Weibull climate quadrat growth

This behavior calculates tree growth as a function of climate and neighbor trees. For processing efficiency, growth is calculated for each species on a per grid cell basis. There is a maximum potential growth rate that is reduced due to several possible factors.

Parameters for this behavior

Parameter nameDescription
Weib Clim Quad Growth - Competition Effect "C" The C parameter for the competition effect.
Weib Clim Quad Growth - Competition Effect "D" The D parameter for the competition effect.
Weib Clim Quad Growth - Max Neighbor Search Radius (m) The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
Weib Clim Quad Growth - Max Potential Growth (cm/yr) Maximum potential diameter growth for a tree, in cm/yr.
Weib Clim Quad Growth - Minimum Neighbor DBH (cm) The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this growth behavior.
Weib Clim Quad Growth - Precip Effect "A" The A parameter for the precipitation effect.
Weib Clim Quad Growth - Precip Effect "B" The B parameter for the precipitation effect.
Weib Clim Quad Growth - Precip Effect "C" The C parameter for the precipitation effect.
Weib Clim Quad Growth - Temp Effect "A" The A parameter for the temperature effect.
Weib Clim Quad Growth - Temp Effect "B" The B parameter for the temperature effect.
Weib Clim Quad Growth - Temp Effect "C" The C parameter for the temperature effect.

How it works

This behavior tracks growth using the Weibull Climate Quadrat Growth grid. Each tree gets the growth rate calculated for the grid cell in which it is found. You can set the grid cell size to set the balance between neighborhood composition resolution ( smaller grid cells) and processing time ( larger grid cells).

For a given species in a given grid cell, the amount of diameter growth per year is calculated as:


Growth = Max Growth * Precipitation Effect * Crowding Effect * Temperature Effect

Max Growth is the maximum diameter growth the tree can attain, in cm/yr, entered in the Weib Clim Quad Growth - Max Potential Growth (cm/yr) parameter. Precipitation Effect, Crowding Effect, and Temperature Effect are all factors which act to reduce the maximum growth rate and will vary depending on the local and plot-wide conditions a tree is in. Each of these effects is a value between 0 and 1.

Precipitation Effect is calculated as:

PE =  Weibull climate growth precipitation effect equation

where:

Temperature Effect is calculated as:

TE =  Weibull climate growth temperature effect equation

where:

Crowding Effect is calculated as:

CE = exp(-C * ND D)

where:

The ND value is a count of all neighbors with a DBH at least that of the Weib Clim Quad Growth - Minimum Neighbor DBH (cm) parameter, out to a maximum distance from the center of the grid cell set in the Weib Clim Quad Growth - Max Neighbor Search Radius (m) parameter. The value is a straight count - it is not scaled or relativized in any way. Seedlings never compete.

The amount of growth is in cm/year. For multi-year timesteps, the annual growth rate is multiplied by the number of years per timestep.

How to apply it

This behavior can be applied to seedlings, saplings, and adults of any species. You can use either the diam with auto height or diam only version.