NCI crowding effects

Most crowding effects must be paired with an NCI term. The NCI term returns one or more values representing different indexes of neighborhood competitiveness. Each crowding effect term can be matched with a variety of different competitiveness indexes and each one below describes how it uses each NCI value it receives.

Note: If these effects are used with NCI Mortality, the time period unit for parameters must match the value specified in the NCI Parameter Period (years) parameter.

Default crowding effect

This can be paired with NCI terms returning either one or two values.

Parameters

How it works

Crowding Effect is calculated as:

where:

• C is the NCI Crowding Effect Slope (C) parameter
• NCI1 is either the first term returned from a multi-value NCI, or in the case of a single-value NCI term, the diameter of the target tree, in cm (d10 for seedlings, DBH for all others)
• γ is the NCI Size Sensitivity to NCI (gamma) parameter for the target tree's species
• D is the NCI Crowding Effect Steepness (D) parameter
• NCI2 either the second term returned from a multi-value NCI term, or the single value returned from a single-valued NCI

The valid ranges on parameter values will depend on the choice of the NCI term.

Crowding effect 2

This can be paired with NCI terms returning either one or two values.

Parameters

How it works

Crowding Effect is calculated as:

where:

• C is the NCI Crowding Effect Slope (C) parameter
• NCI1 is either the first term returned from a multi-value NCI, or in the case of a single-value NCI term, the diameter of the target tree, in cm (d10 for seedlings, DBH for all others)
• γ is the NCI Size Sensitivity to NCI (gamma) parameter for the target tree's species
• D is the NCI Crowding Effect Steepness (D) parameter
• NCI2 either the second term returned from a multi-value NCI term, or the single value returned from a single-valued NCI

The NCI term is a separate term you select. For a list of options click here. The valid ranges on parameter values will depend on the choice of NCI.

Crowding no size term

This can be paired with NCI terms returning either one or two values, but it will only use one of them.

Parameters

How it works

Crowding Effect is calculated as:

where:

• C is the NCI Crowding Effect Slope (C) parameter
• D is the NCI Crowding Effect Steepness (D) parameter
• NCI either the second term returned from a multi-value NCI term, or the single value returned from a single-valued NCI

The NCI term is a separate term you select. For a list of options click here. The valid ranges on parameter values will depend on the choice of NCI.

Temperature dependent crowding

In this crowding effect term, plot temperature influences the effects of crowding. This can be paired with NCI terms returning either one or two values.

Parameters

How it works

Crowding Effect is calculated as:

where:

• NCI1 is either the first term returned from a multi-value NCI, or in the case of a single-value NCI term, the diameter of the target tree, in cm (d10 for seedlings, DBH for all others)
• γ is the NCI gamma parameter for the target tree's species
• D is the NCI Crowding Effect D parameter
• NCI2 either the second term returned from a multi-value NCI term, or the single value returned from a single-valued NCI

where:

• C is the NCI Crowding Effect C parameter
• X₀ is the NCI Crowding Effect CX0 parameter
• X_b is the NCI Crowding Effect CXb parameter
• T is the value in the Mean Annual Temperature, degrees C parameter of the Plot, converted to K

The NCI term is a separate term you select. For a list of options click here. The valid ranges on parameter values will depend on the choice of NCI.