1. Tools for quantifying GHG emissions from Agroecosystems
E. Pattey, R.L. Desjardins and W. Smith
Agriculture and Agri-Food Canada, Research Branch, Ottawa
CAgM Expert Team Meeting
on the Contribution of Agriculture to the State of Climate
Ottawa, Canada, September 2004

2. INTRODUCTION
Goals:
Develop a set of reliable Models for estimating net GHG emissions from agricultural sources/sinks and for deriving emissions factors relevant of a given country situation.
Establish a series of databases of the various agricultural activities for integrating the GHG emissions over space and time domains (land use, mgt practices, animal production, climate…) .

3. INTRODUCTION (Cont’d)
A “reliable” Model is:
sensitive to input conditions such as management practices;
adapted to the geographical and climatic conditions under which it will be used;
based on sound scientific knowledge.
…Ideally it requires a set of input descriptors easily available.
Framework:
Any national GHG emission accounting system needs to be transparent (well-documented), verifiable (pilot test sites, scaling-up experiments etc.) and consistent with the Kyoto Protocol.

4. OUTLINE
Speaker more familiar with Canadian situation Example of Canada…
GHG emission estimates from agricultural sources in Canada, CO2, CH4, N2O
Tools for developing models (chamber, tower)
Tools for verifying temporal dynamic and top-down constraints (tower, aircraft)
Results from tower- aircraft-based measuring systems
Modeling results from Ecosys, DNDC and Daycent
Summary

5. Greenhouse Gas Emissions from Canada’s Agroecosystems
(100 Year Time Horizon - Tg of CO2 equivalents)
1981
1986
1991
1996
2001
CO2 8 7 5 2
CH4 22 19 20 23 24
N2O 27 30 28 38 40
We are targeting 16 Mt CO2 eq of reduction in 2008
We promised to reduce CO2 by 11Mt ( C sequestration) and reached 5-6
We promised to reduce CH4 by 4-5 Mt and we do not have any reduction
We promised to reduce N2O by 1 Mt and our emissions increased by 12 Mt
BFE impact 15$per cow because CDN is not allowed to export in US
Total 57 56 53 63 64

6. Atmospheric Inversion
GHG flux measuring techniques only cover a limited portion of the space and time domains
Area m2 1 10
102
103
104
105
106
107
108
109
Chamber
Aircraft
BLS
&
Tracer 1
Mass
Balance 10
Atmospheric Inversion
Time h
Tower
102
Backward Lagrangian Stochastic technique
Soil
Cores
Satellite
103
Regional and sub-continental estimates using tall towers and CBL budgets
104

7. Benchmark Sites Inventory/ Monitoring Sites
Proposed Framework for a Accounting/Verification System
Regional/ National
Estimates
Regional Flux and
Surface Feature
Measurements
Verification
Scaling Up
Model Refinement
climate
soils
topography
land use
land
management
Data collection
Regional (Spatial)
databases
Auditing/ Monitoring
Process Studies
“Ecosystem Models”
Research Needs
Driving variables
Model Refinement
Verification
Verification
Long Term Experimental Sites: Flux, Meteorological and Ancillary Measurements
FGHG
Benchmark Sites Inventory/ Monitoring Sites
DCs

8. How do we improve and verify models?
Regional & Nat’l GHG budget
(with uncertainty estimates)
Verifying temporal dynamic
Top-Down constraint
Measuring towers, blimps aircraft
Modeling
Virtual Farm
(with uncertainty estimates)
Measuring chambers, towers
Developing new knowledge on mgt practices
time

9. Non-Flow Through, Non-Steady State Chamber Measurements
Fg = dC V Mw dt A Mv
Experimental design for comparing management practices and environmental conditions

10. Tower-based Measurements Closed-path Tunable Diode Laser
Sonic anemometer
Air Intakes
Closed-path Tunable Diode Laser

11. Setup for quantifying N2O fluxes for two management practices
1 TDL connected to 2 micromet. towers

12. Meas. model
Urea applied at the following rates:
Non-linear increase of N2O emissions with fertilizer application rate
ECOSYS
Grant, R. and Pattey, E., Modelling variability in N2O emissions from fertilized agricultural fields. Soil Biology and Biochemistry:35(2):

