U.S. Department of Agriculture

Forest Service Research Note S E - 286 February 1980

SURVIVAL AND GROWTH OF OAKS PLANTED

FOR WILDLIFE IN THE FLATWOODS

by William H. Moore’

ABSTRACT.-In the cutover pinelands of south Florida, hammocks of evergreen forests are

oases of wildlife habitat, but they are too widely scattered to be effective. The artificial establishment of hammocks in the flatwoods has potential for enhancing forest wildlife. To dqrmme minimum requirements for the establishment of native oaks in the flatwoods, a comparison was made

between live oak (Quercus virginiana Mill.) and laurel oak (Q. laurifolio Michx.). Results indicate

that live oak is superior to laurel oak, that bedding is necessary to establish oaks, and that protection from grazing for a few years is desirable for the best results.

Keywords: Hammocks, Quercus spp., habitat management, forest wildlife, bedding.

Flatwoods pinelands in Florida, withunderstories

dominated by saw-palmetto (serenoa repens (Bartr.)

Small), common gallberry (ZIex glubra (L.) A. Gray),

wiregrass (Aristida spp., Sporobolus spp.), and other

species are often of little value as wildlife habitat.

Soils are poorly drained and low in fertility. In south

Florida, where extensive acreages of pinelands have

been clearcut, wildlife habitat has been further reduced. Frequent burning and heavy year-long grazing

maintain a condition of reduced cover and reduced

winter foods (Harlow 1959).

The artificial establishment of hammock communities throughout the cutover pinelands has the

potential for enhancing wildlife populations by providing a habitat diversity now lacking.

Site

Natural “hammocks” in south Florida flatwoods

are evergreen hardwood forests-usually less than

1 hectare in size-dominated by cabbage palm (Subal

palmetto (Walt.) Lodd.), oaks (Quercus spp.), and

bays (Persea spp., Magnolia spp.), but which also

support a wide variety of plants-more than any other

vegetation type in the State (Davis 1943).

Soil series are primarily the Immokalee (pinepalmetto), which are imperfectly drained acid sands

with organic-stained pan, and Charlotte (wet prairie),

1 Moore is Wildlife Biologist, Southeastern Forest Experiment Station, Gainesville, Florida 326 11.

which are poorly drained shallow sands over calcareous materials. The soils are saturated much of the

year, and during most of the summer the water table

is at or near the surface of Immokalee soils to several

centimeters above the surface on the Charlotte series.

The average annual rainfall is 135 centimeters, of

which 75 percent falls during the summer months.

Wildlife Potential

Hammocks are found on soils that are slightly

elevated and better drained than the surrounding

area (Laessle 1942). They often have a marl substratum, and an acidic humus usually builds up with

the developing vegetation. As a result, they are comparatively high in plant nutrients and organic matter,

and are rated as one of the more productive sites in

the State (Davis 1943; Harlow 1959). Several species

of wildlife use them as refuge and as a source of food

(Frye 1954; Harlow 1959) although these oases are

too scattered to be effective habitats.

Establishing such hammocks throughout the flatlands has the potential for enhancing wildlife populations. Game species such as white-tailed deer (Odocoileus vil;piniunus Osceola Bangs), wild turkey (Meleagris

gallopavo L.), and gray squirrel (Sciurus carolinensis

Gmelin)-as well as many nongame species-would be

expected to benefit.

The Study

Plants that can be successfully established and

Southeastern Forest Experiment Station - Asheuille, North Carolina
maintained with minimum effort and that are of

known value to wildlife can be used to develop hammock communities. Oaks were selected for this study

because they are native to the region and have the

potential to produce overhead cover and an abundance

of acorns-a staple food of many wildlife species.

This study was designed to determine minimum

site preparation and protection requirements for the

establishment of live oak (Q. vi&ziana Mill.) or

laurel oak (Q. laurifolia Michx.).

The study was installed during the spring of 1969

in Charlotte County, Florida, in cooperation with the

Florida Game and Fresh Water Fish Commission that

provided land (Webb Wildlife Management Area) and

prepared the planting sites.

