图3. 邻体对目标个体的直接(直线箭头)与高阶相互作用(曲线箭头)。参数$\alpha_{i_{m}j_{p}}$表示的是邻体j_p对目标个体i_m的直接相互作用, 参数$\beta_{i_{m}j_{p},k_{q}}$表示的是邻体k_q通过个体j_p对目标个体i_m的高阶相互作用。森林群落研究中一般假定直接相互作用发生于邻体j_p在目标个体i_m半径为R的邻域内(实直线箭头), 因而高阶相互作用发生于当邻体j_p在目标个体i_m半径为R的邻域内且邻体的邻体k_q在邻体j_p的邻域内(实曲线箭头)。虚线箭头表示邻域外不需要考虑的直接与高阶相互作用。

Fig. 3. Direct (straight arrows) and higher-order interactions (curve arrows) of neighbouring trees on a focal tree. The parameter $\alpha_{i_{m}j_{p}}$ quantifies the direct effect of a neighbour (individual p of species j) on the focal tree (individual m of species i). The direct interaction occurs only when a neighbour (j_p) is located within a maximum radius (R) of i_m (solid straight arrows). The parameter $\beta_{i_{m}j_{p},k_{q}}$ quantifies the higher-order effect of a neighbour (individual q of species k) on the focal tree through another neighbour (individual p of species j). Higher-order interaction occurs only j_p is located within the maximum radius (R) of i_m and k_q is located within the maximum radius (R) of j_p (solid curve arrows). Dashed arrows indicate direct interactions and higher-order interactions that are not considered when a neighbour is located outside the maximum radius (R) of the focal tree or its neighbour(s).