Estimating the contribution of agricultural land use to terrestrial

carbon fluxes in the continental US

Keith Paustian1,2, Steven Ogle2, Scott Denning3 and Erandi Lokupitiya3

1Dept. of Soil and Crop Sciences, Colorado State University2Natural Resource Ecology Lab, Colorado State University3Dept. of Atmospheric Sciences, Colorado State University

Outline

• Agriculture’s role in the US C balance

• Bottom-up ‘inventory’ modeling of C dynamics in cropland and grassland

• Agricultural influences on process-based CO2 flux and transport modeling

The (familiar) overarching ?s

• What is the current C balance and magnitudes of sources and sinks in the US?

• Will sinks decrease in the future with LU changes and/or with CC?

• Can sinks be increased by management? How much? How fast?

What is agriculture’s role in all of the above?

• Responsible for ~ 7% of US GHG emissions (mostly from non-CO2)

• C balance on agricultural land dominated by soil carbon stock changes (and commodity exports)

• Policy needs– National inventory reporting (UNFCCC)– National (and market-based) GHG mitigation efforts

(50-250 Tg C/yr potential)– Resource conservation policies (national, state, local)– Biofuel development the new ‘wildcard’

Database Management

Run Control

Simulation Model: Century

Structural UncertaintyEstimator

Management ActivityCURRENT LAND USE INFORMATION FROM LOCAL KNOWLEDGE (SHEET A)

STATE INDIANA COUNTY BLACKFORD

FOR INDICATED SOILS ON MAP DETERMINE:MUID (STATSGO ASSOCIATION) IN004 IN005 IN029 IN032

LAND USE INFORMATION72.9 90.7 74 83.4

CLASS I & II

CLASS III & IV

CLASS V & VI

FOREST OR TREES 10.9 0.9 17.5 11.9

GRASS LANDS 14 7.7 8.5 3.1

WATER / WETLANDS 0.1 0.6 0 1.7

URBAN / OTHER 2 0.05 0 0TOTAL 99.9% 100.0% 100.0% 100.1% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%

LANDSCAPE DESCRIPTIONFLAT

ROLLING HILLS

STEEP HILLS

FLOOD PLAIN

OTHERTOTAL 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0% 0.0%

TOTAL CROPLAND: % OF THIS SOIL IDENTIFIED AS CROPLAND . THE SUM OF LAND CAPABILITY CLASS I & II, III & IV, AND V & VI MUST ADD TO THIS %.

CLASS I & II: % OF THIS SOIL THAT IS CLASS I & II CROPLAND.

CLASS III & IV: % OF THIS SOIL THAT IS CLASS III & IV CROPLAND.

CLASS V & VI: % OF THIS SOIL THAT IS CLASS V & VI CROPLAND.

FOREST OR TREES: % OF THIS SOIL IDENTIFIED AS FOREST OR TREES.

GRASS LANDS: % OF THIS SOIL IDENTIFIED AS GRASS LANDS.

WATER / WETLANDS: % OF THIS SOIL IDENTIFIED AS WETLANDS.

URBAN / OTHER LANDS: % OF THIS SOIL IDENTIFIED AS OTHER LANDS INCLUDING URBAN LANDS, DEVELOPED LANDS, ABANDONED LANDS.

LANDSCAPE DESCRIPTION: % OF THIS SOIL IN EACH LANDSCAPE DESCRIPTION.

CARBON SEQUESTRATION RURAL APPRAISAL

TOTAL CROPLAND

GENERAL LAND USE INFORMATION FROM LOCAL KNOWLEDGE (SHEET B)

STATE INDIANA COUNTY BLACKFORD

HAS ANY PART OF THE COUNTY BEEN DRAINED (YES/NO):IF YES, ANSWER THE FOLLOWING.

MUID % OF SOIL % OF SOILDRAINED DRAINED

IN004

IN005

IN029

IN032

MUID: SOIL MAP UNIT ID FROM STATSGO. (FROM MAP)

% OF SOIL DRAINED: GIVE AN ESTIMATE FOR THESE SOILS OF THE AMOUNT OF DRIANAGE INSTALLED.

TILE DRAINAGEOPEN DITCH DRAINAGE

CARBON SEQUESTRATION RURAL APPRAISAL

TIME PERIOD OF INSTALLATION: GIVE THE TIME PERIOD WHEN DRAINAGE PRACTICES WERE INSTALLLED. (i.e. 1930-1950, 1940-1960, 1970-1990, ETC.)

TIME PERIOD OF INSTALLATION

TIME PERIOD OF INSTALLATION

GENERAL LAND USE INFORMATION FROM LOCAL KNOWLEDGE (SHEET C)

STATE INDIANA COUNTY BLACKFORD

IS 10% OR MORE OF ANY MUID IRRIGATED (YES/NO):

IF YES, ANSWER THE FOLLOWING.

