Management Strategies for Gambel Oak Communities

RANGELANDS11(5), October 1989
213
Management Strategies for Gambel Oak Communities
Chris L. Lauver, Donald A. Jameson, and Larry R. Rittenhouse
TheGambeloakcommunityusuallyoccurs asawoodlandvarying from small shrubsto medium-sized trees on
mountainfoothillrangesbetween thepinyon-juniperand
ponderosa pinezones.Maturestandsof oak are characterized by relatively dense clumps of trees rangingfrom
15-30 feet tall interspersed with manyopen spacesoccupied by shrubs, grasses, and forbs. These communities
contain usefulforage and wood productsas well as providing valuablewildlife habitat. Gambel oak is thedominantoverstoryspecies on about 9.3 millionacres ofrangeland in the southwesternUnited States (Kuchler 1964).
Over 90% of thisarea lies within the states of Colorado,
Utah, and Arizona (Harperet al. 1985). In southwestern
Colorado,the optimalelevation forGambel oakis 7,000to
9,000 feet. Gambel oak often achieves full tree form on
gentle to moderateslopes with relatively deep soils in
areas where about 20 inches of annual precipitation is
available (Brown 1958). The combination of ecological
aspects and management considerationsof Gambel oak
communitiespose a numberof interestingquestionsfor
natural resourcemanagers.
foliage as longas thesediets also containother nutritious
foragesthat are lower in tannin content than oak (Nastis
and Malechek 1981).
Fuelwood
Gambel oakwasoccasionallyused by early settlers for
firewood, but extensive harvesting of the species for
fuelwoodis limited (Harperetal.1985). Interest in useand
management of Gambel oak for fuelwood has recently
grownfora varietyof reasons. The use of oakwood,with
its superior heat-producingqualities, as a major home
energysourcebeganto increase during theenergycrises
of the 1970s (Wagstaff 1984). Increased demand, coupled
with large areas of oak communities,accessibleand in
close proximity to major populationcenters,has generated considerableinterestin management of thespecies
(Harper et al. 1985). Wagstaff (1984) found fuelwood
volumes in north-central Utah ranging from 6.5 to 130
cordsper acre of merchantable oak,and estimated retail
stumpage prices ranged from $20 to $425 per stocked
acre. Shuster(1984) reportedthat contractors paidup to
$9.60 per cord to thin mature Gambel oak stands in
southwestern Colorado. From these factors, Wagstaff
ManagementUses
(1984) concludedthat "Gambel oakcansuccessfullyand
Herbaceous Forage Production
economically be managed for fuelwood where markets
Productionof herbaceous foragefordomesticand wild exist and competitiveuses of the land are limited."
animalsin Gambeloakcommunitiesiscontrolledby precipitation andsite conditions.Several studieshaveshown
that herbaceous forage production can be up to several U 1080
times greater in the openings between Gambel oak ra
U,
900
clumps than oak canopies (Moinat 1956); this phenomena is particularly noticeable with young oak sprout
720
stands.As thesestandsmature and begintoexpress their
self-thinning characteristic(Brown 1958), they become 0
C540
more open, and herbaceous production may increase C-,
beneath the canopies.
Oak Foragefor Domestic Animal Use
Harper et al. (1985) reported that "cattle and sheep
utilize oakonlyafter the moredesirableplantspecies are
diminished."Goats, however, preferGambel oakfoliage
to other available forages when oak foliage is plentiful
(Davis etal. 1975).Several researchers have reportedthat
goats perform well on diets consisting mainly of oak
Authors are community ecologist, Kansas NaturalHeritageProgram,KansasBiological Survey,Lawrence66045; and professors.Departmentof Range
Science,Colorado StateUniversity,FortCollins 80523, respectively.Thework
was supported by the Colorado Agricultural Experiment Station Project
Number 15-012, whiletheseniorauthor was agraduate research assistantat
Colorado State University.
0)
C
-i-I
360
180
U,
0
5
15
25 35 45 55 65 75 85 95
Percent Oak C)ver
Immature stands
(6 and 10 years)
Older and mature stands
(26 and 80 years)
FIg. 1. Standing cropofherbaceousforage (lbs/acre) inmatureand
immature Gambel oak stands.
RANGELANDS11(5), October 1989
214
rlg.. uensesprowsor ramoei oa following complete removalofoakcrowns.
