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Growth of southern pines at Growth of southern pines at different stand configurations different stand configurations
in silvopastoral practicesin silvopastoral practices Adrian Ares, David K. Brauer, Adrian Ares, David K. Brauer, David M. Burner and Daniel H. PoteDavid M. Burner and Daniel H. Pote
Dale Bumpers Small Farms Research Center Dale Bumpers Small Farms Research Center Agriculture Research ServiceAgriculture Research Service U.S. Department of AgricultureU.S. Department of Agriculture
Tree growth in agroforestry (AF) Tree growth in agroforestry (AF) standsstands
Lack of reliable growth and yield data for AF practices can make economic predictions uncertain and hinder adoption
Growth models for forests may not apply to AF systems because of spacing and configuration effects
Single-rowSingle-rowconfigurationconfiguration
Double-rowDouble-rowconfigurationconfiguration
Some research approachesSome research approachesConstant initial stand density Varied: Configuration (S, D, T, Q-row) Alley width Distance between trees within rowsConstant alley width Varied: Configuration Initial stand density Distance between trees within rowsComparison with stands/plots planted in forest-
type arrangements
Location of pine agroforestry studies Location of pine agroforestry studies
Gulf of Mexico
45 yr-old AF stand in Georgia45 yr-old AF stand in Georgia
Stand age (year)0 10 20 30 40 50
Bas
al a
rea
(m2 /
ha)
0
5
10
15
20
25
Liv
esto
ck g
ain
s (k
g/h
a)
0
100
200
300
262 trees/ha731 trees/ha
731 trees/ha
262 trees/ha
Basal area and livestock gainsBasal area and livestock gains
Drawn from Lewis et al., 1985
Basal area (m2/ha)
5 10 15 20 25 30 35 40
Wo
od
vo
lum
e (m
3 /h
a)
0
30
60
90
120
150
180
Can
op
y co
ver
(%)
0
20
40
60
80
100Wood volumeCanopy cover
Basal area and canopy coverBasal area and canopy cover
Northern Florida, slash pine, 1135 trees/haNorthern Florida, slash pine, 1135 trees/ha
Bas
al a
rea
(m2 /
ha)
0
5
10
15
20
2513-yr-old 18-yr-old
Single-row Double-row
Alley width (m) 7.3 14.6 7.3 12.2 26.7
Ba
sa
l a
rea
(m2/h
a)
0
5
10
15
20
2513-yr-old 32-yr-old
Configuration
(1.2 x 2.4) 12.2 m (0.6 x 2.4) 26.7 m
Central Florida, slash pine, 1135 trees/haCentral Florida, slash pine, 1135 trees/ha
Central Louisiana, 18 yr-old stands, 1165 trees/haCentral Louisiana, 18 yr-old stands, 1165 trees/ha
Bas
al a
rea
(m2 /
ha)
0
10
20
30
Loblolly pine Slash pine
Single row Triple row6.7-m alley 15.2-m alley
Configuration Spacing Basal area (m2/ha) 2002 2003 2004
Double- (1.20 x 2.40) 7.20 m 22.9 28.4 33.4 row Quadruple- (1.20 x 2.40) 16.0 m 19.1 23.3 27.5 row
Western Arkansas, 11-yr-old loblolly Western Arkansas, 11-yr-old loblolly pine stands,1541 trees/hapine stands,1541 trees/ha
Basal are
a (
m2 /h
a)
0
10
20
30
40
50
60
Single- row
Double- row
Quadruple- row
Stand density (trees/ha)
908547306
Central Arkansas, 18-yr-old loblolly pine Central Arkansas, 18-yr-old loblolly pine stands,14.6-m alley widthstands,14.6-m alley width
300 600 900 1200 1500
Basal are
a (
m2/h
a)
10
20
30
40
50
Forest standsSilvopastoral single-row Silvopastoral double-row Silvopastoral quadruple-row
Stand density (Trees/ha)300 600 900 1200 1500
10
20
30
40
50Forest standsSilvopastoral double-rowSilvopastoral quadruple-row
