Integrated timber and livestock systems (silvopastoral) are common in several regions of the United States. Grazing of three timber stands in eastern Nebraska showed no signs of tree damage due to rubbing or soil compaction. Steer gains were lower under the silvopastoral system compared to a typical pasture system (1.05 lb/day versus 1.70 lb/day). Growth of timber in silvopastoral stands was reduced (35.0 cubic feet per year versus 37.8 cubic feet per year); however, total productivity of the silvopastoral system (timber plus livestock) was greater ($20.98/acre) than with traditional timber systems

Brandle, James R.

Klopfenstein, Terry J.

Tiller, Jeremy

Wilson, Casey B.

English

DigitalCommons@University of Nebraska

University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln Nebraska Beef Cattle Reports Animal Science Department January 2005 Tree Growth and Cattle Weight Gain in a Ponderosa Pine System James R. Brandle University of Nebraska-Lincoln, jbrandle1@unl.edu Jeremy Tiller University of Nebraska-Lincoln Casey B. Wilson University of Nebraska-Lincoln Terry J. Klopfenstein University of Nebraska-Lincoln, tklopfenstein1@unl.edu Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr  Part of the Animal Sciences Commons Brandle, James R.; Tiller, Jeremy; Wilson, Casey B.; and Klopfenstein, Terry J., "Tree Growth and Cattle Weight Gain in a Ponderosa Pine System" (2005). Nebraska Beef Cattle Reports. 154. https://digitalcommons.unl.edu/animalscinbcr/154 This Article is brought to you for free and open access by the Animal Science Department at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Nebraska Beef Cattle Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. Page 21 — 2005 Nebraska Beef ReportTree Growth and Cattle Weight Gain in aPonderosa Pine System(Continued on next page)Jim R. BrandleJeremy T. HillerCasey B. WilsonTerry J. Klopfenstein1SummaryIntegrated timber and livestock sys-tems (silvopastoral) are common inseveral regions of the United States.Grazing of three timber stands in east-ern Nebraska showed no signs of treedamage due to rubbing or soil compac-tion. Steer gains were lower under thesilvopastoral system compared to atypical pasture system (1.05 lb/dayversus 1.70 lb/day). Growth of timberin silvopastoral stands was reduced(35.0 cubic feet per year versus 37.8cubic feet per year); however, total pro-ductivity of the silvopastoral system(timber plus livestock) was greater($20.98/acre) than with traditionaltimber systems.IntroductionSilvopastoral systems are de-fined as the intentional integrationof timber and livestock production.They are common in the pine for-ests of the southeastern UnitedStates, the conifer forests of thePacific northwestern United Statesand are used in a number of situa-tions in the Pine Ridge area ofnorthwestern Nebraska. Severalbenefits are associated with thepractice, foremost of which is thecash flow advantage of annual saleof cattle while the timber cropdevelops. In addition, there aredirect benefits to tree growth due tothe reduction in competitionbetween the trees and understoryvegetation for soil nutrients, water,and sunlight. Grazing is also acost-effective method of control ofthe understory vegetation withoutthe use of herbicides. From the for-age perspective, shade and lowerair temperatures tend to produce ahigher quality forage. Cattle havethe advantage of shade, reducinganimal stress due to high tempera-tures. There are, however, severalpotential disadvantages of silvo-pastoral systems. Foremost is theconcern of soil compaction and rootdamage due to grazing when thesoils are wet. Cattle can damagetrees by rubbing them, reducing thepotential timber value, especiallyon fine hardwoods such as blackwalnut. If a forest system is over-grazed, forest reproduction may bedamaged leading to a loss in forestdiversity over the long term. How-ever, with good management, cattleand timber production can be aprofitable enterprise providing bothshort-term cash flow from livestockproduction and long-term capitalgains from timber