These are terms meant to be used as part of a crowding effect.
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.
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's growth, 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 NCI growth. |
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. |
NCI is calculated as:
where:
This is the default term with the addition of the effects of storm damage on 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's growth, 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 NCI growth. |
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. |
NCI is calculated as:
where:
For all trees to which this behavior applies, you must also have the Storm damage applier behavior applied.
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.
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 NCI growth. |
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 NCI growth. |
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). |
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 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's growth, 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 NCI growth. |
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. |
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 NCI growth, 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: