tree selection, however, major monetary sacri-
fices make selection cutting unattractive to most
landowners.

Reproduce Pine

One of the largest problems in southern for-
estry is the failure of many landowners to even
attempt to get pine regeneration when they harvest
their pine stands. One reason for this failure
may be an excessive emphasis that professional
foresters place on planting of genetically im-
proved stock. For a variety of reasons, many
landowners spurn the opportunities for high
returns from loblolly pine plantations. That does
not mean that these owners cannot or will not grow
loblolly pine.

This Guide describes silvicultural systems for
natural regeneration of loblolly pine. Within
these systems are alternatives that will permit a
landowner to grow some pine while satisfying other
goals, including attractive appearance. The Guide
suggests that old hardwood trees be injected with
herbicides to make room for pines. If an owner
wants some den trees for squirrels or birds,
however, there is no harm in leaving some old
campaigners and growing pines between them.

Loblolly pine is a flexible species. Foresters
must be equally flexible in prescribing treatments
that regenerate loblolly pine in ways that please
individual landowners.

16


The disadvantages are:

+ Competition from weeds and shrubs is
usually heavy.

¢ The site is exposed to wind and rain.

* With seeds or seedlings in place,
logging slash cannot be burned; thus,
the fire danger is high.

* With seeds or seedlings in place, there
is no natural seed source if drought
kills the first crop of seedlings.

* Treated areas often are visually
unattractive.

* No merchantable material can be harvested
from the new stand for 12 to 20 years after
regeneration.

* There is no control over the trees from
which seeds for regeneration are obtained.

Seed-Tree Method

In the seed-tree regeneration method, all but 6
to 12 evenly spaced trees per acre are harvested
in a single cutting. Since the trees that remain
will be the seed source for regenerating the
stand, ‘only individuals with desirable character-
istics should be chosen. The seed trees should
have deep, strong root systems and wide crowns,
and they should be vigorous and free of disease.
The seedbed should be prepared prior to the
initial harvest, but the logging slash can be
burned with seed trees standing if care is exer-
cised to prevent damage to those trees. The seed
trees should be removed 3 to 5 years after the
initial harvest, when reproduction has become
established. If their removal is delayed, the new
stand may be severely damaged when they are cut.

10


a The Forest Service, U.S. Department of

Agriculture, is dedicated to the principle of
multiple use management of the Nation’s forest resources
for sustained yields of wood, water, forage, wildlife, and
recreation. Through forestry research, cooperation with the
States and private forest owners, and management of the
National Forests and National Grasslands, it strives—as
directed by Congress—-to provide increasingly greater
service to a growing Nation.

USDA policy prohibits discrimination because of race,
color, national origin, sex, age, religion, or handicapping
condition. Any person who believes he or she has been
discriminated against in any USDA-related activity should
immediately contact the Secretary of Agriculture,
Washington, DC 20250.


ABSTRACT

For many landowners, low cost makes natural regen-
eration an attractive alternative to planting when
loblolly pine stands are harvested. Clearcutting,
seed-tree, shelterwood, and selection methods can be
used. Keys to success are a suitable seedbed, an
adequate seed supply, sufficient moisture, and freedom
from excessive competition.

Keywords: Pinus taeda, silvicultural systems, clear-
cutting, shelterwood, seed tree, selection cutting.

Loblolly pine (Pinus taeda L.) became the most
important timber species in the Southern United
States primarily by seeding naturally onto aban-
doned cropland. It is now the dominant species on
more than 31 million acres or 17 percent of the
South's timberland, and its rapid growth and good
form make it an ideal choice for far more acres.
In efforts to maintain the species, however,
foresters have largely abandoned natural methods
for reproducing stands in favor of plantation
forestry. These efforts probably will always be
less than fully successful because not all
landowners favor to plantations.

If wood and dollar yields from loblolly pine
plantations are high, so are the costs of plan-
tation forestry. Site preparation and replanting
cost from $50 to $175 per acre. On a 40-acre
tract, that's the price of a new pickup truck
invested in something that will take 20 years or
more to pay off. In addition to high cost, there
is the appearance. Some people do not like their
trees in neat rows.