sales.The purpose of this study was todemonstrate the interaction of cattleand trees in silvopastoral systemslocated in eastern Nebraska. Estab-lished initially as a demonstrationsite, our goal was to assess damageto two tree plantations — a scotchpine stand (Pinus sylvestris L.) and agreen ash stand (Fraxinuspennsylvanica Marsh.) — by grazinglivestock. As the study progressed,little damage was seen in eitherplantation. In 1999 the decisionwas made to conduct a preliminarystudy on a ponderosa pine (Pinusponderosa P. & C. Lawson) stand todetermine the effect of grazing ontree performance. The study objec-tives were redefined and data ontree growth and cattle performancewere obtained and analyzed todetermine the impact of grazing ontree and livestock performance.Only tree performance data fromthe ponderosa pine plantation arereported here. Cattle performancewas based on the entire silvo-pastoral grazing period.ProcedureSite DescriptionThe study was conducted at theUniversity of Nebraska Agricul-tural Research and DevelopmentCenter (ARDC) Forestry Unit atMead, Nebraska. The soil is aSharpsburg silty clay loam with a1% to 2% slope. The site is approxi-mately nine acres and was plantedto ponderosa pine (Pinus ponderosaP. & C. Lawson) in 1986 as part of aregional provenance test. The trees(one-year-old container grownseedlings) were planted in six repli-cations on a 12-by-12-foot spacingin plots of 400 plants per replica-tion (approximately 1.5 acres perreplication). The site was sown totall fescue in 1988. Since then,smooth brome grass has invadedthe site and dominates most areaswithin the plantation. Replications1 to 4 were thinned in the winter of1997-98 following 10-year data2005 Nebraska Beef Report — Page 22collection for tree performance.Limited labor at the time restrictedthe ability to thin the remaining tworeplications, which were thinned inJanuary 2001. The trees removedwere selected based on tree perfor-mance and insect and disease resis-tance. The resulting stand is asavannah dominated by ponderosapine and a mix of cool seasongrasses. Beginning in late April2001, plots 1 to 4 were grazed by 6head of steers for 52, 32, and 42days in 2001, 2002, and 2003respectively (Table 1). Cattle con-tinued to be grazed on othersilvopastoral sites, when not onponderosa pine, from late Apriluntil early September of each year.Plots 5 and 6 were left ungrazed asa control.Data CollectionHeight and diameter at breastheight (DBH; 4.5 feet above theground) of the trees in all plots weremeasured following grazing in2001, 2002 and 2003. If multiplestems occurred below 4.5 ft, thediameters of all stems were mea-sured.Silvopastoral grazing (SPG)steers were managed in the samesystem as control cattle in everyyear of this study. The only differ-ences would be access to the SPGlocation during corn residue graz-ing and summer grazing. Controlsteers were a contemporary grouputilized for grazing systemsresearch in 2001 (2003 Nebraska BeefReport, pp. 65-68), 2002 and 2003(2005 Nebraska Beef Report, pp. 68-72). Control steers grazed smoothbrome grass from late April untilmid May and warm season nativerange from mid May until Septem-ber. Briefly, steers on the SPG studywere received in November,weaned and placed on corn residueand allowed access to the SPG loca-tion from December until late Febru-ary each year. Following cornresidue grazing steers were placedin a drylot until SPG grazing wasavailable. Following grazing, steersTable 1. Total grazing days for cattle on silvopastoral systems and the ponderosa pinesilvopastoral plot.Item 2001 2002 2003Ponderosa pine (days) 52   34   42Silvopastoral sites (days) 97 112 138Table 2. Revenue generated with silvopastoral systems compared to trees alone.2001a 2002a 2003aGrb UnGrc Grb UnGrc Grb UnGrcStem Vol. (ft3/acre)d 152.0 201.3 186.1 235.4 222.0 276.9Vol./year (ft3/acre)e 34.1 34.1 35.9 41.5Pulpwood ($/acre)f 23.16 30.67 28.35 35.86 33.82 42.18Rev. Incr.