United States

Department of

Argriculture

Southern Forest

Forest Service Research Note

SO-285

Experiment Station November, 1982

Effects of Shallow Water Tables on Height Growth

and Phosphorus Uptake by Loblolly and Slash Pines

A. E. Tiarks and E. Shoulders

SUMMARY

In southern Mississippi, the heights of loblolly

and slash pines at age 20 were positively

correlated with the phosphorus content of the

foliage and with depth in the soil to gray (chromas

52) mottles. Slash pine was taller than loblolly at

equivalent levels of foliage phosphorus, but the

rate of height increase as foliage phosphorus

increased was the same for both species. Neither

species was productive when the winter water

table was at the surface. Phosphorus soil tests

were not useful in predicting height even though

phosphorus was a growth limiting nutrient. As the

available phosphorus content of the soils studied

is very low, the soil depth or volume of soil

available for root exploration is more important

than small differences in soil phosphorus.

Additional keywords: Gray mottles, phosphorus

soil test, soil-site, soil water.

INTRODUCTION

During our evaluation of moisture related

variables associated with 20-year heights of the

four major southern pine species (Shoulders and

Tiarks 1980), we encountered wide variations in

tree heights among plots in an area of uniformly

high summer rainfall in southern Mississippi. The

variations were not related to rainfall, slope, or

potential available soil .moisture in the subsoil.

Since climate was essentially uniform throughout

the problem area and average rainfall exceeded

optimum levels, we reasoned that differences in

soil aeration or nutrient status might be affecting

growth. To test our hypothesis, we related 20.year

heights of dominant and codominant loblolly

(Pinus taeda L.) and slash (P. elliottii Engejm var.

elliotti/) pines to levels of nitrogen, phosphorus,

potassium, calcium, magnesium, sodium, manganese, and aluminum in foliage and to selected soil

parameters not included in the previous investigation.

METHODS

Nine plantations of the larger study (Shoulders

1976, Shoulders and Tiarks 1980) were included in

the current evaluation. They are in a 1000 km2 area

located near McHenry, Mississippi, where annual

rainfall averages about 175 cm and mean warm

season rainfall (April through September) exceeds

99 cm. The plantations originally contained 27

plots of each species. Of these, the survival on 17

lobloliy and 25 slash pine plots was sufficient to

provide reliable growth data through age 20.

Twenty-year heights of at least 10 dominant and

codominant trees on each plot were measured

during the winters of 1973-74, 1974-75, and

1975-76. Soil and foliage were sampled in January

1978.

Foliage samples were current-year needles from

branches in the top one-third of the canopy of 10

dominant or codominant trees per plot. The

needles were dried at 70°C and ground to pass

through a 2-mm screen. Nitrogen was determined

by the Kjeldahl method (Jackson 1958).

Phosphorus, potassium, calcium, magnesium,

sodium; manganese, and aluminum were deterSouthern Forest Experiment StationR-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

1
mined on samples that had been dry ashed at

450% and taken up in 0.3/V HNO,. Phosphorus was

determined by the ascorbic acid method (John

1970). The other elements were analyzed by atomic

absorption spectrophotometry.

Soil samples consisted of a composite of 10

subsamples of the top !O cm from each plot. The

soil was air dried and passed through a 2-mm sieve.

Organic phosphorus was determined by the

ignition method (Saunders and Williams 1955)

using a temperature of bSO’C and 0.2N H,SO, as

the extractant. The phosphorus extracted by 0.2N

H,SO, from the unignited sample used in the

organic phosphorus determinath?n was also

considered to be an estimate of available

phosphorus (Walmsley and Cornforth 1973). Other

procedures used to measure available phosphorus

were shaking the soil with 0.03N NH,F + O.lN HCI

for 15 minutes (Jackson la54 and shaking with 1N

NaOH for 16 hours (Humphreys and Pritchett 1972).

Phosphorus intenqity was determined by equilibrating 5 g of soil kith 50 ml of water for 18 hours

(Humphreys and Pritchstt 1972). Phosphorus

equilibrium conceqtration was defined as the

natural log of the phosphorus concentration after

shaking 2 g of soil ,with 100 ml of solution which

had an initial con4entration of 0.25 pg of phosphorus/ml for 16 hours.