METHODS

The experimental design consisted of a randomized complete block replicated two times. Treatment

plots were established to compare species of oak (live

vs. laurel), flatwoods sites (wet prairie vs. pine-palmetto), livestock grazing (no grazed vs. grazed), and

site preparation (bedding vs. tilling).

High, wide beds were constructed by making a

series of overlapping passes with a road grader; beginning near the center and working outward on both

sides, soil was rolled or worked inward on each pass.

Beds were 4 to 5 meters across, 45 to 60 centimeters

high, well drained, devoid of vegetation, and surrounded by ditches. The relatively large planting area was

designed to simulate the elevation of natural hammocks and to provide the opportunity for associated

vegetation to develop naturally after the establishment

of the oaks.

Tilled sites were prepared near the bedded plots.

A heavy-duty garden roto-tiller was used to remove

existing vegetation and prepare a planting area 2 by 2

meters for each tree.

All study plots were protected from burning.

There was moderately heavy grazing by range

cattle the year round.

Trees were 2-year-old potted seedlings. Five laurel

oak and eight live oak were randomly planted in each

plot 6 meters apart. At the time of outplanting, tree

height averagpd 61 centimeters and crown diameter

averaged 30 centimeters. Cumulative data on survival

and growth for eight growing seasons after outplanting are presented.

Data were analyzed by analysis of variance, with

significant differences at P < 0.01.

RESULTS AND DISCUSSION

SURVIVAL

After 8 years, survival of live oak (95 percent) was

greater than that of laurel oak (76 percent). No significant differences were found between sites, site preparation, and grazing treatment.

Rainfall was below average the year following

outplanting. Live oak seemed better able to survive

on the dryer planting sites and also had a tendency to

more readily sprout back after dieback that resulted

from stress or injury. However, many individual trees

of both species continue to die back after 8 years,

especially on tilled sites.

HEIGHT GROWTH

Height growth was influenced by species, site

preparation, and grazing treatment. Of these, site

preparation was the most important factor affecting

tree growth. Trees planted on tilled plots at the existing elevation grew very little (averaged 0 .l m) regardless of other treat&nts. Summer rains typically result

in high water table&near or above the surface during

most of the growing season and undoubtedly account

for the slow growth and continued dieback. It is

apparent that few of the trees will survive or attain a

site useful to wildlife (fig. 1).

Figure 1 .-A typical live oak on tilled plot at existing elevation,

8 years after outplanting, 1977.

On beds, height growth was affected by species

and grazing treatment. On average, live oak grew 60

percent faster than laurel oak, and all trees protected

from grazing grew more than those subjected to grazing (table 1). Live oaks planted on protected beds

apparently grew faster than any other treatment combination (fig. 2) and laurel oak on unprotected beds
Table 1 .-Average height growth and crown diameter

growth of live and laurel oaks on bedded plots

for the first 8 years after outplanting, by grazing

treatment (in meters)

Species

Live oak

Laurel oak

Average

Live oak

Laurel oak

Average

Not grazed Grazed Average

HEIGHT GROWTH

2.6 1.6 2.1

1.7 0.9 1.3

2.2 1.3 1.7

CROWN DIAMETER GROWTH

2.5 1.6 2.1

1.9 0.7 1.3

2.2 1.2 1.7

Species effect, grazing effect, and grazing x species

interaction are significant at P < 0.01.

CROWN VOLUME

Crown volume, rather than crown growth, is

probably of more significance for wildlife because it

better expresses extent of cover and potential acorn

production. Total crown volume after 8 years was

computed assuming crowns to be spherical. This

assumption, though not entirely true, serves to illustrate the vast differences in crown size among species

and treatments. Means were not statistically tested,

but differences are undoubtedly similar to those shown

for crown diameters. After 8 years, live oaks planted

on protected beds had crown volumes that averaged

almost 2 times that of protected laurel oak, 3 times

that of grazed live oak, and 12 times that of grazed

laurel oak (table 2). Total heights and crown areas

after eight growing seasons are compared in figure 3.

