Thinning is defined as the mechanical removal of
individual trees or entire rows of trees from a stand.
This allows the residual trees more space to continue their vigorous
growth and health. As the basal
area of a stand increases beyond 100 ft2/acre the risk of
southern pine beetle mortality increases. Basal area is a measure of
stocking and is defined as the cross-sectional area of tree boles on an unit
area. There are two types of
thinning: pre-commercial and commercial.
Thinning: Cutting in immature stands before trees reach their marketable
size, usually less then 5 inches, is called pre-commercial thinning.
Generally pre-commercial thinning is not required if trees are planted at
wider spacings (10' X 10' or greater). At narrower spacings,
pre-commercial thinning my be needed to allow additional space for the
remaining trees to grow. Trees may be thinned by using chainsaws or a
row(s) can be removed with a bush-hog or drum chopper. Pre-commercial
thinning is a cost generator with no immediate income for the
landowner. However, it will improve the overall health of the stand
when closely-spaced, young trees are competing with each other.
Thinning: This thinning occurs much later when the canopy has closed and
the trees are reaching pulpwood class, usually 12 to 15 years old. The goal is to lower the basal
area of the stand to 70 or 80 square feet per acre. This prevents a
reduction in the radial growth of the trees and helps to protect the stand from SPB
infestations. Additional thinnings should be conducted at older ages
whenever the basal area of the stand exceeds 100 to 120 ft2/acre
or when the canopy closes, allowing additional space for crown expansion to
maintain diameter growth of the remaining trees.
should be given any time that there is a mechanical entry into the
stand. More harm then good is often caused when residual trees are
damaged during operations.