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From source to sink: Tracing the effects of natural disturbance on tropical forest carbon balance. Scott Saleska (U. of Arizona) L ucy Hutyra, Elizabeth Hammond-Pyle, Dan Curran, Bill Munger, Greg Santoni, Steve Wofsy (Harvard University) Kadson Oliveira (LBA-Santarem)

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From source to sink: Tracing the effects of natural disturbance on tropical forest carbon balance

Scott Saleska (U. of Arizona)

Lucy Hutyra, Elizabeth Hammond-Pyle, Dan Curran, Bill Munger, Greg Santoni, Steve Wofsy(Harvard University)

Kadson Oliveira (LBA-Santarem)

Simone Vieira, Plinio Camargo (CENA, U. of São Paulo)



How do we estimate large-scale carbon balance (given that disturbance is intrinsic to old-growth forest dynamics)?


How do we estimate large-scale carbon balance (given that disturbance is intrinsic to old-growth forest dynamics)?

  • Introduction: Two sub-questions

  • Prior findings from an eddy flux study: disturbance-induced carbon loss in old-growth forest?

  • A preliminary test of predictions from prior findings

  • Conclusion: Understanding disturbance


NPP (net primary productivity)

20

Rhet (heterotrophic respiration)

10

Mg (C) ha-1 yr-1

0

NEP (net ecosystem productivity) = NPP - Rhet

-10

-20

Forest Gap Age (time since disturbance in years)

Introduction: Modeled carbon flux following disturbance in gap of “balanced-biosphere” Amazon rainforest

Positive NEP (=sink atm CO2)

Negative NEP (=source to atm)

0 20 40 60 80

Source: Moorcroft, Hurtt, & Pacala (2001)


NPP (net primary productivity)

20

Rhet (heterotrophic respiration)

10

0

NEP (net ecosystem productivity) = NPP - Rhet

-10

-20

Introduction: Modeled carbon flux following disturbance in gap of “balanced-biosphere” Amazon rainforest

Key point:

  • Landscape in carbon balance, but…

  • Individual gaps may never be in carbon balance

Mg (C) ha-1 yr-1

0 20 40 60 80

Forest Gap Age (time since disturbance in years)


NPP (net primary productivity)

20

Rhet (heterotrophic respiration)

10

0

NEP (net ecosystem productivity) = NPP - Rhet

-10

-20

What is large-scale Carbon balance?Two sub-questions:

  • What is the distribution of gap ages across the landscape?

  • What are the detailed dynamics of forest response to disturbance?

Mg (C) ha-1 yr-1

0 20 40 60 80

Forest Gap Age (time since disturbance in years)


NPP (net primary productivity)

20

Rhet (heterotrophic respiration)

10

0

NEP (net ecosystem productivity) = NPP - Rhet

-10

-20

What is large-scale Carbon balance?Two sub-questions:

  • What is the distribution of gap ages across the landscape?

  • What are the detailed dynamics of forest response to disturbance?

Mg (C) ha-1 yr-1

(see Jeff Chambers talk coming up…)

0 20 40 60 80

Forest Gap Age (time since disturbance in years)


LBA project near Santarem: Controls on Carbon Balance in the Tapajós National Forest, Brazil

Rio Amazonas

Santarém

Rio Tapajós

Km 67 site

Km 83 site


Profile the systeminlets (8 levels)

Methods

  • Eddy Flux: 64m tall tower at Km67 in Tapajos forest

  • Biometry: ~3000 trees and dead wood measured in 20 ha in footprint of eddy tower

58 m: Eddy flux


Prior findings 1 eddy flux measurement show net loss of c in tapajos national forest of amaz nia
Prior findings the 1: eddy flux measurement show net loss of C in Tapajos National forest of Amazônia,

Average Annual C- Balance

6

5

4

3

2

1

0

-1

-2

loss to

atmosphere

Accumulated Mg(C) ha-1

uptake

Source: Saleska et al. (2003) Science

2001 2002 2003


4 the

recruit

2

growth

mortality

0

decomp-osition

mortality

-2

-4

-6

Prior findings 2: Carbon fluxes to biomass and dead wood  suggests C-loss is transient consequence of disturbance

Two observations suggest disturbance-recovery process:(1) The balance for live wood and dead wood is in opposite directions

live wood change: +1.4  0.6 MgC ha-1 yr-1

dead wood change: -3.3  1.1 (loss)

whole-forestnet:-1.9 1.0 (loss)

net C loss |net C uptake

growth/loss rate (Mg C ha-1 yr-1)

Live Biomass(145-160 MgC/ha)

Dead Wood(30–45 MgC/ha)


loss to the

atmosphere

Recruitment

Net Accumulation(1.4 Mg C ha-1yr-1)

Growth

uptake

Mortality

Outgrowth

10

35

60

85

110

135

160

Prior findings 2: Carbon fluxes to biomass by size-class  suggests C-loss is transient consequence of disturbance

3

  • Observation 2:

  • Demographic shift:

  • The increase in flux to biomass isin the smaller size classes

  • Corresponding increase in density of tree stems in the smaller size classes

2

1

flux, MgC ha-1yr-1

0

-1

-2

size class, cm DBH


NPP (net primary productivity) the

20

Rhet (heterotrophic respiration)

10

0

-10

-20

Predictions for continued observations following disturbance

(1) What is the distribution of gap ages across the landscape?

(2) What are the detailed dynamics of forest response to disturbance?

Mg (C) ha-1 yr-1

NEP (net ecosystem productivity) = NPP - Rhet

0 20 40 60 80

Forest Gap Age (time since disturbance in years)


NPP (net primary productivity) the

20

Rhet (heterotrophic respiration)

10

0

-10

-20

Predictions for continued observations following disturbance

(1) What is the distribution of gap ages across the landscape?

(2) What are the detailed dynamics of forest response to disturbance?

Mg (C) ha-1 yr-1

NEP (net ecosystem productivity) = NPP - Rhet

Tapajos Km 67 site?(loss)

0 20 40 60 80

Forest Gap Age (time since disturbance in years)


NPP (net primary productivity) the

20

Rhet (heterotrophic respiration)

10

0

-10

-20

Predictions for continued observations following disturbance

Mg (C) ha-1 yr-1

NEP (net ecosystem productivity) = NPP - Rhet

Tapajos Km 67 site?(loss)

0 20 40 60 80

Forest Gap Age (time since disturbance in years)


Predictions the for continued observations following disturbance

Rhet (respiration)

(1) Whole-Ecosystem flux Predictions

(a) NEP should move from source to sink

NPP

Mg (C) ha yr-1

Positive NEP (=sink)

Negative NEP (=source)

NEP (net ecosystem productivity) = NPP - Rhet


Predictions the for continued observations following disturbance

Rhet (respiration)

(1) Whole-Ecosystem flux Predictions

(a) NEP should move from source to sink

(b) Due to decline in respiration (as deadwood substrate decays away)

NPP

Mg (C) ha yr-1

Positive NEP (=sink)

Negative NEP (=source)

NEP (net ecosystem productivity) = NPP - Rhet


Predictions the for continued observations following disturbance

recruit

growth

Mort.

De-comp.

Mort.

4

2

0

-2

-4

Live Biomass

Dead Wood

(2) Forest Demography Predictions

(a) Shift from uptake towards balance in live biomass (i.e. decrease in growth/ recruitment, increase in mortality)

prediction

(a)

net C loss |net C uptake

growth/loss rate


Predictions the for continued observations following disturbance

recruit

growth

Mort.

De-comp.

Mort.

