ECOLOGICAL BASES FOR SILVICULTURAL PRESCRIPTIONS
FOR CONTROL OF DWARF MISTLETOE I N LODGEPOLE PINE-^
Phil Guthrie-2/
Abstract: Preparation of s i lvicul tural prescriptions
i s a complex process in lodgepole pine ecosystems. Ecological
factors and management decisions must be considered. The presence or absence of dwarf mistletoe in a stand i s one ecological
factor that must be considered. Control of dwarf mistletoe i s
possible through application of sound s i 1vicul tural principles.
Key Words: Silvicul tural prescriptions; dwarf mistletoe
control; Arceuthobium americanum; Pinus contorta.
SILVICULTURE AND ECOLOGY
Silviculture has been defined as "the
a r t and science of growing trees". The a r t
of growing trees refers t o management of trees
by i n s t i n c t , "gut feelings" and a t times flying by the seat of our pants. There always
has been and probably always will be a place
in silviculture for t h i s a r t which comes from
familiarity with a given ecotype and experience in how the ecotype reacts t o a given
type of treatment. The a r t should n o t , however, be our dominant form of management.
The science of growing trees i s plant
ecology.
Past management efforts by foresters often placed much more emphasis on the a r t than
on the science. There are many reasons for
t h i s , but the main ones are: 1 ) The d i f f i culty of remaining professionally current in
a f i e l d as diverse as forestry; and, 2 ) The
lack of time t o prepare prescriptions that
analyze and document the bases for management actions.
This reliance on the a r t rather than the
science of stand management resulted in some
stand treatments in lodgepole pine (Pinus
contorta Doug1 . ) that were ecologically questionable and/or socially insensitive.
-'presented a t the Symposium on Dwarf Mistletoe Control Through Forest Management, Berkeley, California, April 11-13, 1978.
z'~upervisory Forester, Santa Fe National
Forest, Santa Fe, New Mexico, stationed in
Coyote, New Mexico.
Adverse pub1 i c reaction t o 1arge clearcuts and drastic s i t e preparation and brush
disposal methods necessitated some change in
our ways of treating stands. I t soon became
obvious that i t was time t o rely more on the
sciences of forest and plant ecology than on
the a r t of growing trees.
SILVICULTURAL PRESCRIPTIONS
Reasons for Si lvicul tural Prescriptions
All of our research, education, training
and experience are of l i t t l e value i f they are
not eventually expressed in on-the-ground
treatments. The s i lvicul tural prescription
provides the medium for translating t h i s knowledge into a plan of action. Northern Region
Guide1 ines for Development of Si 1vicul tural
Prescriptions l i s t four basic purposes of a
prescription :
1.
The prescription provides a logical
method of analysis of a stand to
determine a1 ternative cultural t r e a t ments. The prescription will also
a s s i s t in the evaluation of the environmental impact of such treatments.
2.
The prescription provides direction
for carrying out cultural treatments.
3.
The prescription documents the scient i f i c basis for the alternative
treatments.
4.
The prescription i s a record that a1lows for l a t e r evaluation of the effectiveness of the cultural treatments (Anon. 1976).
Uses of Standard Prescriptions
Me used t o prescribe treatments t h a t were
considered as standard f o r certain t r e e species in a given locality. Examples of these
might include "clear-cut, burn, and plant white
pine" in northern Idaho; "thin to favor larch"
in western Montana; and "the bigger the bett e r " when referring t o clearcuts in dwarf
mi stletoe--(Arceuthobium americanum N u t t . ex.
Engelm. ) infected lodgepole pine. Each region, s t a t e and private company has used standard prescriptions.
The more you prescribe treatment f o r various stands, the more evident i t becomes t h a t
these standard prescriptions a r e no longer acceptable. Complex ecosystems require more
in-depth analysis than can be applied through
standard treatments. This i s true even in
lodgepole pine type, which appears to be both
consistent and monotonous. Lodgepole pine has
been identified in 82 habitat types or phases
of habitat type in Montana alone ( P f i s t e r e t
a1. 1977). Lodgepol e pine i s one of the
most widespread tree species in western North
America. The capacity of lodgepole to grow
in such a variety of environments over such
a broad geographic area i s surpassed by few
other conifers in North America (Cri tchfiel d
1957, Tackle 1961, 1965). Pfister and Daubenmire noted that lodgepole pine occurs in
166 of 264 identified forest habitat types,
community types, sample stands, forest zones,
forest associations, s i t e types and biogeoclimatic zones, from the central and northern
Rockies and the Inland Empire in the United
States northward into Alberta and British
Columbia in Canada ( P f i s t e r and Daubenmire
1975).
The broad ecological amplitude indicates
that lodgepole pine i s a more complex ecolog.
ical e n t i t y than i s often recognized.
Management Direction
Silvicultural prescriptions must s t a t e
clearly how treatments wi 11 meet management
direction as defined in the land use planning
process or as expressed by land managers
(Anon. 1976).
In the Forest Service, t h i s involves an
interdisciplinary team. The manager (Forest
Supervisor or District Ranger) with input
from the team, resolves any conflict between
competing resource uses on the same piece of
ground and establishes the management direction f o r a large area.
I t i s then u p to the s i l v i c u l t u r i s t to
prescribe an ecologically sound treatment
that meets the management goals f o r a particular timber stand.
Primary Prescription Elements
The Northern Region has identified seven
elements a1 1-inclusive t h a t must be included
in a silvicul tural prescription (Anon. 1976) :
Objectives - After obtaining the land
management objectives, the silvicult u r i s t defines silvicul tural objectives which s a t i s f y management objectives.
S i t e Data - Slope, aspect, elevation,
physiographic s i t e , landform, geology,
soi 1s , climate, habitat type and re1 ative productivity are described.
Areas of potential resource damage or
conflict are identified. These areas
include streams, bogs, f r o s t pockets,
areas of concentrated wind, c r i t i c a l
big-game habitat, or landscape management features.
Stand Data - These data include species composition, stand structure by
age as well as s i z e class distribution, density, stand history and successional trend, true crown condition,
growth rates, timber volumes, and understory conditions. The status of
insects and diseases (including dwarf
mist1 etoe) , windthrow hazards, e s t i mates of fuel loadings within and
around the stands, and factors affecting slash disposal, s i t e preparation
or regeneration a r e discussed.
Treatment - The treatment to be applied a t t h i s stand entry i s described.
This description i s detailed enough
so that marking guides o r other pertinent preparation guides can be written from i t . Some of the details
discussed include the following:
a. Type of treatment: (1) Timber
Cutting: What type silvicultural
system i s to be applied; intermediate, salvage or regeneration
cut? What method of the system
i s to be applied? The composition and density of the resultant
stand must be indicated. ( 2 ) S i t e
Preparation: What method i s t o be
applied and t o what degree?
(3) Reforestation: What method i s
planned? What species and stockinq level i s desired? When i s
b.
c.
d.
e.
f.
t h e desired stocking level t o be
achieved?
Logging method proposed - S i l v i c u l t u r i s t s a r e not logging systems spec i a l i s t s , but they must be aware of
t h e c a p a b i l i t i e s of t h e various logging systems t o meet t h e s i l v i c u l t u r a l
o b j e c t i v e s of t h e prescribed treatment.
Methods f o r hazard reduction and prot e c t i o n t o a manageable understory.
I n s e c t and d i s e a s e protection and/or
c o n t r o l . So f a r I have s a i d l i t t l e
about dwarf m i s t l e t o e o r i t s impact
on timber stands. There a r e numerous
examples of stands which were t r e a t e d
without regard t o t h e presence of
dwarf m i s t l e t o e . These treatments a1most i n v a r i a b l y have serious long term
impacts on stand productivity. Susc e p t i b i l i t y of t h e stand t o i n s e c t s
and o t h e r diseases must a l s o be considered. In t h e case of lodgepole
pine, i f t h e stand i s of t h e s i z e ,
vigor, phloem thickness and age t o be
highly s u s c e p t i b l e t o a t t a c k by t h e
mountain pine beet1 e (Dendroctonus
ponderosae Hopki ns ) , a f i n a l removal
should be prescribed i n t h e near fut u r e o r a n t i c i p a t e d losses should be
documented (Amman 1975). The pres c r i p t i o n must consider presence o f ,
and stand s u s c e p t i b i l i t y t o , i n s e c t s
and d i s e a s e s .
