shuguang liu and thomas loveland usgs national center for earth resources observation and science

March 17, 2005 2005 USDA Greenhouse Gas Symposium 1

US Carbon Trends

Spatial and Temporal Patterns of the Contemporary Carbon Sources and Sinks in

the Ridge and Valley Ecoregion of the United States

Shuguang Liu and Thomas Loveland

USGS National Center for Earth Resources Observation and ScienceSioux Falls, SD 57198


US Carbon Trends

Outline

The US Carbon Trends ProjectResearch QuestionsMethodology

The Ridge and Valley EcoregionLand Cover ChangeSpatial and Temporal Variability of C

Stocks and Fluxes


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Overarching Research Questions of Overarching Research Questions of the US Carbon Trends Projectthe US Carbon Trends Project

What is the spatial, temporal, and sectoral variability of What is the spatial, temporal, and sectoral variability of conterminous conterminous U.S. land cover changeU.S. land cover change from 1973 to 2000. from 1973 to 2000.

What are the spatial and temporal distributions of What are the spatial and temporal distributions of carbon sources and sinkscarbon sources and sinks, and therefore the dynamics of , and therefore the dynamics of carbon storage in the conterminous U.S.?carbon storage in the conterminous U.S.?

What are the What are the major driving forcesmajor driving forces that dictate the that dictate the evolution of US terrestrial carbon storage and the CO2 evolution of US terrestrial carbon storage and the CO2 exchange between the land and the atmosphere? exchange between the land and the atmosphere?

What are the major What are the major uncertaintiesuncertainties and knowledge gaps and knowledge gaps associated with estimating regional and national carbon associated with estimating regional and national carbon dynamics?dynamics?


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US Land Cover ChangeUS Land Cover Change

There is no consistent database available There is no consistent database available that characterizes the contemporary US that characterizes the contemporary US land cover change, because land cover change, because Land cover change mapping over Land cover change mapping over

large areas is a major effortlarge areas is a major effort Labor intensiveLabor intensive Money (funding sources)Money (funding sources)


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Thousands of Sampling Blocks

• Sampling units are 20- or 10-km2.

• Samples randomly selected within strata.

• Sample size based on expected spatial variability of change in the strata.

US Land Cover Change US Land Cover Change DetectionDetection

Probability-based sampling strategy used to provide efficient and reliable estimates of land cover change over large areas. Goal is to detect within one percent of actual change at 85% confidence level.

Ecoregions are sampling strata Land cover change was detected using Landsat images (i.e., 1973,

1980, 1986, 1992, and 2000)


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Spatially Explicit Modeling

GEMS (General Ensemble Biogeochemical Modeling System)

o An advanced modeling systems for spatially explicit simulation of biogeochemical cycling over large areas

o Developed at USGS National Center for Earth Resources Observation and Science

o Deployment of the encapsulated plot-scale model in space is based on a Joint Frequency Distribution of the major controlling variables (e.g., land cover, climate, soil, etc.).

o Included data assimilation algorithmso It includes a dynamic land cover/use change submodelo Stochastic simulations to incorporate uncertainties in input datao Uncertainty estimate of carbon dynamicso Major applications (US, Africa, and Central America)


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Land Cover: USGS Land Cover TrendsSoil: STATSGOClimate: CRTUS2.0 (1900 – 2000)N Deposition: National Atmospheric Deposition ProgramCrop Information: USDA Agricultural Census DataFIA: Forest biomass, NPP, Age Distribution

Thousands of Sampling Blocks

GEMS

Carbon dynamics simulated at 60 m x 60 m spatial resolution within 20 km x 20 km or 10-km by 10-km sampling blocks

National Benchmark Databases



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Blue Ridge (66)

Year

1970 1975 1980 1985 1990 1995 2000

NPP

(M

g C

ha-

1y-

1)

0

2

4

6

8

BLK1 BLK2 BLK3 BLK4 BLK5 BLK6 BLK7 BLK8 BLK9 BLK10

Year

1970 1975 1980 1985 1990 1995 2000

C S

ourc

e (-

) an

d S

ink (M

g C

ha-

1 y

-1)

- 0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

eco43 eco45 eco62 eco64 eco66 eco67 eco69

Block Ecoregion Nation

Quantify the spatial and temporal changes of C stocks, fluxes, and uncertainty at various scales

(10 km)

(60 m resolution)



US Carbon Trends Ridge and Valley Ecoregion

Geographic Location and Samples

The ecoregion spans 8 states.

A total of 40 10-km by 10-km sample blocks were randomly selected for land cover change detection and subsequent carbon simulations.



