Historically Two Approaches
description
Transcript of Historically Two Approaches
Biospheric Process Models: The Challenge of Integrating Ecosystem
Dynamics and Land Cover Change
A. David McGuireUSGS and University of Alaska
Historically Two Approaches
CO2 and Climate
Process-BasedEcosystem
Models
Landuseand
Disturbance
Book-keepingModels
Modeling Integration for Investigating Global Change in Terrestrial Ecosystems
CLIMATE
DISTURBANCE
Physical Properties
EcosystemStructure
EcosystemFunction
HumanDimensions
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
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.
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
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
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.
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.
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)
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)
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
Biomass of Boreal Forest Ecosystemshas been Changing in Recent Decades
From Myneni et al. (2001)
Courtesy of K. McDonald
Growing seasons are occurring earlier
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
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)
After crown fires, boreal conifer forests are often replaced by less flammable deciduous broad-leaved vegetation
Fire in Canada has became more frequent after 1970
[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)
Firescars and Cohorts
Long-term Fire Return Interval for Alaska
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
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
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
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
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
Ground fires are typical in fire regime of Scots Pine Forests in Central Siberia
Courtesy of Doug McRae
Crown fires are typical in fire regime of Boreal Forests in Far East Siberia and North America
Courtesy of Doug McRae
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).
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
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
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
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
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%.
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
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
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
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
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
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.
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
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
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
• 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