10
The Role of Extended Rotations
Robert 0. Curtis
&tended Rotations
167
v\Udlife and Biodiversity Values
The T.!mber Supp!J Problem
Conclusion
169
Uterature Oted
.
·.
. .
169
169
170
The theme of this chapter is that progressive short­
ening of rotations in recent decades has been a factor
in the genesis of current forest resource mana·gement COntroversies, and that a shift to extended rotations ?n some part of the land base-combined with cer­
tain other measures-can be a valuable component oi any overall strategy to deal with these problems. Forest management practices in the Pacific North­
evolved from beginnings in the 1850s. During
next three-quarters of a century, most cutting
place on private lands. Early cutting practices
were essentially liquidation, at rates determined by
market forces, of what was then regarded as a wast­
ing asset. With the gradual adoption of planned for­
est management over the period from about 1920 to
1950, systematic planning for long-term production
was introduced. A basic principle, accepted by all at
the time, was that old stands were essentially static
and unproductive and should be replaced by young
rapidly growing stands as quickly as possible. With
dwindling old growth and a growing appreciation of
the inherent high productivity of northwestern
165
Section II. Silvicultural Systems and Management Concerns
168 crease value production, and would certainly increase
aesthetic and some wildlife and biodiversity values.
The traditional economic arguments lead to the ro­
tation that maximizes soil expectation value-the
discounted value of all future costs and returns. Ex­
0.80
"'
E
"'
.0
0.60
:0
cept at very low interest rates, this gives great weight
=
u
x
g o.4o
--Site II
--Site Ill
--Site IV
:;{
!: 0.20 !: ..
0.00 +---r---r--....---r----r-....-r---.,..--1
100
20
70 40
60
80
90
30
50
Age-years
Figure I 0.2 Fraction of potential volume yield at­
tained at various ages on good (II), medium (III), and
poor (IV) sites as predicted by DFSIM (Curtis et al.
1982) for stands established at 300 stems per acre and
receiving repeated commercial thinning.
to short-term results and negligible weight to the
long term. A noneconomist might well argue that no
(
individual or society bases decisions solely on dis- ,
counted monetary values; each determines goals on ·
other bases and then uses economics as an aid in de- �·
·;.�
ciding how best to reach those goals.
More concretely, one can point out shortcom­
ings_:_perhaps not inherent-that are characteristic
of the most common and simplistic presentations.
They commonly ignore wildlife, water, fish, and
amenity values, which usually do not accrue to the
landowner. They usually do not recognize that public
policy considerations include maintaining productiv­
ity of all values and that public perceptions-justified
or othervvise-are the driving force behind costly and
..
increasing regulatory constraints and pressures for
wildlife benefits and do not give high priority to max­
imizing returns on capital value of timber.
But culmination age is not a fixed known guantity.
It is influenced by management and obscured by dif­
land withdrawals for special uses. We have no satis­
factory way to assign dollar values to most nontimber
outputs, although costs of specified management
modifications to provide them can be estimated.
ferences among available estimates. For many years,
Estimates of future returns often do not adequately
estimates were based on the work of McArdle et al.
account for the fact that longer rotations with thin­
(1930, 1961) (Figure 10.1). It now appears that these
ning are expected to produce stands with higher val­
estimates were seriously in error, in part because of
ues per unit volume because of the higher value of
errors in the height development curves used and in
large trees and guality improvement from selection
part because systematic density control affects pat­
of leave trees. With unknown future markets and fu­
terns of stand development. A recent analysis of re­
ture guality premiums, estimates are necessarily un­
sults from 17long-term thinning trials, some extend­
certain, and the natural tendency is to be conserva­
ing to maximum ages of about 70 years on the best
tive.
sites to 117 years on a poor site, showed that MAl
These factors are real even though expression in
had not culminated in any of the stands examined
monetary terms is imprecise or impossible. Non­
(Curtis 1995). To the upper limits of the data, PAl re­
timber values and public perceptions have become
mained nearly constant or only slowly declined over
dominant forces influencing management of national
an extended period of years. Development patterns
forest and other public lands. T he political and regu­
were very different from those portrayed in Figure
latory consequences of these changes cannot be ig­
10.1 for heavily stocked unmanaged stands. The MAl
nored by any owner.
curve is relativelv
of culmination
flat in the vicinitv
'
"
age, and there is a considerable range of possible ro­
The short rotations now used by many owners
produce considerably less volume and value than the
tation ages that will produce approximately the same
MAI Moderate extension of rotations would not de­
crease long-term volume production, might well in­
and supply considerations and owner objectives. Ro·
tations of maximum MAI in volume or in value a re
.
potential. But rotations are influenced by financia l
·
·
·
The Role of Extended Rotations
169
trees can be killed or treated to provide snags, cavi­
not appropriate for many private owners.
of the recent trend toward very short
'int::ttto11s on many noniederal lands, however, can
mea n sharply reduced productivity, restricted
management options, reduced nontimber
and exacerbation of antiforestry attitudes
major segments of the public.
