112508b dale johnson carbon cycle and the role...

Carbon Cycle and the Role of ForestryCarbon Cycle and the Role of Forestry

D.W. JohnsonD.W. Johnson

Natural Resources and Environmental ScienceNatural Resources and Environmental ScienceUniversity of Nevada, RenoUniversity of Nevada, Reno

Oceans38,000

Fossil Fuels7.6

Litter~60

Respiration~60

Fire2-5?

Soil and Litter1500-2300

Terrestrial Biota350-650

Atmosphere = 750Annual Increase = 4.1

Photosynthesis~120

The Global Carbon Cycle, 2000The Global Carbon Cycle, 2000--20062006GigatonsGigatons, or 10, or 101515 gg

92

Net veg destruction1.5

Net ocean:+2.2

Decomposition~60

9090

Net terrestrial:+2.8

Other Notes on the Global Carbon BudgetOther Notes on the Global Carbon Budget

••Soils are a very large C poolSoils are a very large C pool••Small changes in soils could have very large effectsSmall changes in soils could have very large effects

••Large numbers for photosynthesis, Large numbers for photosynthesis, litterfalllitterfall, and , and decomposition compared to fossil fuelsdecomposition compared to fossil fuels

••Are they really in balance? Are they really in balance? ••Reasons for recent COReasons for recent CO22 increase:increase:

••Fossil fuel combustion is considered the major causeFossil fuel combustion is considered the major cause••Reduction in forest cover (mainly in the tropics)Reduction in forest cover (mainly in the tropics)••This has reversed in North America since 1900This has reversed in North America since 1900

North American C Budget (North American C Budget (GtGt yryr--11))

+1.35+1.35+0.16+0.16+0.10+0.10+1.09+1.09Net BudgetNet Budget-0.09<0.01-0.03-0.06Other*

-0.12NDND-0.12Woody Encroachment

-0.07ND-0.01-0.06Wood products-0.23+0.05-0.03-0.27Forest growth+1.86+0.11+0.15+1.58Fossil Fuels

TotalTotalMexicoMexicoCanadaCanadaUSUSSource (+) or Source (+) or Sink (Sink (--))

*Ag soils, wetlands, rivers and reservoirs*Ag soils, wetlands, rivers and reservoirs

From From PacalaPacala et al. 2007. The North American Carbon Budget, Past and Presentet al. 2007. The North American Carbon Budget, Past and Present. . Ch. 3 In: The First State of the Carbon Cycle Report (SOCCR). Ch. 3 In: The First State of the Carbon Cycle Report (SOCCR). http://www.climatescience.gov/Library/sap/sap2http://www.climatescience.gov/Library/sap/sap2--2/final2/final--report/sap2report/sap2--22--finalfinal--chapter3.pdfchapter3.pdf

http://www.climatescience.gov/Library/sap/sap2http://www.climatescience.gov/Library/sap/sap2--2/final2/final--report/default.htmreport/default.htm

Key Findings of the SOCCR:Key Findings of the SOCCR:

•• North American fossil fuel emissions in 2004 = 25% of global North American fossil fuel emissions in 2004 = 25% of global emissionsemissions

•• US emissions account for 86%of North American Emissions (22% US emissions account for 86%of North American Emissions (22% of global)of global)

•• Approximately 30% of North American fossil fuel emissions are Approximately 30% of North American fossil fuel emissions are offset by natural sinks including forest growth and wildfire offset by natural sinks including forest growth and wildfire suppressionsuppression

•• Future offsets by natural sinks likely to decline as forests matFuture offsets by natural sinks likely to decline as forests matureure•• Declines could be offset by increased N deposition or increased Declines could be offset by increased N deposition or increased

forest growth (better silviculture, biomass plantations) or forest growth (better silviculture, biomass plantations) or enhanced by increased wildfireenhanced by increased wildfire

•• Fossil fuel emissions still likely to dominate the C budgetFossil fuel emissions still likely to dominate the C budget

Externalities Affecting C Sequestration in ForestsExternalities Affecting C Sequestration in ForestsThings you cannot control but need to plan forThings you cannot control but need to plan for

•• Climate change: Climate change: ••Projected to be warmerProjected to be warmer••Will it be drier or wetter? Critical to forests in SW US!Will it be drier or wetter? Critical to forests in SW US!••Effects on wildfire?Effects on wildfire?