The best course for many landowners who are
planning to harvest mature loblolly pine stands is
some form of natural regeneration. This Guide is
meant for the forester who is helping landowners
to reproduce loblolly pine by natural means. It
is a refresher course for foresters who are
accustomed to plantation management.


Recommended Reading

Baker, James B. 1981. Natural regeneration of loblolly and
shortleaf pines. In: Low cost alternatives for regenerating
southern pines. Proceedings of a conference; 1981 August 4-5;
Auburn University, AL: Auburn University.

Brender, Ernst V. 1973. Silviculture of loblolly pine in the
Georgia Piedmont. Rep. 33. Macon: Georgia Forest Research
Council. 74 pp.

Brender, E.V.; McNab, W. Henry. 1972. Loblolly pine seed
production in the lower Piedmont under various harvesting
methods. Journal of Forestry 70(6):345-349.

Campbell, T.E. 1967. Loblolly-shortleaf pine seedfall in
Louisiana. Journal of Forestry 65(12) :894-895.

Langdon, 0. Gordon. 1981. Natural regeneration of loblolly
pine: a sound strategy for many forest landowners. Southern
Journal of Applied Forestry 5(4):170-176.

Mobley, Hugh E.; Jackson, Robert S.; Balmer, William E. [and
others]. 1973. A guide for prescribed fire in southern forests.
Atlanta: U.S. Department of Agriculture, Forest Service, South-
eastern Area, State and Private Forestry. 40 pp.

Trousdell, Kenneth B.; Langdon, 0. Gordon. 1967. Disking and
prescribed burning for loblolly pine regeneration. Journal of
Forestry 65(8) :548-551.

Trousdell, Kenneth B.; Wenger, Karl F. 1963. Some factors of
climate and soil affecting establishment of loblolly pine
stands. Forest Science 9(2):130-136.

Wahlenberg, W.G. 1960. Loblolly pine: its use, ecology,
regeneration, protection, growth and menagement. Durham, NC:
Duke University, School of Forestry. 603 pp.

Wenger, Karl F. 1957. Annual variation in the seed crops of
loblolly pine. Journal of Forestry 55(8) :567-569.

Williston, Hamlin L.; Balmer, William E. 1974. Managing for
natural regeneration. For. Manage. Bull. Atlanta: U.S.
Department of Agriculture, Forest Service, Southeastern Area,
State and Private Forestry. 6 pp.

17




Advantages of shelterwood cutting are:

¢ Large quantities of well-distributed seeds
are provided.

* There is less need for slash disposal than
with the clearcutting or seed-tree methods.

* The overwood reduces early competition from
hardwoods.

* The site is well protected and has a better
appearance than after the clearcutting or
seed-tree methods.

Disadvantages of the shelterwood method are:

+ Reproduction may be heavily damaged when
the overwood is harvested.

* The new stand may be overly dense and
require precommercial thinning.

* The overwood will slow the height growth
of the pine seedlings until it is removed.

* Since the bulk of the harvest is not taken
in a single cutting, the economic return
from the harvest will be lower than with
clearcutting.

Selection Method

The selection method of natural regeneration
creates stands in which trees of all ages from
seedlings to mature trees are present at the same
time. A target diameter distribution for the
stand is established, and trees of various sizes
are cut in each harvest operation to achieve the
desired diameter distribution.

Some form of selection cutting may be appro-
priate when the management objective is to
maintain an uneven-aged stand with seedlings,
saplings, pulpwood-size trees, and sawtimber-size

14


seeds are on the ground by mid-December. Very
large numbers of seeds are required because they
are a favorite food of birds and rodents during
months between seedfall and germination.

Depending on the method of regeneration chosen,
it may be necessary to estimate the size of the
seed crop in the year of the harvest. With the
aid of binoculars, the numbers of cones in sample
trees can be counted and an estimation made to
account for the ones that are not visible from
the ground. The total can be multiplied by 45,
the average number of sound seeds in a typical
loblolly pine cone.

Adequate Soil Moisture

Little can be done to influence the supply of
moisture for germination and seedling establish-
ment, but you should know that variations in
moisture supply are the main causes for variable
results with natural regeneration systems. A com-
bination of moisture and warming temperature is
required for loblolly pine seeds to germinate.
The proper conditions usually are present about
April, but the time of germination varies from
year to year and place to place. An unusually
cold spring usually reduces germination.

