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 name	Description
Post Harvest Growth - DBH Growth Effect	The effect of DBH on growth.
Post Harvest Growth - DBH NCI Effect	The effect of DBH on the neighborhood competition index.
Post Harvest Growth - Max Growth Constant	Maximum annual radial growth, in mm.
Post Harvest Growth - NCI Constant	A 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 Param	A 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 = ARG_pre + (PARG - ARG_pre) * (1 - exp(-τ * H * t))

where:

ARG is annual radial growth (mm/y) for the current timestep
ARG_pre 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.