alemdag: Alemdag's (1978) tree competition index

In johngodlee/compInd: Forest tree-tree competition indices

Alemdag's (1978) tree competition index

Description

Alemdag's (1978) tree competition index

Usage

alemdag(dbh, dist, focal_dbh)

Arguments

dbh	vector of DBH (diameter at breast height) measurements of competitor trees
dist	vector of distances from focal tree to competitor trees
focal_dbh	DBH of focal tree

Details

A spatially explicit competition index originally used in white spruce plantations. The value of this function increases when competitor trees are closer to the focal tree, or when competitor trees are larger. Alemdag's competition index is defined by the following equation:

\sum^{n}_{j\neq{}i}(\pi[(l_{ij}d_{i})/(d_{i} + d_{j})]^2 (d_{j} / l_{ij}) / \sum(d_{j} / l_{ij}))

where l_{ij} is the distance between focal tree i and competitor tree j, and d_{i} is the diameter (DBH) of focal tree i.

Value

value of competition index for focal tree

References

Alemdag I. S. (1978). Evaluation of some competition indexes for the prediction of diameter increment in planted white spruce. Forest Management Institute, Ottawa, Canada.

Examples

data(bicuar)
nb <- nearNeighb(bicuar$x, bicuar$y, bicuar$stem_id, k = 4) 
lapply(nb, function(x) {
  nb <- merge(x, bicuar, by.x = "nb", by.y = "stem_id")
  focal_diam <- unique(bicuar[bicuar$stem_id == nb$focal,"diam"])
  alemdag(nb$diam, nb$nb_dist, focal_diam)
  })

johngodlee/compInd documentation built on Aug. 5, 2024, 8:44 a.m.