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© 2012, H.L. Allen, ProFOR Consulting1
Soil and Site Productivity Concepts for Forestry
H. Lee AllenProFOR Consulting
Cary, [email protected]
Progressive Forestry for Production Forests
Sustainability?• Broad view
– Maintain capacity of a landscape to provide the range of products, services, and values desired by society for future generations
• Narrow view– Maintain capacity of the soil to produce a non‐declining amount of woody biomass
• System inputs?– Required, desired, not feasible, not allowed
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© 2012, H.L. Allen, ProFOR Consulting2
SoilI am soil.Look at me!Smell me, touch me, feel mewalk on me with your bare feetsing and dance on meobserve me closely…as a living, changing , vital linkin a vast and ancient webintricate and delicateof which you too are part…
Nurture meplant in meshelter me with treesrescue me whereI am thin and wornbut above allteach your children…to know meand to value me…I am soil.
Excerpts from Shelia M. Weaver’s 1987 poem “Soil”The Canadian Theosophist 68(4).
0
50
100
150
200
250
300
0 2 4 6 8 10 12 14 16 18 20 22 24 26
Annu
al Growth ft3/acre/yr
Age years
Narrow View of Sustainability
Next Rotation? MAI =65 ft3/acre/yr
Next Rotation? MAI = 200 ft3/acre/yr
This Rotation MAI = 130 ft3/acre/yr
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© 2012, H.L. Allen, ProFOR Consulting3
Managing for Sustained Productivity Requires an Understanding of the Factors Affecting Productivity
Production Varies Across SitesWhy?
• Species composition• Stocking• Site conditions
– Soil– Climate
• Age• Management
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© 2012, H.L. Allen, ProFOR Consulting4
Southern Pine Success Story1 to10 tons/acre/yr
Fox, Jokela, Allen 2004
Stand Productivity• Physiological processes
– Light interception– Light use efficiency
• Carbon gain (photosynthesis)• Carbon partitioning
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© 2012, H.L. Allen, ProFOR Consulting5
Light Interception and Leaf Area Index
Beer’s-Lambert Law
I = 1 – (e (-k *L))
k = 0.6
0102030405060708090
100
0 1 2 3 4 5 6 7
Leaf Area Index
% L
ight
Inte
rcep
tion
LAI = 1
LAI = 4
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© 2012, H.L. Allen, ProFOR Consulting6
0
100
200
300
400
500
600
0 1 2 3 4 5
VOLU
ME GRO
WTH
ft3/acre/yr
LEAF AREA INDEX
Light Interception
Growth Efficiency
Stand Productivity• Factors affecting physiological processes
– Genetics• species, genotype within species
– Stand density– Resource availability
• Light, water, NUTRIENTS, temperature
– Age• Size and maturity
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© 2012, H.L. Allen, ProFOR Consulting7
0
100
200
300
400
500
600
700
800
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
Ann
ual V
olum
e G
row
th f
t3 /ac
/yr
Leaf Area Index
Nutrients
Genetics
Water
Temperature
Factors Influencing Leaf Area and GrowthLoblolly Pine – Southeast USA
Density
Biomass HarvestingQuestions about Sustainability and Nutrition
• Will repeated harvest of timber crops deplete soil organic matter and nutrients enough to reduce productivity?
• How do intensive management practices affect soil nutrient availability?
• How do we determine if a forest stand's growth is limited by nutrients?
• If nutrients are limiting, what elements, rates, sources, and timing of application should be used?
