Section II. Silvicultural Systems and Management Concerns

Chapter 10. The Role of Extended Rotation

Professor. Koa DanaPresented by: Oeun Koem Oun

Content

• Key Words• Objective• Introduction• Extended Ration• Wildlife and Biodiversity Values• The Timber Supply Problem• Summary

Key WordsRotation- the planned number of years between stand regeneration and final harvest. Extended rotation forest- forest stand for which the harvest age is increased. 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.

Key WordsYield- 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. (API )

Objective

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 extended rotations.

Introduction

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.

Extended Rotation

• 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 advanced ages.

Extended RotationAdvantages 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

stages, hence—– Reduced frequency of drastic disturbance affecting biodiversity– Less need for herbicides, slash burning, etc. – Reduced visual impacts – Lower regeneration and respacing cost

Extended Rotation

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.

+Thinning Extended Rotation

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 variation.

• Thinning entries will usually be infrequent during the latter part of the rotation.

The Timber Supply Problem• Extended rotations would, if anything, increase long-

term timber supply.

• Rotations are easily to shorten, but difficult to lengthen.

• 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.

Summary

• The choice of rotation is an integral part of a management regime and has reciprocal ties to the nature and appropriateness of other silvicultural measure.

• 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.