Difference between revisions of "Structural Diversity Results"
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First trees are sorting in ascending order so that ''g<sub>i</sub>'' < ''g''<sub>''i''+ 1</sub>, where ''g<sub>i</sub>'' = 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). | First trees are sorting in ascending order so that ''g<sub>i</sub>'' < ''g''<sub>''i''+ 1</sub>, where ''g<sub>i</sub>'' = 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). | ||
| − | <math>\displaystyle G = 1 - \frac {\sum\limits_{i=1}^n ( | + | <math>\displaystyle G = 1 - \frac {\sum\limits_{i=1}^n (f_g_i)(S_{i-1} + S_i) }{S_n} </math> |
<br><br>where | <br><br>where | ||
| − | <math> S_i = \sum_{j=1}^i f( | + | <math> S_i = \sum_{j=1}^i f(g_j)g_j</math>, and |
<br>''S''<sub>0</sub> = 0, and | <br>''S''<sub>0</sub> = 0, and | ||
<br>''f''(''i'') = Frequence distribution, i.e. proportion of trees that type tree i constitutes of all ''n'' type type trees. | <br>''f''(''i'') = Frequence distribution, i.e. proportion of trees that type tree i constitutes of all ''n'' type type trees. | ||
Revision as of 09:38, 22 March 2016
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.
|
| 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-coefficent is defined primarily for population with discrete unit. In Heureka, a stand is represented by type trees, where each type tree represents a cohort of trees, where each type tree has a tree expansion factor (a wieght) for the number of trees it represents. This prevents any of the currently available formulas to be applied correctly. As an approximation, the Gini coefficient is calculated with the formula for a discrete probability distribution.
First trees are sorting 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(i) = Frequence distribution, i.e. proportion of trees that type tree i constitutes of all n type type trees.
References
- ↑ . 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.