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© 2012, H.L. Allen, ProFOR Consulting8
Nutrient Cycling Primerfor
Foresters
Vegetation
Forest Floor
Soil
REMOBILIZATION
CANOPYLEACHING
LITTERFALLPLANT
UPTAKE
IMMOBILIZATIONLITTER
LEACHING
MINERALIZATION
WEATHERING LEACHING
RAIN,DUST
GASEOUSCYCLES
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© 2012, H.L. Allen, ProFOR Consulting9
Carbon and Nutrient Cycling
• Pools – what is out there today ‐ “yield”– Important for estimating removals
• Fluxes – movement between pools– Geochemical – ecosystem inputs and outputs
• Important for long term sustainability
– Biochemical – within vegetation cycling• Conservation of nutrients already taken up
– Biogeochemical – within ecosystem cycling• Important for current production
Switzer and Nelson, 1972
020406080
100120140160180200220240
0 10 20 30 40 50 60
Stan
d Nutrie
nts (lbs/acre)
Age (years)
NCaKMgSP
Above‐ground Nutrient AccumulationLoblolly Pine
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© 2012, H.L. Allen, ProFOR Consulting10
DISTRIBUTION OF BIOMASS AND NUTRIENTS16‐Year Old Loblolly Pine Stand
Wells et al. (1975)
16.4
6.8
48.9
10.4
5.7
Carbon
57
3271
54
122
Nitrogen
46.433.9
66
46.2
22.3
Calcium
1000 lbs/acre lbs/acre lbs/acre
Roots Bark Wood Branch Foliage
DISTRIBUTION OF BIOMASS AND NUTRIENTS40‐Year Old Upland Oak Stand
Frederick et al. (1988)
12.7
4.50.8
6.7
Carbon
6454
46 62
0
Nitrogen
244
201
27 185
0
Calcium
1000 lbs/acre lbs/acre lbs/acre
Overstory Wood Overstory Branch Overstory Foliage Understory
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© 2012, H.L. Allen, ProFOR Consulting11
Henderson Site Productivity StudyHarvest Removals @ 22 years
Stem Only
Complete Tree
AdditionalRemoval(tops)
% Increase
in Removal
Nutrients Removedlbs/dry ton of stem
Nutrients Removedlbs/dry ton of tops
Biomass (dry tons/acre) 30.9 37.9 7.0 23
C (dry tons/acre) 15.4 18.9 3.5 23 1000 1000
N (lbs/acre) 54.2 120.7 66.5 123 1.8 9.5
P (lbs/acre) 4.4 9.9 5.5 127 0.1 0.8
K (lbs/acre) 33.7 57.4 23.8 71 1.1 3.4
Ca (lbs/acre) 49.6 76.3 26.6 54 1.6 3.8
Mg (lbs/acre) 13.2 20.4 7.1 54 0.4 1.0
Adapted from Tew, Morris, & Allen, 1986
Wood Nutrient Concentrations ‐ Species Differences
0.50 0.25 0.00 0.25 0.50 0.75 1.00 1.25
Loblolly Pine
Chestnut Oak
Yellow‐poplar
Hickory
White Oak
N % Ca %
From Johnson et.al., 1990
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© 2012, H.L. Allen, ProFOR Consulting12
Nutrient Pool SizesMature Forest Stands in the SE USA
N P K Ca Mg
lbs/acre
Vegetation 300 – 500 20‐60 100‐350 200‐700 40‐120
Forest Floor 200‐400 10‐30 20‐40 100‐200 20‐40
Soil 2000‐8000
100‐500 >500 >1000 >500
Total 3000‐9000
100‐600 600+ 2000+ 550+
Soil N is total, soil P is extractable, soil K, Ca, and Mg are exchangeable
Vegetation
Forest Floor
Soil
REMOBILIZATION
CANOPYLEACHING
LITTERFALLPLANT
UPTAKE
IMMOBILIZATIONLITTER
LEACHING
MINERALIZATION
WEATHERING LEACHING
RAIN,DUST
GASEOUSCYCLES
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© 2012, H.L. Allen, ProFOR Consulting13
Nutrient Outputs Below Rooting Zonekg/ha
N P K Ca Mg
Loblolly PineSantee, SC 0 0 1.0 9.3 2.1
Loblolly PineClemson, SC 0 0 0.7 1.2 0.9
Loblolly PineDuke Forest 0 0 7.0 10.6 3.3
Mixed HardwoodsMaryland
0.3 0 3.8 4.3 3.5
From: Binkley et.al. 1989
Vegetation
Forest Floor
Soil
REMOBILIZATION
CANOPYLEACHING
LITTERFALLPLANT
UPTAKE
IMMOBILIZATIONLITTER
LEACHING
MINERALIZATION
WEATHERING LEACHING
RAIN,DUST
GASEOUSCYCLES
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© 2012, H.L. Allen, ProFOR Consulting14
RETRANSLOCATION FROM FOLIAGE
0
10
20
30
40
50
60
70
80
90
N P K Ca Mg
% Retranslocated
LoblollySweetgumSycamore
Mobility
• Very mobile– N, P, K
• Intermediate mobility– Mg, S, Mn, Cu, Zn
• Immobile– Ca, B, Fe
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© 2012, H.L. Allen, ProFOR Consulting15
Vegetation
Forest Floor
Soil
REMOBILIZATION
CANOPYLEACHING
LITTERFALLPLANT
UPTAKE
IMMOBILIZATIONLITTER
LEACHING
MINERALIZATION
WEATHERING LEACHING
RAIN,DUST
GASEOUSCYCLES
How much N, P, K…. are needed to grow a ton of wood?
