CIRCULAR 190 JUNE 1971

Dry XWeight and Nutricnt Accumulation in Young Stands of Cottonwood (Popuu/us dc/Itoi~Iej Ba rtr.)

Agricultural Experiment A U BU RN
E. V. Smith, Director

Station
Auburn, Alabama

U NI VE RS IT Y

CONTENTS
Page
INTRODUCTION----------

METHODS

RESULTS AND

DISCUSSION

5 13

LITERATURE

CITED _-

SUMMARY Dry matter accumulation in young cottonwood stands was high compared to many coniferous forests. But dry matter production did not appear to be closely related to site quality over the range of sites studied. Nutrient concentrations varied with crown position and crown class and were generally higher than most reported figures for conifers. Nutrient accumulations were rapid as would be expected from the high dry matter production rate. Cottonwood at age 7 accumulated nearly as much N, P, K, and Ca as 36-year-old Dougas fir or 26-year-old Pinus radiata.

FIRST

PRINTING

3M, JUNE 1971

Dry Weight and Nutrient Accumulation In Young Stands of Cottonwood (Populus deltoides Bartr.)
MASON C. CARTER and E. H. WHITE
2

INTRODUCTION

IN

there has been an increasing amount of literature dealing with the growth of tree stands including knowledge of primary production, mineral cycling, and tree nutrition (2,9,13). Consideration of the entire tree, the complete tree concept, has been proposed (18). As a result of this concept and the increased interest in using weight as a basic unit of measurement for forest products, reports have been made on the weight and nutrient element contents of complete trees (18,19). The objective of this study was to obtain above ground weights and nutrient element contents of young stands of eastern cottonwood. Such information should be useful in understanding the primary productivity and mineral cycling in natural ecosystems and as an aid in developing base lines for preventing damage to natural ecosystems as well as for the rehabilitation of ecosystems that have deteriorated.
THE PAST
SEVERAL YEARS

METHODS Six natural stands and two plantations of eastern cottonwood were selected for study. All stands were located in the overflow bottom of the Alabama and Tombigbee rivers in southwestThis work supported in part through the Hardwood Forestry Research Fellowship Program. 2 Respectively, Alumni Associate Professor, Department of Forestry, Auburn University, and Assistant Professor, Department of Forestry, University of Kentucky.

ern Alabama. The stands were at least 2 acres in size, fully stocked, nearly 100 per cent pure, and essentially free from understory vegetation. Periodic flooding and siltation prevented the formation of a litter layer and mineral soil was exposed over most of the stands. Two 1/20-acre plots were established in each stand. Five dominant or codominant trees were selected at random on each plot for total height measurements. Diameters breast high outside bark (DBHOB) of all trees were recorded and grouped into three classes representing suppressed, codominant, and dominant crown classes. In August, one tree from each crown class on each plot was felled at the ground-line for stem analysis and total tree sampling (8,11,16). Total tree height, length of live crown, and DBHOB were measured and recorded. The crown was divided into upper and lower crown by measuring from the lowest limb bearing green leaves to the apex and dividing into two equal parts. All leaves, including petioles, were stripped from the branches and collected by upper or lower crown position. All branches were collected in a similar manner. The boles of the trees were cut into 6-foot sections which were weighed in the field with a large platform balance. Fourinch discs were cut from the butt of the first bolt of each tree and from the tops of all bolts. The discs were weighed while fresh and their diameters measured in the field. Foliage, branches, and discs were transported to the laboratory for further processing. All tree components were dried to a constant weight at 65 0 C and the dry weights recorded. Discs were weighed with the bark on, the bark removed, and with both bole bark and bole wood redried and reweighed. A ratio of oven-dry to fresh weight of discs was used to calculate dry weights of sample tree, bole wood, and bole bark. Bole wood, bole bark, branches, and foliage were ground separately in a Wiley mill to pass a 40-mesh sieve. Sub-samples were analyzed for N by the Kjeldahl procedure modified to include nitrates (12). Other subsamples were ashed for 412 hours at 450°C and the ash dissolved in dilute HC1 for analysis. Aliquots of these solutions were analyzed for P by the vanadate procedure (4,7); K by Beckman DU flame spectrophotometer; Mg and Ca by a Perkin-Elmer 303 atomic absorption spectrophotometer using lanthium oxide to suppress interferences (1).
[4]

