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Mathias Göckede 1 , Beverly Law 1 , Tara Hudiburg 1 , David Turner 1 , Warren Cohen 1,2

Synthesizing multiple approaches to obtain comprehensive regional scale carbon budgets The ORCA2 West Coast Project. Mathias Göckede 1 , Beverly Law 1 , Tara Hudiburg 1 , David Turner 1 , Warren Cohen 1,2 1 OSU Dept. Forest Ecosystems & Society; 2 USFS Pacific Northwest Research Station.

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Mathias Göckede 1 , Beverly Law 1 , Tara Hudiburg 1 , David Turner 1 , Warren Cohen 1,2

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  1. Synthesizing multiple approaches to obtain comprehensive regional scale carbon budgets The ORCA2 West Coast Project Mathias Göckede1, Beverly Law1, Tara Hudiburg1, David Turner1, Warren Cohen1,2 1OSU Dept. Forest Ecosystems & Society; 2USFS Pacific Northwest Research Station

  2. ORCA2 project • Three states • - California- Oregon- Washington • Three approaches • - Bottom-up modeling- Top-down modeling- Biometric inventories • Project focus- climate variability- disturbance history- stand age- drought stress

  3. Biometric Inventory • Results based on • Forest Inventory and Analysis plots (~7000) • ~200 additional intensive study areas • Basic results • Biomass (e.g. live/dead trees, detritus) • Net primary production (increment data) • Extended results • Net ecosystem production (includes e.g. wood decomposition, litterfall, Dsoil C) • Net biome production (include havest, fire) • (Hudiburg et al., EcolAppl 2009)

  4. Inventory Results • Current NBP • 9.0 ∙ 106 12.2 ∙ 106 12.2 ∙ 106 • Fluxes in [Tg C yr-1] • High net uptake in California forests • High productivity along CA coast • CA harvest half of OR and WA • [gC m-2 yr-1] • (Hudiburg et al., in review)

  5. Biome-BGC Bottom-Up Modeling • Main features • Fully coupled C/N/H2O cycles • Prognostic phenology • Considers disturbances (e.g. crop/forest harvest, wildfires) • Reference datasets • Biometric inventories • - biomass - foliar C/N ratios • Trained at the ecoregion scale • (Turner et al., BioGeoSciences 2007)

  6. Bottom-Up Results • Main sinks • Coastal forests • Croplands (CA, WA) • Disturbance • Clearcuts and wildfireshighly important for regional carbon budget • Spatial setup • <1k grid resolution needed to capture disturbance mosaic • (Turner et al., in prep.)

  7. State-Level Carbon Fluxes • NBP/ff: 0.50 • NBP/ff: 0.96 • NBP/ff: 0.12 • NBP offsets a significant portion of fossil fuel emissions in Washington and Oregon, but just a small fraction in California

  8. ORCA2 Top-Down Modeling • 5 sites for continuous CO2 mixing ratios • 3 provide input for inversion • 2 used for quality assessment • Background CO2: NOAA CarbonTracker • Fossil fuel source: VULCAN database • (Göckede et al., JGR 2010a)

  9. ORCA2 Top-Down Results Background offsets • Regional CO2 budgets highly sensitive to background CO2 • 0.1 ppm offset in incoming air masses shifts Oregon CO2budget by ~10% • Correcting for biases in background CO2 mixing ratios reduced the statewide CO2 sink by ~47% (32 TgC yr-1) NEP • (Göckede et al., JGR 2010b)

  10. Methods comparison over Oregon • All fluxes • Annual NEP, 2007 • Forest fluxes • 5-yr avg, 2000-05 103± 20 gC m-2 yr-1 80± 24 gC m-2 yr-1 • Bottom-Up model 125± 13 gC m-2 yr-1 145± 31 gC m-2 yr-1 • Biometric inventory • Top-Down model

  11. Bottom-Up vs. Inventory Approach • Good agreement for many ecoregions, but some outliers

  12. Uncertainties in Top-Down Model • Background CO2 correction • Regional flux budget highly sensitive to incoming [CO2] • Large uncertainties associated with monitoring and correction • Concentration footprints • Information focused on center and coast • Coverage gaps particularly in SW and NE corners of state

  13. Analyzing / Interpreting Differences • Bottom-Up NEP • Concept • Fit an independent model that explains spatiotemporal flux differences based on auxiliary variables (e.g.RS, meteorol,...) • Research tool • Geostatistic inverse modeling • Important factors • Stand age influence • Drought stress • New model explaining differences • Top-Down NEP • (Göckede et al., in prep., cooperation with A. Michalak, V. Yadav, K. Mueller, S. Gourdji)

  14. Effects of biofuel management on regional forest carbon budget • Fire prevention: minimum impact, only aim to reduce wildfires • Economically feasible: medium impact, offset cost by wood sale • Bioenergy production: highest impact, thin 50% everywhere • (Hudiburg et al., in review)

  15. Biofuel management impacts • Managing forests for biofuels may increase emissions in region • Net impacts depend on current sink and forest sector FFE • (Hudiburg et al., in review)

  16. Summary of Analysis • Range of NEP estimates for the West Coast region, agreement between three methods improved with latest results • Each approach has individual strengths and weaknesses, combination helps to identify problems and uncertainties • NBP offsets a significant portion of fossil fuel emissions in Washington and Oregon, but just a small fraction in California • Disturbance (harvest, fire) is a significant driver of NEP and NBP in region (harvest dominates) • Thinning forests for bioenergy production increasesemissions of the region (20 year life cycle analysis)

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