| |
|
|


Longleaf pine is the longest lived of the southern pine
species. Throughout most of its range, individual longleaf pines can reach
250 years in age (with trees in excess of 450 years old having been documented).
To reach that point of old age the life history of longleaf pine can be
described in several stages. However, due to the large occurance of small
scale disturbances, the forest as a whole is at all times transitioning
through at least one of these stages of growth simultaneously. Research
has shown that although a longleaf forest looks like and is defined as
an "old-growth" stand (i.e., large, scattered, old trees), it
still has approximately 2/3 of its trees less then 50 years old.
1) Seed Stage - after falling from the tree in October to late
November, winged seeds whirl to the forest floor and await adequate moisture
before germination. In heavy mast years, a rain shortly after seed fall
will yield a green blanket of germinants on the forest floor. Seeds either
germinate within a few weeks after falling or they won't germinate. Although
seeds will germinate almost anywhere (on rocks, logs, forest mulch), they
generally need to land on mineral soil to survive subsequent droughty
periods. During this first stage, the seedlings are very susceptible to
fire, drought and predation and will take upwards to a year to reach the
next life stage. 
2) Grass-Stage - an inconspicuous yet unique stage of a longleaf
pine's life history where the seedling resembles a clump of grass more
then a tree (and hence the name). During the grass-stage the growing tip
(bud) of the tree is protected under a thick arrangement of needles at
ground level. When fires sweep through, the needles may burn but the tip
of the bud remains protected. New needles quickly replace those that were
burned off. During the grass-stage, longleaf pine seedlings are virtually
immune to fire. At this stage, although the tree will not be growing upwards,
the seedling will be putting down an impressive root system underground.
Also during this stage, longleaf may become infected with a fungus called
brown spot needle blight. Brown spot causes the needles to brown, fall
off, and hamper growth.
Repeated defoliation will cause the seedling to die. The grass-stage may
last anywhere from one to seven years depending on the degree of competition
with other plants for resources. Rare instances of 20 years have been
documented.
3) Bottlebrush Stage - when the diameter of the root collar (that
area right at ground level) reaches 1-inch, the longleaf grass-stage will
begin to initiate height growth. Beginning in about late February to mid-March,
a single, white growing tip will emerge upwards from the protective sheath
of needles. This white tip, called a candle, may grow a few feet in just
a few months. By about late May, green needles begin to emerge from the
candle and white candle begins to turn scaly and brown as bark begins
to form. At this point, the longleaf is growing proportionally more in
height then it is in diameter. There are no branches spreading out horizontally
during this time causing the tree to look like a three to four-foot bottlebrush.
By growing rapidly in a short period of time, the seedling is able to
secure an advantageous position to gather sunlight and to get its growing
tip above the frequent fires. However,
during this stage of growth, longleaf pine trees are slightly more vulnerable
to fire. It may take a year or so before the bark thickens enough to withstand
most fires. The longleaf may remain in this stagefor a couple of years.
4) Sapling Stage - when the longleaf reaches about 6 to 10 feet
in height, lateral branches begin to emerge and signal the beginning of
the sapling stage. Diameter increases and bark thickens modestly, but
the tree continues to grow in height at upwards of 3 feet per year. About
late February to mid-March white growing tips can be seen extending upwards
from the tufted needles at the end of the branches. As the tree grows
taller and the bark becomes thicker, the longleaf become less susceptible
to fire. After tree reaches 8 feet in height and about 2 inches in diameter
at ground level, it becomes very robust and is rarely killed by fire.
The tree will remain in this stage for several years.
5) Mature Stage - somewhere around 30 years after height growth
initiation; trees begin to produce cones with fertile seeds. As the forest
begin to mature, lower limbs may be shed or pruned off by fire. The trunk
of the tree begins to fill out into a straight, relatively branch free
tree that resembles a living telephone pole (in fact, many longleaf pines
are sold for telephone poles). On more fertile soils, the tree may continue
to grow in height up to 110 feet. On poorer soils, the tree may only grow
to 60 feet. After about 70 -100 years longleaf essentially ceases height
growth. During the later stages of this period, trees may begin to show
signs of decay and rot. In particular, longleaf pine reaching 80 years
in age may become infected with a fungus called red heart that causes
the otherwise dense heart of the tree to become punky, soft, sappy and
full of small channels. 
6) Old-Growth - during this period most trees have reached a steady
state. Large diameter trees with flat-topped crowns dominate the forest.
Historical accounts describe longleaf pines in excess of 120 feet tall
and 3 feet in diameter. Conventional wisdom suggests that old-growth longleaf
pine trees stop growing in size at these advanced ages. However, many
instances exist where old-growth longleaf pine trees have actually increased
growth rates at 200 years (+) when resources became available. At older
ages, more and more trees begin to show signs of internal rot from red-heart
fungus. In some localities, as many as half the trees per acre can be
affected with red-heart in the crowns. 
7) Death - in a landscape that sees lightning, tornadoes, wildfires,
drought, hurricanes, or even ice storms on a regular occurrence, it is
really quite remarkable for a longleaf pine to die from old age. After
300 years, trees that survive everything that Mother Nature has to throw
at them will eventually weaken and begin to loose the ability to fend
off forest pests like black turpentine or southern pine beetles. Slowly
the trees begin to die off. The initial signs of this weakening include
a thinning of green needles in the tree crown, followed by signs of beetle
activity on the bark, then wilting of needles and finally by complete
defoliation. 
7) After Death - usually when we think of the contribution of
an organism (like a longleaf pine) to an ecosystem, we focus merely on
the living organism. However, a longleaf pine is perhaps just as significant
to the ecosystem after the tree is dead as when it is alive. Once the
tree dies, its bark quickly sloughs off or is torn off by foraging woodpeckers.
What remains is the white skeleton of the tree; known as a snag. Snags
that don't fall will typically remain for only a few years. Without the
protective bark in place, the resinous inner wood of the longleaf is exposed
and often causes the snag to ignite during a forest fire and burn to the
ground.
(back)
|
|