CHRISTOPHER POTTER and RAMAKRISHNA NEMANI, NASA Ames Research Center

Continental Modeling and Analysis of the North American Carbon Cycle

U.S. Investigators NACP MeetingJanuary 23, 2007

Synthesis Questions

1. Which ecosystems types and/or regional land cover areas in North America have been the largest contributors to annual net carbon fluxes for the continent over the past 5-10 years?

2. What are the principal sources of uncertainty in the estimate(s) from Question 1 above?

Outputs: landscape-to continental scale predictive maps of above and below

ground distributions of sequestered

carbon for different climate scenarios

.

.

Land Cover Products

Inputs include continental-scale

land cover, EVI, FPAR, LAI, elevation, soils, and

climate data …

NPP/Rh Flux

BiomassPools

Climate data

Elevation

Multi-scale Validation Information

Inventory and Analysis Data

User Defined Output

Region of InterestTime FrameBiophysicalManagementClimate Scenario

Carbon Sequestration Predictions

Ecosystem Modeling & Remote Sensing Approaches

Process Model

Tower Data

Interannual Variability in MODIS NPP Carbon FluxesSource: Maosheng Zhao, Steve Running, et al. (2006)

Uncertainties from FPAR

Analysis for 2002; AGRO is for 2000(Turner et al. 2006, ITGRS)

Compared to inventory data, the default MODIS algorithm tends to underestimate NPP for the northern hardwood forests and overestimates NPP for coniferous and mixed forests-- But can be corrected by modeling soil moisture limitations.

Biome-BGC vs Flux (Evergreen Needleleaf Forest)

GPP (gC/m2/y) GPP CV (%)

NEE σ

Terrestrial Carbon Cycle from Biome-BGC (1950-2003)

NEE (gC/m2/y)

Post et al. (2006): The impact of ENSO cycles on NEP of North America terrestrial ecosystems indicated by the simulations of GTEC.

• During the unusual El Niño of the early 1990’s when Mount Pinatubo erupted, there is a large increase in the simulated North America carbon sink.

• Maps of the modeled NEP summed for X years indicate an increased carbon uptake by nearly all terrestrial ecosystems with the largest changes occurring in the eastern and boreal forests.

f(Temp)f(Water) f(Lit q)

(a) Daily Soil Moisture Balance and Irrigation of Cultivated Land

(b) Plant Production and Nutrient Mineralization

(c) Fertilizer Application and Trace Gas Emissions

Leaf Litter

CO2 (CH4)

Soil Nf(Lit q)

SoilProfile Layers

Freeze/ThawHeat &WaterFlux

PPT

N2O (NH3 & NO)

Crop/Grass Shrub TreeLAND COVER TYPES

PET

FPAR/EVI

NPP

M 0

M 1

M 2

M 3

Wood Litter

M 0

M 1

M 2

M 3

M 0

M 1

M 2

M 3

Soil Surface

TEMPPPTPETSOLAR

} NEP

NASA-CASA Simulation Model

Biomass

Root Litter

Soil OrganicMatter

Microbes

CO2

Fertilizer N

f(pH)f(Temp)f(Water)

f(N form) f(Application)

Air ChemistryModel

EOS Satellite Product Inputs

Smoothed Temperature

-2.0

-1.0

0.0

1.0

2.0

Year

60-30 N

NASA-CASA Model Prediction of North American Carbon SinkFall AGU ‘01 B52B-03 “The North America Carbon Sink from 1982-1998”

-100-75 -50 -25 0 25 50 75 100

1996 1997 1998

Summary: (a) Since 1982, the terrestrial ecosystem sink for

atmospheric CO2 in North America has been fairly consistent (at ca. 0.3 Pg C per year), except during relatively cool periods.

(b) Regional warming has had the greatest impact on high latitude (boreal) forest sinks for atmospheric CO2 in North America.

0.14 Pg C sink

0.39 Pg C sink 0.32 Pg

C sink

C Source C Sink-100 -50 0 +50 +100-100 -50 0 +50 +100

g C m-2 yr -1 Smoothed Annual Temperature30o - 60o N. America

CASA-Tower NPP Comparison Harvard Forest 2002

0

40

80

120

160

200

1 2 3 4 5 6 7 8 9 10 11 12

Month

NPP (g C m

-2 mo

-1)

BOREAS

NASA-CASA Model Prediction of U.S. Annual NEP FluxPotter et al. (submitted); Estimated using MODIS 8-km EVI Products

Terrestrial Carbon Budget of the Continental United States

All numbers are in units of Pg C for the late 1990s (Potter et al., 2006)

3.4

3.5

29 7.4

Woody Litter

23

1.6

Surface Soil Organic

NASA-CASA Model Prediction of Surface Soil C PoolsPotter et al. (2006); Does not include soil C stored below 30 cm depth

Source: Potter, C., S. Klooster, et al. 2007, Methane emissions from natural wetlands in the United States: Satellite-derived estimation based on ecosystem carbon cycling, Earth Interactions (in press). Estimated total U.S. annual emissions = 5 Tg CH4

Agricultural Management Impacts on Soil Carbon Storage (Download available at http://geo.arc.nasa.gov/sge/casa/cquestwebsite/ )

References for the Data Set:

• Eve, M.D., M. Sperow, K. Paustian, and R. Follett. 2002. National-scale estimation of changes in soil carbon stocks on agricultural lands. Environmental Pollution, 116: 431-438.• USDA National Resources Inventory (NRI): http://www.nrcs.usda.gov/technical/NRI/

NASA/USDA Carbon Cycle Science project: CO2 Fluxes Between Agricultural Lands and the Atmosphere: Towards More Complete Accounting by Integrating Remote Sensing with Simulation Modeling PI: Stephen Ogle, Colorado State University

Soil Carbon-Climate Feedbacks

Positive and negative values (in %) indicate an increase or decrease,respectively, in soil C sequestration occurring between 1981-2000.

Source: Jain, West, Yang, & Post. 2006.Geophysical Research Letters 32, L19711,doi:10.1029/2005GL023922

Net cumulative change in soil carbon from 1991-2000caused by changes in tillage intensity and crop rotations.

Change considering no loss fromintermittent tillage is 73.6 Tg C.

Net change is67.7 Tg C.

Source: T. West, et al. (2006)

I. Numerous regional-to-global modeling approaches show similar patterns in predicted NPP and carbon cycle variations over the U.S. continental region.

II. Areas of the contiguous U.S. that are contributing the most (in magnitude and variability) to the annual carbon cycle are in the Southeast, Gulf Coast, and Mountain West regions.

III. Uncertainties on which NACP Investigators should focus most of their efforts are the roles of major disturbances (drought, wildfire, and hurricane) and forest management practices in these three above-named regions of the U.S.

Observations and Recommendations

Wildfire

Drought

Coldwave

TropicalStorm

Large-scale events of the past20 years (Source: Potter etal, 2005, Ecosystems)

Insects