•• Increased N depositionIncreased N deposition••Likely to continueLikely to continue••Likely to increase forest growth somewhat (although there is Likely to increase forest growth somewhat (although there is debate on this)debate on this)

•• Increased atmospheric COIncreased atmospheric CO22

••Likely to continueLikely to continue••Likely to increase forest growth somewhat despite N and Likely to increase forest growth somewhat despite N and water limitationswater limitations

Increased N Deposition: The Negative ViewIncreased N Deposition: The Negative View

•• Nadelhoffer et al (1999): Nadelhoffer et al (1999): ““Nitrogen makes a minor contribution to Nitrogen makes a minor contribution to carbon sequestration in temperate forestscarbon sequestration in temperate forests”” (Nature 398: 145(Nature 398: 145--148)148)

•• 1515N tracer studies showed that most applied N was recovered N tracer studies showed that most applied N was recovered in forest floor and soil (as is always the case with fertilizatiin forest floor and soil (as is always the case with fertilization)on)

•• However, atmosphericallyHowever, atmospherically--deposited N can be taken up by deposited N can be taken up by foliage, bypassing soil microbes!foliage, bypassing soil microbes!

•• Fenn et al (2003): Fenn et al (2003): ““Ecological Effects of nitrogen deposition in Ecological Effects of nitrogen deposition in the western United Statesthe western United States”” (Bioscience 53:404(Bioscience 53:404--420)420)

•• ““Greater plant productivity is counterbalanced by biotic Greater plant productivity is counterbalanced by biotic community changes and deleterious effects on sensitive community changes and deleterious effects on sensitive organismsorganisms……. .

•• Chronic N deposition in the West is implicated in increased Chronic N deposition in the West is implicated in increased fire frequency in some areas:fire frequency in some areas:

Increased N Deposition: The Positive ViewIncreased N Deposition: The Positive View

•• MagnaniMagnani et al (2007): et al (2007): ““The human footprint in the carbon cycle of The human footprint in the carbon cycle of temperate foreststemperate forests”” (Nature 447: 848(Nature 447: 848--852)852)

•• “…“…forest net carbon sequestration is found to be forest net carbon sequestration is found to be overwhelmingly driven by nitrogen deposition, largely the overwhelmingly driven by nitrogen deposition, largely the result of anthropogenic activities.result of anthropogenic activities.””

•• KauppiKauppi et al (1992): et al (1992): ““Biomass and Carbon Budget of European Biomass and Carbon Budget of European Forests, 1971 to 1990 Forests, 1971 to 1990 ”” Science 256: 70Science 256: 70--7474

•• ““The fertilization effects of pollutants override the adverse The fertilization effects of pollutants override the adverse effects at least for the time being. effects at least for the time being.

•• ““If there has been similar development in other continents, If there has been similar development in other continents, biomass accumulation biomass accumulation …… can account for a large proportion can account for a large proportion of the estimated mismatch between sinks and sources of of the estimated mismatch between sinks and sources of atmospheric carbon dioxide.atmospheric carbon dioxide.””

Increased N Deposition: The Positive View (cont.)Increased N Deposition: The Positive View (cont.)

•• Pregitzer et al (2007): Pregitzer et al (2007): ““Simulated chronic nitrogen deposition Simulated chronic nitrogen deposition increases carbon storage in northern temperate forestsincreases carbon storage in northern temperate forests”” (Global (Global Change Biology 14: 142Change Biology 14: 142--153)153)

•• Experimental additions of 30 kg haExperimental additions of 30 kg ha--1 yr1 yr--1 of N to hardwood 1 of N to hardwood forests in Michiganforests in Michigan

•• ““Our results Our results ……. Support the hypothesis that chronic N . Support the hypothesis that chronic N deposition may increase C storage in northern forests, deposition may increase C storage in northern forests, potentially contributing to a sink for anthropogenic COpotentially contributing to a sink for anthropogenic CO22 in the in the northern hemisphere.northern hemisphere.””

