Figure legends
Figure 1 . Abundance of nematode trophic groups as affected by N treatments and soil depth. Treatment and soil depth from two-way ANOVA are provided in each subpanel. Within each depth, different lowercase letters indicate significant differences of means (P < 0.05) under a LSD test among N treatments. Bars indicate standard errors of means (n = 3).
Figure 2. The diversity of soil nematodes as affected by N treatments and soil depth. Treatment and soil depth from two-way ANOVA are provided in each subpanel. Different uppercase letters indicate significant differences of means (P < 0.05) under a LSD test among soil depths. Bars indicate standard errors of means (n = 3).
Figure 3. Ecological indices of soil nematodes as affected by N treatments and soil depth. Treatment and soil depth from two-way ANOVA are provided in each subpanel. Within each depth, different lowercase letters indicate significant differences of means (P < 0.05) under a LSD test among N treatments. Bars indicate standard errors of means (n = 3).
Figure 4. The co-occurrence networks of nematode genera under different N treatments (a) and the robustness of nematode genera networks under different treatments (b). The size of each node indicates the proportion of total nematode abundance represented by the indicated genus. BF: bacterial-feeding nematodes; FF: fungal-feeding nematodes; PF: plant-feeding nematodes; OP: omnivorous-predatory nematodes.
Figure 5. Structural equation model (SEM) examining the direct and indirect effects of N addition on nematode trophic groups (a) and the standardized total effects (direct plus indirect effects) of each nematode trophic group derived from the SEM (b-e). Black and red lines indicate positive and negative effects, respectively. Line thickness in SEM indicates the strength of significant path coefficient and gray lines present the non-significant paths. Values associated with arrows are standardized path coefficients. r 2values linked with response variables indicate the proportion of variation explained by relationships with other variables. PCT: the first component of TC, TN and TP determined by principal component analysis; PCA: the first component of AP, NO3+-N and NH4+-N determined by principal component analysis; FF: fungal-feeding nematodes; BF: bacterial-feeding nematodes; PF: plant-feeding nematodes; OP: omnivorous-predatory nematodes. ***P < 0.001, **P < 0.01, *P < 0.05, n = 36.