/-

@

United States

Department of

Agriculture

Southern Forest

Forest Service ReseaMNoh

Experiment Station

SO-209

April, 1983

Acorn Production and Tree Growth of Nuttall Oak in a

Green-Tree Reservoir

John K. Francis

SUMMARY

Green-tree reservoirs, created by flooding live

timber stands, provide resting places and food for

wintering waterfowl. The effects of winter flooding

in terms of acorn production and growth of Nuttall

oaks were studied in a reservoir which had been

flooded annually for 15 years and in a nearby unflooded site. The study, which lasted for 5 years,

included four tree sizes and three thinning treatments. Acorn production was about half as great in

the winter-flooded site as in the control area. Large

trees were better mast producers than small trees

within the same stand. Thinning had no effect on

mast production, but significantly affected diameter

growth.’ Diameter growth was about the same in

flooded and nonflooded areas. Eleven percent of

the flooded trees died, while none of the nonflooded

trees died.

Additional keywords: Quercus nuttallii Palmer,

winter flooding, mast.

Green-tree reservoirs are created by artificially

flooding live timber stands during the fall and winter. Many have been built in the South as habitat for

wintering waterfowl and to increase hunting opportunities. In recent years, green-tree reservoirs have

become a convenient means of mitigating the impact of waterfowl habitat destruction by large water

projects.

Minckler (1960) showed on increase in pin oak

(Quercus palustris Muenchh.) acorn production associated with winter flooding in a green-tree reservoir. However, McQuilkin and Musbach (1977) monitored the same area for an additional 14 years and

concluded that the production of acorns did not vary

significantly between flooded and nonflooded areas.

They found that acorn production increased with

tree size and stocking. Broadfoot (1967) cited a 50-

percent increase in radial growth of timber in stands

that were flooded from February to July over a 4-

year period. Filer (1975) reported that the, kinds of

mycorrhizal fungi present were not altered by winter and spring flooding but the concentration of

individuals was reduced. Much remains unknown

about the benefits and liabilities of fall, winter, and

spring flooding. The results of a study of mast production and growth of Nuttall oak (Quercus nuttalh’i

Palmer) in a single, but not atypical, green-tree

reservoir are given in this paper.

PROCEDURE

A site within the green-tree reservoir of the Sunflower Waterfowl Project, near Rolling Fork, Mississippi, was compared with a nearby site outside

the reservoir. The soils of both areas are in the

Sharkey series (Vertic Haplaquepts). The timber

stands are dominated by Nuttall oak, green ash, and

overcup oak. Understories of the two areas are

similar.

Annual flooding of the green-tree reservoir begins each fall between the 1st and 15th of October.

Drainage starts about February 15, but sometimes

is not complete until mid-June due to poor internal

drainage and overflows from the Sunflower River.

Southern Forest Experlment Station/T-102fO 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
In wet springs, when the Sunflower River overflows,

the control area is also flooded, but the water leaves

sooner than from the reservoir. Annual flooding of

the green-tree reservoir began in 1959 and continues until the present. Events in years 16 (1975)

through 20 (1979) were monitored during this study.

Both areas were divided into three blocks. In each

block, 12 trees were chosen, 3 from each of the

following size classes: small (8.5 to 11.5 in or 22 to

29 cm dbh), medium (14.5 to 17.5 in or 37 to 44 cm

dbh), large (20.5 to 23.5 in or 52 to 60 cm dbh), and

extra large (26.5 to 29.5 in or 67 to 75 cm dbh). Three

thinning treatments were imposed: no thinning,

moderate (adjacent trees were removed to create

a minimum 15 ft or 4.6 m of crown clearance), and

heavy (30-ft or 9.1-m minimum crown clearance).

Thinning was conducted in the late summer previous to year 16. The result was that each block

contained all of the size and thinning combinations.

At the beginning of the experiment, and again 5

years later, study trees were measured for dbh and

crown area (vertical projection to ground surface).

The average crown radius used to calculate crown

area was obtained by measuring distances from tree

center to points directly below the edge of the

crown in eight cardinal directions.

Acorns were collected in four traps underneath

each tree. A trap consisted of a post set in the

ground supporting a pair of wire screen-protected

bushel baskets. The traps were located at random

intervals along the main axis of the crown. Acorns

were retrieved from the traps at about P-week intervals during seedfall. Seedfall continued from

October through January, the peak being sometime

in December. The collected acorns were separated

into sound and unsound seed and dried for 24 hours

at 70° C (158” F) and weighed. “Unsound” was defined as being hollow or having more than half of

the seed eaten by insects. The number of unsound

acorns was so small that it was not analyzed statistically. Eighty-two percent of this unsound seed

came from the nonflooded area.

The results were evaluated using analysis of variance with p=O.95. Due to the lack of replication of

the flooding treatment, it was impossible to test the

significance of flooding. However, the two areas

were compared with a test equivalent to the t-test

using replications within the area. Tree size and

thinning were evaluated by the usual F-tests. The

means of significant main effects were compared

by Duncan’s New Multiple Range test.

RESULTS AND DISCUSSION

Acorns were produced and collected in years

1, 4, and 5. Weather-related failures of the acorn

crop in both flooded and nonflooded areas occurred

in years 2 and 3. Means shown hereafter are total

acorns produced divided by 5 to obtain average annual production.