Stem analysis data from the 48 sample trees were used to construct volume and weight equations by standard statistical procedures (3,14). No attempt was made to determine root mass. All weights and nutrient contents in the ensuing discussion refer to above ground biomass only. RESULTS AND DISCUSSION Mensurational data for the sample stands are presented in Table 1. All stands were located on what appeared to be good cottonwood sites (5), but a range in site quality was found. Average height of dominant and codominant trees at age 6 years was estimated from stem analyses and used as an indicator of site quality. On this basis, a two-fold difference in site quality existed between the best and the poorest sites, Table 1. The two best growing stands (Stands 1 and 2 in Table 1) were plantations. Stand 2 received weed and insect control during the first growing season while stand 1 received a weeding at the beginning of the second growing season. The control of stocking and cultural treatments may have contributed to the superior growth rates of these two stands.
TABLE 1. SUMMARY OF MENSURATIONAL
STANDS,

DATA FOR YOUNG
1

COTTONWOOD

ALABAMA

Stand 2

1 2 3 4_........... 5 6 7 8

Height age 6 Ft. 66.5a 56.8b 55.4b 50.1c 48.0d 44.2e 43.1e 82.4f

Av. Current Height 3 DBHOBarea/ Ft. 71.Sa 65.6b 58.2cd 60.6c 60.1c 48.9e 56.0d 82.4f In. 6.8a 5.7b 4.0d 4.8c 4.0d 2.3e 3.8d 1.8f Yr. 7 8 7 9 8 7 8 6

Stems/

Basal acre Sq. ft. 104 89 102 80 103 88 80 82

No. 390a 470a 990b 610a 1,090b 3,260c 890b 7,020d

Total volume/ acre Cu. Ft. 2,566a 2,034bc 2,116b 1,806d 2,434a 1,872c 1,581e 864f

SMeans in any one column followed by the same letter do not differ significantly at the 5% level (Duncan's Test). 2 Ranked 1-8 based upon average height of codominant and dominant trees at age 6. Average height of codominant and dominant trees at current stand age.

'

Data on the 48 sample trees are shown in Table 2. Heights ranged from 15.6 to 77.8 feet, DBHOB ranged from 0.8 to 10.5 inches, and dry weights ranged from 1.6 to 477.1 pounds. Regression equations relating DBHOB to dry weight of various [5]

TABLE 2.

SUMMARY OF SIZES AND WEIGHTS FOR THE

48

SAMPLE TREES

Dry weights
Stand Crown2 DBHOB Height class Foliage Branches In. 2.8 4.1 6.3 7.3 8.9 10.5 2.9 2.7 5.4 5.8 7.5 8.1 2.0 2.3 3.5 4.2 6.4 7.5 2.6 2.9 5.1 4.2 7.3 6.5 2.5 2.2 4.6 4.6 6.0 7.9 1.6 1.6 2.5 2.8 4.7 5.0 2.5 2.0 4.3 5.0 5.8 6.3 .9 .8 1.9 2.4 2.9 3.0 Ft. 35.4 45.4 65.8 69.2 74.4 77.8 36.1 34.0 60.7 63.7 68.7 69.5 29.0 30.0 48.0 52.0 63.3 69.3 36.4 46.4 56.9 52.3 65.7 67.3 40.4 29.5 56.5 55.0 61.5 67.5 25.0 26.2 37.4 43.0 48.0 55.3 30.7 24.5 51.8 56.8 57.2 58.1 15.7 15.6 28.7 32.9 35.0 33.3 Lb. .5 .9 5.0 8.5 15.9 31.3 1.9 1.6 4.1 4.9 13.3 17.9 .7 .9 .8 1.5 5.7 10.0 .7 1.9 2.5 2.4 7.7 14.1 1.2 .5 1.8 1.5 4.9 7.7 .6 .6 1.0 .6 2.7 2.7 1.1 .6 2.7 3.0 5.5 5.8 .2 .5 .7 1.6 2.1 2.6 Lb. 2.2 5.5 17.4 26.3 40.1 98.5 3.6 4.2 12.1 18.2 25.9 69.8 2.1 1.9 10.8 6.1 37.0 53.3 3.2 2.3 19.1 7.9 42.9 26.1 2.9 1.6 11.1 8.5 26.8 58.5 11.0 .8 1.7 1.2 8.7 9.7 2.3 .9 8.5 7.7 23.0 29.1 .3 .3 1.0 2.7 2.9 5.1 Bole Bole bark Lb. 2.4 5.7 17.9 23.4 37.5 41.9 2.5 3.1 7.7 20.5 27.0 39.2 1.0 1.6 5.1 6.4 12.1 29.2 2.9 4.8 12.2 6.9 29.3 20.2 3.3 1.5 6.9 6.4 10.2 22.1 1.1 .9 3.0 3.1 8.2 6.3 3.2 1.4 9.5 12.3 24.0 17.7 .3 .6 1.6 2.2 3.1 3.2 Bole Bole wood Lb. 12.1 8.9 110.4 164.7 250.1 305.4 14.1 11.0 59.4 119.1 177.5 263.5 4.9 8.7 8.0 17.2 111.5 212.5 12.0 23.5 56.7 40.5 137.9 152.1 15.7 9.2 44.9 46.5 94.2 162.1 3.3 4.1 13.5 17.0 44.6 58.8 10.3 5.3 43.0 56.1 107.4 95.1 .8 1.2 6.0 9.4 15.1 16.2 Total Lb. 17.2 21.0 150.7 222.9 343.6 477.1 22.1 19.9 83.3 162.7 243.7 390.4 8.7 13.1 24.7 31.2 166.3 304.7 18.8 32.5 90.5 57.7 217.8 212.5 23.1 12.8 64.7 62.9 136.1 250.6 6.0 6.4 19.2 21.9 64.2 77.5 16.9 8.2 68.7 79.1 159.9 147.7 1.6 2.6 9.3 15.9 23.2 27.1

