forestry & society silviculture hort/rgsc 302 j.g. mexal fall 2005

Forestry & Society

Silviculture

HORT/RGSC 302

J.G. Mexal

Fall 2005

Forestry & Society

Silviculture/Outline

• Allowable Cut Effect• Site Index (SI)• Regeneration• Stocking• Thinning

• Fertilization• Competition Control• Pruning• Wood Quality• Agroforestry

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Allowable cut/ Kimmins

Allowable Cut = 1/6/decade

Function of: site index, silviculture, tree improvement, rotation age

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Site Index• Site Index is a measure of site productivity

and refers to the height of dominant and codominant trees in even-aged stands at a particular index age, usually 25, 50, or 100 years.

• Site Index is a function of environmental factors (soil depth, rainfall, tree species, growing season).

Forestry & Society

Silviculture - Site Quality/ Spurr 1964

Sandy loam Clay loam Heavy Clay

Forestry & Society

Silviculture - Site Index/ Spurr 1964

Height (ft)Pine - Finland

SI100

SI50

SI25Cladina type

Calluna typeVaccinium typeMyrtillus type

Forestry & Society

Site Index (SI50)/Wenger 1984

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100

SI 60

SI 80

SI 100

SI 120

Years

Height (ft)

Loblolly pine

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100

SI 60

SI 80

SI 100

SI 120

Douglas-fir in WA

Forestry & Society

Site Index (SI50)/Wenger 1984

0

20

40

60

80

100

120

140

160

180

0 20 40 60 80 100

SI 40SI 60SI 80SI 100SI 40SI 80SI 120

Years

Height (ft)

Ponderosa pine in CA

SI50SI100

Forestry & Society

Silviculture/Site Quality/ Schultz 1997

SouthwideFlatwoods (heavy clay)

Plantation age (yrs)

Southern Pines

SI25

Forestry & SocietySilviculture/DBH vs Hgt & Biomass -Shepherd1986

0

40

80

120

160

200

240

280

10 12 14 16 18 20

Biomass (kg)DBH

Biomass (kg)

Height (m)

24

20

16

12

8

4

DBH (cm)

Pinus radiata- NZ-16 yr plantation

50 60 70 80

Site Index

Dry Weight (ton/ac) Age

Needles

Branches

Total

Forestry & Society

Silviculture/Site Quality vs Biomass Distribution/Tree Physiol. 3:42:1987

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Forestry & Society

Silviculture/Natural Regeneration

Time

2,000,000

200,000

20,000

2,000

200

No./ha Volume Growth (m3/ha/yr)

5

10

15

20

Forestry & Society

Silviculture/Artificial Regeneration

Time

2,000,000

200,000

20,000

2,000

200

No./ha Volume Growth (m3/ha/yr)

5

10

15

20

Forestry & Society

Silviculture/Clearcut does not eliminate species (necessarily)/ Bettis, 9th So.Silv.Res.Conf.

0

300

600

900

1200

1500

1800Clearcut (leave <6' tallSilvi-cut (cut<6'tall)Herb or Fell & Burn

Planted 600 tpa

Stems/acre

Pine

Oak Ridge, TN

Forestry & Society

Silviculture/Clearcut does not eliminate species (necessarily)/J.For. 24(1)37-44:2000

0500

1000150020002500300035004000

Clearcut & PlantFell,Burn & PlantSeed Tree

Stems/acre Coastal Plain, AL

*

*

Planted 300 tpa

Forestry & Society

Silviculture/Change is Inevitable /Mich. Forest Ecology 1964

0

50

100

150

200

250

300

350

1930 1935 1940 1945 1950 1955 1960 1965

Sugar maple Red maple Red oakPaper birch Yellow birch Aspen

Trees/acre B.A. ft2/ac

0

10

20

30

40

50

60

70

1930 1935 1940 1945 1950 1955 1960 1965

Forestry & Society

Silviculture/ Change is Inevitable Forest Ecology, 1964

02468

101214161820

1922 1924 1927 1932 1938 1945 1948

100 largestOthersDied-1948Died-1938Died-1927Died-1924

Year

DBH (in)

D D D D

Pseudotsuga menziesii - NZ

Forestry & Society

Old Orchard Plantation (NC)/Pinus strobus

March1899 April 1999thinned

J. For. 98:18-23:2000

0

50

100

150

200

250

300

0 20 40 60 80 100 120

SI 75SI 56SI 71-thinned

SI 75SI 56

SI 71 thinned

BA (ft2/ac)

Years

Forestry & Society

Old Orchard Plantation (NC)/Pinus strobus

Plot Density (trees/ac)

Height (ft)

DBH (in)

Gross Vol. (ft3/ac)

SI50 56 unthinned

280 107 12.9 20,217 (86%)1

SI50 75 unthinned

168 122 17.2 28,070 (80%)

SI50 71 thinned

88 124 20.9 24,514 (73%)

1 % = % standing volume (gross volume less removals and mortality)

