Economic assessment

Here it is outlined how the model estimates the financial outcome of harvest operations in each management unit, combining biological and economic processes into a reproducible workflow.

Harvest Aggregation by Management Unit

Harvested trees are summarized by species, management unit, and year.
For each combination, the model computes:

• Total harvested volume (m³): stem volume is estimated from its diameter and height using a Denzin-type formula.
• Tree height is estimated from DBH using an allometric exponential equation
• Quadratic mean diameter (QMD) of removed trees is also calculated
• Proportion of broadleaves in the harvest mix per MU it is also calculated

These summaries serve as the input for both price and cost calculations.

Price Estimation

Species-specific Gompertz functions are used to estimate wood revenues (average price in CHF per m3) as a function of QMD.
Each species has its own parameterization, reflecting differences in market value and log-size premiums.
The function increases with QMD but eventually saturates, capturing the nonlinear relationship between stem size and market price.

Cost Estimation

Harvesting costs (CHF per m³) are computed using negative Gompertz functions, parameterized by:

• Terrain type (flat or steep)
  
• Harvesting method (motor-manual or mechanized)
  
• Stand composition (broadleaf share)

These combinations account for productivity differences and operational constraints in various harvesting contexts.

Revenue Calculation

At the management-unit level, the model computes:

Net revenue (CHF) = Harvested volume × (Price – Cost)

This provides a consistent and scalable way to compare the profitability of alternative management options simulated in Model Forest Studio+.