 1.9 percent of the total dry weight.

The stand was quite heterogeneous at the .Ol -a scale.

The number of stems per acre averaged 5,888, ranging

from 2,400 to 24,100 (table 2). Basal area averaged 55

ftVa with a range of 20 to 86 ftVa. Standing dry weight per

acre was calculated at 37,114 Ibs for the summer and

31,964 Ibs for the following winter. The average annual

productivity, based on winter weight divided by 11 years,

was 1.45 t / a. The figure is close to the 1.62 t I a I yr

obtained from an 11 -year-old direct-seeded oak site (Krinard and Johnson 1981) and the 1.40 t I a / yr from a 6-

year-old upland hardwood stand in Tennessee (HitchTable 1 .-Total stems and proportion of stems, basal area, and dry weight of green ash and other species in sixteen ,137 -a plots in an 7 1 -year-o/d bottom/and hardwood stand

Species Stems Basal area Dry weight

no. percent ftz percent Ibs percent

Green ash 776 82.4 5.58 63.5 1,477 58.9

American elm 3 9 4.1 .81 9.2 315 12.6

Black willow 10 1.0 .77 8.8 174 6.9

Cottonwood 9 1.0 .76 8.6 216 8.6

Red maple 2 8 3.0 .15 1.7 4 0 1.6

Miscellaneous species 8 0 8.5 .72 8.2 239 9.5

Standing dead (all spp.) _____. __.__- ______ ..____ 4 5 1.9

Total 942 100 8.79 100 2,506 100

John K. Francis is Soil Scientist, Southern Hardwoods Laboratory, maintained at Stoneville, Mississippi, by the USDA Forest Service Southern Forest

Experiment Station in cooperation with the Mississippi Agricultural and Forestry Experiment Station and the Southern Hardwood Forest Research

Group, also at Stoneville.

2
Table 2.-Stems, basal area, and dry weight per acre in an 1 l-year-old

bottom/and hardwood stand

Season and plot Stems/a

thousands

Summer 1 5.4

2 6.4

3 4.4

4 2.9

5. 7.8

6 24.1

7 4.9

8 2.4

Winter 9 4.7

1 0 2.7

1 1 4.1

1 2 2.3

1 3 6.1

1 4 6.7

1 5 3.3

1 6 6.0

Mean 5.9+ 10.9

*Includes dead stems

Basal area/a Dry weighffa*

square feet tons

4 5 16.4

8 6 31.8

6 3 21.4

3 1 14.1

2 0 5.6

8 0 20.8

8 5 25.9

2 9 12.4

4 6 14.3

3 0 10.0

4 0 9.7

6 3 19.2

5 9 16.0

8 5 25.6

4 8 14.6

6 9 18.4

!j5 + 47 ______.

cock 1979). Although closely spaced sycamore and

poplar on managed, short rotations are more productive

than natural stands, the establishment cost is also much

higher.

The stand average dbh, 1 .O inches, reflects the relatively small average diameter of the green ash component. The number of trees ranging from 2.0 to 6.6 inches

dbh is more important than it would seem. Because dry

weight increases with height and the square of the diameter, dry weight is heavily concentrated within a few of the

larger trees. The relationship between percentage of total

stems-and dry weight is illustrated in figure 1. For example, 5 percent of the largest stems contain 50 percent of

the dry weight. On the other hand, removing 50 percent

of the stems, smallest first, still would leave 95 percent of

the dry weight.

Concentrations of N, P, K, and Mg in chip samples

from summer-harvested plots were generally higher than

in samples from winter-harvested plots (table 3). Calcium

averaged higher in winter-harvested plots. The other tissue fractions of the chipped material were higher for all

nutrients than the woody fractions. The loss of leaves was

probably the greatest cause of nutrient differences

between seasons. However, Ca can accumulate in tissues, especially bark, during the dormant season (Francis and Baker 1982).

Nutrient concentration figures and dry weight yields

were used to calculate weights of nutrient exported from

the site during harvest. Summer chipping removed the

equivalent of 176 Ibs N, 22 Ibs P, 115 Ibs K, 240 Ibs Ca,

and 23 Ibs Mg per acre. Winter harvesting removal

equaled 146 Ibs N, 17 Ibs P, 95 Ibs K, 305 IbsCa, and 20

Ibs Mg per acre. Removal of nutrients by winter harvest

was about 20 percent smaller than by summer harvest

except for Ca, of which 27 percent more was removed in

winter than summer. Obviously, to preserve nutrients,

winter is the preferable time to harvest whole trees. Ku,

1007

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*SMALLEST

2 60 / *

REMOVED FIRST

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LARGEST REMOVED FIRST

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2 0 /.

0 2-o 4 0 6 0 8 0 100

PERCENT OF WEIGHT

Figure 1 .--Distribution of dry weight on trees within an 7 l-year-old bottom/and hardwood stand removed sequentially by magnitude of dbh.

Baker, Blinn, and Wllliams (1980) studied understory

hardwoods in pine on the Silty Uplands of Arkansas.

Their summer harvest yielded a little more than half the

biomass and a little less than half the nutrients per acre

than the harvest in this study. However, the ratio of the

five nutrients to one another in chipped material from

both studies was essentially the same.

Concentration of total nutrients in the soil (available

plus fixed) was surprisingly high and quite uniform with

depth (table 4). Nitrogen in the first foot averaged .26

percent; P averaged .085 percent; K averaged 2.66 percent; Ca averaged .70 percent; and Mg averaged .95

percent. Concentrations in the second foot did not differ

significantly. Two feet of soil weighs about 8,000,OOO Ibs/

a. The calculated total nutrient reserves in the upper 2

feet would be:

N z 20,000 Ibs/a

P z 7,000 Ibs/a

Kg 212,000 Ibs/a

Ca g 55,000 Ibs/a

Mg g 76,000 Ibs/a

These reserves are so large that, assuming no growth

reduction due to diminished nutrient supply, it would take

more than 100 rotations of 11 years harvested by summer whole-tree chipping to consume all the N in the

upper 2 feet. The other nutrients would last even longer.

Under normal circumstances, natural gains exceed

natural losses and the site accumulates nutrients as a

young stand develogs. A principal source of additions is

rainfall. The folbwing 11 -year accumulations were c&u3
Table 3.-Nutrient content in tissues of summer- and winter-harvested biomass and nutrient withdrawn

from the site

N P K C a

Stand average (summer)

Wood

Other tissue

Total

Stand average (winter)

Wood

Other tissue

Total

Nutrient withdrawn

Summer

Winter

,237 ,041 ,212 ,224 ,032

1.019 ,098 ,540 1.616 ,130

,475 ,058 ,312 ,647 ,062

,253 ,043

,662 ,054

,396 ,047

176+168 22+20 115k107 240 + 255 23+24

147+ 98 17k12 95+ 60 305 k 208 20+13

--percent -----.

,189

,380

,256

.-lbs/acre ------

,243 ,030

1.907 ,094

,824 ,052

lated from nutrient contents in rainfall collected over a 2-

year period about 1 mile from the study site (Lockaby

1981): 102 Ibs N/a, 11 Ibs P/a, 38 Ibs K/a, 61 Ibs Ca/a,

and 16 Ibs Mg/a. In every case in this study, nutrients

withdrawn by harvest exceeded nutrients potentially

added in rainfall during an 11 -year period. The net loss,

however, would be small.

From the foregoing evidence, it is clear there is little

danger of depleting an Alligator soil of its vital nutrients by

intensive harvests on 1 l-year rotations. However, this

conclusion should not be extended to soils with low

cation exchange capacity and low base saturation.

Tab1 : 4.--Mean total nutrient concentration found in the first and second foot of Alligator soil

Depth N P K C a Mg

inche< .__.........._______~~~....-....~~~..~ percent _.......____________-...--.........---....

o-1 .260+.14 .085+.018 2.66k.20 .70+.24 .95+.26

12-24 ,231 k.16 ,081 k.018 2.63t.19 .67+.24 .95+.27

LITERATURE CITED

Blackman, B. G. Estimates of nutrient drain by dormantseason harvests of coppice American sycamore. Res.

Note SO-245 New Orleans, LA: US. Department of

Agriculture, Forest Service, Southern Forest Experiment Station; 1979. 5 p.

Francis, J. K.; Baker, J. B. Potential for nutrient depletion

by short rotation harvest of sweetgum. Soil Sci. Sot.

Am.J.46(5):1116-1118;1982.

Hitchcock, H. C., III. Biomass of southern hardwood

regeneration estimated by vertical line sampling. J.

For. 77: 474 - 477; 1979.

Kennedy, H. E., Jr. Influence of cutting cycle and spacing on coppice sycamore yield. Res. Note SO-193.

New Orleans, LA: US. Department of Agriculture,

Forest Service, Southern Forest Experiment Station;

1975.3 p.

Krinard, R. M.; Johnson, R. L. Description and yields of

an 1 l-year-old hardwood stand on Sharkey clay soil.

Res. Note SO-265. New Orleans, LA: U.S. Department

of Agriculture, Forest Service, Southern Forest Experiment Station; 1981. 2 p.

Ku, T. T.; Baker, J. B.; Blinn, C. R.; Williams, R. A.

Understory biomass from southern pine forest-an

energy source. In: Agron. Abstr. 1980: 203.

Lockaby, B. G. Nutrient cycling in eastern cottonwood

plantations on alluvial soils of the southern Mississippi

floodplain. Mississippi State, MS: Mississippi State

University; 1981. 162 p. Ph.D. Dissertation. University

Microfilms 81-19207, Ann Arbor, MI. (Diss. Abstr. 42:

865-B.)

Saucier, J. R.; Clark, A., III; McAlpine, R. G. Above

ground biomass yields of short-rotation sycamore.

Wood Sci. 5: 1 - 6; 1972.

Smith, B. F. L.; Bait-r, D. C. A sodium hydroxide method

for the determination of total phosphate in soils. Commun. Soil Sci. Plant Anal. 13: 185 - 190; 1982.

Steinbeck, K.; Brown, C. L. Yield and utilization of hardwood fiber grown on short rotations. In: Timell, T. E.,

ed. Proceedings Eighth Cellulose Conference. II.

Complete-tree utilization and biosynthesis and structure of cellulose. New York: John Wiley and Sons;

1976. Applied Polymer Symposium 28: 393 - 401.

* U.S. G”“tKNMENT PKIN’IING OFFICE: 1984-769-089:11