1-.............-

S S CD CD D D 2______________ S S CD CD D D 3______________ S S CD CD D D 4______________ S S CD CD D D 5 S S CD CD D D 6_5.... . S S CD CD D D 7_5..... S S CD CD D D 8 _5.... . S S CD CD D D
1Ranked 2 S=

1-8 based upon height of codominant and dominant trees at age 6. suppressed, CD - codominant, D= dominant.

[6]

components are shown in Table 3. Using these equations, the weight of foliage, branches, bole bark, and bole wood for various diameter classes were calculated and plotted as a percentage of total tree dry weight, see Figure. The proportional weight of foliage increased only slightly with tree size and branch weights remained at a rather consistent 15 to 16 per cent of total tree weight. Bole bark decreased from 33 per cent for 1-inch trees to 10 per cent for 10-inch trees while bole wood increased from 49 to 70 per cent for 1- and 10-inch trees, respectively.
TABLE 3. REGRESSION
TO

CONSTANTS,

COEFFICIENTS,

AND
TREE

r VALUES

RELATING

DBHOB

THE WEIGHT

OF COTTONWOOD

COMPONENTS

Component

a

b

r

St. error 1.70730 0.15130 0.11970 0.14880

stimate

reg. coef.

St. error 0.00112 0.08675 0.08675 0.08584

Foliage Branches Bole bark Bole wood

0.33155 -0.56362 -- 0.39440 0.06151

0.2504 2.40148 2.00955 2.42189

0.957 0.971 0.974 0.973

1 Equation for estimation of foliage biomass is of the form Y = a + bX where Y is weight of foliage in pounds and X is the DBHOB cubed. Equations for estimation of branch, bole bark, and the bole wood weights are of the form Y - a + bX where Y is the logarithm of the biomass in pounds and X is the logarithm of tree DBHOB.

Regression equations shown in Table 8 are the overall equations based on all 48 sample trees. When individual equations were calculated for each stand, differences between stands were observed. Differences in age and site quality were largely responsible for these variations. To obtain an estimate of total stand weight, individual stand equations were used to calculate the weight of each tree on a sample plot. The results, totaled and expanded to per acre values, are given in Table 4. Examination of these data do not suggest any strong relationships between site index based on height at age 6 and any of the dry weight values. To overcome differences in stand age, stem analyses data were used to adjust diameter distribution on each plot to age 6 and tree component weights were recalculated. Thus it was possible to estimate total dry matter at age 6 for all stands, Table 5. Dry matter production and site quality still did not appear to be related. Similar results have been obtained for other forest types (13). The cottonwood stands in this study produced large amounts of dry matter compared to many temperate forests. Satoo (13) reported the total biomass for a 15-year-old natural stand of Pinus desiflora in eastern Japan was approximately 28.5 tons [7]