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© 2012, H.L. Allen, ProFOR Consulting16
Loblolly Pine Nutrient UseSETRES Control – Age 8, CAI = 1.8 tons/acre/yr ‐ LAI = 0.6
N P K Ca Mg
lbs/acreFoliage 18.6 1.9 5.9 3.5 1.6
Branch 2.6 0.4 1.2 1.7 0.4
Stem 2.6 0.4 1.8 1.6 0.5
Coarse Roots 1.7 0.3 1.6 1.3 0.4
Fine Roots 12.8 1.3 4.0 3.8 1.1
Total 38.2 4.1 14.5 11.9 3.9
Nutrient/ton wood
21.2 2.3 8.0 6.6 2.2
From Albaugh, Allen, & Fox 2008
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© 2012, H.L. Allen, ProFOR Consulting17
Loblolly Pine Nutrient UseSETRES Fert Only – Age 21, CAI = 7.1 tons/acre/yr ‐ LAI = 2.6
N P K Ca Mg
lbs/acreFoliage 75.3 6.8 28.3 9.4 5.1
Branch 8.4 1.0 4.1 4.0 1.3
Stem 7.2 0.4 3.1 3.6 1.3
Coarse Roots 6.3 0.5 4.7 1.8 0.4
Fine Roots 14.4 1.3 3.8 3.3 1.1
Total 111.5 10.1 44.0 22.1 9.2
Nutrient/ton wood
15.7 1.4 6.2 3.1 1.3
From Albaugh, Allen, & Fox 2008
0
20
40
60
80
100
120
140
160
180
0 2 4 6 8 10 12 14 16 18 20 22 24
Nitrogen
lbs/acre/year
Age
REMOBILIZED
UPTAKE FROM SOIL
Potential Nutrient Use
Adapted from Allen et al 1991
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© 2012, H.L. Allen, ProFOR Consulting18
How much N, P, K…. are needed to grow a ton of wood?
How much N, P, K… can the soil supply?
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40
60
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120
140
160
0 2 4 6 8 10 12 14 16 18 20 22 24
Nitr
ogen
lb
s/ac
re/y
ear
Age
Soil Supply
Adapted from Allen et al 1991
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© 2012, H.L. Allen, ProFOR Consulting19
0
20
40
60
80
100
120
140
160
180
0 2 4 6 8 10 12 14 16 18 20 22 24
Nitrogen
lbs/acre/year
Age
SOILSUPPLY
POTENTIAL USE
ACTUAL USE REMOBILIZED
UPTAKE FROM SOIL
Nitrogen Deficiency
Adapted from Allen et al 1991
Nutrient Limitations
develop where or when
Soil Supply < Potential Stand Use
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© 2012, H.L. Allen, ProFOR Consulting20
Where does the nitrogen come from?
Fixation of atmospheric Ninto organic matter
Factors Influencing N Mineralization• Environmental conditions that influence microbial activity– Temperature– Aeration– Moisture
• Substrate (Labile Carbon)– Quantity– Type of compounds
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© 2012, H.L. Allen, ProFOR Consulting21
Big Questions• What is the capacity of soils to supply nutrients to forest stands?
• What nutrient(s) already limit stand growth?
• Can fertilization be used to effectively ameliorate existing and future nutrient limitations?
0
2
4
6
8
10
12
14
16
0 2 4 6 8 10 12 14 16 18 20 22 24
kg/h
a/ye
ar
Stand Age
Soil Supply
?
Phosphorus (P)Potassium (K)Calcium (Ca)Iron (Fe)Sulfur (S)Magnesium (Mg)Boron (B)Copper (Cu)Manganese (Mn)Zinc (Zn)
?
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© 2012, H.L. Allen, ProFOR Consulting22
Unavailable Nutrients Available Nutrients
Cation and anionexchange
Long Term Short Term
Soil Solution
Colloids
Soil Minerals
Organic Material
Silviculture in the 21st Century• Manipulation of:
– Species composition• Species, genotypes, clones
– Stocking• Quantity and distribution of crop and non‐crop vegetation
– Site resource availability• Quantity and quality of the soil rooting environment
to optimize value for the current landowner and future generations
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© 2012, H.L. Allen, ProFOR Consulting23
Site Resource AvailabilityNatural variation through time and potential for management
Potential for change with management
activity
Natural change through time
No Yes
No FixedNon‐manipulatable
VariableNon‐manipulatable
Yes FixedManipulatable
VariableManipulatable
Soil Resources• Quantity ‐ Soil Volume
– Depth to restrictive layer (water table, bedrock, hardpan, ironstone)
– % rock
• Quality ‐ Physical environment– Soil strength, available water holding capacity– Aeration
• Quality ‐ Chemical environment– Nutrient availability, acidity/alkalinity
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© 2012, H.L. Allen, ProFOR Consulting24
Soil, Site, and Climatic Factors Affecting Soil Strength
Potential for change with management
activity
Natural change through time
No Yes
NoTexture Precipitation
Type of Clay
Yes
Organic MatterPorosity
Water Table Soil Water Content
Soil, Site, and Climatic Factors Affecting Soil Water Availability
Potential for change with management
activity
Natural change through time
No Yes
NoTexture Precipitation
Type of Clay Vapor Pressure DeficitLandscape Position
Yes
Soil DepthOrganic Matter
PorosityWater Table
Irrigation
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© 2012, H.L. Allen, ProFOR Consulting25
Seasonal Fluctuations in Soil Strength and Water Content – Poorly Drained Clay Loam
0
5
10
15
20
25
30
35
40
45
50
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
N D J F M A M J J A S O N D J F M A M J J A S
Soil
Wat
er C
onte
nt (%
)
Soil
Stre
ngth
(MPa
)
Time (Months)
Kelting 1999
Critical Level
Soil Water Content
Soil Strength
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© 2012, H.L. Allen, ProFOR Consulting26
Soil CompactionCompression of an unsaturated soil resulting in areduction in pore volume
Undisturbed
Compacted
1.32 g/cm350% Solid50% Pores
1.60 g/cm360% Solid40% Pores
Key Factors Affected:
Bulk Density
Soil Strength
Soil Aeration
Water Movement
Soil PuddlingDeformation of a saturated soil resulting in the destruction of soil structure
Key Factors Affected:
Soil Aeration
Water Movement
Undisturbed Puddled
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© 2012, H.L. Allen, ProFOR Consulting27
Soil, Site, and Climatic Factors Affecting Soil Nitrogen Availability
Potential for change with management
activity
Natural change through time
No Yes
NoTexture Precipitation
Type of Clay TemperatureLandscape Position
Yes
Soil DepthOrganic Matter
Aeration PorositySoil Water ContentMicrobial Populations
Nitrogen Additions
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Soil, Site, and Climatic Factors Affecting Soil Phosphorus Availability
Potential for change with management
activity
Natural change through time
No Yes
No
Parent Material Texture Precipitation
Type of Clay TemperatureLandscape Position
Yes
Soil DepthOrganic Matter
Aeration PorositySoil Water ContentMicrobial Populations
Phosphorus Additions
Soil, Site, and Climatic Factors Affecting Soil Calcium Availability
Potential for change with management
activity
Natural changes through time
No Yes
No
Parent Material Texture Precipitation
Type of ClayLandscape Position
YesSoil Depth
Soil Water ContentCalcium Additions
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Geology of South Carolina
Nutrients in Piedmont Rocks
Nutrient Granite Diorite Gabbro Ultrabasic Shale Sandstone Argillite
- - - - - - - - - - - - - - ppm - - - - - - - - - - - - - - - - -
P 600 920 1,100 220 700 170 1,500K 42,000 25,200 8,300 40 26,600 10,700 25,000
Ca 5,100 25,300 76,000 25,000 22,100 39,100 29,000Mg 1,600 9,400 46,000 204,000 15,000 7,000 21,000S 300 300 300 300 2,400 240 1,300
Mn 390 540 1,500 1,620 850 0 6,700Cu 10 30 87 10 45 0 250Zn 39 60 105 50 95 16 165B 10 9 5 3 100 35 230
Adapted from Turekian and Wedepohl (1961)