The NCI crown depth and radius relationships

This calculates crown dimensions as a function of tree size and local crowding. The equations are the same for crown depth and crown radius, but they each have separate parameters.

NCI Crown Depth Parameters

Parameter nameDescription
NCI Crown Depth - Alpha NCI function exponent.
NCI Crown Depth - Beta NCI function exponent.
NCI Crown Depth - Crowding Effect "n" Crowding effect exponent.
NCI Crown Depth - Gamma NCI function exponent.
NCI Crown Depth Lambda for Species X Neighbors The competitive effect of neighbors of species X.
NCI Crown Depth - Max Potential Depth (m) The maximum possible value for crown depth, in m.
NCI Crown Depth - Max Search Distance for Neighbors (m) The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Crown Depth - Minimum Neighbor DBH (cm) The minimum DBH for trees of that species to compete as neighbors. Values are needed for all species.
NCI Crown Depth - Size Effect "d" Size effect function exponent.

NCI Crown Radius Parameters

Parameter nameDescription
NCI Crown Radius - Alpha NCI function exponent.
NCI Crown Radius - Beta NCI function exponent.
NCI Crown Radius - Crowding Effect "n" Crowding effect exponent.
NCI Crown Radius - Gamma NCI function exponent.
NCI Crown Radius Lambda for Species X Neighbors The competitive effect of neighbors of species X.
NCI Crown Radius - Max Potential Radius (m) The maximum possible value for crown radius, in m.
NCI Crown Radius - Max Search Distance for Neighbors (m) The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Crown Radius - Minimum Neighbor DBH (cm) The minimum DBH for trees of that species to compete as neighbors. Values are needed for all species.
NCI Crown Radius - Size Effect "d" Size effect function exponent.

The crown dimensions are calculated as:

CR / CD = [Max CR / Max CD] * Size Effect * Crowding Effect

where:

Size Effect is calculated as:

SE = 1 - exp(-d * DBH)

where:

Crowding Effect is calculated as:

CE = exp(-n * NCI)

where:

NCI is calculated as:

where: