SORTIE-ND

Software for spatially-explicit simulation of forest dynamics

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NCI terms

NCI effects calculate various indexes of neighborhood competitiveness that are used in crowding effects. NCI effects can calculate one or more values that are inserted into the appropriate places in the crowding effect that the NCI term is paired with. Look carefully at the documentation for both NCI and crowding to determine how many values are calculated with NCI and how they are used in crowding.

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 NCI term

NCI is a function of neighbor distance and size. The neighbor's species also matters; the effect depends on the relationship between the target species and the neighbor species. Seedlings never compete. You set whether or not snags compete in the Include Snags in NCI Calculations parameter.

This returns one value: the NCI as described below.

Parameters

NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
Species i NCI lambda neighbors	The competitive effect of neighbors of species i on the target tree species, between 0 and 1.
NCI Maximum Crowding Distance, in meters	The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.
NCI DBH Divisor (q)	The value by which neighbor DBHs are divided when calculating NCI. This can be used to make units adjustments.
Include Snags in NCI Calculations	Whether or not to include snags when finding competitive neighbors for NCI.

How it works

NCI is calculated as:

where:

the calculation sums over j = 1...S species and k = 1...N neighbors of each species of at least a DBH of NCI Minimum Neighbor DBH, in cm, out to a distance of NCI Maximum Crowding Distance, in meters
α is the NCI Alpha parameter for the target tree's species
β is the NCI Beta parameter for the target tree's species
DBH_jk is the DBH of the kth neighbor, in cm
q is the NCI DBH Divisor (q) parameter. Set this to a value greater than 1 to rescale the competitive effects of neighbors
λ _ik is the Species j NCI Lambda parameter for the target species relative to the kth neighbor's species
distance_ik is distance from target to neighbor, in m

NCI with neighbor damage

This is the default term with the addition of the effects of storm damage on neighbors.

This returns one value: the NCI as described below.

Parameters

NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
Species i NCI lambda neighbors	The competitive effect of neighbors of species i on the target tree species, between 0 and 1.
NCI Maximum Crowding Distance, in meters	The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.
NCI Neighbor Storm Damage (eta) - Complete (0-1)	The fraction to which a neighbor's competitive effect is reduced when the neighbor has sustained complete storm damage.
NCI Neighbor Storm Damage (eta) - Medium (0-1)	The fraction to which a neighbor's competitive effect is reduced when the neighbor has sustained medium storm damage.
NCI DBH Divisor (q)	The value by which neighbor DBHs are divided when calculating NCI. This can be used to make units adjustments.
Include Snags in NCI Calculations	Whether or not to include snags when finding competitive neighbors for NCI.

How it works

NCI is calculated as:

where:

the calculation sums over j = 1...S species and k = 1...N neighbors of each species of at least a DBH of NCI Minimum Neighbor DBH, in cm, out to a distance of NCI Max Radius of Crowding Neighbors, in m
η _k is the storm damage parameter of the kth neighbor, depending on the damage status (optional). If the neighbor is undamaged, the value is 1. If the neighbor has medium damage, the value is the NCI Neighbor Storm Damage (eta) - Medium (0-1) parameter for the target species. If the neighbor has complete damage, the value is the NCI Neighbor Storm Damage (eta) - Complete (0-1) parameter for the target species.
α is the NCI Alpha parameter for the target tree's species
β is the NCI Beta parameter for the target tree's species
DBH_jk is the DBH of the kth neighbor, in cm
q is the NCI DBH Divisor (q) parameter. Set this to a value greater than 1 to rescale the competitive effects of neighbors
λ _ik is the Species j NCI Lambda parameter for the target species relative to the kth neighbor's species
distance_ik is distance from target to neighbor, in m

How to apply it

For all trees to which this behavior applies, you must also have the Storm damage applier behavior applied.

Count of larger neighbors

This value is a count of all larger neighbors with a DBH at least that of the NCI Minimum Neighbor DBH, in cm parameter, out to a maximum distance set in the NCI Maximum Crowding Distance, in meters parameter. The value is a straight count - it is not scaled or relativized in any way. Seedlings are never counted.

This effect cannot be used if the NCI behavior is applied to seedlings.

This returns one value: the neighbor count.

Parameters

NCI Maximum Crowding Distance, in meters	The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.

BA of neighbors

This returns one value: the neighbor basal area.

Parameters

NCI Maximum Crowding Distance, in meters	The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.
NCI BA Divisor	The value by which to divide neighbor basal area.
NCI - Use Only Larger Neighbors	Whether to use all neighbors larger than the minimum DBH (false) or only neighbors larger than the target tree (true).

How it works

This value is the sum of basal area for neighbors with a DBH at least that of the NCI Minimum Neighbor DBH, in cm parameter, out to a maximum distance set in the NCI Maximum Crowding Distance, in meters parameter. If the parameter NCI - Use Only Larger Neighbors is set to true, only those neighbors larger than the target are used. Otherwise, all neighbors above the minimum DBH are used. Seedlings are never counted.

Basal area is reported in total cm². It is divided by the value of the parameter NCI BA Divisor, which can be used to adjust units if desired.

This effect may be used when NCI is being applied to seedlings, but only if the NCI - Use Only Larger Neighbors parameter is set to false.

NCI with seedlings

This returns one value: the NCI as described below.

Parameters

NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
Species i NCI lambda neighbors	The competitive effect of neighbors of species i on the target tree species, between 0 and 1.
NCI Maximum Crowding Distance, in meters	The maximum distance, in m, at which a neighboring tree has competitive effects on a target tree.
NCI Minimum Neighbor Diam10, in cm	The minimum d₁₀ for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.
NCI Diam10 Divisor (q)	The value by which neighbor d₁₀s are divided when calculating NCI. This can be used to make units adjustments.
Include Snags in NCI Calculations	Whether or not to include snags when finding competitive neighbors for NCI.

How it works

The NCI value sums up the competitive effect of all neighbors with a d₁₀ at least that of the NCI Minimum Neighbor Diam10, in cm parameter, out to a maximum distance set in the NCI Maximum Crowding Distance, in meters parameter. The competitiveness of a neighbor increases with the neighbor's size and decreases with distance. The neighbor's species also matters; the effect depends on the relationship between the target species and the neighbor species.

Unlike the default NCI, this competitiveness index uses d₁₀ instead of DBH; so seedlings can compete. For adults, the d₁₀ is calculated from DBH using the DBH - diameter at 10 cm relationship. You set whether or not snags compete in the NCI - Include Snags in NCI Calculations parameter.

NCI is calculated as:

where:

the calculation sums over j = 1...S species and k = 1...N neighbors of each species of at least a d₁₀ of NCI Minimum Neighbor Diam10, in cm, out to a distance of NCI Maximum Crowding Distance, in meters
α is the NCI Alpha parameter for the target tree's species
β is the NCI Beta parameter for the target tree's species
D10_jk is the d₁₀ of the kth neighbor, in cm
q is the NCI Diam10 Divisor (q) parameter. Set this as necessary to rescale the competitive effects of neighbors
λ _ik is the Species j NCI Lambda parameter for the target species relative to the kth neighbor's species
distance_ik is distance from target to neighbor, in m

BA ratio

This creates two terms: the first is basal area ratio, and the second is total neighbor basal area.

Parameters

Parameter name	Description
Maximum Adult Crowding Distance, in meters	The maximum distance to look for crowding adult neighbors.
Maximum Sapling Crowding Distance, in meters	The maximum distance to look for crowding sapling neighbors.

How it works

This creates two terms: total neighbor basal area (in m²), and basal area ratio. Neighbors are all adults within a radius of Maximum Adult Crowding Distance, in meters, and all saplings within a radius of Maximum Sapling Crowding Distance, in meters. The basal area ratio is the ratio of mean neighbor basal area to target tree basal area.

BA ratio with target default

This creates two terms: the first is basal area ratio, and the second is total neighbor basal area.

Parameters

Parameter name	Description
Maximum Adult Crowding Distance, in meters	The maximum distance to look for crowding adult neighbors.
Maximum Sapling Crowding Distance, in meters	The maximum distance to look for crowding sapling neighbors.
Default DBH, in cm	The value to be used for target DBH.

How it works

This works exactly like the NCI term BA ratio, except the ratio is always mean neighbor basal area to the basal area calculated from the Default DBH, in cm. Use this when using a version of the NCI Quadrat master, when a target diameter would not be available.

NCI + BA ratio

This creates two terms: the first is the basal area ratio, and the second is NCI as described below.

Parameters

DBH Adjustment Factor	Any corrective or units adjustment factor to be multiplied by neighbor DBH.
Maximum Adult Crowding Distance, in meters	The maximum distance to look for crowding adult neighbors.
Maximum Sapling Crowding Distance, in meters	The maximum distance to look for crowding sapling neighbors.
NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
Species i NCI lambda neighbors	The competitive effect of neighbors of species i on the target tree species, between 0 and 1.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.