Wildlife Use
Gambel oakcommunitiesin Coloradoprovidevaluable
habitatfor wildlife, most notable as winter range for big
game animals. Since availabilityand condition of winter
ranges affect big game populations (Kufeld 1983), oakbrush communitiesplay an important role in big game
ecology. Because manyspecies of game and nongame
wildlife are dependentupon oak associations (Reynolds
etal. 1970),management strategies forGambeloakrangelands that contain prescriptionsfor maintaining or improvingthesevaluablehabitats are required.
ManagementControl Efforts
Much of the rangelandoccupied by the Gambel oak
type has excellent production potential of forage for
domesticlivestock;considerableefforts have been made
to clear and control oak on these ranges. A doubling of
forage production and a 60% increase in animal weight
gains per acre resulted from Gambel oak control in
southwestern Colorado(Marquiss 1972).Additionalbenefitsincludedincreased availabilityofforageandenhanced
livestock handling. However, benefits derived from any
control method are typically short-livedsince complete
eliminationof Gambel oak is rare. Oak is a natural partof
the vegetation.Creating open grasslands by removing
matureoak standsis a short-termremedy, and recurrent
treatments are necessary to control oak growth.
The majorproblemassociated with Gambel oakcontrol
isprolificsproutingthat occursfromoak roots, rhizomes,
and basalstems following treatment (Engle et al. 1983).
Treated ranges often develop a thicket-like appearance
that complicatesfuture control efforts. The productive
life-spanof most oak control projects is limited by rapid
and abundant resproutingthat follows treatment.
Methods of Oak Control
Fire—The extent and density of Gambel oak in westcentral Colorado has been influencedmore by fire than
by any other factor (Brown 1958). Although prolific
sproutingfollowing burningof oakstandshas been documented(Plummeret al. 1970), research has shownthat
Gambel oak sproutscan be limited by seeding competitive grasses following fire. Kufeld (1983) recommended
that "prescribedburningratherthan sprayingor chaining
be used to manage Gambel oakbrushrangelands for elk,
deer, and cattle."
Herbicides—Many studieshave shown herbicidesto be
ineffective in controlling Gambel oak both as a mature
plant and as a sprout. Applications of 2,4,5-T, 2,4,5-TP
(Silvex),and picloramareeffectivein killing Gambel oak
foliage. However, prolific sprouting following herbicide
applicationproducedlessdesirableranges thantheoriginal stands (Marquis 1973). Vallentineand Schwendiman
(1973) and Van Epps (1974) demonstrated nearly complete control of Gambel oak stems (with minimalsubsequent sprouting) with a mixture of picloram and Silvex,
and with fenuron, butthe applicationrates weretoohigh
to be economicallyacceptable.
In Texas, tebuthiuron has shown good control of oak
speciesassociated with Gambel oak.Scifreset al. (1981)
RANGELANDS11(5), October 1989
215
demonstrated 99% control of blackjackoak and post oak Gambel Oakand HerbaceousForage Relationships
3yearsaftera springtreatmentoftebuthiuron.TebuthiuThe relationshipamongoak cover, peak standingcrop
ron was also reportedto give good control over Harvard ofherbaceous forage,andoak standage in southwestern
oak(Jacobyetat. 1983),aspecies that is known to hybrid- Colorado is shown in Figure 1. For immature stands,
ize with Gambel oak. However, Bartel and Rittenhouse maximum forage production decreases with increasing
(1982) concluded that tebuthiuron should not be consi- oakcoverwhile the reverse is true with older and mature
dered an acceptable herbicide for controlling Gambel stands. Although all ages of oak stands have frequently
oak in southwesternColorado because of poor brush been treatedin thepast,thesefindingsshowthat age and
control andsevere damageto the herbaceous understory structureof Gambel oaksproutsand trees strongly influence productionof herbaceous foragearound them, and
following treatment.
Recentstudiesin southwesternColorado with glypho- suggest that stands of different age should be treated
ateand glyphosate:triclopyr-picloram combinationsshowed differently (Fig. 2 and 3).
excellent stem and plant kill of Gambel oak, and nearly
complete root-sproutsuppression for a minimum of five
years (Rittenhouse and Bartel 1986,unpublishedreport).