Land Cover Composition Around 1973Land Cover Composition Around 1973

Forest: 57.1%Cropland:31.4%Urban: 7.9%



water Urban A.Trans Mine/QuarryN.Bare Forest Grs/Shrub Agricult. Wetland1973 2.2 7.9 0.4 0.2 0.0 57.1 0.1 31.4 0.71980 2.4 8.1 0.4 0.2 0.0 56.8 0.1 31.3 0.71986 2.5 8.4 0.4 0.2 0.0 56.5 0.1 31.2 0.71992 2.5 8.7 0.5 0.2 0.0 56.4 0.1 30.9 0.72000 2.5 9.3 1.0 0.3 0.0 55.6 0.1 30.6 0.7

Extensification of forest harvesting activities

Forest area reduction: for2trans > trans2for

Ag land reduction: ag2for for2ag and urbanization

Urbanization (for2urban, ag2urban)

Annual change rate increases with time

Extensification of forest harvesting activities

Forest area reduction: for2trans > trans2for

Ag land reduction: ag2for for2ag and urbanization

Urbanization (for2urban, ag2urban)

Annual change rate increases with time

Land cover compositions (%)

(A) Annual rate of land cover change during four time periods. (B) the total share percentage of six major land cover change activities (C through F) in the total change rate, and (C through F) the share percentages of the major land cover change activities.

Land Cover Change 1973-2000Land Cover Change 1973-2000


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Forest Inversion

FIA data: biomass stock by age class (therefore biomass accumulation rates implicitly used) and total standing biomass

MODIS: annual NPP 2000-2001


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C Sink vs. C Sequestration

C Sequestration = C Sink - C Removal

and

C Removal = GrainYield + WoodHarvested



Interannual and Spatial Variability (Blocks)Interannual and Spatial Variability (Blocks)Data show block-scale annual averages from 1973 to 2000;X axis shows spatial variability across 10-km by 10-km blocks;Y axis shows interannual fluctuations by blocks.

Data show block-scale annual averages from 1973 to 2000;X axis shows spatial variability across 10-km by 10-km blocks;Y axis shows interannual fluctuations by blocks.



Interannual and Spatial Variability (Blocks)Interannual and Spatial Variability (Blocks)Data show block-scale annual averages from 1973 to 2000;X axis shows spatial variability across 10-km by 10-km blocks;Y axis shows interannual fluctuations by blocks.

Data show block-scale annual averages from 1973 to 2000;X axis shows spatial variability across 10-km by 10-km blocks;Y axis shows interannual fluctuations by blocks.

Net Primary Productivity (NPP)

Total Carbon Stock Change

Soil Organic Carbon Change

Large interannual variability

C sequestration strength increases from north (lower block ID numbers) to south;

Large interannual variability

Relatively smaller variability



C Stock and Land Cover Composition (Blocks)C Stock and Land Cover Composition (Blocks)

C stock at the block scale is

1. Positively correlated to forest fraction;

2. Negatively correlated to cropland fraction;

3. Not related to other land cover types.

C stock at the block scale is






C Sequestration and Land Cover Composition (Blocks)C Sequestration and Land Cover Composition (Blocks)

C sequestration at the block scale is




C sequestration at the block scale is






Carbon Rich Gets Richer (Blocks)Carbon Rich Gets Richer (Blocks)

Soil sequestration accounted for about 35% of the total C sequestration

Soil was a C source when total C sequestration was less than 50 g C m-2 y-1

C change rate in biomass and soils increases with total C stock



Temporal Change of C Stocks (Ecoregion)Temporal Change of C Stocks (Ecoregion)



Temporal Change of C Fluxes (Ecoregion)Temporal Change of C Fluxes (Ecoregion)

Large inter-annual variability in NPP, C sequestration, and total C sink.

Soil C sink and total C sink is decoupled.

C sequestration is tightly coupled with C sink strength.

Harvested wood C increased over time because of extensification of clearcutting.

The average C sequestration rate was 96 12 (1) gC m-2 y-1.



C Sinks and C Sequestration (Ecoregion)C Sinks and C Sequestration (Ecoregion)



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Summary

Land cover change was very dynamic. Major changes include urban expansion, reduction in cropland area, and extensification of clearcutting activities.

Large spatial and inter-annual variability in NPP, C sequestration, and total C sink.

C change rate in biomass and soils increases with total C stock

Soil C sink and total C sink is decoupled.


Harvested wood C increased over time because of extensification of clearcutting.

The average C sequestration rate was 96 12 (1) gC m-2 y-1.

Soil sequestration accounted for about 35% of the total C sequestration. Soil was a C source when total C sequestration was less than 50 g C m-2 y-1


US Carbon Trends

Poster 312

Soil Organic Carbon Budget as Related to Land Use History in the Northwestern Great Plains

shuguang liu and thomas loveland usgs national center for earth resources observation and science

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