Climate ChangeClimate Change

•• Projections are for warmer climatesProjections are for warmer climates•• What will happen to precipitation may be even more importantWhat will happen to precipitation may be even more important•• ShortShort--term effects of warming may be positive with increased term effects of warming may be positive with increased

soil N mineralizationsoil N mineralization

Elevated COElevated CO22

•• Large increases in growth have been found with elevated Large increases in growth have been found with elevated COCO22 in lab studies, open top chamber, and freein lab studies, open top chamber, and free--air COair CO22

(FACE) studies(FACE) studies•• How is this possible in the face of water and nutrient How is this possible in the face of water and nutrient

limitations?limitations?••Increased water use efficiency: Stomata do not need to Increased water use efficiency: Stomata do not need to stay open as long to capture COstay open as long to capture CO22, therefore there is less , therefore there is less water usewater use••Increased nitrogen use efficiency: less need for Increased nitrogen use efficiency: less need for rubiscorubisco, , so foliar N declinesso foliar N declines••Greater root production, soil exploration and N uptakeGreater root production, soil exploration and N uptake

•• Therefore, a growth response is possible even with water Therefore, a growth response is possible even with water and N limitationsand N limitations

J.T. Ball1, D.W. Johnson2, B.R. Strain3

1 Desert Research Institute, Reno, Nevada, USA2University of Nevada, Reno Nevada, USA3Duke University, Durham, North Carolina, USA

•A six-year open-top chamber study of the effects of elevated CO2 and N on ponderosa and loblolly pine seedlings•Funded by the Electric Power Research Institute, Southern California Edison, U.S. Department of Energy

Forest Response to CO2

Time 0 (planting)Time 0 (planting)One year oldOne year old

Five years oldFive years old Six years oldSix years oldIncreasing chamber heightIncreasing chamber height

0

10

20

30

40

50

60

360 525 700

Mg

ha-1

0

50

100

150

200

250

300

350

400

450

500

360 525 700

kg h

a-1

Carbon Nitrogen

CO2 (CO2 (ppmppm))

Carbon and nitrogen contents of 6Carbon and nitrogen contents of 6--yearyear--old old ponderosa pine saplings treated with ambient and ponderosa pine saplings treated with ambient and

elevated COelevated CO22 since planted from seed since planted from seed (Johnson et al., 2006)(Johnson et al., 2006)

FACE Facility at Oak Ridge, TennesseeFACE Facility at Oak Ridge, Tennessee

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Am b Ele

kg h

a-1

TurnoverIncrement

0

10

20

30

40

50

60

70

Am b Ele

kg h

a-1

TurnoverIncrement

FACE Results at Duke (FACE Results at Duke (FinziFinzi, 2002), 2002)

Biomass NitrBiomass Nitrogenogen

Where does the extra N come from? Where does the extra N come from? Probably soil miningProbably soil mining

Forest Management Effects on C Sequestration: Forest Management Effects on C Sequestration: Things you can effectThings you can effect

•• Harvesting practicesHarvesting practices•• Prescribed fire and fire mitigationPrescribed fire and fire mitigation•• PostPost--wildfire managementwildfire management

An Important Note: Soil C changes are linked to N!An Important Note: Soil C changes are linked to N!

•• C:N ratios in soil organic matter typically range at from 10 to C:N ratios in soil organic matter typically range at from 10 to 40 40 and most soil N is associated with soil organic Cand most soil N is associated with soil organic C

•• Thus, a modest 1 Mg haThus, a modest 1 Mg ha--11 (1000 kg ha(1000 kg ha--11) change in soil C must ) change in soil C must be accompanied by a 25 to 100 kg habe accompanied by a 25 to 100 kg ha--1 change in N to stay 1 change in N to stay within normal, observed ranges. Not trivial!within normal, observed ranges. Not trivial!

•• If C:N goes higher than 40 (for example, by attempting to If C:N goes higher than 40 (for example, by attempting to increase soil C by adding high C:N ratio woody material), then increase soil C by adding high C:N ratio woody material), then N is immobilized by microbesN is immobilized by microbes

•• N is frequently the growthN is frequently the growth--limiting nutrient, and therefore limiting nutrient, and therefore microbial immobilization of N may well lead reduced tree microbial immobilization of N may well lead reduced tree growth and overall ecosystem C sequestration!!growth and overall ecosystem C sequestration!!

•• Thus, I will include N in the following discussions of Thus, I will include N in the following discussions of management effects on C. management effects on C.

