Use of Biome-BGC with the ChEAS flux tower network to address scaling issues Faith Ann Heinsch NTSG, School of Forestry The University of Montana ChEAS Meeting July 1, 2003

The BIOME-BGC Terrestrial Ecosystem Process Model BIOME-BGC estimates fluxes and storage of energy, water, carbon, and nitrogen for vegetation and soil on a daily basis. Model algorithms represent physical and biological processes that control fluxes of energy and mass: New leaf growth and old leaf litterfall Sunlight interception by leaves, and penetration to the ground Precipitation routing to leaves and soil Snow (SWE) accumulation and melting Drainage and runoff of soil water Evaporation of water from soil and wet leaves Transpiration of soil water through leaf stomata Photosynthetic fixation of carbon from CO2 in the air N uptake from the soil Distribution of C and N to growing plant parts Decomposition of fresh plant litter and old soil organic matter Plant mortality Plant phenology Fire/disturbance

BIOME-BGC Major Features: Daily time step (day/night partitioning based on daily information) Single, uniform soil layer hydrology (bucket model) 1 uniform snow layer of SWE (no canopy snow interception/losses) 1 canopy layer (sunlit/shaded leaf partitioning) Dynamic phenology and C/N allocation (e.g. LAI, biomass, soil and litter) Disturbance (fire) and mortality functions Variable litter and soil C decomposition rates (3 litter and 4 soil C pools) Major Features:

Meteorological Parameters Required by Biome-BGC Daily maximum temperature (°C) Daily minimum temperature (°C) Daylight average temperature (°C) Daily total precipitation (cm) Daylight average partial pressure of water vapor (Pa) Daylight average shortwave radiant flux density (W/m2) Daylength (s)

LAI Site Data Latitude Elevation Slope/Aspect Soil Depth Soil Texture   Site Data Latitude Elevation Slope/Aspect Soil Depth Soil Texture Atmospheric CO2 Plant Soil Organic Matter Atmospheric N Soil Mineral N Allocation to New growth N Uptake MR Litter PSN GR HR Meteorological Data Air Temperature Radiation Precipitation Humidity Evaporation/ Transpiration Photosynthesis Total Respiration Soil and Litter Respiration LAI Snow Soil Outflow Temperature C Annual Input N Deposition N Fixation Daily - Annual Evapotranspiration Respiration Absorbed PAR Daily - Annual Allocation  Carbon, Nitrogen -leaf (LAI) -stem -coarse root -fine root N Flux C Flux H2O Periodic Input  Disturbance -fire -harvest -grazing -agriculture

BIOME-BGC Eco-physiological Parameters Biome-BGC uses a list of 43 parameters to differentiate biomes. general eco-physiological characteristics must be specified prior to each model simulation can be measured in the field, obtained from the literature or derived from other measurements. Default Biome types with defined parameters Deciduous Broadleaf Forest (temperate) Deciduous Needleleaf forest (larch) Evergreen Broadleaf Forest (subtropical/tropical) Evergreen Needleleaf Forest Evergreen Shrubland C3 Grassland C4 Grassland

Integration Simulation Validation Model Estimates of: Hydrograph data Biome BGC Landcover database Other inputs: soils, elevation, N-deposition Surface weather Disturbance history Vegetation parameter Simulation Model Estimates of: Outflow Snow ET Rh NEE NPP Soil C fPAR Biomass LAI Hydrograph data SNOTEL Flux tower Ancillary measurements at flux sites Satellite data (MODIS, AVHRR) FIA, FHM, Ecodata (Inventory) FIA = Forest Inventory and Analysis Program (USDA FS) FHM = Forest Health Monitoring (EPA) Ecodata = European – forest industry products, energy, and transportation data Validation

BIOME-BGC Simulated Daily Carbon and Water Exchange (1Barrow Tussock / Wet Sedge Tundra Site, 2000) Daily 1Meteorology Daily C Budget good job of biomass, but showing much less C uptake than tower data – must all be going underground (can’t msr well) doubled precip to prevent dryout. 1 Daily meteorological data obtained from Barrow W Post Station, 71.28N 156.76W

BIOME-BGC Simulated Cumulative Net Carbon Exchange (1Barrow Tussock / Wet Sedge Tundra Site) C sink (+) run for a couple of years with re-init every yr resp dominate – source for much of yr may not be true if sat during winter really more like what Atqasuk where it is drier (BGC does not do Barrow well). C source (-) 1 Daily meteorological data obtained from Barrow W Post Station, 71.28N 156.76W

Biome-BGC runs for 4 areas in Alaska Site Name Latitude C source (+) C sink (+) Biome-BGC runs for 4 areas in Alaska Alaska Study Region C source (+) C sink (+) electra sites sap flow, etc. grew forest, compared with Seawinds data and now MODIS latit variation between sites for C02 exchange -> freeze-thaw variation Site Name Latitude Kenai AK 60.18N Bonanza Creek AK 64.70N Coldfoot AK 67.15N Atigun AK 68.02N

Biome-BGC Estimates of LAI Park Falls, WI

Biome-BGC Estimates of NEE and GPP

Suggested Improvements to Biome-BGC Simulations at ChEAS Flux Tower Sites

Wetland-BGC Presently being tested in Barrow, AK and the Niyak floodplain near Glacier Park, MT Dynamic groundwater component Previously 1 soil layer, now 2 (saturated/unsaturated) Designed to be require minimal additional data Methane??

Unique Site Disturbance History Natural Disturbances Timing Intensity Examples Fire Blowdown Managed Disturbances Timing Intensity Examples Fertilization Harvest Slash burn Plant

Ensembling of Simulations Temporal Necessary for historic disturbances 1 simulation for each year of the meteorological record Obscures effects of meteorology to allow recovery to be seen Spatial Non-interactive Age class Old growth forests Selective harvest and replant Vegetation Type ENF vs. DBF Hydrology Upland vs. wetland

Disturbance History Credit: P. Thornton, NCAR

Seasonal Cycle of GEP Credit: P. Thornton, NCAR

Annual LAI in Final Simulation Year Credit: P. Thornton, NCAR

Annual NEE in Final Simulation Year Credit: P. Thornton, NCAR

Annual ET in Final Simulation Year Credit: P. Thornton, NCAR

Suggested Improvements Difficult to attribute discrepancies to either the model or measurements Probably a combination of: Site-specific parameterization Low maximum stomatal conductance Incorrect treatment of respiration at low Tair Site-specific measurement biases Undermeasurement of warm season respiration Need to find a way to decompose NEE

Biome-BGC Default Eco-physiological Parameters: Evergreen Needleleaf Forest

Example Initialization File MET_INPUT (keyword) start of meteorology file control block BIOME-BGC Example Initialization File metdata/TDE.mtc41 meteorology input filename 4 (int) header lines in met file RESTART (keyword) start of restart control block 1 (flag) 1 = read r estart file 0 = don't read restart file 0 (flag) 1 = write restart file 0 = don't write restart file 0 (flag) 1 = use restart metyear 0 = reset metyear restart/TDE_n.endpoint input restart filename restart/TDE. endpoint output restart filename TIME_DEFINE (keyword - do not remove) 8 (int) number of meteorological data years 8 (int) number of simulation years 1993 (int) first simulation year (flag) 1 = spinup simulation 0 = normal simulation 6000 (int) maximum number of spinup years (if spinup simulation) CLIM_CHANGE (keyword - do not remove) 0.0 (deg C) offset for Tmax 0.0 (deg C) off set for Tmin 1.0 (DIM) multiplier for Prcp 1.0 (DIM) multiplier for VPD 1.0 (DIM) multiplier for shortwave radiation CO2_CONTROL (keyword - do not remove) 1 (flag) 0=constant 1=vary with fil e 2=constant, file for Ndep 356.0 (ppm) constant atmospheric CO2 concentration TDE_co2.txt (file) annual variable CO2 filename SITE (keyword) start of site physical constants block 0.765 (m) effective soil dept h (corrected for rock fraction) 28.0 (%) sand percentage by volume in rock - free soil 64.0 (%) silt percentage by volume in rock - free soil 8.0 (%) clay percentage by volume in rock - free soil 290.0 (m) site elevation 35.95 (degrees) site latitude ( - for S.Hem.) 0.2 (DIM) site shortwave albedo 0.0005 (kgN/m2/yr) wet+dry atmospheric deposition of N 0.0004 (kgN/m2/yr) symbiotic+asymbiotic fixation of N