How it works

NCI is calculated as:

where:

the calculation sums over j = 1...S species and k = 1...N neighbors of each species of at least a DBH of NCI Minimum Neighbor DBH, in cm, out to a distance of Maximum Adult Crowding Distance, in meters (for adult neighbors) or Maximum Sapling Crowding Distance, in meters (for sapling neighbors)
α is the NCI Alpha parameter for the target tree's species
β is the NCI Beta parameter for the target tree's species
DBH_jk is the DBH of the kth neighbor, in cm
q is the DBH Adjustment Factor parameter. Use this to correct units or make other adjustments
λ _ik is the Species j NCI Lambda parameter for the target species relative to the kth neighbor's species
distance_ik is distance from target to neighbor, in m

This also calculates basal area ratio. Neighbors are all adults within a radius of Maximum Adult Crowding Distance, in meters, and all saplings within a radius of Maximum Sapling Crowding Distance, in meters. The basal area ratio is the ratio of mean neighbor basal area to target tree basal area.

NCI + BA ratio with target default DBH

This creates two terms: the first is the basal area ratio, and the second is NCI.

Parameters

DBH Adjustment Factor	Any corrective or units adjustment factor to be multiplied by neighbor DBH.
Default DBH, in cm	The value to be used for target DBH.
Maximum Adult Crowding Distance, in meters	The maximum distance to look for crowding adult neighbors.
Maximum Sapling Crowding Distance, in meters	The maximum distance to look for crowding sapling neighbors.
NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
Species i NCI lambda neighbors	The competitive effect of neighbors of species i on the target tree species, between 0 and 1.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.

How it works

This works exactly like the NCI term NCI + BA ratio, except the ratio is always mean neighbor basal area to the basal area calculated from the Default DBH, in cm. Use this when using a version of the NCI Quadrat master, when a target diameter would not be available.

NCI with temp dependent lambda + BA ratio

NCI is a function of neighbor distance, size, and species. The competitive effect of neighbors is a function of plot temperature.

This creates two terms: the first is the basal area ratio, and the second is NCI as described below.

Parameters

DBH Adjustment Factor	Any corrective or units adjustment factor to be multiplied by neighbor DBH.
Maximum Adult Crowding Distance, in meters	The maximum distance to look for crowding adult neighbors.
Maximum Sapling Crowding Distance, in meters	The maximum distance to look for crowding sapling neighbors.
NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.
Species i NCI lambda X0 neighbors	X0 in the function to calculate the competitive effect of neighbors of species i on the target tree species.
Species i NCI lambda Xa neighbors	Xa in the function to calculate the competitive effect of neighbors of species i on the target tree species.
Species i NCI lambda Xb neighbors	Xb in the function to calculate the competitive effect of neighbors of species i on the target tree species.

How it works

NCI is calculated as:

where:

the calculation sums over j = 1...S species and k = 1...N neighbors of each species of at least a DBH of NCI Minimum Neighbor DBH, in cm, out to a distance of Maximum Adult Crowding Distance, in meters (for adult neighbors) or Maximum Sapling Crowding Distance, in meters (for sapling neighbors)
α is the NCI Alpha parameter for the target tree's species
β is the NCI Beta parameter for the target tree's species
DBH_jk is the DBH of the kth neighbor, in cm
q is the DBH Adjustment Factor parameter. Use this to correct units or make other adjustments
distance_ik is distance from target to neighbor, in m

λ _ik is the competitive effect of the kth neighbor's species on the target. It is calculated each timestep as a function of plot temperature, as follows:

where:

X_a is the Species i NCI lambda Xa neighbors parameter
X₀ is the Species i NCI lambda X0 neighbors parameter
X_b is the Species i NCI lambda Xb neighbors parameter
T is the value in the Mean Annual Temperature, degrees C parameter of the Plot, converted to K

NCI with temp dependent lambda + BA ratio, target default DBH

This creates two terms: the first is the basal area ratio, and the second is NCI.

Parameters

DBH Adjustment Factor	Any corrective or units adjustment factor to be multiplied by neighbor DBH.
Default DBH, in cm	The value to be used for target DBH.
Maximum Adult Crowding Distance, in meters	The maximum distance to look for crowding adult neighbors.
Maximum Sapling Crowding Distance, in meters	The maximum distance to look for crowding sapling neighbors.
NCI Alpha	NCI function exponent.
NCI Beta	NCI function exponent.
NCI Minimum Neighbor DBH, in cm	The minimum DBH for trees of that species to compete as neighbors. Used for all species, not just those using this NCI behavior.
Species i NCI lambda X0 neighbors	X0 in the function to calculate the competitive effect of neighbors of species i on the target tree species.
Species i NCI lambda Xa neighbors	Xa in the function to calculate the competitive effect of neighbors of species i on the target tree species.
Species i NCI lambda Xb neighbors	Xb in the function to calculate the competitive effect of neighbors of species i on the target tree species.

How it works

This works exactly like the NCI term NCI with temp dependent lambda + BA ratio, except the ratio is always mean neighbor basal area to the basal area calculated from the Default DBH, in cm. Use this when using a version of the NCI Quadrat master, when a target diameter would not be available.