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