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Regenerating Longleaf Pine
Forests Naturally
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Mature Longleaf Forest
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Facts
• The southern pines are generally shade
intolerant
• Natural disturbances occur on many scales
• Southern pines occur naturally in both evenaged and uneven-aged systems
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Choices
• Natural regeneration:
• Requires a suitable, well distributed seed source
• Can be used in even-aged and uneven-aged
management systems
• Sacrifices advantages of stocking control for low
“upfront” regeneration costs
• Uncertain seed crops make planning difficult if
time is a factor
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Effect of gap size on stand conditions
• Small gaps or small scale disturbances can
lead to stands of multiple ages as the gaps
are filled in with regeneration.
• Large gaps can result in even-aged stands,
with all trees being regenerated within a few
years of each other following the
disturbance.
Current Southern Pine Management
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Trends
• Most southern pines are managed today in
even-aged systems :
– Optimizes growth rates by allowing maximum
sunlight on growing crop
– Takes advantage of economies of scale for
silvicultural treatments
– Enables easy scheduling for harvests,
treatments
Trends
favoring
uneven-aged
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management
• Changing landowner demographics,
owner’s objectives may favor uneven or allaged management because:
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Trends
– Retains appearance and much of the
function of a forest throughout
– Can take advantage of natural regeneration,
reducing upfront costs
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Regeneration
• In all regeneration systems, the greatest
challenge is to get reliable and timely
regeneration and give it room to grow into
the larger, more valuable size classes
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Regeneration Management
• Competition may be intra-specific or
interspecific
• Control usually means control of competing
vegetation or release harvest
• Intermediate cuts, herbicides and fire are
techniques of choice in most southern pine
management schemes
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Regeneration
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Species Considerations
• Longleaf Pine
– Sporadic seed producer
– Seed generally only disperses 100 feet or so
from the seed tree
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Pine (contd.)
– Fire tolerant at virtually any size after year
of germination
– Could be planted in gaps to augment
natural seedling numbers
– Two year cones allow for some planning
and preparation
Regenerating
degraded
stands
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naturally..
• The shelterwood system, as utilized in longleaf
management, can result in either even-aged or
multi-aged longleaf stands.
• The first step in natural regeneration should be to
control the woody understory prior to opening up
the canopy with a cut.
• Fire, particularly growing season fire, or fire and
herbicide used in combination can be effective in this
effort. Combinations of dormant season and
growing season fires may be necessary to reduce
initial fuel loads.
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Mixed Pine Stands
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Mixed pine stands
• If sufficient numbers of well-distributed longleaf are present
in the overstory to provide some seed, the stand can be
managed to regenerate naturally.
• Fire should be a regular part of a management regime until
woody understory competition is controlled.
• One treatment to control woody brush that has proven
successful employs Garlon 4TM (triclopyr) applied with
ground equipment or backpack sprayers in early Fall,
followed by an early Spring fire.
• Fire must be employed to prevent seedlings from other pine
species from occupying the site before longleaf can become
established. Longleaf has sporadic seed crops, unlike the
annual seed crops of other southern pines, and may fail to
capture the openings when they occur.
Mixed stands containing other pine species might be thinned
to create gaps to release longleaf seedlings already present in
the understory
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stands…
• Successive cuts to increase the number and/or size
of the previous gaps will create a mixed stand of
several age classes, that will, over time, become an
all-aged longleaf stand.
• It may be desirable to keep some pines of species
other than longleaf in the overstory to help provide
fuel for fires.
• It is difficult to burn into the center of gaps larger
than ¼ acre because of the lack of pine fuels.
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Even-aged natural
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Low upfront costs
Fairly consistently successful
Stocking control can be a problem
Growth on best trees
Best trees at risk
Unreliable seed production
Can be used to begin transition to all-aged stand
condition (Modified Shelterwood)
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ThetoShelterwood
• When the understory is reduced to a manageable level, a
preparatory cut is used to reduce Basal Area to 50 to 60
square feet per acre, favoring trees of good form, large
crowns, and good seed producers. The residual trees should
be well-distributed across the area.
• After several years, the crowns will have expanded into the
intervening gaps and regeneration has begun to accumulate.
At that time, a second “seed” cut should be used to reduce
Basal Area to 25 to 30 square feet per acre, again favoring
well formed good seed producers distributed evenly across
the stand.
• When a good seed crop is anticipated (through flower
and/or cone crop counts), the stand should be burned in the
winter or early growing season prior to seed fall to prepare
a good seed bed.
The
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cutedit
should
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basalstyle
area to
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about 30 square feet per acre
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Shelterwood Regeneration
• Longleaf is a sporadic seed producer, producing seed
anywhere from annually to once every 20 years in
some areas.
• Longleaf is a “two-year” cone, with female cones or
flowers appearing one year and maturing the next,
the year of seed fall.
• Surveys of female flowers anticipate cone crops but
can be difficult for inexperienced observers. Cone
counts are easier, but give less lead time to prepare
the site to receive seed.
• There should be about 30 cones per tree or 1000
cones per acre to provide adequate seed to naturally
regenerate an entire area with longleaf seed.
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natural
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cones may
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takes a trained eye to count flowers
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Systems
• A minimum of 4,500 germinants per acre are
considered sufficient to consider a site successfully
regenerated from natural seed. At least 75% of all
0.001 acre plots should have at least one live
seedling present.
• If the above conditions can be met, the site can be
considered stocked with new seedlings and, if
desired, the overstory trees removed within two
years of the seed year. This will yield an even-aged
stand.
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system..
• Naturally regenerated stands cannot be burned in the year
following seedfall without endangering the new seedlings.
Seedlings with a root collar diameter of 0.25 inch or greater
generally can survive most fires.
• If even-aged stands are not desirable, all or a portion of the
seed trees may be retained, creating a two-aged stand.
Subsequent repetitions of this process with later seed crops
will eventually yield a multi-aged stand.
• Seedling growth rates may be adversely affected by
competition from the residual overstory.
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Naturally
stands should
4,500 to 6,000 seedlings per acre the spring after
seed fall
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Harvesting the Overstory
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New longleaf seedlings cannot survive fires until they reach a
root collar diameter of at least 0.25 inches (6 mm)
Retaining
all of the
seed
trees
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produces a two aged stand
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Shelterwood
with Retention
• Overstory of 30-40 square feet of BA removed
in several stages over an extended period to
allow several cohorts of seedlings to develop,
potentially creating an uneven-aged stand.
• Because longleaf is a sporadic seed producer,
seed crops may be several years apart.
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Systems
• Longleaf stands or stands that are predominantly
occupied by longleaf may also be regenerated and
managed using uneven-aged systems.
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Uneven-aged choices..
• Stands may be managed in uneven aged conditions
using several natural management alternatives,
assuming regeneration is obtained.
• Single tree selection
• Group selection
• Stoddard-Neel System
• Reverse “J” or BDQ method
Overview
of “Natural”
Standtitle
Management
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(Uneven-Aged)
•
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Retains appearance of a “forest”
Retains full range of habitat/species diversity
Retains market flexibility
Can require individual attention
Economies of scale may be limiting
Should obtain regeneration catch before creating
gaps to release it
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(Continued)
• Provisions must be made for regeneration and fire
• Produces constant flow of high value timber and
non-timber products
• Requires fairly frequent entries and disturbances to
yield comparable income
• Requires “informed” management to be successful
• No upfront establishment costs
Creating
uneven
agetitle
forest
from
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regeneration
• With each successive seed crop, gaps can be created
or enlarged to release the new seedlings.
• Gaps can be systematically or randomly located
depending on the landowner’s objectives
• “Domes” of regeneration take shape over time, with
the tallest seedlings in the center.
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Regeneration “Domes”
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or “All-Sized”
• Makes little difference for future management since
longleaf responds to release at almost any age unless
critically suppressed.
• Longleaf grows naturally at different rates, possibly
as a hedge against lethal fires.
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“All-aged” or “All-sized”
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control
• When natural regeneration works, it can work too
well.
• The 1996 seed crop resulted in some stands at the
Dixon Center with over 400,000 longleaf
germinants per acre
• Fire, drought and other mortality factors gradually
reduced those numbers, but some stands retained
high levels of stocking
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preparation
• If seeds fall on deep litter, they typically germinate
anyway, but die at the first dry spell or first fire
because roots are anchored in mineral soil.
• If seeds fall on bare soil, seed predators may devour
the crop unless it is an unusually large crop.
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• Not only is longleaf seed tasty and preferred by birds,
small mammals, and other predators, it is edible and
palatable for humans. At the current rate of $160
per pound, it would be an expensive meal.
• The new germinants reportedly make a tasty
addition to salads!
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Questions???