13. Flux Towers are the only suitable measuring approach …
during Snow melt (Permanent Site, Ottawa)

14. Harvested corn field - Snow melt

15. The global Fluxnet project features towers tracking the movement of carbon dioxide between various ecosystems and the air with emphasis on forest
Establish a network of towers for measuring N2O fluxes to verify temporal dynamics of models and assist in scaling up from individual agricultural fields to region
Biocap
Euroflux
Ameriflux
Japanflux

16. Aircraft-Based Measurements

17. The REA sampling system and TDL Laser
Aircraft REA system
Laboratory
TDL Laser

18. AC/Tower Study Sites, Spring 2001, 2003 and 2004
Canada
Casselman Flight Track
Tower Site
Morewood Flight Track km

19. Casselman Flight Track
LEGEND N
soy
cereals
pasture/grass
alfalfa
forest
corn
town
Highway 417
Casselman
13km
12 km

20. Morewood Flight Track N

21. Mean Crop Cover in 2000 within Footprint of Aircraft Transects5 10 15 20 25 30
Hay
Alfalfa
Corn
Soybean
Forest
Pasture
Cereals
Percentage (%)
Casselman
Morewood

22. Aircraft Results, 2001

23. Combining Tower and Aircraft N2O Fluxes
Unknown
FN2O by AC
kg N2O-N
ha day
FN2O by AC
(1130 to 1430)
ng N2O-N
m2 s
FN2O by Tower =
FN2O by Tower
kg N2O-N
ha day

24. Tower and Aircraft Results, 2004

25. Modeling and Aircraft Results, 2004

26. Schematic of the major components
of the DNDC model
Ecological drivers
Climate
Soil
Vegetation
Anthropogenic
activity
Decomposition
Crop Growth
Soil Climate
Soil environmental factors
Temperature
Moisture pH
Anaerobic
balloon
Substrates
(NH4+, NO3- and DOC)
Denitrification
Nitrification
N Gas Emissions
Fluxes of NO, N2O, N2 and NH3
Exchange of NO
and N2O
Effect of temperature and moisture on decomposition

27. Using models for obtaining regional and national estimates
Regional & Nat’l GHG budget
(with uncertainty estimates)
Measuring
Modeling
time

28. Cumulative net GHG emissions
Challenge: The net impact of management practices changes with time 20 40 60 80
100 1 2 3 4 5
Time (years)
Cumulative C (T ha-1)
Cumulative CO2-C from N fertilizer
(50 kg N ha-1)
Soil C gain
Net gain
Option A
time
Cumulative net GHG emissions
Option A
Option B
Option C

29. Estimated Direct N2O-N Emissions from Agriculture Soils in Canada Using DNDC (1970-1999)90
Estimated direct annual N2O-N emissions 80
Estimated direct spring N2O-N emissions 70 60 50
Gg N2O-N 40 30 20 10
1970
1972
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
Year

30. National C and GHG Accounting and Verification System
“Situations” defined by:
Soil
Climate
Land use
Management
country
province
“Model”
region
SLC polygon
SOC & GHG
Emissions for each
“situation”

31. Verification by direct measurement of national GHG estimates best done through holistic top-down national, continental, or global scale GHG budgets
N2O emissions?

32. Scientific uncertainty80
Relative
uncertainty
(estimated) 60 40
(Mt CO2 equiv. per year)
GHG emission 20
-20
-40
CO2
CH4
N2O

33. Scientific uncertainty
Understanding

34. Tools to quantify uncertainties
Sensitivity tests of models
Monte-Carlo approach for evaluating uncertainty

35. Summary
Tools for measuring GHG fluxes only cover a limited portion of the space and time domains
The combination of tower and aircraft-based GHG flux measurements provide valuable information to estimate regional fluxes on a daily basis
Models are essential for deriving national estimates of GHG emissions
Models still require lots of verification and improvement to provide more accurate estimates