Treatmentcosts and damage to the understory may be
high with theseherbicide combinations.
MechanIcal ManipulatIon—Corn mon mechanical treatments used to break down oakbrush stands include
chaining, roller chopping, root plowing, brush raking,
and bulldozing. Chaining, probably the most popular
method, appears desirablewhen judged on a short-term
basis (Bartel and Sims 1978), but the prolific sprouting
that follows treatmentand resultsin dense thickets injust
a few years makes thiscontrol methodunsatisfactory.
BIologicalControl—Ina goat browsingstudy in southwesternColorado,Davis et al. (1975) reportedthat goats
could be effective in oakbrush control programs: "the
oakbrush mustfirst be treated mechanically to allow the
animalsfull access to all thefoliage" (Davis et al. 1975).
FIg. 3. An olderstandofGambel oak that has been thinned.
However, the use of goatsto control oakbrushis problematic. In theabsence of a viable market,useof goats is
impractical in many situations(Engleet al. 1983).
ManagementRecommendations
Because dense Gambel oak sprout stands in southA Colorado Study
westernColorado that are 6-10yearsof age reduceforproduction, we recommend that such stands, if
A study of Gambet oakwasconductedinsouthwestern age
treated, be only thinned to maintain less than 35-45%
ColoradoontheMancos District oftheSan JuanNational
averageoakcover. Thinningprograms shouldbedesigned
Forestand adjoining landsnearMar,cos, Colorado. Oak- to
promotegrowthoftheremainingstems and toresu It in
serviceberry and oak-herbaceous associations in the some forage increases for domestic and wild animals.
study areatypically have 2500-3500 oak stemsper acre, Spot treatments could be
advantageous on selected
most of which are less than 4 inches in diameter. Howof
dense sproutthickets (Vallentine and Schwenpatches
ever, Borman(1981) reportedup to 15,500stemsperacre diman
1973).
on recently roller-choppedareas.
In standsof 28-80 yearsofage, livestockaccess maybe
MatureGambel oakstandsthat had been mechanically enhanced
thinning to 45% average cover, but such
disturbed6, 10, and 28yearsago, and adjacentuntreated treatments by
will
not resultin increased forageproduction
standsestimated tobe 80yearsold, wereidentified inthe
However, thinning of older standsbelowcritical
(Fig.
1).
research area. These stands were sampled from early cover values
may result in vigorous sprouting and in a
June to late August in 1984 and 1985 for percent oak decrease of herbaceous
forage production. Additional
canopy cover with the use of a spherical densiometer research needs to be conducted to determine "safe"
(Lemmon 1956) and for peak standing crop of the her- lower
thinning levels for mature standsand critical indicabaceous forage(consideringonly thepalatable grass and tors for
a stand to be considered"mature."
forb species) by a double samplingtechnique(Carande
A
wood harvest is an alternativefor older mature
partial
and Jameson 1986). Sites weresampled for herbaceous stands that have accumulatedmarketable
fuelwood. A
peakstanding crop with 15 plots of 0.1 m2 within 11 oak partial harvest designed to maintain or
the
improve
coverclasses, rangingfrom0 to 99% on ungrazed sites. mature stand structure
be preferable to a complete
may
All forage production values reported are expressed as harvest that would most
likely returnthe areatoasproutoven-dryweights.
dominated community.Withcompleteharvestofamature
RANGELANDS11(5), October 1989
216
Gambel oak stand, resource managers would then need
to considerthinning the immaturestandsin the following
few years.
Need for an Integrated ManagementApproach
There are numerous reasonsfor advocating an integrated approachto management of Gambel oak rangelands. First is the recognitionthat control methodscurrently available to completely eradicate oak from its
native range are ineffective, costly, and largely result in
less desirable ranges in just a few years following single
applications.Secondly, a method of Gambel oak managementis needed that recognizes the advantages and
problems each kind of control treatment offers. Third,
Gambel oakcontrol programsshould bedirectedat longtermcontrol, in viewofthepersistence of oakin its native
range;thus, programsthat incorporateand evaluate multiplecontrol applicationsover time are desirable. Lastly,
management emphasis is shifting from destruction of
Gambel oakto investigationof inherentvalues associated
with rangelands whereGambel oakis a naturaldominant,
specifically In thearea of fuelwood management (Engle
et al. 1983,Wagstaff1984, Harperet al. 1985).