Forestry & SocietyConversion from Even-Aged to Uneven-Aged/

GTR SO 118, 1996

Southern Pine - 50 yrs old

Removed 2,114 b.f.Reproduction

DBH (in) DBH (in)

Before

After

Forestry & SocietyConversion from Even-Aged to Uneven-Aged/

GTR SO 118, 1996

Southern Pine - 50 yrs old

ReproductionReproduction

Forestry & Society

Silviculture/Changing Harvest Strategies/

USFS SO-112, 1994

Year Uneven Aged Manaement

(ac/yr)

Even Aged Management

(ac/yr) 1967-1988 0 12,800

1988-1992 2,876 4,890

Ouachita Nat’l For. Harvested AcresClearcut

Forestry & Society

Silviculture/Changing NFS Harvest Strategies/ Policy Studies J. 23:274:1995

0%

20%

40%

60%

80%

100%

1984 1985 1986 1987 1988 1989 1990 1991

Selection cutEven-aged cutClearcut

Forestry & Society

Silviculture/Harvest Marking Costs / USFS SO-112, 1994

0

1

2

3

4

5

Commercialthinning

Single-treeselection

Shelterwood Clearcut

SuppliesLabor

$/100 ft3

Southern Pines/ Ouachita N.F. AR

Harvesting Method

Forestry & Society

Silviculture/Harvest Costs / SJAF 18:168-174:

0

5

10

15

20

25

30

35

Single-treeselection

Shelterwood Clearcut

$/CCF

Southern Pines/ Ouachita N.F. AR

Harvesting Method

Cable SkidderGrapple Skidder

Felling

Forestry & Society

Silviculture/Thinning Method vs Damage/WJAF 15:27-33:2000

0

2

4

6

8

10

12

50-55 tpa 110-120 tpa 110-120 patch

SkylineTractorCut-to-LengthHelicopter

Residual Stand (tpa)

Scar Area (ft2/ac)

Pseudotsuga menziesii- OR

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Forestry & Society

Silviculture/ Stocking affects Growth/ Shepherd 1986

0

10

20

30

40

50

0 500 1000 1500 2000 2500 3000

Eucalyptus grandis-4 yr

Pinus radiata-15 yr

Basal Area

DBH

Stocking (trees/ha)

DBH (cm) or BA (m2/ha)

Forestry & Society

Silviculture/ Stocking affects Growth/ USDA Hndbk 713, 1997

0

5

10

15

20

25

0 1000 2000 3000 4000 5000 6000 7000

10 yrs14 yrs20 yrs

Trees/ha

DBH (cm)

Pinus taeda

Forestry & SocietySilviculture/ Stocking affects Biomass Distribution/ Shepherd 1986

0%

20%

40%

60%

80%

100%

550 1070 2200 4330

Stocking (trees/ha)

Twigs + needlesBranchesStembar,Stemwood

92127

171190

(tons/ha)

Pinus resinosa- (27 yrs)

k

Forestry & SocietySilviculture/ Stocking affects Biomass Distribution/ Shepherd 1986

Pinus resinosa- (27 yrs)

2.4m1.7m 1.2m 1.0m

Trees/ha

550 1070 2220 4330

crowndiameter

170 kg 120 kg 80 kg 40 kgBiomass

Forestry & SocietySilviculture/ Stocking affects Volume Growth/

Shepherd 1986

0

5

10

15

20

25

30

35

0 10 20 30 40 50 60

15-17 yrs20-23 yrs27-31 yrs

Basal Area (m2/ha)

Volume growth (m3/ha) Pinus radiata- NZ

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Forestry & Society

Silviculture/Weed Control & Fertilization/ New For. 14:233:’97

y = 19.29 - 0.006x

R2 = 0.82

y = 47.09 - 0.015x

R2 = 0.78

0

10

20

30

40

50

0 500 1000 1500 2000 2500

FertilizedNot Fertilized

Herbaceous Cover (kg/ha)

Tree Volume (m3)

Forestry & SocietySilviculture/Fertilization/ Shepherd 1986

0

1

2

3

4

Nil N (200 kg/ha) P (125 kg/ha) N + P

Fertilizer Regime

Height (m)

Pinus radiata - 3.5 yr)

Ponderosa pine growth after 31 yrs vs competition/PSW-RP-231, ‘97

Survival = 99%DBH = 7.8 cmCover = 24,000 ft2/acPine cover = 100%



Survival = 81%DBH =2.148 cmCover = 33,150 ft2/acPine cover = 12%

Forestry & SocietySilviculture/Fertilization + Weed Control/

Shepherd 1986

0

1

2

3

4

Nil Herbicide N + P Herb. + NP

Fertilizer Regime

Height (m)

Pinus radiata - NZ(4 yr)

Forestry & SocietySilviculture/Fertilization + Weed Control/

Shepherd 1986

0

1

2

3Nil P

N+P N+P+K

Height (m)Pinus radiata - NZ(4 yr)