4

2

0

-2

-4

Live Biomass

Dead Wood

(2) Forest Demography Predictions

(a) Shift from uptake towards balance in live biomass (i.e. decrease in growth/ recruitment, increase in mortality)

(b) Shift from loss towards balance in dead wood

prediction

(a)

(b)

net C loss |net C uptake

growth/loss rate


Predictions the for continued observations following disturbance

3

recruit

2

growth

Mort.

1

De-comp.

Mort.

4

0

2

-1

0

-2

-2

-4

Live Biomass

Dead Wood

(2) Forest Demography Predictions

(a) Shift from uptake towards balance in live biomass (i.e. decrease in growth/ recruitment, increase in mortality)

(b) Shift from loss towards balance in dead wood

(c) Shift in tree growth from smaller to middle size classes

prediction

(a)

(b)

net C loss |net C uptake

growth/loss rate

(c)

Tree Size-class



loss to the

atmosphere

uptake

Test of predictionsCumulative km67 Carbon Flux, 2001-2005

source

Mg (C) ha-1

-3 -2 -1 0 1 2 3 4 5

Jan Jul

2001 2002 2003 2004 2005


loss to the

atmosphere

uptake

Test of predictionsCumulative km67 Carbon Flux, 2001-2005

source

sink

Mg (C) ha-1

-3 -2 -1 0 1 2 3 4 5

Jan Jul

2001 2002 2003 2004 2005


loss to the

atmosphere

uptake

Test of predictionsCumulative km67 Carbon Flux, 2001-2005

2002

Cumulative Mg (C) ha-1

2005

2003

2004

Day of Year


Test of predictions: the Trends in Annual sums of carbon flux

Resp (declining at 0.9 MgC/ha/yr2)

Component fluxes(MgC/ha/yr)

GPP (increasing at 0.6 MgC/ha/yr2)

Net Exchange (loss) (= Resp – GPP)(MgC/ha/yr)


Precip controls short-term, the but not long-term, integrated Resp flux

Annual resp vs precip

Monthly resp vs precip

2002

2003

Respiration (MgC/ha/yr)

2004

Resp = 29.2 + 0.02(±.003)·Precip (R2 = 0.5)

Monthly precip (mm/month)

Annual precip (mm/year)


Test of predictions: the Forest Demography (a): Live biomass pool shifts toward balance

Carbon fluxes to Live Biomass at km 67

6

Recruitment

Growth

Mortality

0.85

Net Uptake

0.45

4

1.68

2

0.59

3.24

3.16

net C loss |net C uptake

MgC / ha / yr

0

Net Uptake

Net Uptake(near zero)

-2

-2.41

-3.02

-4

1999 - 2001

2001 - 2005


2.0 the

1.5

1.0

0.5

0.0

10

35

60

85

110

135

160

Test of predictions: Forest Demography (c): “Grow-in” shifts tree growth from smaller to larger size-classes

annual growth increment (MgC) by size class

1999-2001

2001-2005

MgC/ha/year

Size-class (cm DBH)

0.05

1999-2001

2001-2005

0.03

MgC growth/ MgC live

0.01

0.0

10-35

35-60

60-85

85-110

110-135

135-160

160-185

size class, cm DBH


Summary
Summary the

Preliminary pattern confirms disturbance recovery hypothesis:

(1) for eddy flux predictions:

  • Net ecosystem exchange shifts from source towards sink

  • Due in part to decline in ecosystem respiration

    (2) for demographic predictions:

  • Live biomass pool shifts towards balance

  • Grow-in shifts growth fluxes towards larger size classes


Iv conclusions
IV. Conclusions the

  • Multiple measures (demography, component fluxes, net C-balance) can be integrated to detect and track whole-forest response to disturbance

  • Detailed quantification of: - Flux magnitudes & Response times- demographic stateallows tests of models of important forest dynamics

  • We are making progress on understanding key factors for predicting large-scale forest carbon balance


Aboveground Biomass timeseries in 0.5-ha plots of Linhares Atlantic rainforest

Large-impact ENSO events

Rolim et al. (2005)


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