Figure 2.-A typical live oak 8 years after outplanting on bed

protected from cattle, 1977.

spp., Paspalum spp.) that became established there.

As a result, young trees often were rubbed, trampled,

and heavily browsed. Most oaks, however, were in

reasonably good condition and, for the most part,

will survive and eventually grow out of reach of

cattle. Live oaks, as reflected by their greater growth

on grazed beds. sopear better able to withstand cattle

activity.

CROWN GROWTH

As with height growth, crown growth varied by

species, site preparation, and grazing treatment. Site

preparation was the most important factor influencing

growth. There was crown development only on the

bedded trees (table l), and trees planted& tilled

sites grew very little regardless of specfes or grazing

treatment.

On beds, live o&generally outperformed laurel

oak, and crowns of both species grew considerably

faster when protected from grazing (table 1). Live

oaks protected from grazing developed crowns faster,

while laurel oaks exposed to grazing performed the

poorest. Crowns of grazed live oak grew about as well

as crowns of protected laurel oak.

had less growth than the other treatment combinations (table 1). Growth rates on beds were similar for

protected laurel oak and live oak exposed to grazing.

On native ranges of south Florida where roughage

is abundant, cattle normally browse oak only lightly,

but they tend to use beds as refuge from high water

during the summer and as a dry place to bed down.

However, cattle were attracted to these beds to graze

the high-quality grasses (Andropogon spp., Panicurn

Table 2.-Computed crown volume of live and

laurel oaks on bedded plots 8 years after

nutplanting (in cubic meters)

Species Not grazed Grazed Average

Live oak 11.4 4.2 7.8

Laurel oak 6.4 1 .o 3.7

Average 8.9 2.6 5.7
SEW TlLLED

Figure 3.-Comparison of total growth 8 years after outplantirlg, 1977.

CONCLUSIONS

Results indicate that bedding will be required to

establish oaks in the low flatwoods of south Florida.

Optimum bed size was not determined, but apparently

beds must be sufficiently high to permit root development above the high summer water table. Although

beds were constructed to allow associated hammock

vegetation to develop after the oaks were established,

with the exception of species of Andropogon, Panicum, and Paspalum, this has not yet occurred. The

sites are still young, and seed sources of hammock

vegetation are widely scattered. As the oaks mature,

hammock dwelling birds and other wildlife can be

expected to increasingly use these sites and deposit

seeds ingested in natural hammocks.

In this study, live oak was clearly superior to

laurel oak, and it developed much better when protected from cattle. Protection from grazing would

seem desirable for a few years; however, it may not

be essential because many live oaks exposed to the

moderately heavy year-long grazing now have crowns

above the reach of cattle. Laurel oak would provide

an additional element of variety in these artificial’.

hammocks, but it is more essential that they be protected from cattle for an undetermined period of time.

Live and laurel oaks must be protected from fire

for many years, if not always. When the beds were

constructed for this study, surrounding ditches were

made sufficiently deep and wide to function as protective moats. These ditches were flooded part of the

year and supported vegetation too sparse to carry fire.

Several live oaks have produced a few acorns since

the 3rd year after outplanting, but production is not

yet significant. Mockingbirds (Mimus polyglottos L.)

have been observed r&sting in several of the larger live

oaks for several years.‘;.

LITERATURE CITED

Davis, J. H., Jr.

1943. The natural features of southern Florida. Fla.

Dep. Conserv. Geol. Surv. Bull. 25,311 p.

Frye, E. O., Jr.

1954. Aspects of the ecology of the bobwhite quail in

Charlotte County. Unpubl. Fed. Aid Rep., Proj.

W-31-R, Fla. Game and Fresh Water Fish Comm.

339 p.

Harlow, R. F.

1959. An evaluation of white-tailed deer habitat in

Florida. Fla. Game and Fresh Water Fish Comm.

Bull. 5,64 p.

Laessle, A. M.

1942. The plant communities of the Welaka area. Univ.

Fla. Publ. Biol. Sci. Ser. 4(l). 143 p.

*U.S. GOVERNMENT PRINTING OFFICE: 1980-640-190/4531. Region 4.