Manage. 25:146-150.
MarquIs., R.W.1973. Gambeloak control studies on SW.Colorado.
J. Range Manage. 26:57-58.
Molnat, AD. 1956. Comparativeyields of herbagefromoak scrub
and interspersedgrasslandin Colorado. Ecol. 37:852-854.
Nastis, A.S., and J.C.Malechek. 1981. Digestion and utilization of
nutrients in oak browseby goats. J. Animal Sci. 53:283-290.
Plummer, A.P., D.R. ChrIstensen,R. Stevens,and K.R. Jorgansen.
1970. Highlights, results, and accomplishments of game range
restoration studies. Utah Div. of Fish and Game, PubI. No.
70-3:26-30.
Literature Cited
Bartel, L.E.,andP.L. Sims.1978. EconomicconsiderationsforGambeloak rangelandconversioninsouthwesternColorado.Abstracts
of Papers. Soc. Range Manage. Annual Meeting.p. 30.
Bartel, L.E., and L.R. Rlttenhouse. 1982. Effects of tebuthiuron on
Gambel Oak and associated understory vegetation. Progress
Report, CSU Expt. Sta., Colorado State Univ., FortCollins.
Berman,N.M.1981. Influence ofGambeloak sprouts on understory
production in relation to habitat factor. MS. Thesis, Colorado
State Univ., Fort Collins. 60 pp.
Brown, H.E. 1958. Gambel oak In west-central Colorado. Ecology
39:317-327.
Engle,D.M., C.D.Bonham,andL.E. Bartel.1983. Ecologicalcharacteristics andcontrolofGambeloak.J.RangeManage. 36:363-365.
Harper, K.T., F.J. Wagstafl, and L.M. Kunzler. 1985. Biology and
management of the Gambel oak vegetative type: a literature
review. USDA Forest Service Gen. Tech. Report INT-179, Inter.
For. and Range Exp. Sta., Ogden, Utah.
Jacoby, P.W.,J.E. Slosser, and C.H. Meadors. 1983. Vegetational
responsesfollowing control andsand shinneryoak with tebuthiuron. J. Range Manage. 36:510-512.
Kuchier,A.W.1964. Potentialnatural vegetationofthe conterminous
United States.AmericanGeographySociety, Special Publication
36. New York, N.Y.
Kuleld, R.C.1983. Responsesofelk, mule deer, cattle, and vegetationto burning, spraying, and chaining of Gamboloak rangeland.
Colorado Division of Wildlife Tech. Pub. No. 34. Fort Collins,
Colorado.
Lemmon, P.E. 1956. A spherical densiometerfor estimating forest
overstory density. Forest Sci. 2:314-320.
Marqulss, R.W. 1972. Soil moisture, forage, and beef production
benefits from Gambel oak control in SW. Colorado. J. Range
Caranad.. V.,and D.A. Jameson.1986. Combination of weight estimateswith clipped sampledata. J. Range Manage. 39:88-89.
DavIs, GO., L.E. Bartel, and C.W. Cook. 1975. Control of Gambel
oak sprouts by goats. J. Range Manage. 28:216-218.
Reynolds,H.G.,W.P. Clary, and P.F. Ffolllot. 1970. Gambel oak for
southwesternwildlife. J. Forest.68:545-547.
Sclfres, C.J., J.W. Stuth,and R.W. Bovey. 1981. Control of oaks
(Quercusspp.)andassociatedwoody speciesonrangelandswith
tebuthiuron. Weed Sci. 29:270-275.
Shuster, W.C.1984.Oak thinningon the SanJuan National Forest.
Rocky Mountain Habitat Express. USFS P.O. Box 25127, Lakewood, CO 80225. 2 pp.
Vallentlne, J.R., and D. Schwendlman. 1973. Spot treatment for
Gambol oak control. J. Range Manage. 26:382-383.
Van Epps,GA.1974. Control ofGamboloak withthree herbicides.J.
Range Manage. 27:297-301.
Wagstaff,F.J. 1984. Economic considerations in use and management of Gambol oak for fuelwood. USDA, For. Serv.; Intermountam Forest and Range Experiment Station: Ogden, Utah. Gen.
Tech. Report INT-165.
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