Comparisons Comparisons between between loblolly pineloblolly pinebasal area inbasal area insilvopastures silvopastures and adjacent and adjacent forestsforests
Central Central Arkansas,Arkansas,18-yr-old18-yr-old
Western Western Arkansas,Arkansas,11-yr-old11-yr-old
ConclusionsConclusions
Stand basal area in silvopastures appear to equal or surpass that of forest stands
Research favors single and double-row configurations in silvopastures
Other aspects of silvopastures such as biomass partitioning, bole diameter distribution and wood quality deserve further examination
Biomass partitioningBiomass partitioning
Carbon partitioning to tree components is linked to timber production, tree function and ecosystem C stores
Patterns of C partitioning extensively studied in loblolly pine in natural stands and plantations but not in AF systems
AF configurations may greatly modify biomass partitioning
2.4 m
14.6 m14.6 m
2.4 m
Single Double QuadrupleN(308 trees/ha) (568 trees/ha) (932 trees/ha)
Felled trees separated into stem, branch, twigs (< 2 cm in diameter) and foliage
Sixty sampled trees(3 per row x 5 rows x 2 pruning x 2 replicates)
Sampling designSampling design
2.1 m
Configuration Row Pruning DBH Height to Total Log
1st branch height quality
(cm) (m) (m) (0-4)
Single
Double
Quadruple
Yes 27.9 4.7 13.7 2.2
No 28.6 2.8 13.1 0.5
1 Yes 27.7 4.6 13.6 2.2
No 26.9 4.0 13.6 1.0
2 Yes 28.2 5.9 13.1 1.8
No 26.3 3.9 13.2 1.0
1 Yes 27.5 5.6 14.2 1.8
No 27.3 4.3 13.2 0.3
2 Yes 25.6 7.4 13.4 1.5
No 25.0 6.4 13.6 1.5
Tree characteristics in different configurationsTree characteristics in different configurations
Configuration Stem Branch Twig Foliage Leaf Area
Configuration (C)
Row (R)
Pruning (P)
C x R
C x P
R x P
* ns ns *** *
* * ns ns ns
ns ns ns ns ns
ns ns ns *** ***
ns ns ns ns ns
ns ns ns ns ns
DBH and growing space not significant as covariates
Effects of configuration on biomass partitioningEffects of configuration on biomass partitioning
P
erc
en
tag
e o
f t
ota
l a
bo
ve
gro
un
d
bio
ma
ss
0
25
50
75
100
StemBranchTwigFoliage
Single Double Quadruple-row
Row 1 Row 2 Row 1 Row 2
P NP P NPP NP P NP P NP
12.5% 8.1%
51.3%
62.8%
30.3%23.6%
Biomass in tree componentsBiomass in tree components
Configuration Row Age Stocking % partitioning to yrs trees/ha Bole Branches Foliage Single- 18 308 51.5 35.8 12.7 row Double- 1 18 568 54.0 36.1 9.9 row 2 59.1 29.4 11.5 Quadruple- 1 18 932 58.2 32.3 9.5 row 2 62.5 28.9 8.6 Adjacent 19 983 79.0 18.8 2.2 forest Ku and 18 n/a 83.1 13.5 3.4Burton (1973) 18 81.6 14.9 3.5
Biomass partitioning in Biomass partitioning in silvopastures and forestssilvopastures and forests
This study
ConclusionsConclusionsConsiderable extent of ontogenetic control
in loblolly pine in AF plantationsDifferences up to 11% in biomass
partitioning to stems and up to 7 % to branches
Possible need for allometric functions for agroforestry pine stands (e.g., single, double-row configurations)
Wood qualityin AF stands ?
AcknowledgmentsAcknowledgmentsEarl Hardin, Tammy Horton, Jim Misner, Mike
Rogers and Jim Whiley for technical assistance
Roy Clardy, Teri Clason, Paul Eberhard, David Haywood, Cliff Lewis, Henry Pearson, USDA Forest Service and Winrock International for granting access to data and study sites
ARS/USDA for financial support