Section II. Silvicultural Systems and
Chapter 10. The Role of Extended Rotation
Professor. Koa Dana
Presented by: Oeun Koem Oun
• Key Words
• Extended Ration
• Wildlife and Biodiversity Values
• The Timber Supply Problem
Rotation- the planned number of years between stand
regeneration and final harvest.
Extended rotation forest- forest stand for which the harvest age
Thinning- cutting trees to improve functions of a forest other
than timber production.
Forest regeneration- renewing tree cover by establishing young
trees naturally or artificially.
Slash-and-burn- an agricultural technique that involves the
cutting and burning of plants in forests to create fields.
Stem exclusion- when some stands are disturbed by others to
grow as their potentials.
Yield- the sum of standing volume plus the cumulative amount
cut since stand establishment at specified age. (Yt)
Mean annual increment (MAI)- volume produced (standing
volume plus thinning) divided by stand age; that is, average
production rate from establishment to the age in question.
(MAI = Yt/t)
Current annual increment (CAI)- growth rate in volume per year
at a specified age. (Y2 – Y1)
Periodic annual increment (PAI)- the difference in stand volume
at two successive measurements, divided by the number of
years between measurements. PIA is an approximation to
current annual increment, which is not directly measurable.
This chapter aim at introducing an alternative
way of managing forest in the more productive
and sustainable ways from current commonly
use—short rotations—to longer rotations use or
The theme of this chapter is that progressive
shortening of rotations in recent decades has been a
factor in the genesis of current forest resource
management controversies, and that a shift to
extended rotations on some part of the land base—
combine with certain other measures—can be a
valuable component of any overall strategy to deal
with these problems.
• As rotation become shorter, a greater percentage of forest
land is cut annually.
• With the short rotations:
– trees become smaller,
– wood quality and value are lower,
– wood productivity and productivity of other forest values are
reduced in comparison with their potentials.
• Long rotations are biologically reasonable in the Pacific
Northwest because Douglas-fir and its associates are very
long-lived and can maintain rapid growth to rather
Advantages of extended rotations (plus commercial thinning):
• Larger trees and higher-quality wood
• Opportunity to adjust present unbalanced age distributions
• Higher-quality wildlife habitat
• Hydrological and long-term site productivity benefits
• Increase carbon storage associated with larger growing stock
• Preservation of options for future adaptive management
• Reduced land area in regeneration and early development
– Reduced frequency of drastic disturbance affecting biodiversity
– Less need for herbicides, slash burning, etc.
– Reduced visual impacts
– Lower regeneration and respacing cost
Continuation of the recent trend toward very
short rotations on many nonfederal lands, will:
• reduced productivity,
• restricted future management options,
• reduced nontimber benefits,
• and exacerbation of antiforestry attitudes among
major segments of the public.
Wildlife and Biodiversity Values
• Attempts to rescue individual species:
– Can be extremely disruptive and expensive and
– are often too late.
• By develop forest management regimes:
– provide both commodity production and
– support for most forest-dwelling species.
• This will be politically and economically feasible only if
severe conflicts with the economic and social well-being
of natural communities and forest-based
industries can be avoided.
Wildlife and Biodiversity Values
Aspects of extended rotations, thinning , and regeneration
options will be favorable to wildlife:
• Wide range of age classes, tree sizes, and structures, and more balanced
stand age distribution.
• Rich forest floors and complex trophic pathways.
• Reduce spatial isolation of high-quality forest habitat.
• Minimize the influence of the stem exclusion stage.
• Thinning provides flexibility in control of stand density and structure that
can be used to promote wildlife values through development of
understory and creation of small openings and within-stand density
• Thinning entries will usually be infrequent during the latter part of the
The Timber Supply Problem
• Extended rotations would, if anything, increase long-term
• Rotations are easily to shorten, but difficult to
• Stand age distributions are highly unbalanced both
regionally and locally.
• A move toward more balanced distributions:
– some stands should be carried to advanced ages
– other should be harvested at ages substantially less than
might otherwise be desirable.
• The choice of rotation is an integral part of a
management regime and has reciprocal ties to
the nature and appropriateness of other
• A shift from common-used short rotation to
longer rotations on some portion of the land
base should mitigate problems and conflicts.
• From the apply of longer rotation, it is expected
to increasing production of aesthetic, wildlife,
and other nontimber values.