($/acre/year)g 5.19 5.19 5.47 6.32Cattle rev. ($/acre) 25.71 23.00 19.81Gr. Rev. Incr ($/acre)h — 23.00 18.96aTree measurements following grazing expressed as total amount.bGr (grazed) = Mean number of 66 Ponderosa pines per acre in the grazed plotcUnGr (ungrazed) = Mean number of 98 Ponderosa pines per acre in the ungrazed plotsdStem Vol. (volume) = stem only volumes calculated based on basal area and stemheighteVol. (volume)/year = increase in tree volume from previous year.fPulpwood prices are the value of pulpwood per acre per year assuming a one timecomplete harvest, based upon volume per acre and pine pulpwood ($19.50/128 cubicfeet) prices from the 2004 central timber market.gRevenue increase per year from tree growth calculated as ((Vol./year/128 cubic feet) x$19.50).hGr. Rev. Incr. (Gross revenue increase) = revenue increase per year over timber alone;value based on differences in growth each year.Table 3. Ponderosa pine stand characteristicsa.Item Grb SE UnGrc SE2001Trunk diameter (in) 7.2 0.8 6.8 0.9Tree height (ft) 21.5 2.2 23.6 2.2Basal Area (ft2/acre) 20.9 5.0 25.8 7.1Stem Vol. (ft3/acre)d 152.0 29.9 201.3 41.62002Trunk diameter (in) 7.7 0.9 7.1 1.0Tree height (ft) 22.9 2.1 24.9 2.4Basal Area (ft2/acre) 24.1 6.1 28.6 7.7Stem Vol. (ft3/acre)d 186.1 41.1 235.4 56.62003Trunk diameter (in) 8.17 1.0 7.6 1.1Tree height (ft) 24.2 2.6 25.9 2.4Basal Area (ft2/acre) 27.2 6.8 32.3 9.0Stem Vol. (ft3/acre)d 222.0 46.4 276.9 61.2aTree measurements following grazing expressed as total amount.bGr (grazed), Mean number of 66 Ponderosa pines per acre in the grazed plotcUnGr (ungrazed), Mean number of 98 Ponderosa pines per acre in the ungrazed plotsdStem Vol. (volume) stem only volumes calculated based on basal area and stem height(Tree Volume = (Tree Basal Area × Tree Height ÷ 3)were placed in the feedlot andfinished.Data AnalysisData were analyzed to determinemean DBH, mean tree height, andbasal area for each tree and for eachreplication. (Note: Basal area is thecross-sectional area of a tree at 4.5ft. and is a common forestry mea-sure of stand density.) In addition,stem volume per acre, stem volumeincrease per acre per year andPage 23 — 2005 Nebraska Beef Reportapproximate pulpwood value werecalculated. The stem volume gainswere compared within years andamong treatments using 2001 treemeasurements for each treatment asthe starting value for comparisons.Additional revenue generated withthe SPG steers was determined byevaluating the difference in eco-nomic value compared to the con-trol cattle each year, usingbreakeven calculations as describedin the 2001 Nebraska Beef Report, pp.29-34. Briefly, SPG final slaughterweights were multiplied by controlcattle breakeven. This resulted in asteer value for SPG steers. Follow-ing this calculation, all costs associ-ated with the SPG system exceptthose associated with grazing weresubtracted from steer value. Theamount remaining after costs wasthen divided by total SPG days.This allocated a dollar value to theSPG area on a per steer basis.ResultsThe analysis of tree responseshowed only small differences instem volume increase betweengrazed and ungrazed plots (Table2). While it is difficult to generalizethese data to the long-term case, asTable 4. Steer performance of silvopastoral and control cattle.2001 2002 2003Silvopastoral Control Silvopastoral Control Silvopastoral ControlWinterDays 154 154 141 141 135 135Initial wt, lb 526 527 567 565 512 514Daily gain, lb 1.61 1.41 1.74 1.50 1.79 1.83SummerDaysa 145 145 116 116 139 139Initial wt, lb 774 740 813 777 762 761Daily gain,lb 0.85 1.68 1.30 1.93 1.01 1.50FinishingDays 86 86 92 92 82 82Initial wt, lb 898 973 964 1002 903 970Daily gain, lb 5.22 4.5 4.81 4.24 4.74 4.30Final wt, lb 1351 1360 1418 1381 1292 1360Economic analysisBreak Even, $/cwt 64.11 64.97 63.26Grazing valueb, $/hd 47.53 78.88 65.33P. Pine valuec, $/acre 25.71 23.00 19.81aDays grazed on the silvopastoral grazing location may be different due to steer management.bGrazing value of the silvopastoral grazing location ((Silvopastoral final wt x Breakeven for control steers) - all cost, associated withsilvopastoral system (not including grazing) = Grazing