Pct total tree dry weight 70

60
o foliage

50
IrLt

A branches

bole bark o bolewood

·uu

40

30 -

20 -

10

-

I

0
0 2 4 6

8

IO

DBHOB, inches
Changes in relative proportions of foliage, branches, bole bark, and bole wood
with variations in tree diameter.

per acre. Stand 3, also a natural stand, equalled this dry matter production in above ground overstory alone in 7 growing seasons. Stands 1 and 6 produced even more in 7 years. Data reported by Cole, et al. (6) indicate that the mean annual accumulation of dry matter in a 36-year-old plantation of Douglas fir in Washington was 2.5 tons per acre. Twenty-six-year-old Pinus radiata
[8]

TABLE 4.

WEIGHTS OF YOUNG COTTONWOOD STANDS SOUTHWEST ALABAMA

ON ALLUVIAL SITES IN

Stand'

Dry weights
Age

Foliage

Branches

Bole

hark

wood

Bole

Total

Yr.

Ton/A.

Ton/A.
5.4 4.8 6.5 4.7 6.6 3.2 3.4 1.5

Ton/A.
4.2 3.8
3.5 3.7

Ton/A.
25.1 24.9
17.7 20.1

Ton/A.
36.4 35.1
28.9 29.4

1_________________________ 1.7 7 2------------8 1.6 3------------------------7 1.2 4------------------------9 0.9 5---------8 1.2 6------------------------7 1.6 7________________________ 8 1.1 8_6___________________ 1.1
1Ranked

3.5
3.8

25.0
20.9

36.3
29.5

3.7

16.4

24.6

3.2

11.6

17.4

1-8 hased upon height of codominant and dominant trees at age 6.

TABLE 5. WEIGHTS OF YOUNG COTTONWOOD STANDS ON ALLUVIAL SITES IN SOUTHWEST ALABAMA AFTER ADJUSTMENT OF ALL STANDS TO AGE 6

Dry weights
Stand'

Stand

1

Foliage

Branches

Boe hark
o

Ton/A.
1--------------------------------2--------------------------------3--------------------------------4---------------------------------

Ton/A.

Ton/A.
2.8 2.6 2.7 2.0 2.2 3.0
1.6

ol wo Ton/A. 15.1 15.6 13.1 10.5
9.1

Toa Ton/A. 22.3 22.7 22.0 15.2
21.6

1.0 3.4 1.2 3.3 0.9 5.3 0.5 2.2 5 ________________________________ 0.7 3.6 6--------------------------------1.3 2.4 7------------------------------0.5 1.2 8-------------------------------1.1 1.5
1Banked

15.114.8
11.6

21.5
12.4

3.2

17.4

1-8 hased upon height of codominant and dominant trees at age 6.

in New Zealand accumulated 3.8 tons per acre (10), and Pinus taeda accumulated 2.5 tons per acre for the first 30 years in Mississippi (15). Cottonwood stand 1 had a mean annual accumulation of 5.2 tons per acre over the first 7 years, Table 4. Nutrient concentrations by tree component and crown class averaged over all stands are shown in Table 6. Suppressed trees contained higher concentrations of most nutrients than dominant and codominant trees. Concentrations differed between the upper and lower halves of the crown, Table 7. These findings have
been discussed in more detail

With the chemical analyses and the known dry weights for each of the 48 sample trees, Table 2, it was possible to calculate
the total amount of each element in each

in a previous paper (17).

From these data, regression equations relating DBHOB to element content were developed, Table 8. Substituting the diameter tallys for each plot into the proper equations produced the data
[9
]

of, the

sample trees.

TABLE 6.

