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Historically Two Approaches

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Biospheric Process Models: The Challenge of Integrating Ecosystem Dynamics and Land Cover Change A. David McGuire USGS and University of Alaska. Landuse and Disturbance. CO 2 and Climate. Process-Based Ecosystem Models. Book-keeping Models. Historically Two Approaches. CLIMATE. - PowerPoint PPT Presentation
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Biospheric Process Models: The Challenge of Integrating Ecosystem Dynamics and Land Cover Change A. David McGuire USGS and University of Alaska
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Page 1: Historically Two Approaches

Biospheric Process Models: The Challenge of Integrating Ecosystem

Dynamics and Land Cover Change

A. David McGuireUSGS and University of Alaska

Page 2: Historically Two Approaches

Historically Two Approaches

CO2 and Climate

Process-BasedEcosystem

Models

Landuseand

Disturbance

Book-keepingModels

Page 3: Historically Two Approaches

Modeling Integration for Investigating Global Change in Terrestrial Ecosystems

CLIMATE

DISTURBANCE

Physical Properties

EcosystemStructure

EcosystemFunction

HumanDimensions

Page 4: Historically Two Approaches

McGuire and CCMLP Participants. 2001. Carbon balance of the terrestrial biosphere in the twentieth century: Analyses of CO2, climate and land use

effects with four process-based ecosystem models. 2001. Global Biogeochemical Cycles 15:183-206.

Dargaville and CCMLP Participants 2002. Evaluation of terrestrial carbon cycle models with atmospheric CO2 measurements: Results from

transient simulations considering increasing CO2, climate, and land-use effects. Global Biogeochemical Cycles 16, 1092,

doi:10.1029/2001GB001426.

Dargaville, R., A.D. McGuire, and P. Rayner. 2002. Estimates of large-scale fluxes in high latitudes from terrestrial biosphere models and an

inversion of atmospheric CO2 measurements. Climatic Change 55:273-285.

Process Models and Atmospheric Constraints

Page 5: Historically Two Approaches

Goal of Study:

… to simulate the concurrent effects of cropland establishment and abandonment, increases in atmospheric CO2, and interannual climate variability on terrestrial carbon storage between 1920 and 1992.

Page 6: Historically Two Approaches

Simulating the Effects of CO2, Climate, and Cropland Establishment and Abandonment by

Terrestrial Biosphere Models (TBMs)

CO2

Concentration

Climate(Temperature,Precipitation)

LanduseMap

TBMCarbon Pools

NPP RH Conversion Flux

Product Pools

NET

FireDisturbance

ProductDecay

Flux

1 yr

10 yr

100 yr

Page 7: Historically Two Approaches

Driving Data Sets

Historical CO2: based on Etheridge et al. (1996) and Keeling et al. (1995)

Temperature: based on Cramer and Leemans climatology and Jones et al. (1994) temperature anomalies

Precipitation: based on Cramer and Leemans climatology and Hulme et al. (1992, 1994, updated) precipitation anomalies

Solar Radiation: based on Cramer and Leemans climatology

Historical Landuse: based on Ramankutty and Foley (1998)

Relative Agricultural Productivity: based on Esser (1990)

Other Data Sets: vegetation and soils - model specific

Page 8: Historically Two Approaches
Page 9: Historically Two Approaches

1920 1930 1940 1950 1960 1970 1980 1990 2000

S3

Ne

t F

lux

(Pg

C y

r-1

)

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

CO2/O2 Budgets

Net Biota-to-Air

HRBM IBIS LPJ TEM

Comparison between net fluxes simulated by terrestrial biosphere models with a long-

term inversion analysis of terrestrial C exchange with the atmosphere

Modeled terrestrial exchange is consistent (within the

uncertainty) with the long-term inversion analysis.

Page 10: Historically Two Approaches

Partitioning effects of CO2, climate, and cropland establishment and abandonment on global terrestrial carbon storage for HRBM,IBIS,LPJ and TEM

The models indicate that the effects of CO2 and cropland establishment/abandonment play important roles in terrestrial carbon

storage. The models agree that the effects of climate are small relative to the effects of CO2 and land use, but disagree about whether climate

variability tends to cause net uptake or release of CO2.

Page 11: Historically Two Approaches

gC m2 yr-1

-1000

-10 -1 1 10 100 1000

HRBM IBIS

LPJ TEM

Mean Annual Net Carbon Exchange for the 1980s(CO2, Climate, and Land Use)

Page 12: Historically Two Approaches

gC m2 yr-1

-1000

-10 -1 1 10 100 1000

HRBM IBIS

LPJ TEM

Mean Annual Net Carbon Exchange for the 1980s(Land Use)

Page 13: Historically Two Approaches
Page 14: Historically Two Approaches
Page 15: Historically Two Approaches

McGuire et al. 2004. Canada and Alaska. Csiszar, I., et al. 2004. Land use and fires.

Chapters 9 and 19 in Land Change Science: Observing, Monitoring, and Understanding Trajectories of Change on the Earth’s Surface. Dordrecht,

Netherlands, Kluwer Academic Publishers.

Zhuang et al. 2003. Carbon cycling in extratropical terrestrial ecosystems of the Northern Hemisphere during the 20th Century: A modeling analysis

of the influences of soil thermal dynamics. Tellus 55B:751-776.

McGuire et al. 2002. Environmental variation, vegetation distribution, carbon dynamics, and water/energy exchange in high latitudes. Journal of

Vegetation Science 13:301-314.

Regional Changes in Carbon Storage may be Caused by Responses that affect Ecosystem

Physiology, Disturbance, and Land Cover Change

Page 16: Historically Two Approaches
Page 17: Historically Two Approaches

Biomass of Boreal Forest Ecosystemshas been Changing in Recent Decades

From Myneni et al. (2001)

Page 18: Historically Two Approaches

Courtesy of K. McDonald

Growing seasons are occurring earlier

Page 19: Historically Two Approaches

8.0 –18.0 Weeks – Region 118.0 – 28.0 Weeks – Region 228.0 –37.0 Weeks – Region 3

Duration of Snow FreePeriod 1972-2000

Snow

Fre

e D

urat

ion

An

omal

y (w

eeks

)

Weeks of Snow Free Duration (1972-2000)

Mean SD CV

Region 1TEM 14.1 3.5 0.24

Dye* 14.3 1.4 0.10

Region 2TEM 23.3 2.1 0.09

Dye 23.1 1.2 0.05

Region 3TEM 30.2 0.7 0.02

Dye 30.9 1.0 0.03*D. Dye, Hydrol. Process., 2002

Region 1

Slope = 0.035 Intercept = -0.499

R2 = 0.22

-2

-1.5

-1

-0.5

0

0.5

1

1972

1975

1978

1981

1984

1987

1990

1993

1996

1999

Based on TEMsimulationfor north of30o N

Page 20: Historically Two Approaches

Observed and simulated atmospheric CO2 concentrations at Mould Bay Station, Canada

(-119.35oW, 76.25oN) during the 1980s

-75 -60 -45 -30 -15 0 10 25 g C m-2 yr-1

Sink Source

90°

60°

30°

Spatial patterns of change in vegetation carbon over the twenty year period spanning from 1980-2000 as simulated by the Terrestrial Ecosystem Model (TEM)

Strategy to evaluate seasonal exchange of carbon dioxide simulated by terrestrial biosphere models

Incorporation of freeze-thaw dynamics into the Terrestrial Ecosystem model improves the simulation of the seasonal and decadal exchange of carbon dioxide exchange with the atmosphere

(Zhuang, Euskirchen, McGuire, Melillo, Romanovsky)

Page 21: Historically Two Approaches

After crown fires, boreal conifer forests are often replaced by less flammable deciduous broad-leaved vegetation

Page 22: Historically Two Approaches

Fire in Canada has became more frequent after 1970

Page 23: Historically Two Approaches

[CO2] and [O3]and N

Deposition

Climate(Temperature,Precipitation)

TEMCarbon Pools

NPP RH

NCE

Fire Emissions

Fire regime(Severity,History)

Simulation of the effects of changes in [CO2], [O3], N deposition,Climate, and Disturbance by the Terrestrial Ecosystem Model (TEM)

Page 24: Historically Two Approaches

Firescars and Cohorts

Page 25: Historically Two Approaches

Long-term Fire Return Interval for Alaska

Page 26: Historically Two Approaches

Cumulative Changes in Carbon Stocks for Alaska from 1950 - 1995

-200

0

200

400

600

800

1000

1950 1955 1960 1965 1970 1975 1980 1985 1990 1995

Tg

PFRI* = 50% FRI

PFRI = 100% FRI

PFRI = 150% FRI

* Pre-historical Fire Return Interval (before 1950)

** Fire Return Interval (1950-1995)

Uptake

Release

JSC 7/23/02

Page 27: Historically Two Approaches

Forested Area by Age Category

0

5

10

15

20

25

Stand Age

Pe

rce

nt

of

To

tal A

rea

of

Inte

rio

r A

las

ka Estimate from Forest Inventory Data

TEM 55% Fire Return Interval

Page 28: Historically Two Approaches

Cumulative Changes in Carbon Stocksin Alaska and Canada, 1960 to 1995

1960 1970 1980 1990 2000

Tg

C

0

500

1000

1500

2000

CO2CO2 + Climate

CO2 + Climate + Fire

CO2 + Climate + Fire +O3

CO2 + Climate + Fire + O3 +Ndep

Page 29: Historically Two Approaches

The high latitude transects span significant variationin several environmentalvariables and provide a network for improving our understanding of controls over vegetation dynamics, carbon dynamics and water/energy exchange in high latitudes

Page 30: Historically Two Approaches

alpin

e tundra

tundra

fore

st-tundra

boreal

southern

-bore

al

extra-b

oreal

Per

cen

t A

rea

Bu

rned

0.0

0.5

1.0AlaskaBFTCSFinlandEST FEST

Percent Area Burned in IGBP Transects

Page 31: Historically Two Approaches

Ground fires are typical in fire regime of Scots Pine Forests in Central Siberia

Courtesy of Doug McRae

Page 32: Historically Two Approaches

Crown fires are typical in fire regime of Boreal Forests in Far East Siberia and North America

Courtesy of Doug McRae

Page 33: Historically Two Approaches

Comparison of the average change in Seasonal Severity Rating (SSR) for Canada and Russia using the Canadian General Circulation Model (GCM) under left) a 1 x CO2, and right) a 2 x CO2 climate (from Stocks et al. 1998). Severity rating ranges

from extreme (red), high (orange), moderate (yellow) to low (green).

Page 34: Historically Two Approaches

Joyce et al. Harvesting disturbances on U.S. forestland from 1600 to present. In preparation.

McGuire et al. Historical changes in carbon storage of the eastern United States: Uncertainties associated with forest

harvest and agricultural activities. In preparation.

Regional Processes:The Challenge of Multiple Disturbances

Page 35: Historically Two Approaches

Overall Goals

• Develop land use model that allows native ecosystems to convert to agriculture, harvest occurrence inforests, and the creation the age cohorts followingharvest and cropland abandonment.

• Compare modeled age class distribution with independent inventory data on stand agedistributions

• Use data sets on forest disturbance to drive the Terrestrial Ecosystem Model (TEM) and evaluate how assumptions about CO2 fertilization and depletion of soil N by agricultural activities influence estimates of changes in carbon storage of the eastern US

Page 36: Historically Two Approaches

Methods to Estimate Harvest Area• Anecdotal information prior to 1952

• Used inventory data summarized by state/region from 1952, 1962, 1977, 1987, 1992, 1997, and 2002

• 1600 to 1952– Trend extrapolation based on state population – Assume no harvest disturbance prior to

European settlement

• 1952 to 2002– Model harvested area using inventory data

(volume, removals, timberland and forest area) and the limited data available on actual harvested area

– Linear interpolation between inventory years

Page 37: Historically Two Approaches

Development of the Land Use Model

• Agricultural Land Use– If cropland increases, conversion

draws from oldest native vegetation, with a preference for secondary growth.

– If cropland decreases, the oldest cropland is converted back to native vegetation

• Forest Harvest– Harvest oldest native vegetation first,

with a preference for primary forest

Page 38: Historically Two Approaches

USA Forest Area Comparison

600

700

800

900

1000

1100

1200

1600 1649 1698 1747 1796 1845 1894 1943 1992

Year

Ac

res

(m

illi

on

s)

Model Estimate Inventory Estimate

Modeled estimates of total forestland area follow the temporal dynamics of inventory

forestland estimates and are within 6 to 10%.

Page 39: Historically Two Approaches

Forest Harvest Area by Region and US1980-90 FIA Data and Modeled Estimates

0

2,000

4,000

6,000

8,000

10,000

12,000

Alaska Pacif ic NW Pacif ic SW Intermountain Great Plains North Central Northeast South Central Southeast United States

An

nu

al

Acre

s H

arv

este

d (

tho

usan

ds)

FIA 1980-90 Estimates Adjusted Ratio Estimates 1992

Page 40: Historically Two Approaches

Summary: Estimating Harvested Area

• Development of a method to obtain nationally consistent estimates of harvested area from 1600 to 2002

• Linked forest land use change with agricultural land use; resulting projections of forest land are within 6 to 10 percent of recent inventory

• Comparison with independent data on stand age is good where harvest is the major disturbance