C:N Ratio of Organic Organic MatterC:N Ratio of Organic Organic Matter

Soil Organic NSoil Organic N NHNH44++

As a rule of thumb:As a rule of thumb:At C:N >20:1, NHAt C:N >20:1, NH44

++ is immobilizedis immobilizedAt C:N < 20:1, NHAt C:N < 20:1, NH44

++ is mineralizedis mineralized

C:N >20:1C:N >20:1

C:N < 20:1C:N < 20:1

Typical C:N ratiosTypical C:N ratiosConifer foliage 40Conifer foliage 40--5050Hardwood foliage 30Hardwood foliage 30--4040Wood 200Wood 200--400 400 Soil 10Soil 10--40 40

Forest Management Effects on C Sequestration: Forest Management Effects on C Sequestration: Things you can effectThings you can effect

Harvest: Harvest: ••Obvious shortObvious short--term reduction in biomass Cterm reduction in biomass C••Possible longPossible long--term gains in biomass C with thinning response term gains in biomass C with thinning response and mitigation of fire hazardand mitigation of fire hazard••Usually very little effect on soil C or NUsually very little effect on soil C or N••Fate of harvested product must be considered!Fate of harvested product must be considered!

Johnson, D.W., and P.S. Curtis. Johnson, D.W., and P.S. Curtis. 2001. Effects of forest management 2001. Effects of forest management on soil carbon and nitrogen on soil carbon and nitrogen storage: Meta Analysis.storage: Meta Analysis. For. Ecol. For. Ecol. ManagemManagem.. 140: 227140: 227--238.238.

•• Forest harvesting Forest harvesting without cultivation does without cultivation does little to soil C or N in little to soil C or N in most casesmost cases

•• Increases can occur Increases can occur with slash incorporation with slash incorporation into soil, decreases with into soil, decreases with plowing and burningplowing and burning

Is leaving coarse woody debris (logs) on site Is leaving coarse woody debris (logs) on site carbon friendly or carbon hostile?carbon friendly or carbon hostile?

••Case study on harvesting:Case study on harvesting:•• Mixed oak forest, Oak Ridge, TNMixed oak forest, Oak Ridge, TN•• SawlogSawlog and wholeand whole--tree harvesting in 1980tree harvesting in 1980•• Vegetation, forest floor, and soil C and nutrient Vegetation, forest floor, and soil C and nutrient

inventories before and 15 years after harvestinginventories before and 15 years after harvesting

PrePre--Harvest Stand ContentHarvest Stand Content

Carbon67-71% contained in aboveground biomass

0

20000

40000

60000

80000

100000

120000

140000

160000

WTH SAW

kg h

a-1

FoliageBranchBoleStumpForest FloorSoil, Extr.Soil, Non-Extr

Harvest Removals Compared to Forest Floor and Soil ContentHarvest Removals Compared to Forest Floor and Soil Content

Carbon59% removed with WTH, 22% removed with SAW

0

20000

40000

60000

80000

100000

120000

140000

WTH SAW

kg h

a-1 Branch Harvest

Bole HarvestForest FloorSoil

SAWSAW WTHWTH00

2000020000

4000040000

6000060000

kg h

akg

ha-- 11

Sapling Biomass 15 Years After HarvestSapling Biomass 15 Years After Harvest

0

20000

40000

60000

80000

100000

120000

140000kg

C h

a-1

Soil

Forest Floor

Residue

Vegetation

Carbon Contents in 1980 and 1995

SAWSAW WTHWTH

Net loss =38,220

Net gain =29,080

1980 19951980 1995 1980 19951980 1995

Fifteen years after harvest: Fifteen years after harvest: •• No difference in sapling biomass between harvest No difference in sapling biomass between harvest

treatmentstreatments

•• 90% of carbon left in residues in 90% of carbon left in residues in sawlogsawlog treatment treatment had disappeared with no effect on soil C had disappeared with no effect on soil C –– it it simply burned off as COsimply burned off as CO22!!

•• Thus, leaving residues on site in SAW treatment Thus, leaving residues on site in SAW treatment was carbon negative because firewood cutting in was carbon negative because firewood cutting in WTH treatment resulted in fossil fuel offsets!WTH treatment resulted in fossil fuel offsets!

Forest Management Effects on C Sequestration: Forest Management Effects on C Sequestration: Things you can have an effect onThings you can have an effect on

Fire:Fire:•• Wildfire:Wildfire:

•• PostPost--fire salvage loggingfire salvage logging•• PostPost--fire vegetation managementfire vegetation management

•• Prescribed FirePrescribed Fire•• ShortShort--term reduction in forest floor and understory Cterm reduction in forest floor and understory C•• Possible longPossible long--term gains in biomass C mitigation of fire term gains in biomass C mitigation of fire

hazardhazard•• Possible longPossible long--term losses in tree growth because of term losses in tree growth because of

cumulative N losscumulative N loss ((MonleonMonleon et al., 1997; Johnson et al., 1997)et al., 1997; Johnson et al., 1997)

Soil Organic Carbon

Litter Layer Organic Carbon

What burns completely volatilizes toCO2, CH4 Very hot fires

can cause soil organic C losses

Fire Effects on Litter and Soil Organic C

Soil Organic Nitrogen NH4+

Litter Layer Organic Nitrogen

What burns completely volatilizes toN2, N2O, NH3

Fire Effects on Litter and Soil N

NO3-

Nitrification(later)

Nitrate leaching(later)

Ammonium leaching (inhibited by strong soil absorption)

Very hot fires can cause immediate volatilization of organic N, NO3

-, and NH4

+ from mineral soil

Less intense fires cause NH4

+

increase because of

denaturing proteins, etcand has little effect on soil organic N

pH-induced NH4

+ --> NH3volatilization after the fire

NV

CA

RenoReno

GondolaWildfire in 2002

LakeLakeTahoeTahoe

Case studies from Sierra Nevada Mountains Site Locations

Case studies from Sierra Nevada Mountains Case studies from Sierra Nevada Mountains Site LocationsSite Locations

Little ValleyFire in 1981

CaliforniaCalifornia NevadaNevada

TruckeePrescribed fire in 2001

North Lake TahoePrescribed fire in

2003

A Wildfire on 3 July 2002 burned 9 of 16 previously A Wildfire on 3 July 2002 burned 9 of 16 previously established plots, allowing preestablished plots, allowing pre-- and postand post--fire sampling fire sampling

with unburned controls!with unburned controls!

Gondola FireGondola Fire

1 3 5 7 9 11 13 15

2 4 6 8 10 12 14 16

PrePre--fire and control plots:fire and control plots:Pinus Pinus jeffreyiijeffreyii, , AbiesAbies amabilisamabilis

Immediate postImmediate post--fire:fire:••Complete forest floor combustionComplete forest floor combustion••Nearly complete foliage combustionNearly complete foliage combustion••Soil organic matter losses measuredSoil organic matter losses measured

Little Valley, Nevada: Reconstructing nutrient budgets from a wildfire in 1981

Little Valley, Nevada: Reconstructing nutrient budgets from a wildfire in 1981

PrePre--fire fire Pinus Pinus jeffreyiijeffreyii PrePre--fire fire Pinus Pinus contortacontorta

Immediate postImmediate post--firefire••Foliage and forest floor are totally Foliage and forest floor are totally combustedcombusted••Soil organic matter losses unknownSoil organic matter losses unknown

20 years post20 years post--firefire••80% N80% N--fixing fixing Ceanothus Ceanothus velutinusvelutinus••20%20% nonnon--fixing shrubsfixing shrubs

EntisolsEntisols and and InceptisolsInceptisols derived from decomposed granitederived from decomposed granite

Pre Post (1 yr) Forest Pre Post (1 yr) Forest Fire (20 yr)Fire (20 yr)

Carbon

0

50

100

150

200

250

Mg

ha-1

VegetationO horizon + WoodSoil

Gondola Little ValleyGondola Little Valley

Gondola: Gondola: ••Soil C losses were minimalSoil C losses were minimal••Most C was lost from forest floor Most C was lost from forest floor and understoryand understory

Little Valley: Little Valley: ••Soil C in former fire is only slightly Soil C in former fire is only slightly higher than in nearby forest higher than in nearby forest ••Ecosystem C content is much lower Ecosystem C content is much lower in former fire and will not recover in former fire and will not recover until site is reforested.until site is reforested.

Carbon BudgetsCarbon Budgets

15

295

53

134

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Salvage Volatilization

Carbon NitrogenCarbon Nitrogen

kg ha-1

kg ha-1

Mg ha-1

Mg ha-1

Little Valley Fire Reconstructed Budgets: C and N LossLittle Valley Fire Reconstructed Budgets: C and N LossTo salvage log or not?To salvage log or not?

•• Most N lost by volatilization during fireMost N lost by volatilization during fire•• Most C lost by postMost C lost by post--fire salvage loggingfire salvage logging•• But: leaving logs on site to decay would have been carbon But: leaving logs on site to decay would have been carbon

negative and added little to soil C!!negative and added little to soil C!!

Nitrogen

0

500

1000

1500

2000

2500

3000

3500

4000

kg h

a-1

VegetationO horizon + WoodSoil

Pre Post (1 yr) Forest Pre Post (1 yr) Forest Fire (20 yr)Fire (20 yr)Gondola Little ValleyGondola Little Valley

Gondola: Gondola: ••Soil N losses were minimalSoil N losses were minimal••Most N was lost from forest floor Most N was lost from forest floor and understoryand understory

Little Valley: Little Valley: ••Soil N in former fire is significantly Soil N in former fire is significantly higher than in nearby forest because higher than in nearby forest because of Nof N--fixation by snowbrushfixation by snowbrush••Ecosystem N content is significantly Ecosystem N content is significantly greater in former fire than in the greater in former fire than in the nearby forest.nearby forest.

Nitrogen BudgetsNitrogen Budgets

Wildfire caused:Wildfire caused:•• Large losses of C and N by volatilizationLarge losses of C and N by volatilization•• Significant increases in N leaching, but volatilization Significant increases in N leaching, but volatilization

dominates N loss (>90%) dominates N loss (>90%)

Comparisons with older burned sites shows that:Comparisons with older burned sites shows that:••C losses not made up until the site is reforestedC losses not made up until the site is reforested••N losses can be made up quickly if N fixers are presentN losses can be made up quickly if N fixers are present

Conclusions from Gondola and Conclusions from Gondola and previous studies on older firesprevious studies on older fires

Prescription FirePrescription FirePrescription Fire

LOW TO MODERATE BURNSOIL TEMPERATURE < 50o C

0.50.535350.40.4????

1212--1818??

??????222266??

kg hakg ha--11

yryr--11

176176414414106106146146211211

7474--109109192192--666666

223223--57157177--604604376376440440158158239239

kg hakg ha--11

Klopatek et al (1991)Klopatek et al (1991)MonleonMonleon et al (1997)et al (1997)JurgensenJurgensen et al (1981)et al (1981)DeBanoDeBano and Conrad (1978)and Conrad (1978)Ellis and Ellis and GraleyGraley (1983)(1983)Raison et al. (1985)Raison et al. (1985)Little and Little and OhmannOhmann (1988)(1988)

Little and Little and KlockKlock (1985)(1985)Feller (1988)Feller (1988)Macadam (1987)Macadam (1987)Wells (1971)Wells (1971)TrabaudTrabaud (1994)(1994)Clinton et al (1996)Clinton et al (1996)

Arizona, USAArizona, USAOregon, USAOregon, USAMontana USAMontana USACalifornia, USACalifornia, USATasmaniaTasmaniaAustraliaAustraliaOregon and Oregon and Washington, USAWashington, USAOregon, USAOregon, USABritish ColumbiaBritish ColumbiaBritish ColumbiaBritish ColumbiaSouth Carolina, USASouth Carolina, USAFranceFranceNorth Carolina, USANorth Carolina, USA

ReferenceReferenceLocationLocation

N losses from Prescribed Fire: Many studiesN losses from Prescribed Fire: Many studies

????

????

kg hakg ha--11

yryr--11

5656--362362150150

1111--40405656--138*138*

kg hakg ha--11

Caldwell et al (2002)Caldwell et al (2002)Covington and Covington and SackettSackett(1984)(1984)Richter et al(1982)Richter et al(1982)GiardinaGiardina et al (2000)et al (2000)

Nevada, USANevada, USAArizona, USAArizona, USA

South Carolina, USASouth Carolina, USAMexicoMexico

ReferenceReferenceLocationLocation

*Loss from 0-10 cm soil only

N losses from Prescribed Fire: Many studiesN losses from Prescribed Fire: Many studies

Truckee Harvest x Prescribed Fire StudyTruckee Harvest x Prescribed Fire StudyPinus Pinus jeffreyiijeffreyii forestforest

XXXXXXNo fireNo fire

XXXXXXPrescribed Prescribed firefire

No harvestNo harvestCutCut--toto--length length

thinning thinning (bole only)(bole only)

WholeWhole--tree tree thinning thinning

(aboveground)(aboveground)

UlticUltic HaploxeralfsHaploxeralfs derived from derived from andesiteandesite

The prescription fire at Truckee showed no significant The prescription fire at Truckee showed no significant

effects of any treatment on: effects of any treatment on:

••Soil solution nutrient concentrationsSoil solution nutrient concentrations

••Cumulative soil leaching (resin Cumulative soil leaching (resin lysimeterslysimeters))

••Soil C or nutrient contentsSoil C or nutrient contents

The only effects treatments were on nutrient budgets: The only effects treatments were on nutrient budgets:

••C and nutrient export via harvested materialC and nutrient export via harvested material

••C, N, and S losses from the forest floor and C, N, and S losses from the forest floor and

understory during burningunderstory during burning

••Approximately half the forest floor was consumed Approximately half the forest floor was consumed (typical of prescribed fire in the Sierra Nevada)(typical of prescribed fire in the Sierra Nevada)

••No changes in soil C or N contentNo changes in soil C or N content

Carbon

0

10

20

30

40

50

60

Preburn Postburn

Mg

ha-1

VegetationForest Floor

-8.3

-8.3

Nitrogen

0

100

200

300

400

500

600

Preburn Postburn

kg h

a-1


-125

-125

Truckee C and N BudgetsTruckee C and N BudgetsTreatment: No harvest, burn onlyTreatment: No harvest, burn only

Truckee C and N BudgetsTruckee C and N BudgetsTreatment: Bole only harvest and then burnTreatment: Bole only harvest and then burn

Carbon

0

10

20

30

40

50

60

70

80

90

100

Pre Post Harvest Post Burn

Mg

ha-1


-17.7 -23.5

+5.0-23.5

-12.7

Nitrogen

0

100

200

300

400

500

600

700

800

900


kg h

a-1


+70-253

-135

-65

-253

Following harvest:Following harvest:Decrease in Decrease in vegetationvegetationIncrease in forest Increase in forest floor due to residue floor due to residue inputsinputs

Following burn:Following burn:Largest decrease in Largest decrease in forest floor poolsforest floor pools

Conclusion:Conclusion:Fire dominates Fire dominates losseslosses

Total loss = -35.2

Total loss = -318

Truckee C and N Budgets:Truckee C and N Budgets:Treatment: WholeTreatment: Whole--tree harvest followed by burntree harvest followed by burn

Carbon

0

10

20

30

40

50

60

70

80

90

100


Mg

ha-1


-26.5

-10.2

-26.5-10.2

Nitrogen

0

100

200

300

400

500

600

700

800

900


kg h

a-1


-169-113

-113

-169

Following harvest:Following harvest:Largest decrease Largest decrease in vegetationin vegetationMinimal change in Minimal change in forest floorforest floor

Following burn:Following burn:Decrease in Decrease in forest floor poolsforest floor pools

Conclusion:Conclusion:Harvest dominates Harvest dominates losseslosses

Total loss = -36.7

Total loss = -282

Summary of Results for C Loss (Mg haSummary of Results for C Loss (Mg ha--11))Truckee Harvest x Prescribed Fire StudyTruckee Harvest x Prescribed Fire Study

--8.88.8--22.522.5--10.210.2Prescribed Prescribed FireFire

--8.88.8--35.235.2--36.736.7TotalTotal

00--12.712.7--26.526.5No fireNo fire


harvest harvest (bole only)(bole only)

WholeWhole--tree tree harvest harvest


Summary of Results for N Loss (kg haSummary of Results for N Loss (kg ha--11))Truckee Harvest x Prescribed Fire StudyTruckee Harvest x Prescribed Fire Study

--125125--253253--113113Prescribed Prescribed FireFire

--125125--318318--282282TotalTotal

00--6565--169169HarvestHarvest


harvest harvest (bole only)(bole only)

