Table 2 Stand spatial structure parameters, species diversity indices and similarity index used in this study
From: Species and structural diversity of trees at the structural type level
Indices | Formula | Explanation | References |
|---|---|---|---|
SSSPs | \({{\text{W}}}_{i}=\frac{1}{4}\sum_{j=1}^{4}{Z}_{ij}\) | When the jth angle \(\alpha\) is smaller than the ith standard angle \({\alpha }_{0}\)=72°, zij is equal to 1. Or, zij is 0 | [29] |
\({{\text{U}}}_{i}=\frac{1}{4}\sum_{j=1}^{4}{K}_{ij}\) | When the reference tree i is smaller than the neighbor tree j, kij is equal to 1. Or, kij is 0 | [29] | |
\({{\text{M}}}_{i}=\frac{1}{4}\sum_{j=1}^{4}{V}_{ij}\) | When the neighbor j is not the same species as the reference tree i, vij is equal to 1. Or, vij is 0 | [29] | |
SDI | \({{\text{H}}}^{\mathrm{^{\prime}}}= -{\sum }_{i=1}^{{\text{S}}}{p}_{i}{\text{ln}}({p}_{i})\) | Hʹ = Shannon–Wiener index, S = number of species, pi = proportion of individuals in the ith species | [14] |
\({{\text{E}}}_{{\text{H}}}=\frac{-\sum {p}_{i}{\text{log}}{p}_{i}}{{\text{ln}}S}\) | \({{\text{E}}}_{{\text{H}}}\)= Pielou evenness index, S = number of species, pi = proportion of individuals in the ith species | [14] | |
SI | \({K}_{j}=\frac{j}{({\text{a}}+{\text{b}}-j)}\) | \({K}_{j}\)= Jaccard similarity coefficient, j = number of common species between two grades of SSSPs, a, b = number of species only occurred in each grade, Kj ≤ 0.5 represents dissimilarity, Kj > 0.5 represents similarity | [41] |