• Where other disturbances such as fire, comparison of stand-age distributions are weak

Page 41: Historically Two Approaches

Simulating the Effects of CO2, Climate, Forest Harvest, and Cropland Establishment and

Abandonment by TEM

CO2

Concentration

Climate(Temperature,Precipitation)

LanduseMap

TEMCarbon Pools

NPP RH Conversion Flux

Product Pools

NET

FireDisturbance

ProductDecay

Flux

1 yr

10 yr

100 yr

Page 42: Historically Two Approaches

Comparison of forest growth curves between TEM and Birdsey (1995)

Southeast Region Coniferous Forest

Stand Age

0 10 20 30 40 50

g C

m-2

0

2000

4000

6000

8000

10000

12000

14000

16000

18000TEM vegc TEM ± 2 stdevSouthern Pine Plantation, site index 79+ Natural Pine, site index 79+ Natural Pine, site index 60-78

Page 43: Historically Two Approaches

1860 1880 1900 1920 1940 1960 1980 2000

g C

m-2

0

2000

4000

6000

8000

10000

12000

14000

Year

1860 1880 1900 1920 1940 1960 1980 2000

g N

m-2

50

100

150

200

250

300

350

400

a) Soil Organic Carbon

b) Soil Organic Nitrogen

Cultivated

Effects of Cropland Establishment and Abandonment on Soil Carbon and Nitrogen Storage

Page 44: Historically Two Approaches

Northeast Region

maximum soil N loss

0 20 40 60 80 100 120

g C

m-2

0

3000

6000

9000

12000

15000

18000

minimum soil N loss

Stand Age

0 20 40 60 80 100 120

g C

m-2

0

3000

6000

9000

12000

15000

18000

after agnever harvested

Temperate Deciduous, VegCmaximum soil N loss

0 20 40 60 80 100 120

g C

m-2

0

3000

6000

9000

12000

15000

18000

after agnever harvested

minimum soil N loss

Stand Age

0 20 40 60 80 100 120

g C

m-2

0

3000

6000

9000

12000

15000

18000

Temperate Coniferous, VegC

Forest growth as a function of stand age in the TEM simulations is sensitive to assumptions about the effects of agriculture on the depletion of ecosystem nitrogen stocks through time. When nitrogen lost in agricultural production is not replaced (maximum N loss), forest regrowth after agricultural abandonment is not able to achieve the biomass of forests that were never harvested. When the lost nitrogen is replaced immediately after lost (minimum N loss), forest regrowth after agricultural abandonment is able to achieve the biomass of forests that were never harvested.

Page 45: Historically Two Approaches

Change in Vegetation Carbon Stocks in the Northeast

1950 1960 1970 1980 1990 2000

Tg

C

-200

0

200

400

600

800

1000

min N loss, transient CO2

min N loss, constant CO2

max N loss, transient CO2

max N loss, constant CO2

Page 46: Historically Two Approaches

Average annual vegetation C flux 1988-1992 (Tg C)

maximum N loss$

Birdsey and Heath*

minimun N loss$

transient CO2$

Northeast 22.1 21.7 33.5

Southeast -4.8 8.2 16.5

constant CO2$

Northeast 16.2 21.7 23.6

Southeast -7.3 8.2 6.2

$ TEM simulations (forest cells only)* Birdsey and Heath posted on the web the carbon estimates in forest land for 1987, 1992, and 1997 by state at http://www.fs.fed.us/ne/global/pubs/books/epa/index.html

Page 47: Historically Two Approaches

Change in Soil Carbon Stocks in the Northeast

1950 1960 1970 1980 1990 2000

Tg

C

-300

-250

-200

-150

-100

-50

0

50

100

min N loss, transient CO2

min N loss, constant CO2

max N loss, transient CO2

max N loss, constant CO2

Page 48: Historically Two Approaches

• Biospheric process models provide a mechanistic means ofevaluating the relative role of different drivers of changes inregional carbon storage, but are poorly constrained by extant atmospheric data.

• At the regional scale, changes in carbon storage may be affected by responses to drivers that affect ecosystem physiology (e.g., CO2, climate, O3, N deposition) as well as changes that affect ecosystem structure (e.g., disturbance and land use).

• It is important to account for historical legacies associated withdisturbance regimes like fire.

• Age class distributions are generally the outcome of multiple disturbances, and it is a challenge to identify all of the disturbances that need to be considered.

• Comparison with inventory analyses is useful, but may not resolve controversies about the relative role of different drivers of

changes in regional carbon storage.

Conclusions


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