AVERAGE CONCENTRATIONS OF NUTRIENT ELEMENTS AND ASH IN TREE
OF SUPPRESSED, CODOMINANT, SITES IN AND DOMINANT COTTONWOOD TREES ON ALLUVIAL SOUTHWEST ALABAMA

COMPONENTS

Tree component

Crown class

1

N

P

Dry Weight K Ca

Mg

Ash

Pct. Foliage____________ Suppressed Codominant Dominant Branches--------- Suppressed Codominant Dominant Bole bark------ Suppressed Codominant Dominant Bole wood-----. Suppressed Codominant Dominant 2.02 2.01 2.08 .56 .50 .44 .63 .58 .55 .11 .10 .10

Pct. 0.18 0.19 0.20 .08 .08 .07 .07 .07 .07 .03 .02 .02

Pct. 1.26 1.22 1.22 .46 .40 .35 .49 .47 .45 .18 .14 .13

Pct. 2.89 2.40 2.66 1.26 .89 .79 2.24 2.14 2.11 .14 .12 .11

Pct. 0.32 0.32 0.29 .10 .09 .08 .16 .15 .14 .03 .03 .03

Pct. 13.40 11.28 10.26 4.14 8.19 3.19 7.79 7.06 6.63 .79 .67 .64

1 Differences between crown classes were significant (P<0.05) for every element and every component. Some of the averages are identical due to rounding to the second decimal. TABLE

7.

AND BRANCHES OF COTTONWOOD

AVERAGE CONCENTRATIONS OF NUTRIENT ELEMENTS AND ASH IN FOLIAGE TREES ON ALLUVIAL SITES IN SOUTHWEST ALABAMA BY POSITION IN CROWN

Tree component

Crown' position

N Pct. 2.09 1.98 .52 .47

P Pct. .20 .19 .08 .07

Dry Weight K Ca Pet. 1.30 1.18 .42 .38 Pct. 2.16 2.78 .94 1.02

Mg Pct. .29 .33 .09 .09

Ash Pct. 10.82 12.48 3.31 3.47

Foliage Branches

Upper Lower
Upper

Lower

1Differences between the upper and lower halves of the crown were significant in all instances (P<0.05). Certain means are identical due to rounding to the second decimal.

in Table 9 showing the total nutrient content for each of the eight cottonwood stands. The content for most elements differed between stands in the same order that biomass differed, Table 4. Between 20 and 30 per cent of the nutrients were in the foliage, 20 to 26 per cent were in the branches, 29 to 39 per cent were in the bole bark, and 20 to 26 per cent were in the bole wood. Nutrient accumulations in young cottonwood stands were very high compared to reported values for certain coniferous forests. Harvesting of bole wood and bark by clear cutting cottonwood Stand 1 would remove 92 pounds N, 15 pounds P, 102 pounds K, and 283 pounds Ca per acre. Corresponding figures
[10]

TABLE

8.

REGRESSION

CONSTANTS,

COEFFICIENTS,
1

AND

r

VALUES

RELATING

DBHOB

TO THE NUTRIENT ELEMENT CONTENT OF COTTONWOOD

TREE COMPONENTS

Component

Element

a

b

r

St. error

St. error 0.12915 0.14480 0.11723 0.02759 0.12146 0.09433 0.19775 0.09626 0.10137 0.12751 0.08992 0.08611 0.07709 0.11333 0.11841 0.09298 0.15997 0.08739 0.08608 0.10772

Foliage

1.86129 -2.41487 N -.......-..... P K Ca Mg N P K Ca Mg N P K Ca Mg N P K Ca Mg -3.43891 -2.68245 -2.21156 -3.12074 -2.77723 -3.35467 -2.85032 -2.39373 -3.44257 -2.60052 -3.51157 -2.70467 -1.99883 -3.18780 -2.87001 -3.27775 -2.58974 -2.76708 -3.40909

Branches__________

Bole bark._________

Bole wood------

1.85411 1.92429 1.61349 1.63181 2.21007 2.60164 2.18691 2.08857 2.11315 1.97355 1.91279 1.91279 1.91835 1.95763 2.31243 1.84934 2.09396 2.28029 2.23082

0.905 0.884 0.924 0.881 0.893 0.960 0.889 0.966 0.950 0.926 0.955 0.956 0.967 0.928 0.925 0.965 0.863 0.962 0.969 0.950

0.22520 0.25250 0.20440 0.22250 0.21180 0.16450 0.34480 0.15040 0.17670 0.22230 0.15680 0.15010 0.13440 0.19760 0.20650 0.16210 0.27890 0.15240 0.15010 0.18780

bX where Y is the logarithm of element weight 1 Equation of the form Y = a in pounds and X is the logarithm of tree DBHOB.