Example Initialization File (cont.) RAMP _NDEP (keyword - do not remove) BIOME-BGC Example Initialization File (cont.) 0 (flag) do a ramped N - deposition run? 0=no, 1=yes 2099 (int) reference year for industrial N deposition 0.0001 (kgN/m2/yr) industrial N deposition value EPC_FILE (keyword - do no t remove) dbf.epc (file) TDE DBF ecophysiological constants W_STATE (keyword) start of water state variable initialization block 0.0 (kg/m2) water stored in snowpack 0.5 (DIM) initial soil water as a proportion of sa turation C_STATE (keyword) start of carbon state variable initialization block 0.001 (kgC/m2) first - year maximum leaf carbon 0.0 (kgC/m2) first - year maximum stem carbon 0.0 (kgC/m2) coarse woody debris carbon 0. 0 (kgC/m2) litter carbon, labile pool 0.0 (kgC/m2) litter carbon, unshielded cellulose pool 0.0 (kgC/m2) litter carbon, shielded cellulose pool 0.0 (kgC/m2) litter carbon, lignin pool 0.0 (kgC/m2) soil carbon, fast microbial recycling pool 0.0 (kgC/m2) soil carbon, medium microbial recycling pool 0.0 (kgC/m2) soil carbon, slow microbial recycling pool 0.0 (kgC/m2) soil carbon, recalcitrant SOM (slowest) N_STA TE (keyword) start of nitrogen state variable initialization block 0.0 (kgN/m2) litter nitrogen, labile pool 0.0 (kgN/m2) soil nitrogen, mineral pool OUTPUT_CONTROL (keyword - do not remove) outputs/TDE_out (text) pr efix for output files 1 (flag) 1 = write daily output 0 = no daily output 0 (flag) 1 = monthly avg of daily variables 0 = no monthly avg 0 (flag) 1 = annual avg of daily variables 0 = no annual avg 1 (flag) 1 = write annual output 0 = no annual output 1 (flag) for on - screen progress indicator DAILY_OUTPUT (keyword) 3 (int) number of daily variables to output 516 0 epv.vwc (%) 43 1 wf.soilw_trans (kg m^ - 2) 38 2 wf.canopyw_evap (kg m^ - 2) ANNUAL_OUTPUT (keyword) 2 (int) number of annual output variables 545 0 annual maximum projected LAI 636 1 vegetation C END_INIT (keyword) indicates the end of the initialization file

What if Some Met Data is Missing? Use a nearby weather station Use MT-CLIM to estimate radiation and humidity measurements from Tmax, Tmin designed to handle complex terrain uses a base station to calculate “site” data Use DAYMET (conterminous U.S. only) uses several met stations surrounding site data available from 1980-1997 takes into account complex terrain

Soil Water Potential Curves BIOME-BGC 1Soil Water – Soil Water Potential Curves (%) (MPa) Soil Class Silt loam Silt Loam β-value -4.625 -3.84 -5.275 VWC_sat 0.48 0.48 0.41 PSI_sat -0.0073 -0.0078 -0.0013 1after Cosby et al., 1984

BIOME-BGC Environmental Controls on Canopy Conductance (Walker Branch Site) M_total,sun,shade = (MPPFD,sun,shade * MTmin * MVPD * MPSI) where multipliers range from 0 (full Gs reduction) to 1 (no effect) Gs, sun,shade = Gs,max * M_total, sun,shade

MODIS vs. Biome-BGC LAI MODIS sees higher lai – modeling for deciduous stand, but pixel sees mixed forest

GPP Estimates of 5X5 km Grid This is the GPP of the 5X5 km grid surrounding each tower site.

Park Falls/WLEF, WI

Park Falls/WLEF, WI: Tower vs. DAO

GPP from MOD17A2 Algorithm Default (DAO) Data As Input Meteorology

GPP from MOD17A2 Algorithm Tower Data As Input Meteorology