WholeWhole--tree tree harvest harvest


Truckee Site Truckee Site -- ConclusionsConclusions

••Substantial effect of harvest and fire on forest floor C Substantial effect of harvest and fire on forest floor C

and N lossand N loss

••Harvest effects > fire effects with wholeHarvest effects > fire effects with whole--tree tree

harvestharvest

••Harvest effects < fire effects in cut to length Harvest effects < fire effects in cut to length

harvestharvest

••Total C and N removals approximately the same in Total C and N removals approximately the same in

both casesboth cases

Simulated N losses with regular prescription fire using a Simulated N losses with regular prescription fire using a spreadsheet model (after Johnson et al., 1998)spreadsheet model (after Johnson et al., 1998)

Although prescription fire is often less severe than wildfire, iAlthough prescription fire is often less severe than wildfire, it t can sum up to greater N losses than wildfire over time and may can sum up to greater N losses than wildfire over time and may

prevent replacement by N fixersprevent replacement by N fixers

Overall ConclusionsOverall Conclusions

Externalities:Externalities:

••Increased N deposition and COIncreased N deposition and CO22 will likely have some will likely have some

positive effect on forest growthpositive effect on forest growth

••Climate change effects (+ or Climate change effects (+ or --) are unclear and may ) are unclear and may

offset one or both of the aboveoffset one or both of the above


Things you can control: HarvestingThings you can control: Harvesting

••Harvesting causes shortHarvesting causes short--term losses of Cterm losses of C

••But harvesting may be beneficial over the long term But harvesting may be beneficial over the long term

(thinning to mitigate fire danger and reduce insect (thinning to mitigate fire danger and reduce insect

attacksattacks

••Harvesting usually has little effect on soil C storesHarvesting usually has little effect on soil C stores

••Leaving coarse woody debris (logs) laying around to Leaving coarse woody debris (logs) laying around to

decay is probably carbondecay is probably carbon--negative negative

Overall ConclusionsOverall ConclusionsThings you can control (sort of): PostThings you can control (sort of): Post--wildfire management wildfire management

optionsoptions

•• Wildfire causes major carbon and nitrogen lossesWildfire causes major carbon and nitrogen losses

•• PostPost--fire N fixers can quickly make up for N lossesfire N fixers can quickly make up for N losses

•• Only reforestation will make up for C lossesOnly reforestation will make up for C losses

•• Tradeoffs between improved soil N status and prolonged Tradeoffs between improved soil N status and prolonged

NN--fixer occupation of the site should be consideredfixer occupation of the site should be considered

•• Salvage logging after fire is probably carbonSalvage logging after fire is probably carbon--friendly as friendly as

opposed to leaving logs to decay in the fieldopposed to leaving logs to decay in the field


Things you can control: Prescribed FireThings you can control: Prescribed Fire

••Regular prescribed fire could cause major nitrogen Regular prescribed fire could cause major nitrogen

losses over the long term (even more than wildfire)losses over the long term (even more than wildfire)

••Replenishment of lost N may be prevented if fire Replenishment of lost N may be prevented if fire

frequency is highfrequency is high

••Tradeoffs between N loss and wildfire danger with Tradeoffs between N loss and wildfire danger with

excessive fuels should be weighed (and probably excessive fuels should be weighed (and probably

comes in on the side of prescribed fire)comes in on the side of prescribed fire)

A Final Note on Soil CA Final Note on Soil C

Why do we see so little change in soil N with logging Why do we see so little change in soil N with logging residues, fire, etc?residues, fire, etc?

Again: Soil C changes are linked to N!!Again: Soil C changes are linked to N!!•• N would have to be added to this coarse woody N would have to be added to this coarse woody

material if it material if it

A Final Note on Soil CA Final Note on Soil C

Why do we see so little change in soil N with logging Why do we see so little change in soil N with logging residues, fire, etc?residues, fire, etc?

•• If C:N goes higher than 40 (for example, by If C:N goes higher than 40 (for example, by attempting to increase soil C by adding high C:N attempting to increase soil C by adding high C:N ratio woody material), then N is immobilized by ratio woody material), then N is immobilized by microbes, possibly reducing tree growth and microbes, possibly reducing tree growth and ecosystem C sequestration overall!! ecosystem C sequestration overall!!

•• Therefore, it is a lucky thing that coarse woody Therefore, it is a lucky thing that coarse woody debris is not incorporated into soil!!debris is not incorporated into soil!!

112508b dale johnson carbon cycle and the role...

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