+

for the previously mentioned 36-year-old Douglas fir stand (6) would be 111 pounds N, 17 pounds P, 85 pounds K, and 104 pounds Ca per acre. For-26-year-old P. radiata the values are 114 pounds N, 16 pounds P, 225 pounds K, and 140 pounds Ca per acre (10). By the time cottonwood Stand 1 reaches the same age, its nutrient content should greatly exceed the nutrient content of these conifers. Although timber harvest will remove appreciable amounts of nutrients from the site, there appears to be little danger that the soil fertility will be significantly reduced. The surface 6 inches of soil supporting Stand 1 contained 14 pounds available P, 360 pounds exchangeable K, and 9,324 pounds of exchangeable Ca per acre (17). Flood waters annually deposit several inches of this fertile alluvial soil on the site which should more than compensate for the nutrients removed by the cottonwood. However, continuous cropping of cottonwood on lands not subject to flooding and deposition could lead to a rapid depletion of the nutrient supply of the soil.

[11]

TABLE 9.

NUTRIENT ELEMENT AND ASH CONTENTS OF YOUNG COTTONWOOD STANDS ON ALLUVIAL SITES IN SOUTHWEST ALABAMA

Stand'

Age Yr. 7

Tree component Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total Foliage Branches Bole bark Bole wood Total u vr\

N

P

K

Ca

Mg

Total'

Ash

Lb./A. Lb./A. Lb./A. Lb./A. Lb./A. Lb./A. 72 88 8 46 7 221 381 6 319 48 36 90 7 187 44 223 5 35 648 317 10 338 10 67 60 13 198 48 29 184 461 37 923 1,686 212 69 35 37 51 192 54 56 45 44 199 54 45 46 39 184 49 62 46 47 204 47 28 36 33 144 47 35 58 35 175 84 30 35 25 174 7 7 6 11 31 5 7 5 6 23 4 5 4 5 18 4 8 4 7 23 6 6 6 13 31 4 4 4 4 16 48 35 47 61 191 31 45 35 41 152 30 31 33 49 143 28 41 30 64 163 28 37 41 66 172 26 23 29 41 119 89 80 159 54 382 43 84 130 39 296 50 82 148 45 325 49 73 123 59 304 77 72 167 53 369 44 65 151 41 301 100 83 131 28 342 9 8 10 11 38 8 9 10 9 36 7 9 12 11 39 8 9 10 10 37 8 6 10 12 36 3 9 11 9 32 15 9 11 9 44 222 165 259 188 834 141 201 225 139 706 145 172 243 149 709 138 193 213 187 731 166 149 260 177 752 124 236 253 130 643 250 153 436 114 730 341 220 493 297 1,351 229 307 436 235 1,207 246 270 523 241 1,280 241 329 487 335 1,392 350 233 522 301 1,406 212 234 549 188 1,183 489 237 213 182 1,353

8

7

9

8

_7

S8

9 42 7 24 6 30 12 40 34 vrul~r 136 rvv~ 1 Ranked 1-8 based upon height of codominant and 2 Summation of N, P, K, Ca, and Mg.

6

dominant trees at age 6.

[12]

LITERATURE CITED
(1) ANONYMOUS. 1966. Analytical Methods for Atomic Absorption Spectrophotometry. Perkin-Elmer Inst. Div., Norwalk, Conn. (2) ANONYMOUS. 1967. Symposium on Primary Productivity and Mineral Cycling in Natural Ecosystems. Ecological Soc. Amer., Univ. Me. Press, 245 pp. (3) ANONYMOUS. Biomedical Computer Program. 1965. Univ. Calif. at Los Angeles, Calif. (4) BLACK, C. A., D. D. EVANS, J. L. WHITE, L. E. ENSMINGER, AND F. E. CLARK. 1965. Methods of Soil Analysis. No. 9 in the Series Agronomy. ASA, Inc. Madison, Wisc. 1,572 pp. (5) BROADFOOT, W. M. 1964. Soil Suitability for Hardwoods in the Midsouth. USFS Res. Note SO-10. 10 pp.
(6)
COLE,

D. W., S. P. Gessel, and S. F. Dice.

1967.

