Structural Diversity Results

From Heureka Wiki
Jump to: navigation, search

This result group contains results that describe the Structural diversity of the trees in a treatment unit.

Variable name Unit Description
Even-aged Class code Even-aged type.
  1. Unknown: No information
  2. EvenAged: In Heureka, calculated at MostlyEvenAged
  3. MostlyEvenAged: If at least 80 % of the volume are within a 20-year age range
  4. UnevenAged: Otherwise.
Note that the definition differs from the one used in the Swedish NFI.
Tree Size Diversity (Gini Coefficient) 0-1 The Gini coefficient is an equality index between 0 (=maximum equality, i.e. all trees have the the same size) and 1 (=maximum inequality). The index has been proposed to be used for forestry planning by Lexerød & Eid (2006)[1].
Tree Size Diversity Class (Hugin def.) code Tree size diversity class according the Hugin system definition. Trees are grouped into four diameter classes, with class width = (dbhmax-dbbmin)/4. If the number of trees in classi > classi+1, the diameter class distribution is set as InverseJShaped, otherwise as Homogeneous.


Calculation of Gini coefficient in Heureka

The Gini coefficient is calculated with the formula for a discrete probability distribution (see https://en.wikipedia.org/wiki/Gini_coefficient).

First trees are sorted in ascending order so that gi < gi+ 1, where gi = basal area of type tree i. Basal area is used to take into account that the stand volume is highly affected by the largest trees (see Lexeröd and Eid 2006).



where , and
S0 = 0, and
f(g_i) = Frequency distribution, where gi, i = 1..n, are the tree basal areas, indexed in increasing order (gi< gi+1)

References

  1. . Lexerød, N.L, Eid, T. 2006. An evaluation of different diameter diversity indices based on criteria related to forest management planning. Forest Ecology and Management 222 (2006) 17–28.