After germination, adequate soil moisture is
critical until the seedling gets its roots well
down into the soil. A drought between April and
June can kill many seedlings. Fortunately, spring
rains usually satisfy this moisture requirement
throughout the range of loblolly pine. A drought
during the summer after germination also is likely
to cause high seedling mortality.

In planning for natural regeneration, foresters
typically worry most about failing to get adequate
stocking. They strive to obtain adequate stock-
ing, even if a moderate drought occurs. The
50,000 seeds per acre recommended here are enough
to obtain 1,000 well-spaced seedlings when the
weather is somewhat unfavorable. When the mois-
ture supply is adequate throughout the spring and

6


Necessary Conditions |

With proper precautions, the probability of
success in naturally regenerating loblolly pine is
quite high. It is not the dominant species on 31
million acres by accident. It is an aggressive
colonizer of recently disturbed sites, and its
resistance to fire damange makes loblolly pine a
subclimax species in natural southern environments
where lighting fires are common. On the Coastal
Plain, loblolly pine forests can be maintained
indefinitely in the face of invading hardwoods by
use of prescribed fires, which weaken or kill the
hardwoods without damaging the pines.

In the absence of fire, hardwoods eventually
replace loblolly pine, which is less able to
compete for sunlight, moisture, and nutrients.
Hardwoods thrive in the understories of unburned
pine stands, and they become increasingly promi-
nent as the pine overstory matures. When the
pines are harvested, these hardwoods will dominate
the new stand. If the hardwoods are cut, they
will sprout prolifically. There is a good case,
therefore, for controlling hardwoods in loblolly
pine stands.

Successful regeneration of loblolly pine from
seeds depends on four critical conditions:

1. A suitable seedbed

2. An adequate supply of seeds

3. Sufficient moisture for seed germination
and seedling establishment

4, Freedom from excessive competition

If these conditions are met, a satisfactory new
stand will almost certainly develop.

Suitable Seedbeds

Disturbance is the key to preparation of a
suitable seedbed. Forest soils normally have a
thick top layer of litter and organic matter, but
loblolly pine seed germination is best on mineral
soil. The litter and organic matter must be elim-
inated or moved aside to favor seed germination.


Pros and Cons

When compared with clearcutting, site
preparation, and planting, natural regeneration
systems offer a number of advantages:

+ Low cost, ranging from $3 to $40 per acre

+ Less labor and heavy-equipment requirements
+ Adaptation of native stock to the site

* Less risk of insect and disease losses

* Less soil movement

* Better appearance

These advantages are gained at some cost.
On its own land, forest industry relies almost
exclusively on planting for reproducing pine
stands for very good reasons:

« Maximum yields

+ Shortest possible rotations

¢ Introduction of genetically improved stock
+ Lower risk of failure

¢ Greater control over tree spacing

* Excellent returns on investment

Before natural regeneration is recommended, a
landowner should know what is being given up and
what risks are being accepted. Yields are not as
great and rotations are usually longer with natu-
ral stands than with plantations. The growth of
the genetically improved seedlings in plantations
is likely to be 10 to 15 percent faster than the
growth of unimproved seedlings under the same
conditions, and the difference will be even larger
for unimproved seedlings in natural stands. If a
drought occurs soon after seeds germinate, most of
the seedlings may die and a poorly stocked stand
may result. If the weather is very favorable and
the seed crop was large, the new stand may be
excessively dense and precommercial thinning may
be necessary.


Regeneration by the selection method (not generally
recommended for use with loblolly pine).

trees present at all times. In general, however,
this method requires great skill to apply prop-
erly. Furthermore, the costs associated with
frequent light cutting are high for the amounts
of timber removed. For these and other reasons,
selective cutting of southern pines should be
approached with caution.

Group selection can work well with loblolly
pine. With this method, groups of trees rather
than single trees are removed from the oldest age
class to create openings for reproduction. The
openings that are created probably should cover at
least 1.0 acre to permit adequate development of
young trees. Even with group rather than single-

15


of burning after the harvest depends upon the
regeneration system that is chosen.

