Modelling the coupling between carbon turnover and climate variability of terrestrial ecosystems

1. Modelling the coupling between carbon turnover and climate variability of terrestrial ecosystems Per-Erik Jansson Department of Land and Water Resources Engineering Royal Institute of Technology KTH, Stockholm Seminar at ICRAF, Nairobi, 1 December 2010

2. Outline of presentation • Some general features of the CoupModel representing coupled ecosystem processes • Examples of how model has been used to describe specific sites with detailed measurements, regional scale with only standared data and climate scenarious • Some implications for future studies

3. A process oriented Ecosystem model - CoupModel Coupled heat and mass transfer model for soil-plant-atmosphere systems

4. Model Availability and Features http://www.lwr.kth.se/Vara%20Datorprogram/CoupModel/index.htm Includes documentation and tutorials

5. Water and Heat Processes

6. Carbon and Nitrogen Processes

7. Process oriented modelling platform with many components

8. Coupling between different submodels

9. Transpiration is a function of net radiation and resistances in plant and atmosphere Photosynthesis is a function of light and the stomata resistance Transpiration and Photosynthesis LAI

10. Single/Multiple Big Leaf Model

11. Emission of NO and N20

12. Methane emission model

13. Modelling of carbon dynamic of Swedish forest soils • Using models for interpretation of data and for upscaling • Development of procedures for calibration and upscaling using Bayesian calibration methods • Producing results for various scales

14. To start... • We have simple data from large regions and detailed data from some few sites • The few sites (Lustra CFS) and regional Forest inventory have been used together • The model has been used as a tool to understand and to make upscaling and downscaling 1 yr x

15. 3 steps ... • (1) estimation of parameters from regional data – 100 years. • (2) site specific data were used to calibrate the model for Flakaliden (dry mesic) and Asa (wet). • (3) climate change scenarios (A2, B2) were used together with parameters from the regional site (1) on a 100 year perspective for dry-mesic sites. 1 yr

16. N Regional approach • Objective: Estimate trends in soil C storage • Approach: Regional scale with representative sites • Data: Standing tree biomass and soil C and N pools

17. N Regional input data

18. TreeBiomass simulation in for four regions

19. Soil C change (g C m-2 yr-1) N • Different decomposition rate coeff. along Swedish transect Decomp. rate coeff. (kh) • Need for another source of N in addition to mineralised N • Current soil C pools in the south increases whereas central and northern soils are close to steady state Organic N uptake Versus min N Uptake

20. Tree and Fieldlayerdynamicsimportant for modelling long term dynamics South North

21. N Flakaliden-calibration Objective:Quantify major fluxes of C, heat and water includinguncertaintyestimates Approach:Bayesianuncertaintytheory Data: • Standing treebiomass and soil C and N pools • Internalfluxes i.e. litterfall, rootlitterproduction and DOC • Eddyfluxmeasurements of CO2, heat and water • Soilphysicalproperties • Soiltemperature

22. Model performance (mean of acceptedruns)

23. Uncertaintyestimates 644±74 570±55 363±43 138±37 207±31 -69±18

24. N Climatechange scenarios • Objective: Effects on C-budget and on governing and limiting factors due to climate change • Approach: Climate change of regional approach • Data: IPCC climate change scenarios Hadley A2 and B2

25. Different response on key components of ecosystemenvironment

26. Response for GPP (North and South)

27. Seasonal Dynamics Differs (north – south)

28. Climate change effect on tree growth and soil C change • NEP increased in all regions along the Swedish transect. • Major part of the increase related to tree growth.

29. Implications for future • Use best uncertainty methods to allow for estimations probabilistic distributions of parameters for specific field investigations • Make simulation experiments to understand uncertainties of coupled models rather than single submodels

30. Coupled models are necessary to understand long term behaviour of ecosystem • Soil climate is strongly coupled with vegetation and atmopheric climate • Soil physical conditions are a dynamic forcing for nitrogen and cabon turnover • Dynamic description of plant cover need to include both field and canopy layers for Swedish forest • Carbon, Nitrogen, Water and Heat have to be considered together

31. 100 yr x 1 yr x x Site Region Current Climate and Management • Upscaling and downscaling is now possible with flexibility and transparency but... • Uncertainties are still very difficult to express for the regional scale • Site specific data has generated new knowledge but no easy answers for upscaling… Future Climate and Management

32. Last comment • An adviser who believes too much in the figures from a mathematical model will be equally poor as the one who fully trusts results from field investigations.

33. Thanks for Thanks for your attention