value for the silvopastoral area).cP. Pine (Ponderosa Pine) value is the grazing value divided by total day on the ponderosa pine area.most tree growth response studiestypically run for a minimum of 10years and usually 20 to 50 years,some observations are appropriate.The initial differences (2001) intree dimensions between grazedand ungrazed plots is likely notrelated to grazing. The differencesin total tree growth (DBH, heightand basal area) between grazedand ungrazed plots (Table 3) maybe due to differences in thinningdates of ponderosa pine and mayreflect a delayed response todrought conditions during thestudy period. However, the changesin stem volume in 2002 and 2003are a valid evaluation of the impacton tree growth of cattle grazing insilvopastoral systems. The changesin stem volume per acre per yearwould suggest that grazing cattle inponderosa pine has limited impacton total tree growth.While there appears to be littledifference in tree growth among thegrazed and ungrazed plots, theeffects upon the cattle were greater.Daily gains were lower during thesummer grazing period when com-pared to control steers. The lowerdaily gains with the SPG systemmay be partially due to SPG pasturebeing dominantly cool seasongrasses. Cool season grass qualitywould decline during the warmsummer months. The increasedcompetition by the trees and grassfor moisture during the summermonths also may depress foragequantity and (or) quality. Controlsteers grazed warm season nativerange from late May until Septem-ber. The improved forage qualityduring warm summer months withwarm season grass may be respon-sible for the improved gain by con-trol steers; however, the SPG steergains were higher during the win-ter and feedlot periods when com-pared to control steers (Table 4).The SPG area may provide addedprotection that may benefit steerperformance during the corn resi-due grazing portion of winter.Additionally, feedlot daily gainshave been consistently higher fol-lowing SPG. This increased gainmay be compensation for thereduced summer gains. Breakevenaveraged $64.11/cwt, giving graz-ing values of about $47 to $79 in thetotal silvopastoral grazing area.The value of the ponderosa pinearea ranged from $20 to $26/acre.The lower daily gains duringsummer grazing are offset by timber(Continued on next page)2005 Nebraska Beef Report — Page 24growth on the SPG area. Whencomparing SPG to grazingunfertilized smooth brome pas-tures, there is a 50% reduction instocking rate. This reduction recog-nizes that unfertilized smoothbrome pasture would supply 80days grazing per steer per acre andthat SPG supplies 43 days grazingper steer per acre on average. Fluc-tuating the stocking density uti-lized under SPG systems may benecessary depending on the stageof tree development. It may be ben-eficial to alter stocking rates as thetree stand density changes. As treesmature, the stocking rates may needto be reduced as tree canopy den-sity increases, shading out thegrass. However, as stands arethinned, grass production increasesand stalking rate may be increasedaccordingly. Conducting grazing asit was in this study would not berecommended on trees less thanfive years old. Rapid grass removalmay be conducted on tree stands asyoung as three years of age withminimal tree damage; however, treespecies should be carefully evalu-ated prior to grazing.Based on the average yearly vol-ume increase of 37.8 cubic feet peracre with the ungrazed locationand a value of $19.50 per cord ofpulp wood (a cord is 128 cubic feet),we could expect an increase ingross return of $5.75 per acre peryear (average increase in grossreturn over two years). However,combining the annual income fromtree growth in the grazed areas andthe additional return from livestock,the silvopastoral grazing systemwould provide $20.98 per acre peryear additional income over timberstands alone (Table 3).1Jim R. Brandle, professor; Jeremy T.Hiller, graduate student, AgroForestry,Lincoln; Casey B. Wilson, researchtechnician, Terry J. Klopfenstein,professor, Animal Science, Lincoln.