Dry weight of acorns produced per square foot

of crown, dry weight per tree, and acorns per tree

were significantly affected by area. Acorns per

square foot of crown for the two areas were not

significantly different. Means for the above are presented in table 1. The means of each significantly

different measure of acorn productivity for the nonflooded area were about twice as large as those of

the flooded area. Although the soils and stands of the

areas appear quite similar, it is impossible to say

with certainty that differences are due to flooding

treatments and not to unknown environmental variation.

Tree size significantly affected all measurements

of acorn productivity (table 2). Acorn production of

the smallest tree size was always inferior to the other

three sizes. These smallest trees were mostly of intermediate crown class at the beginning of the experiment. Even those released by thinning had not

gained sufficient vigor during the 5-year period to

facilitate acorn production per crown area comparable to the larger trees. In the number- and

weight-per-square-foot data there was no difference

between the three largest sizes. Dry weight of

acorns per tree of the largest size was greater than

the other sizes; the largest size tree produced a

greater number of acorns per tree than the two

Table l.-Mean annual acorn production and growth made by

Nuttall oaks on nonflooded and flooded areas over

a 5year period

Item Nonflooded Flooded

Dry weight (g) of acorn/ft* of crown l.llal 0.64b

Number of acorns/ft* of crown 0.44a 0.29a

Dry weight (g) of acorns/tree 2232a 933b

Number of acorns/tree 956a 422b

Increase in diameter (in) 1.35a 1.43a

Increase in crown area (ft*) 906a 3571,

IMeans within rows followed by the same letter are not significantly different (0: = 0.05).

John K. Francis is Soil Scientist, Southern Forest Experiment Station, USDA, Forest Service, Sto,neville, Mississippi, which COOPcrates with the Mississippi Agricultural and Forestry Experiment Station and the Southern Hardwood Forest Research Group, also

at Stoneville.

2
Table 2.-Mean annual acorn production and increase in crown

area ot tour sizes of Nuttail oaks

Item

Tree size

Extra

Small Medium Large large

Acorns/ft’ 0.14tY 0.40a 0.44a 0.46a

Dry weight (g/ft*) 0.32b 1.08a 1.03a 1.08a

Acorns/tree 104c 638b 790ab 1225a

Dry weight (g/tree) 229c 1535b 1576b 2990a

Increase in crown area (ft?) 242b 628ab 576ab 1080a

‘Means within rows followed by the same letter are not signlflcantly dlfferent ( CK = 0.05).

smallest sizes. In contrast to tree size, thinning had

no effect on acorn productivity. Probably not enough

time had elapsed for a response to occur. No significant interaction between area, size, or thinning

occurred.

Diameter growth was not significantly affected

either by area or tree size, but it was significantly

affected by thinning.

Increase in crown area was significantly affected

by area and tree size, but not by thinning. The larger

trees made greater gains in crown area. Trees on

the nonflooded site increased Rheir crown area more

than those on the flooded site. Although mean

crown area increased on the flooded site, several

individual trees lost crown area. An observed dieback of twigs and branches may have been the

cause;

During the 5 years of the study, four measurement

trees died in the green-tree reservoir. None died on

the nonflooded site. The trees that died were located

in a portion of theigreen-tree reservoir that did not

drain well. The loss of these trees was responsible

for a minor portion of the difference in mast production associated with flooding in the last 2 years

of the study (fig. 1).

Overall, the flooded area produced much less

mast than the nonflooded area; also, less increase

in crown area and greater mortality were noted.

Thinning had no significant effect on acorn production but increased diameter growth. The small trees

were poor acorn producers in both areas, even after

release from competitors.

It is pro.bable that reduced vigor of oaks in the

flooded area resulted from inadequately aerated

soil. Soils dry enough to allow the infusion of air

are necessary for root regeneration. Flooding only

75 1976 1977 10 1979

N F

W NONFLOODED AREA

0 FLOODED AREA

0 NO COUNTS WERE DONE IN 1976 OR 1977

Figure 1.-Nuttall oak acorn producdon per square toot of

crown area on flooded and nontiooded sites over

a 5-year period.

every second or third year might assure the high

tree vigor desirable in a green-tree reservoir. Delaying flooding as long as possible in the fall is

suggested by Broadfoot’s (1967) successful flooding

of a natural stand beginning each year in February.

Timely and effective withdrawal of water in the

spring might also improve growing season soil aeration. Once the requirements of Nuttall oak are understood, it should be possible to provide waterfowl

habitat without sacrificing either mast or timber

production.

LITERATURE CITED

Broadfoot, W. M. Shallow-water impoundment increases soil moisture and growth of hardwoods.

In: Proceedings, Soil Sci. Sot. Am. 34: 562-564;

1967.

Filer, T. H., Jr. Mycorrhizae and soil microflora in a

green-tree reservoir. For. Sci. 21: 36-39; 1975.

McQuilkin, Ft. A.; Musbach, R. A. Pin oak acorn production on green tree reservoirs in southeastern

Missouri, J. Wildl. Manage. 41:216-225; 1977.

Minckler, L. S.; McDermott, R. E. Pin oak acorn production and regeneration as affected by stand

density, structure, and flooding. Missouri Agric.

Exp. Stn. Res. Note 750; 1960.24 p.

3