Distribution and

Cycling of Nitrogen, Phosphorus, Potassium, and Calcium in a Second-growth Douglas Fir Ecosystem. Sym. on Primary Productivity and Mineral Cycling in Natural Ecosystems. Univ. of Me. Press, 198232. (7) JACKSON, M. L. 1958. Soil Chemical Analysis. Prentice Hall, Inc., Englewood Cliffs, N. J. (8) MADGWICK, H. A. I. 1962. Studies in the Growth and Nutrition of Pinus resinosa act. Ph.D. thesis, State Univ. Coll. For. at Syracuse Univ., Syracuse, N.Y. (9) NEWBOLD, P. J. 1967. Methods for Estimating the Primary Production of Forests. Int. Biol. Program, Blackwell Sci. Publ., Oxford. 60 pp.

(10)

ORMAN, H. R. AND G. M. WILLS. 1960.

The Nutrient Content of

Pinus radiata Trees. N. Z. J. Sci. 3:510-522. (11) OVINGTON, J. D. 1965. Organic Production Turnover, and Mineral Cycling in Woodlands. Bio. Rev. 40:245-336. (12) PAECH, K. AND M. V. TRACEY. 1956. Modern Methods of Plant Analysis I., Berlin, Germany. 542 pp. (13) SATOO, T. 1967. Primary Production Relations in Woodlands of Pinus desiflora In: Sym. on Primary Productivity and Mineral Cycling in Natural Ecosystems. Univ. Me. Press, pp. 52-81. (14) STEELE, R. G. D. AND J. H. TORRIE. 1960. Principles and Procedures of Statistics. McGraw-Hill Book Co., Inc., N.Y.

(15)

SWITZER, G. L., L. E. NELSON, AND W. H. SMITH.

1966. The Char-

(16)
(17)

acterization of Dry Matter and Nitrogen Accumulation by Loblolly Pine (Pinus taeda L.). SSSA Proc. 30:114-119. WHITE, E. H. 1964. Uptake and Distribution of Nutrient Elements in a Red Pine Plantation. M. S. thesis. State Univ. Coll. For. at Syracuse Univ., Syracuse, N. Y.
WHITE, E. H. AND M. C. CARTER. 1970. Relationships Between

Growth and Foliar Nutrient Levels in Young Stands of Populus deltoides Bartr. 3rd N. Amer. For. Soils Conf. Proc., N. C. State Univ., 283-294. [13]

(18) (19)

1967. Weight, Nutrient Element, and Productivity Studies of Seedlings and Saplings of Eight Tree Species in Natural Ecosystems. Me. Agr. Exp. Sta. Bull. 28. YOUNG, H. E., P. N. CARPENTER, AND R. A. ALTENBERGER. 1965. Preliminary Tables of Some Chemical Elements in Seven Tree Species in Maine. Me. Agr. Exp. Sta. Bull. 20.
YOUNG, H. E. AND P. N. CARPENTER.

[14]

AGRICULTURAL EXPERIMENT STATION SYSTEM OF ALABAMA'S LAND-GRANT UNIVERSITY

With an agricultural research unit in every major soil area, Auburn

0
l7

University serves the

needs of field crop, livestock, forestry, and hor-

ticultural producers in each region in AIabama. Every citizen of the State has a stake in this research program, since any advantage from new and more economical ways of
pioduicing and handling farm products directly benefits the consuming public.

0
20
3
®fa .

c

0

Research

Unit Identification

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21

Tennessee Valley Substation, Belle Mina. Sand Mountain Substation, Crossville. North Alabama Horticulture Substation, Cullman. Upper Coastal Plain Substation, Winfield. Forestry Unit, Fayette County. Thorsby Foundation Seed Stocks Farm, Thorsby. Chilton Area Horticulture Substation, Clanton. Forestry Unit, Coosa County. Piedmont Substation, Camp Hill. Plant Breeding Unit, Tallassee. Forestry Unit, Autauga County. Prattville Experiment Field, Prattville. Black Belt Substation, Marion Junction. Tuskegee Experiment Field, Tuskegee. Lower Coastal Plain Substation, Camden. Forestry Unit, Barbour County. Monroeville Experiment Field, Monroeille. Wiregrass Substation, Headland. Brewton Experiment Field, Brewton. Ornamental Horticulture Field Station, Spring Hill. Gulf Coast Substation, Fairhope.