Stocks and Flows

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This set of features provides the ability to track, for each simulation cell, pools of stocks (e.g. carbon) and flows between pools (e.g. carbon fluxes). The stocks and flows are completely customizable: users can define any number of stocks and flows; furthermore flow pathways can occur automatically each timestep (e.g. biomass growth of carbon in forests), or they can be triggered by a transition in the STSM (e.g. carbon emissions due to fire). The ST-Sim stock-flow module has been designed to allow for the rapid development of IPCC-compliant Tier 2/3 greenhouse gas inventories associated with Agriculture, Forestry and Other Land Use (AFOLU).

Flow Pathways

This property defines how stock amounts move between pools, either automatically or as triggered by a transition event. Like the transition pathways this property has tabs along the bottom of the window. The first tab shows a diagram of the pathways which has similar behavior to the transition pathway diagram version. The second tab lists the stocks in the diagram and their position on the screen. The third tab lists the flow pathways. and includes the following fields:

Iteration

The iteration that this pathway applies to. This is an optional field and if left blank the pathway will apply to all iterations.

Timestep

The timestep that this pathway applies to. This is an optional field and if left blank the pathway will apply to all iterations.

From Stratum

The stratum associated with the flow pathway. This is an optional field and if left blank the pathway will apply to all strata.

From State Class

The unique label (e.g. cover type and structural stage) associated with the source state class of the flow pathway. This is an optional field and if left blank the pathway will apply to all state classes.

From Min Age

The minimum cell age required for the flow pathway. This is an optional field and if left blank the pathway will apply to all ages. When multiple flow pathway records meet the minimum age criterion, the one with the highest minimum age will be used.

From Stock

The source stock for the flow pathway. This is a required field. The flow pathway will move quantities from the source stock and add them to the destination stock.

To Stratum

The destination stratum associated with a flow pathway. This is an optional field and if left blank the flow pathway will apply to all destination strata.

To State Class

The destination state class associated with a flow pathway. This is an optional field and if left blank the flow pathway will apply to all destination state classes.

To Min Age

The minimum destination cell age required for the flow pathway. This is an optional field and if left blank the pathway will apply to all destination ages. When multiple flow pathway records meet the minimum destination age criterion, the one with the highest minimum age will be used.

To Stock

The destination stock for the flow pathway. This is a required field. The flow pathway will move quantities from the source stock and add them to the destination stock.

Transition Group

The transition group associated with the flow pathway. This is an optional field. If left blank the flow pathway is considered automatic and will be invoked every timestep. If the transition group is specified, the flow pathway will only be invoked when the transition group occurs to a cell.

State Attribute

This is an optional field that can be used to specify the [Attributes| state attribute] used to define the quantity of material associated with the flow pathway. For example a Net Primary Productivity state attribute could be defined for each state class which would be used to define the amount of carbon moving from the atmosphere stock to the biomass stock. If left blank, quantities of material moving associated with the flow pathway will be based on the total quantity of material present in the stock at the time the pathway is invoked.

Flow Type

This is a required field specifying the flow type associated with this flow pathway.

Multiplier

This is a required field that is multiplied against the quantity of material being moved from the source to the destination stock. When a state attribute specifies the quantity of material, that absolute quantity is adjusted by the multiplier. When no state attribute is specified, the multiplier defines the proportion of the total material present in the source stock that will be moved to the destination stock.


Initial Stocks

This is a property to initialize the stocks for each cell at the start of the simulation

Output Options

This property allows users to define the types and frequency of Stock and Flow output required.