Effect of t h e treatment on t h e s i t e .
The e f f e c t of t h e treatment on t h e
basic s i t e resource must be evaluated.
For example, s i t e productivity can be
d r a s t i c a l l y reduced through compact i o n of s o i l s i f t h e s o i l s a r e of a
type highly s u s c e p t i b l e t o compaction
( s i l t s o r s i l t loams). In stands
where organic matter i s a scarce component within t h e s u r f a c e s o i l horizons, d r a s t i c s i t e preparation, e i t h e r
by burning o r by machine, can d r a s t i c a l l y reduce s i t e productivity. The
same may be t r u e on well-drained, deep
s o i l s i n a r e a s of moderate t o high
r a i n f a l l , where n u t r i e n t l o s s through
leaching of bare s o i l may c o n t r i b u t e
t o s i t e degradation.
Genetic implications of t h e treatment.
Gains i n t r e e improvement i n t h e near
f u t u r e w i l l be f a r more dramatic from
a p p l i c a t i o n of g e n e t i c a l l y sound s i l v i c u l t u r a l p r e s c r i p t i o n s than from
c o n t r o l l e d breeding programs. This
w i l l be t r u e throughout most of t h e
west f o r t h e next several years because acreage r e f o r e s t e d with c e r t i f i e d improved seed o r planting stock
w i l l be small compared with t h e
t o t a l acreage r e f o r e s t e d . Natural
regeneration wi 11 continue t o play
t h e major r o l e i n r e f o r e s t a t i o n
e f f o r t s i n t h e West. Gains i n
genetic q u a l i t y of stands w i l l be
of two types: The qua1 i t y of pare n t s t h a t a r e s e l e c t e d f o r t h e next
generation; and t h e constant sel e c t i o n of superior phenotypes as
crop t r e e s i n intermediate stand
entries.
Effect of t h e treatment on wild1i f e populations. I n t e r a c t i o n s
between wild1 i f e and s i l v i c u l t u r a l
treatments can be a two-edged
sword. Si 1vicul t u r a l stand e n t r i e s
may improve t h e h a b i t a t f o r some
w i l d l i f e species a t t h e same time
they degrade the-habitat f o r o t h e r s .
In stands c r i t i c a l t o t h e survival
of important w i l d l i f e herds, s i l v i c u l t u r a l treatment may need t o be
deferred o r foregone. On t h e o t h e r
hand, game animals, rodents, and
birds can be extremely damaqi n q t o
young t r e e regeneration (Lawrence
1961 , Lindsey 1975).
Effect of t h e treatment on use of
t h e area by man, h i s visual and
o t h e r values. Recreational use
of t h e National Forests has g r e a t l y
increased t h e demand f o r amenities
such a s natural beauty, s o l i t u d e
and opportunities f o r dispersed
r e c r e a t i o n . A p r e s c r i p t i o n must
evaluate t h e demands f o r and impacts on these amenities created
by t h e proposed treatment.
Needs and possible methods f o r
livestock use and c o n t r o l . Livestock, l i k e w i l d l i f e , can be extremely damaging t o reproduction.
A p r e s c r i p t i o n must analyze whether
o r not livestock needs t o be cont r o l l e d , a n t i c i p a t e d damage, and
methods f o r protection of regeneration.
5.
Long Term Prescription - Treatments
applied t o timber stands today w i l l
a f f e c t f u t u r e management a t l e a s t unt i l t h e next regeneration c u t . The
genetic impacts of t o d a y ' s treatments
may l a s t f o r two o r more r o t a t i o n s .
A s i l v i c u l t u r i s t should consider these
long range implications and p r o j e c t
stand treatments and r e t u r n s from t h e
present through t h e next regeneration
period. Anticipated growth and y i e l d
due t o the prescribed treatments should
be analyzed as well as a n t i c i p a t e d
l o s s e s t o i n s e c t s , d i s e a s e s , and wildfire.
6.
Economic Comparisons - All prescript i o n s should include a b r i e f economic
a n a l y s i s comparing r e t u r n s on t h e investment prescribed with deferred act i o n and o t h e r possible a l t e r n a t i v e s .
7.
A1 t e r n a t i v e s - Viable a l t e r n a t i v e s
should be described b r i e f l y . Deferred
treatment should be one of t h e a l t e r n a t i v e s considered. Reasons f o r not
recommending each a l t e r n a t i v e should
be given.
cheapest method of c o n t r o l . This i s
done by c u t t i n g merchantable t r e e s ,
followed by s i t e preparation and
s l a s h disposal and f i n a l l y removing
any remaining "whips" o r small t r e e s .
Clearcutting more nearly appraoches
t h e natural system of regenerating
lodgepole pine than any o t h e r system.
2.
IMPACTS OF ECOLOGICAL FACTORS AND
MANAGEMENT OBJECTIVES ON CONTROL OF
DWARF MISTLETOE IN LODGEPOLE PINE
Preparation of a s i l v i c u l t u r a l prescri pt i o n involves consideration of t h e ecosystem,
management d i r e c t i o n , and impacts of prescribed
treatments. I t i s an involved process s i m i l a r
t o working through a complex maze. There a r e
many ways i n which t h e a n a l y s i s can a f f e c t our
e f f o r t s t o control dwarf m i s t l e t o e in lodgepole pine. F i r s t l e t ' s review our options.
The shelterwood system i s useful
i n regenerating species t h a t need
only p a r t i a l s u n l i g h t f o r germination
and establishment (Smith 1962). I t
i s a l s o useful on harsh s i t e s . Overuse of t h e system t o blunt t h e visual
impact of c l e a r c u t t i n g must be avoided, however. In s u b s t i t u t i n g shelterwood c u t s f o r c l e a r c u t s , we run
t h e r i s k of c u t t i n g l a r g e r acreages
t o meet volume goals. In a few y e a r s ,
we may f i n d t h a t t h e regeneration i s
not t a l l enough t o ameliorate t h e
visual o r environmental impacts
caused by shel terwood removal. By
removing t h e shelterwood, we have
created t h e same condition we would
have had i n a regenerated c l e a r c u t .
Use of S i l v i c u l t u r a l Systems t o
Control Lodgepol e Pine Dwarf Mistletoe
Control does not mean e r a d i c a t i o n (Hawksworth 1975). The incidence of dwarf m i s t l e t o e
i n f u t u r e managed stands w i l l be n e g l i g i b l e
and growth l o s s e s w i l l be immeasurably small.
Eradication i s n e i t h e r f e a s i b l e nor d e s i r a b l e .
In order t o accomplish c o n t r o l , i t i s
e s s e n t i a l t o know the location and e x t e n t of
i n f e c t e d a r e a s . A well designed stand examination can i d e n t i f y and map i n f e c t e d a r e a s .
The shelterwood system can be
useful in lodgepole pine i f management o r environmental c o n s t r a i n t s do
not allow c l e a r c u t t i n g , i f t h e r e i s
s u f f i c i e n t volume a f t e r t h e s h e l t e r wood i s l e f t t o make a viable timber
s a l e , i f t h e danger of windfall i s
low, and i f t h e shelterwood i s removed before i t i n f e c t s t h e regeneration.
After t h e examination, a p r e s c r i p t i o n i s
then prepared, taking i n t o account t h e ecologi c a l and management bases previously discussed.
The soundest and most f e a s i b l e control
p r a c t i c e i s t o p r o t e c t young stands and prevent t h e invasion of uninfected stands from
adjacent i n f e c t e d ones (Baranyay 1975, Hawksworth 1975). I f t h e stand i s heavily i n f e c t e d ,
i t should be s a n i t i z e d and regenerated by using
one of these t h r e e s i l v i c u l t u r a l systems:
1.
Clearcutting - Eradication of t h e exi s t i n g stand, followed by regenerat i o n i s t h e simplest and usually
Shelterwood - The shelterwood system
can a l s o be used t o regenerate lodgepole pine. Some considerations a r e :
a . I s i t needed f o r ecological o r
management purposes?
b. What i s t h e danger of windfall?
c . How w i l l leaving t h e s h e l t e r wood volume a f f e c t t h e economic
f e a s i bi 1i t y of a commercial
sale?
d. How long can t h e shelterwood
be held on t h e stump without
s e r i o u s l y i n f e c t i n g t h e regene r a t e d stand?
The seed c u t must be followed by
s a n i t a t i o n of t h e stand through eradi c a t i o n of residual stems during o r
immediately following s l a s h disposal
and s i t e preparation.
3.
Seed-Tree - The same considerations
apply t o t h e seed-tree system as t o
t h e shelterwood system. Cone serot i n y i s a f a c t o r in determining numbers of seed t r e e s necessary t o regenerate a stand. Most seed from
nonserotinous cones i s disseminated
within 200-300 f e e t of t h e parent
t r e e (Tackle 1961, 1965). This means
t h a t a minimum of 1 t o 1-1/2 t r e e s
per a c r e i s necessary t o seed t h e
cutover a r e a .
The s e e d - t r e e system can be usef u l i n regenerating lodgepol e pine
i f t h e same conditions a r e met as
with t h e shelterwood system.
- The s e l e c t i o n system i s
generally not applicable t o lodgepole
pine. In dwarf mistletoe-infected
s t a n d s , t h e s e l e c t i o n system c r e a t e s
conditions most favorable t o spread
and i n t e n s i f i c a t i o n of the p a r a s i t e .
There i s one area on t h e G a l l a t i n
National Forest near West Yellows t o n e , Mont., where a p p l i c a t i o n of
t h e system appears possible.
4. S e l e c t i o n
The s o i l s around West Yellowstone
a r e composed of obsidian sands of a l l u v i a l o r i g i n ( P f i s t e r e t a1. 1977).
Lodgepole pine i s climax. The habit a t type i s lodgepole p i n e / b i t t e r brush. Apparently, t h e s i t e s a r e
too f r o s t y t o support Douglas-fir
and too dry (excessively well drained)
f o r subalpine f i r o r Englemann spruce
( P f i s t e r e t a1. 1977). Stands vary
from moderately dense t o moderately
open. The stands a r e not a l l aged
but a r e d e f i n i t e l y uneven aged.
Dwarf m i s t l e t o e - i n f e c t e d areas a r e
we1 1 defined and mappable (Do01i ng
e t a1. 1977).
be acceptable.
5.
Intermediate Cuttings - Hawksworth
has described, i n t h i s symposium, t h e
e f f e c t s of intermediate e n t r i e s i n t o
dwarf mistletoe-infected lodgepole
pine stands so I w i l l not dwell on
t h e s u b j e c t . There a r e two concepts
t h a t have worked well f o r me t h a t I
would l i k e t o d i s c u s s .
Some stands t h a t a r e predominantly lodgepole pine have an unders t o r y of lodgepole pine plus more
t o l e r a n t species. Nonhost t r e e s o f t e n
make up a l a r g e proportion of t h e residual stand. I f t h e dwarf m i s t l e t o e
i n f e c t i o n level i n t h e lodgepole pine
reproduction i s low t o moderate ( i n f e c t i o n l e v e l s 1-3) (Hawksworth 1977)
and i f t h e regeneration of t h e t o l e r a n t species i s manageable, leaving as
many of the t o l e r a n t t r e e s a s possible w i l l lessen the impact of s c a t t e r i n g dwarf mistletoe-infected lodgepole pine. This does not mean t h a t
we manage advanced regeneration t h a t
i s composedof moderately t o heavily
infected ( i n f e c t i o n c l a s s e s 4-6)
(Hawksworth 1977) lodgepole pine o r
badly suppressed t o l e r a n t t r e e s with
1i t t l e o r no hope of r e l e a s e .