Soil series designations and soil profile

descriptions of each plantation were made by Soil

Conservation Service personnel in January 1981

(table 1). Depth to average winter water table was

estimated from depth to gray mottles (chroma of 2

or less) (Soil Survey Staff 1975), except for Atmore,

Smithtori, and one soil whose series was not

designated. The depth to average winter water

table was taken to be 0.0 cm for these three soils

based on observation of the water table, because

organic matter coatings masked other colors. The

profile of the unnamed soil has the characteristics

of the Susquehanna series (Vertic Paleudalf, fine,

montmorillonitic, thermic), except w,ater accumulates on the surface during wet periods.

For statistical tests, the level of significance was

preset to 0.05.

RESULTS

The height of the trees at age 20 was

significantly correlated with the nitrogen, phosphorus, and aluminum concentrations in the

needle samples (table 2) of both species. Height

was also significantly correlated with calcium conTable 1. - Soil series, the/r classification, and measured depth

to gray mottles or dominate/y gray horizons for the

nlne plantations studied

Depth to

Soil series Classlflcatlonl gray mottles

-.....om --.

Atmore Pllnthic Paleaquults, coarse-loamy,

slllceous, thermlc 0

Escambia Pllnthaqulc Paleudults, coarse-loamy,

slllceous, thermlc 2 5

Malbls Pllnthlc Paleudults, fine-loamy,

slllceous, thermlc 6 1

Poarch Plinthlc Paleudults, coarse-loamy,

siliceous, thermlc 150

Saucier Plinthaquic Paleudults, fine-loamy,

slllceous, thermlc 56

Smlthton Typic Paleaquults, coarse-loamy,

slllceous, thermlc 0

Series not

designated -..v..... . . . . . .. .. . . . . . . . . . . w.....m..- . . . . ...s..P...-...-...- 0

’ Soil survey staff. 1980. Classification of soil series of the

United States, Puerto Rico, and the Virgin Islands. Unpublished

report. U.S. Dep. Agrlc. Soll Conservation Servlce.

centrations in slash needles and sodium in

loblollly samples. Because of the high correlation

between height and foliar phosphorus, the

relationship between other elements and helght

were possibly masked. Therefore the residuals, or

the differences between actual heights and the

predicted heights, from the Phosphorus regression

were also related to the concentrations of the

remaining elements. (table 2).

The nitrogen relationship was negative, meaning

the lower nitrogen concentrations were In samples

from the tallest stands. This may be due to a

dilution effect with nitrogen in sufficient supply at

the prevailing environmental conditions. Also, the

range in concentrations measured (table 2) are

above critical limits proposed by Pritchett and

Gooding (1975).

Phosphorus concentrations were positively

correlated with height. Slash pine was taller than

loblolly at a given level of phosphorus concentraA. E. Tiarks Is Soil Scientist and E. Shoulders Is Principal Sllvtculturist, Southern Forest Experiment Statlon, Forest Service-USDA,

Plnevllle, Louisiana. The authors wlsh to thank Rex Davls, Sol1 Sclentlst, Soil Consewatlon Service, U.S. Rap. Agrlc., for series

Identifications.

2
Table 2. -Range of nutrient concentrations in current years

foliage and correlation of fhe concentrations with

height at age 20 and with residuals from fitting

phosphorus to height regression

Correlation

Range in With height With residuals

concentration

Element for both species Slash Lobioily Slash Lobioiiy

. . . . . . . . ..mg/g.-....- . . . . . ..-..---~~ r~~.~......~..~.~.~~~

Nitrogen 9.0-10.2 -0.55’ -0.84’ -0.30 -0.53”

Phosphorus 0.4-0.85 0.88’ 0.80’ . . . . . . . . . .