Tree Growth and Cattle Weight Gain in a Ponderosa Pine System

UNL | Libraries

University of Nebraska - Lincoln 
DigitalCommons@University of Nebraska - Lincoln 
Nebraska Beef Cattle Reports Animal Science Department 
January 2005 
Tree Growth and Cattle Weight Gain in a Ponderosa Pine System 
James R. Brandle 
University of Nebraska-Lincoln, jbrandle1@unl.edu 
Jeremy Tiller 
University of Nebraska-Lincoln 
Casey B. Wilson 
University of Nebraska-Lincoln 
Terry J. Klopfenstein 
University of Nebraska-Lincoln, tklopfenstein1@unl.edu 
Follow this and additional works at: https://digitalcommons.unl.edu/animalscinbcr 
 Part of the Animal Sciences Commons 
Brandle, James R.; Tiller, Jeremy; Wilson, Casey B.; and Klopfenstein, Terry J., "Tree Growth and Cattle 
Weight Gain in a Ponderosa Pine System" (2005). Nebraska Beef Cattle Reports. 154. 
https://digitalcommons.unl.edu/animalscinbcr/154 
This Article is brought to you for free and open access by the Animal Science Department at 
DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in Nebraska Beef Cattle 
Reports by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. 
Page 21 — 2005 Nebraska Beef Report
Tree Growth and Cattle Weight Gain in a
Ponderosa Pine System
(Continued on next page)
Jim R. Brandle
Jeremy T. Hiller
Casey B. Wilson
Terry J. Klopfenstein1
Summary
Integrated timber and livestock sys-
tems (silvopastoral) are common in
several regions of the United States.
Grazing of three timber stands in east-
ern Nebraska showed no signs of tree
damage due to rubbing or soil compac-
tion. Steer gains were lower under the
silvopastoral system compared to a
typical pasture system (1.05 lb/day
versus 1.70 lb/day). Growth of timber
in silvopastoral stands was reduced
(35.0 cubic feet per year versus 37.8
cubic feet per year); however, total pro-
ductivity of the silvopastoral system
(timber plus livestock) was greater
($20.98/acre) than with traditional
timber systems.
Introduction
Silvopastoral systems are de-
fined as the intentional integration
of timber and livestock production.
They are common in the pine for-
ests of the southeastern United
States, the conifer forests of the
Pacific northwestern United States
and are used in a number of situa-
tions in the Pine Ridge area of
northwestern Nebraska. Several
benefits are associated with the
practice, foremost of which is the
cash flow advantage of annual sale
of cattle while the timber crop
develops. In addition, there are
direct benefits to tree growth due to
the reduction in competition
between the trees and understory
vegetation for soil nutrients, water,
and sunlight. Grazing is also a
cost-effective method of control of
the understory vegetation without
the use of herbicides. From the for-
age perspective, shade and lower
air temperatures tend to produce a
higher quality forage. Cattle have
the advantage of shade, reducing
animal stress due to high tempera-
tures. There are, however, several
potential disadvantages of silvo-
pastoral systems. Foremost is the
concern of soil compaction and root
damage due to grazing when the
soils are wet. Cattle can damage
trees by rubbing them, reducing the
potential timber value, especially
on fine hardwoods such as black
walnut. If a forest system is over-
grazed, forest reproduction may be
damaged leading to a loss in forest
diversity over the long term. How-
ever, with good management, cattle
and timber production can be a
profitable enterprise providing both
short-term cash flow from livestock
production and long-term capital
gains from timber sales.
The purpose of this study was to
demonstrate the interaction of cattle
and trees in silvopastoral systems
located in eastern Nebraska. Estab-
lished initially as a demonstration
site, our goal was to assess damage
to two tree plantations — a scotch
pine stand (Pinus sylvestris L.) and a
green ash stand (Fraxinus
pennsylvanica Marsh.) — by grazing
livestock. As the study progressed,
little damage was seen in either
plantation. In 1999 the decision
was made to conduct a preliminary
study on a ponderosa pine (Pinus
ponderosa P. & C. Lawson) stand to
determine the effect of grazing on
tree performance. The study objec-
tives were redefined and data on
tree growth and cattle performance
were obtained and analyzed to
determine the impact of grazing on
tree and livestock performance.
Only tree performance data from
the ponderosa pine plantation are
reported here. Cattle performance
was based on the entire silvo-
pastoral grazing period.
Procedure
Site Description
The study was conducted at the
University of Nebraska Agricul-
tural Research and Development
Center (ARDC) Forestry Unit at
Mead, Nebraska. The soil is a
Sharpsburg silty clay loam with a
1% to 2% slope. The site is approxi-
mately nine acres and was planted
to ponderosa pine (Pinus ponderosa
P. & C. Lawson) in 1986 as part of a
regional provenance test. The trees
(one-year-old container grown
seedlings) were planted in six repli-
cations on a 12-by-12-foot spacing
in plots of 400 plants per replica-
tion (approximately 1.5 acres per
replication). The site was sown to
tall fescue in 1988. Since then,
smooth brome grass has invaded
the site and dominates most areas
within the plantation. Replications
1 to 4 were thinned in the winter of
1997-98 following 10-year data
2005 Nebraska Beef Report — Page 22
collection for tree performance.
Limited labor at the time restricted
the ability to thin the remaining two
replications, which were thinned in
January 2001. The trees removed
were selected based on tree perfor-
mance and insect and disease resis-
tance. The resulting stand is a
savannah dominated by ponderosa
pine and a mix of cool season
grasses. Beginning in late April
2001, plots 1 to 4 were grazed by 6
head of steers for 52, 32, and 42
days in 2001, 2002, and 2003
respectively (Table 1). Cattle con-
tinued to be grazed on other
silvopastoral sites, when not on
ponderosa pine, from late April
until early September of each year.
Plots 5 and 6 were left ungrazed as
a control.
Data Collection
Height and diameter at breast
height (DBH; 4.5 feet above the
ground) of the trees in all plots were
measured following grazing in
2001, 2002 and 2003. If multiple
stems occurred below 4.5 ft, the
diameters of all stems were mea-
sured.
Silvopastoral grazing (SPG)
steers were managed in the same
system as control cattle in every
year of this study. The only differ-
ences would be access to the SPG
location during corn residue graz-
ing and summer grazing. Control
steers were a contemporary group
utilized for grazing systems
research in 2001 (2003 Nebraska Beef
Report, pp. 65-68), 2002 and 2003
(2005 Nebraska Beef Report, pp. 68-
72). Control steers grazed smooth
brome grass from late April until
mid May and warm season native
range from mid May until Septem-
ber. Briefly, steers on the SPG study
were received in November,
weaned and placed on corn residue
and allowed access to the SPG loca-
tion from December until late Febru-
ary each year. Following corn
residue grazing steers were placed
in a drylot until SPG grazing was
available. Following grazing, steers
Table 1. Total grazing days for cattle on silvopastoral systems and the ponderosa pine
silvopastoral plot.
Item 2001 2002 2003
Ponderosa pine (days) 52   34   42
Silvopastoral sites (days) 97 112 138
Table 2. Revenue generated with silvopastoral systems compared to trees alone.
2001a 2002a 2003a
Grb UnGrc Grb UnGrc Grb UnGrc
Stem Vol. (ft3/acre)d 152.0 201.3 186.1 235.4 222.0 276.9
Vol./year (ft3/acre)e 34.1 34.1 35.9 41.5
Pulpwood ($/acre)f 23.16 30.67 28.35 35.86 33.82 42.18
Rev. Incr.($/acre/year)g 5.19 5.19 5.47 6.32
Cattle rev. ($/acre) 25.71 23.00 19.81
Gr. Rev. Incr ($/acre)h — 23.00 18.96
aTree measurements following grazing expressed as total amount.
bGr (grazed) = Mean number of 66 Ponderosa pines per acre in the grazed plot
cUnGr (ungrazed) = Mean number of 98 Ponderosa pines per acre in the ungrazed plots
dStem Vol. (volume) = stem only volumes calculated based on basal area and stem
height
eVol. (volume)/year = increase in tree volume from previous year.
fPulpwood prices are the value of pulpwood per acre per year assuming a one time
complete harvest, based upon volume per acre and pine pulpwood ($19.50/128 cubic
feet) prices from the 2004 central timber market.
gRevenue increase per year from tree growth calculated as ((Vol./year/128 cubic feet) x
$19.50).
hGr. Rev. Incr. (Gross revenue increase) = revenue increase per year over timber alone;
value based on differences in growth each year.