MUID % OF SOIL ANNUAL AMOUNT TYPES OF SYSTEMS

IRRIGATED APPLIED (INCHES)

IN004

IN005

IN029

IN032

M UID: SOIL MAP UNIT ID FROM STATSGO. (FROM MAP)

% OF SOIL IRRIGATED: GIVE AN ESTIMATE FOR THESE SOILS OF THE AMOUNT OF IRRIGATION INSTALLED.

CARBON SEQUESTRATION RURAL APPRAISAL

TIM E PERIOD OF INSTALLATION: GIVE THE TIME PERIOD WHEN IRRIGATION PRACTICES WERE INSTALLLED. (i.e. 1930-1950, 1940-1960, 1970-

1990, ETC.)

ANNUAL AM OUNT APPLIED (INCHES): GIVE AN ESTIMATE OF THE ANNUAL AMOUNT OF IRRIGATION WATER APPLIED IN INCHES. (6 INCHES, 12

INCHES, 15 INCHES, ETC.)

TYPES OF SYSTEM S: TYPICAL TYPE OF IRRIGATION SYSTEM INSTALLED. (CENTER PIVOT, GATED PIPE, ETC.)

TIME PERIOD OF

INSTALLATION

COUNTY LEVEL FARMING AND CROPPING SYSTEM HISTORY FROM PRE 1900 TO PRESENT (SHEET D)

STATE INDIANA COUNTY BLACKFORD

TIME FRAME 1970-1990+

% ESTIMATE OF COUNTY BEING FARMED DURING THIS TIME FRAME: 85%

CROP ROTATIONS (SPECIFY 1 TO 3)

1) CORN-SOYBEAN

2)

3)

FOR INDICATED CROPS

CROP NAME CORN SOYBEAN

YIELD (BU OR TONS/AC) 130 40

N FERT APPLIED (LBS/AC) 110

MANURE APPLIED (TONS/AC) 2

TYPICAL TILLAGE OPERATIONS DISK DISK

CULTIVATE DISK

PLANT PLANT

CULTIVATE CULTIVATE

Comments:

TIME FRAME: PERIOD OF TIME AS SPECIFIED.

FOR INDICATED CROPS: ACTUAL CROP INFORMATION FOR THE INDICATED CROPS IN THE ROTATIONS.CROP: CROP NAME AS SHOWN IN CROP ROTATION.

YIELD: CROP YIELD IN BU/AC FOR GRAINS OR TONS/AC FOR HAY.

N FERT APPLIED: ESTIMATE OF COMMERCIAL NITROGEN FERTILIZER APPLIED ANNUALLY (LBS/AC).

MANURE APPLIED: ESTIMATE OF MANURE APPLIED ANNUALLY (TONS/AC), BY CROP.TYPICAL TILLAGE OPERATIONS: TYPICAL TILLAGE OPERATIONS USED TO GROW THIS CROP. (EXAMPLES ARE FALL PLOW; SPRING PLOW; CHIESEL PLOW; DISK; HARROW; CULTIVATOR; DRILL; PLANT; ETC.)

CARBON SEQUESTRATION RURAL APPRAISAL

% ESTIMATE OF COUNTY BEING FARMED DURING THIS TIME FRAME: GIVE AN ESTIMATE OF THE COUNTY AREA BEING FARMED DURING THIS TIME FRAME.

TYPICAL CROP ROTATION: CROP ROTATIONS INCLUDE (CORN-CORN; CORN-SOYBEAN; CORN-CORN-OATS-MEADOW-MEADOW; CORN-SOYBEAN-CORN-OATS-MEADOW-MEADOW; ETC)

PRACTICES INSTALLED BY COUNTY AND SOIL TYPE

USE IN REPORTING TO DOE FOR CARBON SEQUESTRATION

(USE SEPARATE SHEET FOR EACH SOIL MUID)

STATE INDIANA COUNTY BLACKFORD MUID IN004

1985

1986

1987

1988

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

MUID: SOIL MAP UNIT ID FROM STATSGO. (FROM MAP)

NO-TILL: NO-TILL FARMING SYSTEM.

ANNUAL CONSERVATION PRACTICES INSTALLED

TREE PLANTING: ALL CONSERVATION PRACTICES THAT INCLUDE TREE PLANTINGS. (WINDBREAKS, SHELTERBELTS, AGRO-FORESTRY)

REDUCED TILLAGE: REDUCED TILLAGE FARMING WHICH LEAVE GREATER THAN 15% RESIDUE AFTER PLANTING. (INCLUDES MULCH TILL, RIDGE TILL BUT NOT NO-TILL).

COMMON CROP ROTATION (s)

ACRES OF CONSERVATION PRACTICES INSTALLED (ACRES)

CROP ROTATION: PICK THE TWO MOST COMMON CROP ROTATIONS. IF ONE ROTATION IS >90% OF CROPPED ACRES, REPORT ONLY THAT ROTATION. TOTAL FOR THE COUNTY SHOULD EQUAL THE CTIC REPORTED VALUES FROM 1989 TO PRESENT. SEE SUPPLEMENTAL INFORMATION.