The timber for burning is important because
large hardwood stems are most likely to be con-
trolled by a prescribed summer burn. Although
summer burns require higher relative humidity,
they are very effective in controlling hardwoods.
The rule to remember for natural regeneration is
to burn 3 to 4 weeks prior to seedfall in order
to get the maximum benefit from a single burn.
However, if you chose to burn in winter, remember
that favorable weather conditions usually follow
the passing of a cold front when relative humidity
ranges from 20 to 40 percent and the wind is
steady at 1 to 5 miles per hour.

Adequate Seed Supply

Like those of many species, the seed crops of
loblolly pine vary widely from year to year. The
size of the crop depends upon weather conditions
and insect and disease attacks during the 14
months it takes for flowers to be fertilized and
for cones and seeds to develop. Seed production
also varies directly with tree vigor.

On the Coastal Plain, loblolly pine seed
production is adequate for natural reproduction
in most years. On the Piedmont Plateau, pro-
duction is not as heavy, but enough seeds are
produced for natural regeneration every 3 to 5
years. A minimum of about 50,000 seeds per acre
are required to obtain adequate stocking on a
burned seedbed. With a bumper seed crop, indi-
vidual trees may produce that many seeds, but the
effective dispersal from a single tree is only
about 200 feet. The number of seeds needed for
adequate stocking increases rapidly as the amount
of litter increases. Excess litter should be
removed by burning. Also, soils with heavy tex-
ture are better for germination than soils of
lighter texture.

Loblolly pine cones open in October, and seeds
are dispersed until the following March, but most

5



United States
Department of
Agriculture

Forest Service

Southeastern Forest
Experiment Station

General Technical
Report SE-47

A Loblolly Pine
Management Guide

Natural Regeneration
of Loblolly Pine

M. Boyd Edwards



Silvicultural Systems

The most common silvicultural systems for
regeneration of loblolly pine are clearcutting,
seed tree, shelterwood, and group selection. The
choice of a system should be based on stand con-
ditions and the desires of the owner.

Clearcutting

This system involves removal of the entire
forest canopy from a stand in a single harvest
operation. There are several types of clearcuts,
which differ in the source and condition of
material that will become the new stand.

# j

one OY

ter

ane

Regeneration by clearcutting.


summer after germination, however, you may find
that you have 20,000 instead of 1,000 seedlings
per acre. Overstocking in good years is inevi-
table if you are to have adequate stocking in
average to poor years.

Control of Competition

Loblolly pine is classed as intolerant of
shading. Although it may survive, it will not
thrive in the shade of competitors. It is
considerably less tolerant of shade than its
hardwood competitors, but loblolly pine will
outgrow most of them if it is taller than they are
at age 3. Thus, control of hardwood competition
is crucial when stands are being reproduced.

Prescribed burning will kill hardwood stems
under 3 inches in diameter. Many hardwood root-
stocks survive one or two such burns and produce
new sprouts, but repeated burning will kill them
or weaken them greatly. In this respect, burning
during the growing season is usually more effec-
tive than burning in the dormant season. In
either case, however, hardwood stems over 3 inches
in diameter are not likely to be killed by the
low-intensity prescribed burns that are safe under
pine overstories. Unless the owner wants some
large oaks or other hardwoods for mast production,
large hardwood stems should be cut or deadened
with chemicals. You may be able to find a fire-
wood cutter who will get these trees out of the
way free.

A combination of prescribed burning and
hardwood tree elimination will give the young
seedlings a competition-free start in life.
Thereafter, periodic prescribed burning will keep
hardwoods from getting a foothold in the under-
story. Control of hardwood competition throughout
the life of the stand will enhance loblolly pine
yields by 20 to 40 percent.



A Bp0d seedbed and a source of seeds are necessary
for natural regeneration of loblolly pine.

The most practical way to get rid of litter is
by burning it. Pushing it aside requires heavy
equipment, and when the litter and organic matter
are moved, so are the important nutrients they
contain. Burning releases some nutrients to the
atmosphere, but most remain to nourish a new
stand.

Seedbed preparation for natural regeneration
should begin several years before timber is har-
vested. Two or more annual prescribed burns
before the harvest will create a highly satis-
factory seedbed, and they will kill or weaken
potential hardwood competitors. The efficacy

4





ii

Acknowledgment

Illustrations of the four major regeneration
methods are reproduced with the kind permission
of the Society of American Foresters and the
McGraw-Hill Book Company. They have appeared
earlier in McGraw-Hill's "Secret Life of the
Forest" and in the Society of American Foresters'
and the Wildlife Society's "Choices in Silvi-
culture for American Forests."


