Table 2 The five measures of competition used in this study

Basal area of larger trees

$\mathrm{BA}{\mathrm{L}}_{\mathit{ij}}=\mathrm{\sum }_{\mathit{j}=1}^{\mathit{n}}\mathrm{B}{\mathrm{A}}_{\mathit{j}},$ where BA _j  > BA _i

Local basal area

$1\mathrm{BA}=\mathrm{\sum }_{\mathit{j}=1}^{\mathit{n}}\mathrm{B}{\mathrm{A}}_{\mathit{j}},$ where i ≠ j

Crowding index

$\mathrm{CR}13=\mathrm{\sum }_{\mathit{j}=1}^{\mathit{n}}\mathrm{DB}{\mathrm{H}}_{\mathit{j}},$ where 10 cm < DBH < 30 cm

Iterative Hegyi

$\mathrm{ITH}=\mathrm{\sum }_{\mathit{j}=1}^{\mathit{n}}\left(\frac{{\mathit{D}}_{\mathit{j}}}{{\mathit{D}}_{\mathit{i}}}\frac{1}{\mathrm{DIS}{\mathrm{T}}_{\mathit{ij}}}\right),$ where i ≠ j

Crown competition index KKL

$\mathrm{KKL}=\mathrm{\sum }_{\mathit{j}=1}^{\mathit{n}}{\mathit{\beta }}_{\mathit{ij}}\cdot \left(\frac{\mathrm{CC}{\mathrm{A}}_{\mathit{j}}}{\mathrm{CC}{\mathrm{A}}_{\mathit{i}}}\right)\cdot \mathrm{T}{\mathrm{M}}_{\mathit{j}},$ where i ≠ i