GRASS CONVERSIONS: ALL GRASS PLANTING CONSERVATION PRACTICES.(WATERWAYS, BUFFERS INCLUDING RIPIARIAN BUFFERS, FILTER STRIPS, TERRACES, CRP).USE 12' WIDTH FOR TERRACES (LF*12/43560=ACRE). USE 40' WIDTH FOR ALL OTHER PRACTICES REPORTED IN LINEAR FEET (LF*40/43560=ACRE).

WETLANDS CREATED AND/OR RESTORED: ALL CONSERVATION PRACTICES THAT INCLUDE THE CREATION OR RESTORATION OF WETLANDS.

REDUCED

TILLLAGE

NO-TILL REDUCED

TILLLAGE

GRASS

CONVERSIONS

TREE

PLANTING

W ETLANDS

CREATED

AND/OR

RESTOREDNO-TILL

EnvironmentalConditions

Point Scale Data (NRI Survey)

PDF

Model Inputs Database

Results Database

Bottom-up modeling framework

Data sources

• National Resource Inventory (NRI)– Statically-based sample of ca. 800,000 points since

1979– LU, soils, crop rotations/vegetation– Most land management practices NOT collected

• County-, state- and regional survey data of management practices– E.g. tillage, fertilization, manuring, irrigation

• Regional-level land use practices (pre-1980)

Totals for US Croplands (1990s)

1990-1994: -62.0 ± 22% Tg CO2 eq. yr-1

1995-2000: -64.0 ± 16% Tg CO2 eq. yr-1

Current status – bottom-up efforts

• At national level, estimates of average soil C stock changes are relatively well constrained.

• However, at subregional & local levels uncertainties are high

• Current efforts focus on:– Reducing finer scale uncertainty– Improving estimates of NPP and C inputs– Obtaining bench-mark data on soil C stocks under

field conditions

Approach

• Adapting MODIS/EVI-based production estimates from NASA-CASA into Century

• Testing NPP and yield estimates at field-scale experiments

• Field-scale observation of soil C stocks and establishment of a pilot monitoring system

• Applying the new model to NRI inventory points

MODIS Enhanced Vegetation Index (EVI)

• Frequent (10 d) return interval• Low cost (primary data free)• Better resolution (250m) than previous

imagery (e.g. AVHRR) often used for regional crop modeling

• But still challenges dealing with mixed pixels and using traditional LTEs for ground-truthing.

CASA CQUEST

MODIS Enhanced Vegetation Index (EVI) - May 2004

Spatial Resolution: 250 meter

Farm boundaries and production patterns begin to emerge in details of landscape at 250-m resolution

Courtesy Chris Potter – NASA-Ames

Courtesy Chris Potter – NASA-Ames

Agricultural influences on process-based CO2 flux and transport modeling

• What’s the interannual variability in C fluxes from croplands and how does it influence interannual variability in cropland soil C stocks?

• Capturing within-season dynamics of cropland C fluxes.

NPP g/m2

85- 220220- 320320- 420420- 520520- 930

Cropland NPP the mid-continent region in a dry year (1988) and a wet year (1997)

0

50

100

150

200

250

300

350

400

1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997

Lokupitiya et al. 2007

Tg

C y

r-1Variability in residue C inputs 1982-1997

Permanent area for major crops (90 Mha)

-60

-40

-20

0

20

40

60

1982 1984 1986 1988 1990 1992 1994 1996

soil C stock residue C inputs

Annual anomalies in residue C and SOC stocks

Lokupitiya et al. in prep

(all land use and management changes are excluded)

Measured and modeled (SIB3-RAMS) CO2 concentrations at WLEF tower (400 m) in Wisconsin

Courtesy Scott Denning

Revised phenology and leaf area development algorithms

Cropland modifications to SIB3

Lokupitiya et al. unpubl.

a. before

b. now

Results from testing SIB3 for maize-soybean flux site – Bonneville, IL

Lokupitiya et al. unpubl.

Midcontinent Intensive (MCI)

Focus for initial inter-comparisons and synthesis of bottom-up approaches and bottom-up/top-down estimates within NACP

Field-campaign 2007-2008

Conclusions

• Soil C on US ag. land are currently a small sink

• Estimates relatively well constrained at national level thanks to abundant activity data and LTEs

• But, uncertainties high at local scale – where management decisions are implemented.

• Broad-based soil monitoring network and better fine-scale estimates of C additions to soil needed to reduce uncertainties at local scales.

• Large short-term C fluxes and large interannual variability associated with agricultural crops pose challenges for flux/transport based estimates of long-term C balance in agriculturally dominated ecosystems