Comments

• This diagram attempts to show the order of execution of ecosystem processes that we will use in the TCM.

• I derived this diagram based on a discussion with Peter Thornton and othersb on Oct 24, 2000 at NREL, and on the order of processes in BGC. Peter should look over this diagram.

• This diagram is process oriented, not object oriented.

• The arrows show both the flow of control between processes plus the data flow and data dependencies between processes.

• This diagram apparently does not include all possible processes or data flows. For example, it does not display a soil temperature submodel, or a disturbance submodel, or phenology related routines.

• This diagram assumes a daily time step, with each process occurring one time per day.

Diagram Key

• Blue – hydrologic and biophysics routines
• Green – Vegetation Physiology Routines
• Yellow – Biophysics routines
• Brown – Soil Biogeochemistry routines

• LAI – Leaf Area Index
• SLA – Specific Leaf Area
• PAR – Photosynthetically Active Radiation
• SWE – Snow Water Equivalent of snow on the surface
• GPP – Gross Primary Production
• SWP – soil water potential

List of ecosystem processes

•Allocation:  Allocates carbon and nitrogen to plants.  Requires plant carbon and nitrogen state variables, available soil nutrients, ecophysiological constants, and GPP from the Photosynthesis routine.

•Canopy Evaporation/Transpiration:  Computes the evaporation of intercepted canopy water; canopy water in excess of evaporated water is routed to the soil in a later routine. Requires meteorlogic variables, ecophysiological constants, SWP, and most outputs from the Radiative Transfer routine. Transpiration requires stomatal conductance.

•Decomposition and Organic Leaching:  Computes soil organic matter decomposition , leaching of organic C and N, and nitrogen trace gas fluxes. Requires SWP and soil water flow from the Hydrology routines, soil temperature, and soil carbon and nitrogen state variables.

•Growth Respiration: Computes growth respiration.  Requires allocation fluxes and ecophysiological constants.

•Radiative Transfer:  Calculates LAI, sunlit and shaded canopy fractions, specific leaf area from sunlit and shaded fractions, canopy transmission and absorption of shortwave radiation, and PAR absorbed.  Requires meteorologic variables, leaf carbon, and ecophysiological constants.

•Maintenance Respiration: Computes leaf, stem, fine root, and coarse root maintenance respiration.  Requires meteorologic variables, ecophysiolgocial constants, C and N content of each plant component, soil temperature, and output from Radiative Transfer routine.

•Mortality:  Not shown.  Computes death of live plant components; these become input to the soil decomposition routine in the next time step.  Requires ecophysiological constants, plant carbon and nitrogen state variables

•N leaching:  Computes the leaching of inorganic N in the soil once plant mineral N uptake has been calculated. Requires soil water flow and soil mineral N content.

•Phenology:  Not shown. Determines growing season start and end. Requires ecophysiological constants, daylength, and meteorologic variables.

•Photosynthesis:  Calculates GPP. Requires stomatal conductance, SLA and sunlit and shade fractions from the Radiative Transfer routine, meteorologic variables, ecophysiological constants, and maintenance respiration flux from the Maintenance Respiration routine..

• Precipitation Routing: Determines if precipitation falls as rain or snow, and determines the amount of rainfall that  can be intercepted by the canopy; the amount of rainfall in excess of interception (throughfall) will be routed to the soil in a later routine.  The intercepted water will be evaporated fom the canopy in the Canopy Evaporation routine.  Requires meteorologic variables, ecophysiological constants, and LAI.

•Snow Melt/Sublimation:  Computes the amount of SWE melted and sublimated; snowmelt is routed to the soil in a later routine.  Requires meteorologic variables, SWE.

•Soil Water Infiltration and Bare Soil Evaporation:  Calculates water infiltration through the soil, outflow, and water evaporated from the soil. (Actually two routines in BCG, combined for diagramming convenience).  Requires meteorologic variables, and outputs from Precipitation Routing and Snow Melt/Sublimation routines.

•Stomatal Conductance:  Computes stomatal conductance.  Requires meteorologic variables, SWP from the Hydrology routines, ecophysiological constants, and sunlit and shade fractions from the Radiative Transfer routine.