..........- and Biodiversity Values
recent years, a great deal of emphasis has been
on nongame wildlife and on protection of en­
ties, and coarse woody debris.
•
Thinning provides flexibility in control of stand den­
sity and structure that can be used to promote wildlife
values through development of understory and cre­
ation of small openings and within-stand density
variation. Systematic thinning begun at a relatively
early age can produce large trees and markedly alter
stand structures over relatively short periods of time.
Emphasis will obviously be strongly influenced by
existing land ownership and owner management ob­
jectives.
dangered species and conservation o f biodiversity.
We have learned that attempts to rescue individual
species can be extremely disruptive and expensive
and are often too late. It is not possible to provide for
tach oi the myriad of species individually. The only
viable course is to develop forest management
regimes that provide both commodity production
and su-pport for most forest-dwelling species (Carey
et al. 1996). This will be politically and economically
feasible only if SE;!Vere conflicts with the economic
and social well-being of rural communities and for­
est-based industries can be avoided.
Several aspects of extended rotations and the asso­
ciated thinning and regeneration options will be gen­
.
erally favorable to biodiversity and production of
wildlife (Curtis and Carey
•
•
1996):
Extended rotations would, if anything, increase long­
term timber supply. Unfortunately, changing rota­
tions is a one-way street. Rotations are easy to
shorten, but difficult to lengthen. The practical imple­
mentation problem is maintaining an acceptable
level of timber supply during the transition period.
This cannot be ignored by public owners, and it is a
critical obstacle for others. Reductions in short-term
supply could be offset to some degree by increased
thinning and decreased pressures to remove land
from the timber base .
A number of examples (Curtis
1995)
suggest that
thinning regimes can be designed that combine high
Extended rotations allow development of a wide
range of age classes, tree sizes, and structures, as well
as a more balanced stand age distribution.
intermediate yields and relatively infrequent entries
The combination of extended rotations, thinning, and
alternative regeneration systems will (1) minimize
the iru1uence of the stem exclusion stage and clear­
Many currently perceived problems reflect the fact
(2) pro­
mote development of biologically rich forest floors
:ma complex trophic pathways, and (3) reduce spatial
cuts on dispersal and colonization processes,
JSolation of high-qualitv forest habitat. The combina­
tion can also reduce or' eliminate the unfavorable ef­
fects often thought to be associated with forest frag­
mentation into disconnected units of regeneration
an d old stands.
•
The Timber Supply Problem
Thinning entries will usually be infrequent during the
latter part of the rotation. Therefore, there will be
some natural unsalvaged mortality providing snags
d coarse woody debris additional to that from thin­
rung slash. If these are thought insufficient, additional
with development of stands acceptable for both tim­
ber and non timber values.
that existing stand age distributions are highly unbal­
anced both regionally and locally. A move toward
more balanced distributions implies both that some
stands should be carried to advanced ages and that
others should be harvested at ages substantially less
than might otherwise be desirable. Spatial distribu­
tion, as well as total areas involved, will be important.
Conclusion
Silviculture consists of the techniques for manipulat­
ing the composition, structure, and rates of develop­
ment of forest trees and stands. These techniques are
Section II. Silvicultural Systems and Management Concerns
170
the product of a long history of accumulated research
A considerable part of present forest management
and experience. Although many were originally de­
controversies can be attributed to the visual and eco.
veloped for the purpose of enhancing wood produc­
logical effects of the short-rotation management that
tion, they can be extended with little difficulty to the
has become common in recent decades. A shift to
longer rotations on some portion of the land base
should mitigate these problems and conflicts. The re
broader problems of developing forests and forest
stands with characteristics desired for multiple forest
objectives (DeBell et al., Chapter 8, Tappeiner et al.,
Chapter 9).