The concept i s t o remove a l l
moderately t o heavily infected lodgepole pine and favor heal thy, vigorous
nonhost s p e c i e s .
Some i naicators of manageabi 1i t y
in subalpine f i r and spruce advanced
regeneration include:
a.
Numerous c l e a r c u t s , some q u i t e
l a r g e , have contributed t o these
management d e c i s i o n s . The area rec e i ves very heavy r e c r e a t i o n use because of i t s proximity t o Ye1 lowstone
National Park. Therefore, any addit i o n a l even-aged regeneration c u t s
should be designed with small blocks
and i r r e g u l a r boundaries.
b.
Uninfected stands could be used
t o break up t h e e f f e c t of t h e c l e a r c u t blocks, and may be harvested usi ng individual t r e e and group s e l ect i o n . Use of t h i s combination ena b l e s s a l e of timber in an area
where c l e a r c u t t i n g of comparable
volumes o r acreages would no longer
c.
Good c u r r e n t height growth.
I t i s not reasonable t o expect
t r e e s under an overstory t o grow
a t the same r a t e t h a t they would
in a f r e e growing condition. In
e a s t e r n Montana, t r e e s t h a t have
been growing s i x inches o r more
in height annually f o r t h e p a s t
several y e a r s and appear healthy
and vigorous w i l l probably rel e a s e with overstory removal and
thinning.
Age. Guidelines f o r t h e Central
Rockies suggest t h a t 50 y e a r s
f o r subalpine f i r and 75 y e a r s
f o r spruce a r e t h e maximum ages
t o expect response t o r e l e a s e
and thinning (Roe e t a l . Undated).
Absence of d i s e a s e o r i n j u r y .
Diseased o r injured t r e e s of t o l erant species, particularly true
f i r s are n o t good r i s k s
as crop trees.
This concept should be a p p l i e d
o n l y by s i l v i c u l t u r i s t s experienced
i n t h e management o f t h e species i n volved and f a m i l i a r w i t h l o c a l v a r i a t i o n s . I f a D i s t r i c t Ranger o r
s i l v i c u l t u r i s t uses t h i s discussion
t o j u s t i f y t r y i n g t o manage a 100
y e a r old, badly suppressed t r u e fir
stand t h a t has l i t t l e hope o f s u r v i v a l , much l e s s release, they have
missed t h e p o i n t .
The second concept t h a t I would
l i k e t o s t r e s s i s t h a t dwarf m i s t l e t o e should be d i s c r i m i n a t e d a g a i n s t
a t every stand e n t r y . This does
n o t mean t h a t " t h e o n l y good dwarf
m i s t l e t o e - i n f e c t e d t r e e i s a dead
one," b u t i t does mean t h a t i n f e c t i o n c l a s s i s one o f t h e s t r o n g e s t
s e l e c t i o n c r i t e r i a i n intermediate
stand e n t r i e s .
LITERATURE CITED
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1975. I n s e c t s a f f e c t i n g lodgepole p i n e
p r o d u c t i v i t y . I n Management o f lodgepol e
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Baumgartner, ed. Coop. Ext. Serv., C o n .
Agric., Washington S t a t e Univ. , Pullman,
Wash., 495 p., i l l u s .
.
Anonymous.
1976. Forest Service Manual 2478.3.
Region 1 Supplement 190. U.S. Dep.
Agric., Forest Serv., Northern Region,
Hissoula, Mont.
Baranyay, J .A.
1975. Dwarf m i s t l e t o e as a f a c t o r i n t h e
management o f lodgepole pine f o r e s t s
i n Western Canada. I n Management o f
lodgepole p i n e ecosystems. Vol. 1,
David M. Baumgartner, ed. Coop. Ext.
Serv., C o l l Agric., Washington S t a t e
Univ., Pullman, Mash. 495 p., i l l u s .
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C r i t c h f i e l d , M.B.
1957. Geographic v a r i a t i o n o f Pinus
c o n t o r t a . t l a r i a Horrs Cabot Found.
Publ. 3, Harvard Univ., Cambridge,
Mass.
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