Forestry & SocietySilviculture/Fertilization vs Growth/ Schultz 1997

0

5

10

15

20

25

30

Control Cultivation Cultivation +NPK

Cultivation+2NPK

Cultivation +4NPK

Loblolly

Longleaf

Slash

DBH (cm)Southern Pines

Forestry & SocietySilviculture/ Stocking affects Volume Growth/

PNW-RP-513, 1999

0

300

600

900

1200

1500

24201714119

Treatment (initiated @ Age 9)

Volume (cu ft)

Douglas-fir-ORPlantation age

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Forestry & Society

Piece Size vs Value/Barbour, USFS-1999

0

10

20

30

40

50

0 2 4 6 8 10 12 14 16

8 foot log small end diameter (in)

Value/log ($)

veneer

lumber

pulpfuel

Forestry & Society

Product vs Value

0

3

6

9

12

15

18Initial 3 yr Growth

Forestry & Society

Silviculture/Pruning vs Diameter Growth/ Shepherd 1986

DBH (cm)

Yr-6 Yr-7 Yr-8 Yr-9Pruning Year

C C C CP P P P

52%

40%32%

26%

% pruned

Pinus radiata/NZ

Forestry & Society

Silviculture/Pruning vs Clear wood/ Shepherd 1986

Pinus radiata/NZ7

6

5

4

3

2

1

1st lift

2nd lift

3rd lift

010 1020 20Diameter from center (cm)

Height (m)

Clearwood zone

Knotty core

Forestry & Society

Silviculture/Management Affects Runoff /Erosion in Alabama Grace, JSoilWaterConsv 59:160:04

y = 6.2019Ln(x) - 15.129

R2 = 0.60

y = 3.3811Ln(x) - 10.205

R2 = 0.47

0

5

10

15

20

25

0 50 100 150 200 250 300

Control- runoff

Harvested-runoff

Rainfall event (mm)

Runoff (mm)

Forestry & Society

Silviculture/Management Affects Runoff /Erosion in Alabama Grace, JSoilWaterConsv 59:160:04

0

0.04

0.08

0.12

0.16

0.2

0 50 100 150 200 250 300

Control-erosion

Harvested-erosion

Rainfall event (mm)

Erosion (t/ha)

ErosionControl = 0.07 t/ha/yr (20 mo) Clearcut = 0.8 t/ha/yr (20 mo)

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Forestry & Society

Agroforestry- Windbreaks/ Spurr 1964

H/R 302 Forestry & SocietyAgroforestry Systems/ Clason & Robinson JF98:2000

Yr 20520 tpa

BA = 209 ft2

Ht = 58’DBH = 8.6 “

250 tpa27 cords/ac

Yr 25100 tpa

3 cords +1,600 BF/ac

Yr 3050 tpa1 cords +2,100 BF/ac

Yr 350 tpa1 cords +3,100 BF/ac

Yr 2550 tpa3 cords +2,000 BF/



100 tpa33 cords/ac

Silvopasture

Silviculture

+ 1 - 4 tons forage/ac/yr

Establishment costs of pasture = $260-$470/ac @ yr 20Annual fertilizer application ($60/ac/yr) to pasture also increases wood yield

0

3

6

9

12

15

18

1986 1988 1990 1992 1994 1996 1998

Control-grazedVelpar-fencedControl-fencedSeeded-grazed

H/R 302 Forestry & SocietyAgroforestry Systems/PSW-RP-242, 1999

Year

Height (ft) Ponderosa pine, CA

Forestry & Society

Silviculture/Foliage Biomass vs Height/ Shepherd 1986

0

10

20

30

40

50

60

0 5 10 15 20 25 30

Height (m)

Needle/total biomass (%)

Forestry & Society

Silviculture/Foliage Biomass vs Age/ Shepherd 1986

0

5

10

15

20

25

30

0 10 20 30 40 50 60

Pinus radiataPinus sylvestrisEucalyptus grandisCryptomeria japonica

Plantation Age (yrs)

Foliage Biomass (t/ha)

Forestry & Society

Silviculture/Review Questions

• Define: allowable cut, site index, BA, rotation age, false ring, clear cut

• Describe different silvicultural practices (e.g. fertilization, weed control, etc), their uses and forest response.

• What is the -3/2 rule? How is it used in forestry?• Describe the process of conversion from even-

aged to uneven-aged management to a forest. Why would you want to do that?

Forestry & Society


• Discuss the changes in species composition, stocking and size over time in a forest ecosystem.

• Discuss the effects of clear-cutting and planting only one species on tree species diversity.

• Discuss the advantages and disadvantages of low stocking (300 trees/acre) compared to high sticking (1,000 trees/acre).

• What is agroforestry and why is it practiced?• Compare natural vs artificial regeneration.

Forestry & Society


• What is the average DBH of sugar maple in a forest where there are 200 tpa with a BA of 60 ft2/ac

• Discuss the costs both economic and biologically of different harvest strategies.

forestry & society silviculture hort/rgsc 302 j.g. mexal fall 2005

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