The choice of rotation is an integral part of a man­
agement regime and has reciprocal ties to the nature
is much evidence that this need not reduce long­
term timber outputs and that it might even increase
them while at the same time increasing production of
aesthetic, wildlife, and other nontimber values.
and appropriateness of other silvicultural measures.
Literature Cited
Carey, A. B., C. Elliott,
J. R. Sessions, C. ). Chambers, J. F.
Franklin, C. D. Oliver, and M. J. Raphael. 1996. Washing­
ton landscape nzanagcnumt project report no. 2. Olympia,
\'I'A: Washington Department of Natural Resources. ln
press.
Chang, S. J. 1984.Dctmnination of the optimal rotation age: A
theoretical anal!tsis. Forest Ecologft and Management
8(1984):137-147.
Curtis, R.
0. 1994. Some simulation estimates of mean annual
increment of Douglas-fir: Results, limitations, implications
for management. Research paper PNW-RP-471 Portland,
OR: USDA Forest Service.
.;
--.
1995. Extended rotations and culmination age of coast
Douglas fir: Old studies speak to current issues. Research
f:
L
paper PN\IV-RP-485. Portland, OR: USDA Forest Ser­
vice.
Curtis, R. 0., and A. B. Carey. 1996. Managing for economic
and ecological values in Douglas-fir forests. ]oumal of
Forestry. ln press.
Curtis, R.
0., and D. D. Marshall. 1993. Douglas-fir rota­
tions: Time for reappraisal? Western ]oumal of Applied
Forestry 8(3):81-85.
0., G. W. Clendenen. D . L. Reukema, and D. ).
DeMars. 1982. Yield tables for managed stands of coast
Curtis, R
Douglas fiT: General technical report PNvV-135. Port­
land, OR: USDA Forest Service.
McArdle, R. E., and W. H. Meyer. 1930. The yield ofDouglas­
_fir in the Pac(fic Northwest. Technical bulletin 201. Wash­
ington, DC: USDA.
McArdle, R. E., W. H. Meyer, and D. Bruce. 1961. The yield
of Douglas fir in the Paqfic Northwest. Technical bulletin
201. Washington, DC: USDA.
Newman, D. H.1988. Tile optimal forest rotatio11: A discussion
.
a11d annotated bibliography. General technical report SE­
48. New Orleans: Southeastern Forest Experiment Sta­
tion, USDA Forest Service.
Pearse, P. H. 1967. The optimum forest rotation. Forestry
Chronicle 43:17&-195.
'
'
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'
'
•,
<
..:'-'
!';
'
'
Creating a Forestry for the 21st Century .
:· _The Science of Ecosystem Mt7:nagement .
Edited by Kathryn A. Kohm and Jeny F. Franklin Foreword by Jack Ward Thomas ISLAND PRESS
Washington, D.C.
• Covelo, California
\
Copyright© 1997
by Island Press
All rights reserved under International and Pan-American Copyright Conventions. No part of this book
may be reproduced in any form or by any means without permission in writing from the publisher:
Island Press, 1718 Connecticut Avenue, N.W., Suite 300, Washington, DC 20009.
ISLAND PRESS is a trademark of The Center for Resource Economics.
No copyright claim is made in chapters 2, 3, 6-11, 13-19,21, and 29, work produced in whole or in part
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Grateful acknowledgment is expressed for permission to publish the following copyrighted material:
Figure 3.1, on page 112, from Peet, R.K 1992. "Community Structure and Ecosystem Function." In Pillnt
Succession: Theory and Prediction, edited by D.C. Glenn-Lewin, RK Peet, and T.T. Veblen. New York:
Chapman and Hall.
Library of Congress Cataloging-in-Publication Data
Creating a forestry for the 21st centuiy: the science of ecosystem
management I edited
by Kathryn A Kohm
& Jerry F. Franklin.
P·
em.
Includes bibliographical references and index.
ISBN 1-55963-398-0 (cloth).- ISBN 1-55963-399-9 (pbk.)
1. Forest management-Northwest, Pacific. 2. Forest ecology­
Northwest, Pacific. 3. Forests and forestry-Northwest, Pacific.
4. Ecosystem
management-Northwest,
Pacific. 5. Forest management.
6. Forest ecology. 7. Forests and foreslly. 8. Ecosystem
L Kohm, Katluyn A ll. Franklin, Jerry F.
management.
SD144.A13C74
1997
634.9-dc20
96-32771
CIP
Printed on recycled, acid-free paper
®
Manufactured in the United States of America
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