Table 3. Ponderosa pine stand characteristicsa.
Item Grb SE UnGrc SE
2001
Trunk diameter (in) 7.2 0.8 6.8 0.9
Tree height (ft) 21.5 2.2 23.6 2.2
Basal Area (ft2/acre) 20.9 5.0 25.8 7.1
Stem Vol. (ft3/acre)d 152.0 29.9 201.3 41.6
2002
Trunk diameter (in) 7.7 0.9 7.1 1.0
Tree height (ft) 22.9 2.1 24.9 2.4
Basal Area (ft2/acre) 24.1 6.1 28.6 7.7
Stem Vol. (ft3/acre)d 186.1 41.1 235.4 56.6
2003
Trunk diameter (in) 8.17 1.0 7.6 1.1
Tree height (ft) 24.2 2.6 25.9 2.4
Basal Area (ft2/acre) 27.2 6.8 32.3 9.0
Stem Vol. (ft3/acre)d 222.0 46.4 276.9 61.2
aTree measurements following grazing expressed as total amount.
bGr (grazed), Mean number of 66 Ponderosa pines per acre in the grazed plot
cUnGr (ungrazed), Mean number of 98 Ponderosa pines per acre in the ungrazed plots
dStem Vol. (volume) stem only volumes calculated based on basal area and stem height
(Tree Volume = (Tree Basal Area × Tree Height ÷ 3)
were placed in the feedlot and
finished.
Data Analysis
Data were analyzed to determine
mean DBH, mean tree height, and
basal area for each tree and for each
replication. (Note: Basal area is the
cross-sectional area of a tree at 4.5
ft. and is a common forestry mea-
sure of stand density.) In addition,
stem volume per acre, stem volume
increase per acre per year and
Page 23 — 2005 Nebraska Beef Report
approximate pulpwood value were
calculated. The stem volume gains
were compared within years and
among treatments using 2001 tree
measurements for each treatment as
the starting value for comparisons.
Additional revenue generated with
the SPG steers was determined by
evaluating the difference in eco-
nomic value compared to the con-
trol cattle each year, using
breakeven calculations as described
in the 2001 Nebraska Beef Report, pp.
29-34. Briefly, SPG final slaughter
weights were multiplied by control
cattle breakeven. This resulted in a
steer value for SPG steers. Follow-
ing this calculation, all costs associ-
ated with the SPG system except
those associated with grazing were
subtracted from steer value. The
amount remaining after costs was
then divided by total SPG days.
This allocated a dollar value to the
SPG area on a per steer basis.
Results
The analysis of tree response
showed only small differences in
stem volume increase between
grazed and ungrazed plots (Table
2). While it is difficult to generalize
these data to the long-term case, as
Table 4. Steer performance of silvopastoral and control cattle.
2001 2002 2003
Silvopastoral Control Silvopastoral Control Silvopastoral Control
Winter
Days 154 154 141 141 135 135
Initial wt, lb 526 527 567 565 512 514
Daily gain, lb 1.61 1.41 1.74 1.50 1.79 1.83
Summer
Daysa 145 145 116 116 139 139
Initial wt, lb 774 740 813 777 762 761
Daily gain,lb 0.85 1.68 1.30 1.93 1.01 1.50
Finishing
Days 86 86 92 92 82 82
Initial wt, lb 898 973 964 1002 903 970
Daily gain, lb 5.22 4.5 4.81 4.24 4.74 4.30
Final wt, lb 1351 1360 1418 1381 1292 1360
Economic analysis
Break Even, $/cwt 64.11 64.97 63.26
Grazing valueb, $/hd 47.53 78.88 65.33
P. Pine valuec, $/acre 25.71 23.00 19.81
aDays grazed on the silvopastoral grazing location may be different due to steer management.
bGrazing value of the silvopastoral grazing location ((Silvopastoral final wt x Breakeven for control steers) - all cost, associated with
silvopastoral system (not including grazing) = Grazing value for the silvopastoral area).
cP. Pine (Ponderosa Pine) value is the grazing value divided by total day on the ponderosa pine area.
most tree growth response studies
typically run for a minimum of 10
years and usually 20 to 50 years,
some observations are appropriate.
