Harvest models and silvicultural treatments

SIMANFOR includes a comprehensive suite of harvest and thinning models applicable to both individual-tree projections and stand-level (aggregate) models.

Silvicultural interventions are defined through the simulator's Scenarios, allowing users to evaluate the impacts of varying thinning intensities and regimes on each individual tree, the stand, and all calculated variables.

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Harvest models, criteria and thinning intensity

Every thinning intervention in SIMANFOR is defined by selecting a harvest model (apply thinning), associated with a thinning criterion (type) and a thinning intensity (percent):

• Available harvest models (apply thinning):

  • For individual tree models:
    • Thinning from below
    • Thinning from above
    • Systematic thinning
    • Semi-systematic thinning (as a combination of the above, see details in Semi-systematic thinning)
    • Thinning (from below, from above or systematic) by species (mixed stands)
    • Thinning (systematic or from above) with future crop trees
    • Thinning (systematic or from above) with future crop trees by species (mixed stands)
  • For stand models:
    • Stand models harvests

• Available thinning criteria (type):

  • Density: Number of trees per hectare (trees/ha).
  • Basal area: Stand basal area (m²/ha).
  • Volume: Over-bark stand volume (m³/ha).

• Thinning intensity (percent): Percentage of the selected criterion to be removed during the intervention (value from 0 to 100 %).

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Minimum and maximum harvest age

Scenarios allow specifying an age range (min_age and max_age) to execute each harvest. This is particularly useful when simulating an inventory containing plots with different initial ages using the same scenario:

• min_age: Minimum stand age required to execute the harvest (years).
• max_age: Maximum stand age above which the harvest will not be applied (years).

Behavior outside the age range

If a plot's age is not within the range defined by min_age and max_age, the simulator will simply skip that harvest step for that plot and proceed with the rest of the simulation.

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Individual tree models harvests

Individual tree harvest models operate by selecting and removing specific trees from the tree list according to their size (based on diameter at breast height dbh) and their species.

Thinning from below

Harvesting starts with the trees with the smallest diameter at breast height (dbh) in the plot and progresses upward through larger diameter classes until the target thinning percentage is fulfilled.

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Thinning from above

Harvesting begins with the largest-diameter trees (dbh) in the plot and descends toward smaller diameter classes until reaching the specified intensity.

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Systematic thinning

Harvesting is evenly distributed across all diameter classes, reducing the expansion factor (expan) of every tree in the plot by the same proportion.

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Semi-systematic thinning

Although not programmed as a separate standalone model in SIMANFOR, it can be simulated by combining systematic and selective thinnings within the same scenario. For example, a semi-systematic thinning with a total intensity of 20 % can be simulated by applying a 10 % systematic thinning (representing line or rack opening) immediately followed by a 10 % thinning from below (representing selection among the remaining trees).

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Thinning (from below, from above or systematic) by species (mixed stands)

Allows targeting the harvest on a specific species in mixed stands using the following parameters:

• species: Numerical species code according to the National Forest Inventory (IFN / SFNI, see the model documentation).
• volume_target: Reference scope for the thinning intensity percentage:
  • Plot: The percentage is calculated relative to the total plot accumulation (cutting only trees of the target species).
  • Species: The percentage is calculated strictly relative to the standing stock of that target species within the plot.

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Thinning (systematic or from above) with future trees

• Additional parameter: preserve_trees (% of larger trees on which no action is to be taken, default is 15 %).
• Behavior: A specified upper percentage of dominant or largest trees is protected (preserve_trees). Thinning is then executed immediately on the next largest diameter classes below the protected crop trees.

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Thinning (systematic or from above) with future trees by species (mixed stands)

Combines the capabilities of the preceding thinning types, allowing users to configure target species (species), reference scope (volume_target), and percentage of crop trees to preserve (preserve_trees).

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Stand models harvests

In simulations using aggregate stand models, individual tree lists are not present, so harvests are systematic (with exceptions such as SILVES models, which include specific models to simulate thinnings from below and above). In these models, the configuration is as follows:

• Harvest model: [masa] Corta sistemática ([stand] Systematic thinning)
• Thinning criterion (type): densidad (density), area_basimetrica (basal_area) or volumen (volume)
• Thinning intensity (percent): Percentage to be harvested (0 to 100 %)

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Summary of scenario parameters

Parameter	Type	Description	Allowed values
type	Text / Integer	Thinning criterion	Density, Basal Area, Volume
percent	Integer	Thinning intensity	0 - 100 (%)
preserve_trees	Integer	Percentage of dominant trees protected	0 - 100 (%)
species	Integer	Target species code (IFN)	IFN code (e.g. 21, 24, 41)
volume_target	Text	Percentage calculation scope	Plot or Species
min_age	Integer	Minimum stand age to execute harvest	Years (e.g. 38)
max_age	Integer	Maximum stand age to execute harvest	Years (e.g. 42)