Post Harvest Skidding Mortality

This mortality behavior simulates an increase in mortality after harvesting attributable to skidding damage or other effects. The increase in mortality tapers off through time. DBH and neighborhood basal area can also affect mortality in this behavior.

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

Trees killed by this behavior will have a mortality reason code of "natural".

Parameters for this behavior

Parameter name	Description
Post Harvest Skid Mort - Crowding Effect Radius	Maximum distance, in m, for neighbors to have a competitive effect.
Post Harvest Skid Mort - Pre-Harvest Background Mort Rate	Annual mortality rate, 0-1, if no harvest has occurred this run.
Post Harvest Skid Mort - Snag Recruitment Background Prob	Annual postharvest risk of standing death after harvest effects have completely tapered off.
Post Harvest Skid Mort - Snag Recruitment Basic Prob	Basic probability of standing death after harvest.
Post Harvest Skid Mort - Snag Recruitment Crowding Effect	The effect of neighborhood basal area on standing death probability.
Post Harvest Skid Mort - Snag Recruitment Rate Param	Determines how quickly the effects of harvesting on standing death probability taper off.
Post Harvest Skid Mort - Snag Recruitment Skidding Effect	Effect of harvest intensity on postharvest probability of standing death.
Post Harvest Skid Mort - Windthrow Background Prob	Annual postharvest risk of windthrow after harvest effects have completely tapered off.
Post Harvest Skid Mort - Windthrow Crowding Effect	The effect of neighborhood basal area on windthrow probability.
Post Harvest Skid Mort - Windthrow Harvest Basic Prob	Basic annual probability for windthrow after a harvest.
Post Harvest Skid Mort - Windthrow Harvest Rate Param	Determines how quickly the effects of harvesting on windthrow probability taper off.
Post Harvest Skid Mort - Windthrow Intensity Effect	Intensity effect parameter used for determining risk of windthrow.
Post Harvest Skid Mort - Windthrow Size Effect	Size effect term when determining risk of windthrow.

How it works

If no harvest has occurred yet in this run, the probability of dying in a timestep is:

Prob = 1 - (1 - β )^t

where:

Prob is the probability of dying before the end of the timestep
β is the Post Harvest Skid Mort - Pre-Harvest Background Mort Rate parameter
t is the number of years per timestep

If a harvest has occurred in the tree's cell during the run, the probability of mortality is:

multiplying over years i = 1...t (number of years per timestep);

W_i=(ρ _w + δ _w * DBH + κ _w * m - η _w * BA) * exp(-τ _w * (H * t + i)) + ω

where:

W_i is the annual post-harvest risk of windthrow
ρ _w is the Post Harvest Skid Mort - Windthrow Harvest Basic Prob parameter
δ _w is the Post Harvest Skid Mort - Windthrow Size Effect parameter
DBH is the tree's DBH in cm
κ _w is the Post Harvest Skid Mort - Windthrow Intensity Effect parameter
m is the harvest intensity from the tree's "HarvInten" data member, from the HARP external harvesting program (available for download from the SORTIE web site)
η _w is the Post Harvest Skid Mort - Windthrow Crowding Effect parameter
BA is the neighborhood basal area, in sq m per ha, within a radius set by the Post Harvest Skid Mort - Crowding Effect Radius parameter
τ _w is the Post Harvest Skid Mort - Windthrow Harvest Rate Param parameter
H is the number of timesteps since the last harvest in this tree's grid cell
t is the number of years per timestep
ω is the Post Harvest Skid Mort - Windthrow Background Prob parameter

and

S_i = (ρ _s + κ _s * m + φ _s * BA) * exp (-τ _s * (H * t + i)) + ?

where:

S_i is the annual postharvest risk of standing death
ρ _s is the Post Harvest Skid Mort - Snag Recruitment Basic Prob parameter
κ _s is the Post Harvest Skid Mort - Snag Recruitment Skidding Effect parameter
m is the harvest intensity from the tree's "HarvInten" data member, from the HARP external harvesting program (available for download from the SORTIE web site)
φ _s is the Post Harvest Skid Mort - Snag Recruitment Crowding Effect parameter
BA is the neighborhood basal area, in sq m per ha, within a radius set by the Post Harvest Skid Mort - Crowding Effect Radius parameter
τ _s is the Post Harvest Skid Mort - Snag Recruitment Rate Param parameter
H is the number of timesteps since the last harvest in this tree's grid cell
t is the number of years per timestep
? is the Post Harvest Skid Mort - Snag Recruitment Background Prob parameter

How to apply it

This behavior can be applied to saplings and adults of any species. In order for the harvest intensity term to have an effect, the float data member "HarvInten" must be registered for all species/type combos to which this behavior is applied, by using the HARP external harvesting program along with the Harvest Interface.