Potassium 1.7-4.4 0.28 0.20 0.01 -0.14

Caiclum 0.73-2.5 0.54* 0.25 0.11 -0.02

Magnesium 0.59-1.18 0.43 0.11 -0.11

Sodium 0.23-0.81 -I: -0.82* -0.12 -0.53’

Manganese 0.08-0.47 0.29 0.04 0.15 0.22

Aluminum 0.24-0.88 0.77’ 0.80* 0.20 0.37

*Correlation significant at 0.05 level.

tion in the needles (fig. l), indicating that slash

pine utilizes phosphorus more efficiently.

Concentrations of phosphorus in foliage were

below the critlcal level of 0.09 percent for slash

(Pritchett and Gooding 1975). Therefore, the

relationship between phosphorus and height is

linear. The curve should begin to flatten, however,

as the concentration exceeds the critical level.

Aluminum is not considered to be an essential

element for tree growth. The high correlation

between height and alumlnum concentration is

probably due to aluminum and phosphorus

occurring together in the soil, either in solution or

as an aluminum-phosphorus complex. The

correlation between aluminum and the residuals

from the regression of phosphorus to height is not

significant, supporting this interpretation.

While calcium is an essential plant nutrient, the

relationship between calcium In foliage and height

of slash pine probably is coincidental. Coastal

Plain soils ordinarily contain sufficient calcium to

sustain pine growth (Shoulders and McKee 1973)

and calcium content of needles was not significantly related to residuals from the phosphorusheight equation.

The negative relationships of loblolly pine

heights and of residuals from the phosphorusheight equation to sodium concentrations in

needles suggest that a dilution of sodium in tissue

accompanied a positive growth response to higher

phosphorus levels in the needles.

Potassium, magneslum, and manganese were

not correlated with growth. However, the levels

measured are not considered to be deficient

(Pritchett and Gooding 1975, Leaf 1973).

The soil variable most strongly correlate! with

tree height at age 20 was the depth to gray mottles

or to a seasonally high water table (fig. 2). The

relationship was curvilinear for both species, with

depths to gray mottles of less than 60 cm having

pt‘oportionally more impact on growth than depths

greater than 60 cm. The regression equations

accounted for 60 percent of the variation in heights

of slash pine and 79 percent of the variation in

heights of iobioiiy.

There was also a strong positive relationship

between depth to gray mottles and phosphorus

concentration in needles. Coefficients of determination (IV’s) for the quadratic equations for

these relationships were 0.65 for slash and 0.60 for

lobioily pine. Apparently, the trees’ abilities to

extract phosphorus from the soil were influenced

by the volume of soil their roots could exploit.

Of the several phosphorus determinations made

on the soil, none were significantly correlated to

height for both species (table 3). The combination

of phosphorus intensity and 0.03N NH,F + O.lN

HCI extract was significant for both species.

However, the coefficient for the 0.03N NH,F +

O.lN HCI in the equation predicting lobloily pine

height was negative making meaningful interpretations difficult. After the quadratic relationship

between height and depth to gray mottles has been

fit, organic phosphorus and 1N NaOH extractable

phosphorus also add significant contributions for

loblolly pine, but their coefficients are negative.

Again, at levels indicating a deficiency of

16 -

o-0 SLASH

Y= 32.9x-7.0

*---a LOBLOLLY

Y = 28.7X -9.9

r2= 0.65

I

011 1 I I I I

.4 3 .6 .7 .9 .9

Phosphorus in foliogo tI’ng/Q)

Figure l.-Relationship between phosphorus in foliage and

height at age 20. Slopes of lines are not significanUy

. different at 0.05 level but intercepts are.

3
Table 3. - Coeffldients of determination between height at age

20 and various soil phosphorus rests

Soil phosphorus test Range Slash Loblolly

w-v-v-..---- R2____________

Organic phosphorus 13.2-36.5 pglg 0.01 0.11

0.2N H,SO, 0.8-8.5 pglg 0.01 0.07

0.03N NH,F + O.lN HCI 0.43-2.13 pglg 0.25* 0.18

1N NaOH 2.7-34.9 pglg 0.01 0.29”

Phosphorus intensity 0.27-l .75 pg/ml 0.06 0.27”

Phosphorus equillbrlum

concentration . . . . . 0.05 0.07

Phosphorus intensity;

1N NaOH . . . . . 0.08 0.47*

Phosphorus intensity;

0.03N NH,F + O.lN HCI . . . . . 0.27’ 0.45’

Phosphorus equilibrium

concentration; depth

to gray mottles

(quadratic) . . . . . 0.83’ 0.w

*Regression significant at the 0.05 level.

phosphorus, an equation predicting greater growth

as the phosphorus measured in the soil decreases

is not biologically meaningful.