The initial differences (2001) in
tree dimensions between grazed
and ungrazed plots is likely not
related to grazing. The differences
in total tree growth (DBH, height
and basal area) between grazed
and ungrazed plots (Table 3) may
be due to differences in thinning
dates of ponderosa pine and may
reflect a delayed response to
drought conditions during the
study period. However, the changes
in stem volume in 2002 and 2003
are a valid evaluation of the impact
on tree growth of cattle grazing in
silvopastoral systems. The changes
in stem volume per acre per year
would suggest that grazing cattle in
ponderosa pine has limited impact
on total tree growth.
While there appears to be little
difference in tree growth among the
grazed and ungrazed plots, the
effects upon the cattle were greater.
Daily gains were lower during the
summer grazing period when com-
pared to control steers. The lower
daily gains with the SPG system
may be partially due to SPG pasture
being dominantly cool season
grasses. Cool season grass quality
would decline during the warm
summer months. The increased
competition by the trees and grass
for moisture during the summer
months also may depress forage
quantity and (or) quality. Control
steers grazed warm season native
range from late May until Septem-
ber. The improved forage quality
during warm summer months with
warm season grass may be respon-
sible for the improved gain by con-
trol steers; however, the SPG steer
gains were higher during the win-
ter and feedlot periods when com-
pared to control steers (Table 4).
The SPG area may provide added
protection that may benefit steer
performance during the corn resi-
due grazing portion of winter.
Additionally, feedlot daily gains
have been consistently higher fol-
lowing SPG. This increased gain
may be compensation for the
reduced summer gains. Breakeven
averaged $64.11/cwt, giving graz-
ing values of about $47 to $79 in the
total silvopastoral grazing area.
The value of the ponderosa pine
area ranged from $20 to $26/acre.
The lower daily gains during
summer grazing are offset by timber
(Continued on next page)
2005 Nebraska Beef Report — Page 24
growth on the SPG area. When
comparing SPG to grazing
unfertilized smooth brome pas-
tures, there is a 50% reduction in
stocking rate. This reduction recog-
nizes that unfertilized smooth
brome pasture would supply 80
days grazing per steer per acre and
that SPG supplies 43 days grazing
per steer per acre on average. Fluc-
tuating the stocking density uti-
lized under SPG systems may be
necessary depending on the stage
of tree development. It may be ben-
eficial to alter stocking rates as the
tree stand density changes. As trees
mature, the stocking rates may need
to be reduced as tree canopy den-
sity increases, shading out the
grass. However, as stands are
thinned, grass production increases
and stalking rate may be increased
accordingly. Conducting grazing as
it was in this study would not be
recommended on trees less than
five years old. Rapid grass removal
may be conducted on tree stands as
young as three years of age with
minimal tree damage; however, tree
species should be carefully evalu-
ated prior to grazing.
Based on the average yearly vol-
ume increase of 37.8 cubic feet per
acre with the ungrazed location
and a value of $19.50 per cord of
pulp wood (a cord is 128 cubic feet),
we could expect an increase in
gross return of $5.75 per acre per
year (average increase in gross
return over two years). However,
combining the annual income from
tree growth in the grazed areas and
the additional return from livestock,
the silvopastoral grazing system
would provide $20.98 per acre per
year additional income over timber
stands alone (Table 3).
1Jim R. Brandle, professor; Jeremy T.
Hiller, graduate student, AgroForestry,
Lincoln; Casey B. Wilson, research
technician, Terry J. Klopfenstein,
professor, Animal Science, Lincoln.


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Tree Growth and Cattle Weight Gain in a Ponderosa Pine System

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