SORTIE-ND
Software for spatially-explicit simulation of forest dynamics

# Lagged post harvest growth

This behavior increments growth as a function of DBH and neighboring basal area, and incorporates a lag period after harvesting during which trees acclimate to their post-harvest growing conditions.

### Parameters for this behavior

Parameter nameDescription
Post Harvest Growth - DBH Growth EffectThe effect of DBH on growth.
Post Harvest Growth - DBH NCI EffectThe effect of DBH on the neighborhood competition index.
Post Harvest Growth - Max Growth ConstantMaximum annual radial growth, in mm.
Post Harvest Growth - NCI ConstantA constant adjusting the effects of NCI.
Post Harvest Growth - NCI Distance (m)The maximum distance at which neighboring trees can have competitive effects.
Post Harvest Growth - Time Since Harvest Rate ParamA parameter controlling the rate at which the actual growth approaches the potential growth after a harvest.

### How it works

A tree's potential growth is calculated by:

PARG = α * exp(-δ * DBH) * exp(-η BA * exp(-ω * DBH))

where:

• PARG is potential annual radial growth (mm/y)
• DBH is in cm
• BA is the basal area (in sq m) of adult trees within the distance given in the Post Harvest Growth - NCI Distance (m) parameter
• α is the Post Harvest Growth - Max Growth Constant parameter, the maximum radial growth in millimeters per year
• δ is the Post Harvest Growth - DBH Growth Effect parameter
• η is the Post Harvest Growth - NCI Constant parameter
• ω is the Post Harvest Growth - DBH NCI Effect parameter

If no harvest has occurred yet in this run, then the tree's actual growth, ARG, equals PARG. If a harvest has occurred at some point during this run, then ARG is calculated by:

ARG = ARGpre + (PARG - ARGpre) * (1 - exp(-τ * H * t))

where:

• ARG is annual radial growth (mm/y) for the current timestep
• ARGpre is annual radial growth for the last timestep prior to harvest
• H is the number of timesteps since the last harvest
• t is the number of years per timestep
• τ is the Post Harvest Growth - Time Since Harvest Rate Param parameter

Annual radial growth ARG is used to calculate timestep diameter growth using

DG = ARG * t * 2/10

where t is the number of years per timestep.

Model forms are based on those in Thorpe et al. 2010.

### How to apply it

This behavior can be applied to saplings and adults of any species.