The phosphorus equilibrium concentration

accounted for only 5 and 7 percent of the total

variation in slash and loblolly pine heights,

respectively. However, the phosphorus equilibrium

concentration accounted for 15 and 43 percent of

variation in height of the two species remaining

after fitting the quadratic relationship between

height and depth to gray mottles. For loblolly, the

R* increased from 0.79 to 0.88.

DISCUSSION AND CONCLUSIONS

In relatively small geographical areas of uniform

climate, 20-year heights of slash and loblolly pines

on phosphorus deficient soils can be predicted

with confidence from the depth to gray mottles.

This depth can also be used to predict phosphorus

concentration in the needles but with more

unexplained variation. The depth to gray mottles

and height to age 20 measurements are by their

nature integrated over time. The phosphorus

concentrations were measured only once so the

phosphorus measurements may not be as reliable.

The detrimental effect of a winter water table

near the surface on growth of pines relates to its

impact on root development. Boggie (1977) found

that lodgepole pine (Pinus contorta) rooting depth

was controlled by the depth to a water table in the

winter months. Evidently prolonged saturation of

the soil is fatal to the larger roots and the soil

volume explored by repeated annual root growth is

limited. In Louisiana, the surface area of fine roots

of loblolly did not follow seasonal trends but was

related to the winter water table (Lorio et al. 1972).

None of the phosphorus soil tests by themselves

proved to be useful in predicting the growth of the

two pine species. The uptake of phosphorus from

these phosphorus deficient soils Is controlled by

the volume of soil available for root exploration.

The range in the amount of phosphorus available

per unit volume of soil is small so the

concentration of soil phosphorus has little effect.

Lea et al. (1980) found soil tests failed to predict

phosphorus content of the foliage of loblolly pine

when the soil test values were low. They also

suspected factors other than nutrient availability in

the topsoil were involved.

The improvement in prediction equations

obtained by fitting phosphorus equilibrium

concentrations after depth to gray mottles

probably occurs because the phosphorus

equilibrium concentration is an estimate of the

amount of added inorganic phosphorus that will

remain in solution. In these phosphorus deficient

soils, the main sources of plant available

phosphorus are organic matter decomposition,

0

o-o SLASH

Y:+ 7.8 O.llX -0.00039x2

R2 = 0.90

c--s LOBLOLLY

Y = 4.4 + O.IOX-0.00026X2

R2 = 0.79

0 ’

I I I I I I I I I

0 20 40 60 so 100 120 I40 I60 IS0 :

Depth to gray mottle8 km)

‘0

Figure’S.- Effect of depth to gray mottles (winter water table)

on height at 20 years of dominant and codominant

slash and loblolly pines.
throughfail, and atmospheric fallout. The

phosphorus equilibrium concentration is a

measure of the availability of phosphorus from

these sources. As would be expected, relationship

of phosphorus equilibrium concentrations to

growth were stronger with the more phosphorus

demanding iobioiiy pine than with the less

phosphorus demanding slash.

Because the warm season rainfall exceeds 99

cm in southern Mississippi, slash pine is expected

to be taller than iobioliy, if other factors are equal

(Shoulders and Tiarks 1980). Figure 1 shows that

slash pine is taller . than iobioiiy at a given

concentration of phosphorus in the needles. Figure

2 indicates that slash pine is taller than iobioiiy

when the., water table is at or near the surface.

Unfortunately, the effects of climate, phosphorus

nutrition, and rooting depth cannot be separated

with the data available. White and Pritchett (1970)

reported no interaction between fertilization,

species, and control of the water table. in their

study, fertitization increased the height growth of

slash and iobioiiy pine equally. Water table control

and a combination of fertilization and drainage

also had no effect on the height difference

between shash and iobioiiy pine.