Regeneration by the seed-tree method.

Some advantages of the seed-tree method are:

* Large areas can be harvested in a single
operation.

« Initial regeneration costs are lower than
for clearcutting and planting.

* Seeds from adjacent stands are not relied
upon, and the best trees in the stand can
be selected as seed sources.

« If bad weather or fire delays regeneration,
the seed source remains to regenerate the

area.

11


and the felling of the large trees will cause
great damage. If the density of the new stand
exceeds 1,500 stems per acre, however, killing
some of the young trees is beneficial. Pre-
commercial thinning can be accomplished by
skidding logs through areas of dense reproduction.

It is a good practice to inject large, unwanted
hardwood stems before or soon after the harvest
cut. When the trees in the new stand reach a
height of 18 feet at about age 10, a low-intensity
prescribed burn will not hurt the pines, and a
burning program to prevent hardwood encroachment
can begin.

Regeneration by the shelterwood method.

13


Natural Regeneration
of Loblolly Pine

M. Boyd Edwards
Research Ecologist
Southeastern Forest Experiment Station
Dry Branch, Georgia

A Loblolly Pine Management Guide




Windblown seeds from surrounding stands often
regenerate stands after clearcutting. Several
conditions should be met if this source is to be
used. First, the surrounding stands should con-
tain high-quality loblolly pines of seed-bearing
age. Poor-quality trees often have poor-quality
offspring. Second, the cutting area must be
designed so that all points in it are within 200
feet of a seed tree. Common shapes include small
blocks and long, narrow strips.

Seeds or seedlings in place can be used to
regenerate much larger areas. In both cases, the
seeds for reproduction are obtained from the stand
that is to be harvested. A good seedbed is pre-
pared by the methods already described. In a year
with adequate seed production, the stand is har-
vested sometime after the seeds have fallen. In
the seed-in-place method, harvesting is done from
November through March, after the seeds have
fallen but before they have germinated. In the
seedlings-in-place method, harvesting is delayed
until late summer in the year after a good seed
crop. By that time, the seedlings have become
established, so great care is required in logging
to minimize damage to the new stand. Tree-length
logging severely damages the young seedlings;
harvested trees must therefore be cut into log
lengths before they are skidded.

Distinct advantages to clearcutting over other
methods of natural regeneration of loblolly pine
are:

+ Harvesting costs are minimized by taking
the whole stand in a single operation.

* Loss of seed trees to wind damage is
avoided.

« The new crop of seedlings develops in full
light and free from root competition from
the old stand.

* Regeneration is confined to a small
portion of the rotation.


Some disadvantages of the seed-tree method for
obtaining natural regeneration are:

+ The seed trees, which are among the best
trees in the stand, may be damaged by
wind, lightning, or disease.

* As with clearcuts, most of the area is
exposed and subject to soil erosion.

* Particularly if they have been damaged,
the seed trees may be difficult to sell
after seedlings are established.

Shelterwood Method

A third method for obtaining even-aged new
stands of loblolly pine is the shelterwood system,
in which a relatively large number of trees (20 to
40 per acre) are left in the initial harvest. The
seed-bearing trees should contain 25 to 40 square
feet of basal area per acre.

This rather large number of trees provides a
dependable seed supply as well as a large amount
of protection for the site and the new stand. In
all but the poorest seed years, the shelterwood
system provides enough seeds to reproduce the
stand. This reliable seed supply is a big asset
on some Piedmont sites where good seed years are
rare. On poorly drained sites on the Lower Coast-
al Plain where a rising water table after a har-
vest cut may prevent seedling establishment and
development, leaving about 35 square feet of
shelterwood basal area is quite beneficial. The
trees that are left will keep the water table down
while the new stand is getting started. Also,
the shade provided greatly suppresses competing
hardwood species.

A two-cut shelterwood system--removing an
entire stand in two cuts--is recommended for lob-
lolly pine. After healthy seedlings are ade-
quately established in 3 to 5 years, the entire
sheltering overstory should be removed. If you
wait much longer, the young trees will be brittle,

12