Phosphorus fertilization is needed for maximum

growth of iobioiiiy and slash pines on ail soils

included in the study. Drainage, by bedding or

other techniques, is also indicated for soils having

seasonally high water tables (gray mottles) within

about 60 cm of the surface. Levels of other

nutrients, especially nitrogen and calcium, in these

soils are low throughout the profile (Smith 1975),

and may become limiting for growth if excess

water is drained from the sites and phosphorus

fertilizer is applied. The need for additional

nutrients cannot be determined, however, until the

more limiting factors of excess water and

inadequate available phosphorus have been

removed.

LITERATURE CITED

Boggie, R. Water-table depth and oxygen content

of deep peat in relation to root growth of Pinus

contorta. Plant and Soil 48:447-454; 1977.

Humphreys, F. R.; Pritchett, W. L. A soil-testing

procedure for predicting phosphorus status of

Pinus elliottii plantations. Plant and Soil

37:479-487; 1972.

Jackson, M. L. Soil chemical analysis. inglewood

Cliffs, N. J.: Prentice-Hail; 1958. 498 p.

John, M. K. Coiorimetric determination of

phosphorus in soil and plant materials with

ascorbic acid. Soil Sci. 109:214-220; 1970.

Lea, R.; Ballard, R.; Wells, C. G. Amounts of

nutrients removed from forest soils by two

extractants and their relationship to Pinus faede

foliage concentrations. Commun. Soil Sci. Plant

Anal. 11:957-967, 1980.

Leaf, A. L. Plant analysis as an aid in fertilizing

forests. in: Walsh, M. L.; Beaton, J. D., eds. Soil

Testing and Plant Analysis, rev. ed. Madison, WI:

Soil Sci. Sot. Amer.; 1973: 427-454.

Lorio, Jr., P. L.; Howe, V. K.; Martin, C. N. Lobioiiy

pine rooting varies with microrelief on wet sites.

Ecology 53:1134-1140; 1972.

Pritchett, W. L. Site preparation and fertilization

of slash pine on a wet savanna soil. S. Jour.

Applied For. 3:86-90; 1979.

Pritchett, W. L.; Gooding, J. W. Fertilizer

recommendations for pines in the southeastern

Coastal Plain of the United States. Fia. Agric.

Exp. Sta. Tech. Bull. 774. Gainsviiie, FL: Florida

Agricultural Experiment Station; 1975. 23 p.

Saunders, W. M. H; Williams, E; G. Observations on

the determination of total organic phosphorus in

soils. J. of Soil Sci. 6:254-267; 1955.

Shoulders, E. Site characteristics influence relative

performance of iobiolly and slash pine. Res. Pap.

SO-115. New Orleans, LA: U. S. Department of

Agriculture, Forest Service, Southern Forest

Experiment Station; 1976. 16 p.

Shoulders, E.; McKee, W. H. Jr. Pine nutrition in the

West Gulf Coastal Plain: a status report. Gen.

Tech. Rep. SO-2, New Orleans, LA: U. S.

Department Agriculture, Forest Service,

Southern Forest Experiment Station; 1973. 26 p.

Shoulders, E.; Tiarks, A. E. Predicting height and

relative performance of major southern pines

from rainfall, slope, and available soil moisture.

For. Sci. 26:437-447; 1980.

Smith, W. I. Soil survey of Harrison County,

Mississippi. Washington, DC: U. S. Department

of Agriculture, Soil Conservation Service; 1975.

80 p.

Soil Survey Staff. Soil taxonomy. Agric. Handb. 436.

Washington DC: U.,S. Department of Agriculture;

1975. 754 p.

Waimsiey, D.; Cornforth, I. S. Methods of

measuring available nutrients in West Indian

soils. Plant and Soil 39:93-101; 1973.

White, E. H.; Pritchett, W. L. Water table control

and fertilization for pine production in the

fiatwoods. Fia. Agric. Exp. Sta. Tech. Bull. 743.

Gainsviiie, FL: Florida Agricultural Experiment

Station; 1970. 41 p.

5

*USGOVERNYEflT PRINTING OFFlCE:1982- 669-085/6